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MINE TIMBERING
MINE TIMBERING
BY
WILBUR E. ^ANDERS
BERNARD MacDONALD
NORMAN W. PARLEE
AND OTHERS
I
ly
NEW YORK AND LONDON
HILL PUBLISHING COMPANY
, J J
, .- . . •
* . ■• • ■■
» • * ^
Copyright, 1907, by Hill Publishing Co.
ENTERED AT 8TATI0KERS* HALL
Til ; K :v; iO''K I
FU3LIC U;HARY
826240 A
A?'"0»^». LE ^Or A^-D
TlLn :.^ i' •J.><DAT10N8
p 1(436 L
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The PlimpUm Press Norwood Mass, U,S,A.
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• • •
• • • •
• • •
• • • • *
• • • »
• • • • • . •
• • • • • • •
m •
• • a • • •
'• - • •• •
• » • • •
PREFACE
This book is a collection of articles that have previously
been printed in the Engineering and Mining Journal, The Mineral
Industryj and the transactions of various societies, the source
being stated in a foot-note to each article. The article by Mr.
MacDonald was published originally in the Proceedings of the
Canadian Mining Institute, and that by Mr. Pariee in the Pro-
ceedings of the Canadian Society of Civil Engineers, Permission
to make this republication has been courteously granted by the
Secretaries of both those societies, and the respective authors
have cooperated with suggestions and in the reading of proof.
The last part of the book is made up chiefly of articles that have
appeared in the Engineering and Mining Journal during the last
two or three years. In the absence of any treatise on this impor-
tant subject, which in the hand-books and text-books on mining
is dealt with only in a superficial way, it has appeared worth
while to make the present collection, which is offered not as a
complete treatise on the subject, but rather as a series of essays
which go fully into many important details. It is hoped that a
thorough and systematic treatise on mine timbering will soon be
written. Editor.
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to
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TABLE OF CONTENTS
PAGES
Preface v
List of Illustrations ix
Mine Timbering, by Wilbur E. Sanders 1-52
Timbering of shafts, stations, and levels, 7. Shafts, 7. In-
clined shafts, 10. Stations for inclines, 13. Alinement of
incline sets, 14. Vertical shafts, 16. Cribbed shaft timber-
ing, 16. Halved framing for shaft sets, 18. Square-set shaft
timbers, 20. One-compartment shafts, 20. Locating shaft
sets, 22. Alinement of vertical shafts, 24. Repairing shafts
25. Timbering shafts in loose ground, 26. Timbering shafts
in running ground, 26. Two-compartment shafts, 28. Three-
compartment shafts, 29. Four-compartment shafts, 31. Lad-
ders, 34. Shaft station sets, 35. Stations, 35. Levels, 36.
Timljering levels in loose ground, 39. Timbering of the work-
ing places in a mine, 41. Posts, 41. Cribs, 41. StuUs, 42.
Penning, 45. Square sets in stoping, 46. Reinforcing
sets, 49. Ore chutes, 49. Waste filling, 50. Methods of
framing, 50.
Mine Timbering by the Square-Set System at Rossland, B.C.,
by Bernard MacDonald
Historical, 55. Vein characteristics at Rossland, 56. Pre-
liminary work, 56. Sill-floor construction, 57. Timbers and
methods used after sill floor is laid, 60. Per tonnage cost of
square-set timbering, 64. Cost data per square set, hand
framed, 64. Incidental costs, 67. Limitations of the square
set, 67. Reinforcement methods, 68. Angle bracing, 68.
Cribbing, 68. Bulkheading, 70. Filling, 70. General re-
marks, 70.
5a-71
Methods of Mining and Timbering in Large Orebodies in
British Columbia and Michigan, by Norman W. Par-
lee
Le Roi mine, Rossland, B.C., 76. Old Ironsides mine,
Phcenix, B.C., 85. Baltic mine, Baltic, Mich., 89. Atlantic
vii
7a-102
viii CONTENTS
PAGES
mine, Atlantic, Mich., 92. Bamum mine, Ishpeming, Mich.,
93. Section 16 mine, Ishpeming, Mich., 94. Soft Ore Hema-
tite mine, Ishpeming, Mich., 96. Queen mine, Negaunee,
Mich., 99.
Mine Timbering in Sechon 16 of the Lake Superior Mining
Company, Michigan, by C. St. G. Campbell 103-120
Shaft timbering, 108. Drift sets, 110. Square sets, 112.
Stulls, 112. Timl)er pillars, or cribs, 114. Docks, 115. Chutes,
117. Staging, 118. Ladders and sollars, 119. Miscellaneous,
119.
The Framing of Rectangular Shaft Sets, by Wilbur E. San-
ders 123-130
Square-Set Practice at Bingham, Utah, by Louis S. Cates 131-139
Square-Set Timbering at Bingham, Utah, by Claude T. Rice 140-143
Mining methods, 140. The square-set system, 141. Pecul-
iarities of the Bingham practice, 142. Criticism of the system,
143.
Mine Timbering at Lake Superior, by W. R. Crane 144-149
Timbering in shafts, 145. Concrete lining, 147. Timber-
ing in drifts and stopes, 147.
Timber and Timbering in the Ccbur d*Alene, by J. H.
Batcheller 150-169
Timbering at the Chillagoe Mines, Queensland, by T. J.
Greenway 1 . 170-174
Timbering IN Tasmania, by Mark Ireland 175-176
Index 177-179
LIST OF ILLUSTRATIONS
FIGURES PAGES
1-5. Weight pressure on timbers 5-6
6. Three-piece level set 8
7. Four-piece level set 8
8-10. Three-compartment shaft set 9-1 1
11. Details of the four-piece set 11
12-13. Station for inclined shaft 12-13
14-16. Straight-edge and plumb line 14
17-20. Ladders and hanging bolts 15
21-21 A. Cribbed shaft timbering with poles 16
22-22 A. ■ Cribbed shaft timbering with planks 16
23. Cribbed shaft timbering with framed set 17
24-25. Halved framing for shaft sets 19
26. Timl)ering of a one-compartment shaft. Detaib 21
27. Timbering of a one-compartment shaft. Perspective . 22
28. Method of supporting shaft sets 23
29. Lining for shafts in loose ground* 26
30. Spiling in running ground 28
31. Framing of three-compartment shaft. Perspective. . 29
32. Framing of single-width four-compartment shaft 31
33. Framing of double-width four-compartment shaft. Plan
and details 32
34. Framing of double-width four-compartment shaft.
Perspective 33
35. Single-piece set 36
36. Two-piece set 37
37-38. Three-piece set 38
39. Four-piece set 39
40. Spiling in loose ground 40
41. Post and head board 41
42. Crib 41
43. Crib with waste filling 42
44. Stull 43
45. Stull and false stull 44
46. Double-stull method 44
47. Saddle back and arch 45
48. Saddle back 45
ix
LIST OF ILLUSTRATIONS
FIGURES
49.
50.
51.
52.
53.
54.
55.
56.
57.
58-59.
60.
61-63.
64-66.
67.
68.
69.
70-72.
73.
74r-75.
76-77.
78-79.
80.
81.
82.
83.
84.
85-86.
87.
88.
89.
90.
91.
92-93.
94.
95.
96.
97.
98.
99.
100-101.
102.
103.
104.
105.
106.
107.
108.
PAGES
Penning 46
Angle of underlie of stulLs 47
Square sets in stoping 48
Anaconda method 50
Eureka method 51
Burlingame method 51
Richmond method 51
Anaconda method of framing. Details 52
Square-set timbering at Rossland, B.C 58
Working floors at Rossland, B.C 60-61
Square-set timbering at Rossland, B.C. Details 66
Square-set timl:)ering at Rossland, B.C 69
Stull timbering, Lc Roi mine 77
Mud-sills and ties, Lc Roi mine 79
Details of square sets, Le Roi mine 80
Square sets in position, Lc Roi mine 81
Views of chute, I^ Roi mine 82
General scheme of stope, Le Roi mine 84
Lagging arrangement, Old Ironsides mine .... 87
Chute arrangement, Old Ironsides mine 88
Method of walling up, Baltic mine 90
Longitudinal section of stope, Baltic mine .... 91
Stull timl^ring, Atlantic mine 92
Stopes and pillars 94
Filling system, Section 16 mine 95
Caving system, Soft Ore Hematite mine 97
Stopes and pillars. Queen mine 100
Section 16 Mine. Projection of 2d and 10th levels . 106
Horizontal section through shaft. Section 16 mine 109
Side elevation of drift set. Section 16 mine .... 110
End view of drift set. Section 16 mine Ill
Raker, Section 16 mine 112
StuUs, Section 16 mine 113
Method of setting up machines 114
Docks 116
Mills 117
A typical mill chut« 118
Frame of rectangular shaft set, assembled .... 124
Laying out and framing rectangular shaft set . . . 127
Square-set timl)ering at Bingham, Utah 132
Transverse section of stope 133
Transverse section of stope 135
Short sets 136
Butt cap and ground post 138
Details of square-set timbering 141
Shaft timl^ring. Plan and section 145
Level timl)ering and square setting 146
LIST OF ILLUSTRATIONS xi
FIGURES PAGES
109. Forms of square-set joints 148
110-115. Square-set timbers 151-152
116-117. Square-set stope 153
118. Battered and straight tumiel sets 154
1 19. Tmmel-set timl^ers . 155
120. Two-compartment shaft 156
121. Four-compartment shaft 157
122. Angle braces 158
123. Standard stope set 159
124. Double drift sets • • 160
125. Two-compartment shaft station 165
126. Four-compartment shaft set 166
127-131. Details of framing 167
132-133. Stull stope 168
134-137. Templates and posts 170
138. Caps or stretchers 171
139. Miter box 172
140. Method of framing posts, caps, and stretchers ... 173
MINE TIMBERING
BY
WILBUR E. SANDERS
MINE TIMBERING*
By Wilbur E. Sanders
In this necessarily brief article the systems of timbering dealt
with are those in use among the mines of the mountainous regions
of western United States. This qualification, of itself, requires
no apology; for the cosmopolitan character of our miners — man-
agers and engineers, superintendents and foremen — and their
shrewd keenness in devising ways to meet the problems presented
in underground workings, in selecting means peculiarly adapted
to the end in view, and in improving upon well-known methods
already in vogue, have placed the science of supporting mine
excavations by timbers, as developed by them, far in advance of
that in use among the older and less progressive mining commu-
nities. This monograph does not include the methods used in
coal mining in the East, or that in use in the copper and soft iron
ore deposits of Michigan and Minnesota; nor does it treat of
wood and iron cribbing for round shafts, or of iron supports now
used in many European mines, nor of timbering and metal sup-
ports used in large tunnels.
The mines operated under these methods present every known
characteristic of lode formation. The veins and ore deposits lie
at all angles of inclination or dip; they are of all shapes and sizes,
from the small seam to immense masses hundreds of feet in
width, and of all lengths; while the materials comprising them
and their country formations vary in texture from rock of strength
sufficient to overlie considerable excavations without extraneous
support, to the soft ground which requires not only immense
quantities of timber and waste filling to carry the workings safely,
but an eternal vigilance upon the part of those conducting the
operations.
During preliminary work it is important to explore and de-
velop the orebodies in the surest and least expensive ways, and,
» From The Mineral Industry, 1899, Vol. 8.
3
4 MINE TIMBERING
except in the case of prospecting hidden or blind deposits, by
means of bore-holes from the surface downward, metal mines
are tested and all are exploited during their earlier stages by
shafts sunk or adit-levels driven in and with the ores. This
latter is an axiom in mining during this period of development,
and should be invariably followed where possible. When once
the ores have been opened up so that an estimate may be made
as to their extent and general characteristics, more expensive
works necessary to prepare the mine for the larger operations of
economic ore extraction may be safely entered upon. It some-
times happens that the required information as to orebodies
beneath the surface of a mining claim is sufficiently answered in
and by the workings of adjoining properties to make preliminary
prospecting of the deposits unnecessary; then systematic plans
for operating on a large scale may be properly inaugurated.
It is not the province of this article to touch upon methods
of mining in use above ground, whether by openwork, hydraulic
mining, or by other processes, but rather to deal with the support
of underground excavations by the use of timbers, and the details
of mining therewith connected. Nor is it intended to explain
methods technically foreign to the subject, although such will be
touched upon when used as adjuncts to systems of timbering, as
waste filling, etc. In the figures drawn to illustrate the article,
sizes of timber most frequently used have been arbitrarily taken
for convenience. The figures giving dimensions are working draw-
ings showing the methods of framing, as explained, and can
easily be applied to frames and timbers of any desired dimensions.
In developing and exploiting mines the miner should remember
that unnecessarily large openings for levels, shafts, and other
similar workings, mean not alone the breaking down and trans-
porting of needless quantities of material, but also the added
expense of keeping in repair larger passageways than are neces-
sary, an item of considerable importance in heavy or creeping
ground. On the other hand, the larger excavations are relatively
the easier and cheaper to drive. The rule should be that the size
of workings must be ample to carry out their purposes properly,
but not larger than is necessary for economy in operation.
It often happens that conditions, local or otherwise, are such
that the strongest timbering fails to withstand the pressure to
•which it is subjected, and other means of support must be em-
•I V w • ••
- «. • • •
«■ •• •
MINE TIMBERING
ployed. In exceptional cases large excavations may be supported
with little or no timbering, but usually waste filling must be
extensively used as an adjunct to timbering if the mine is to be
kept oi>en. Swelling or "creeping" ground, resulting from the
exposure of certain rocks and clays to the air, whereby they
expand with a force no timbering can resist, demands prompt
attention that the timbers may be relieved from abnormal strain.
This is done by making use of an open lining of lagging, through
the interstices of which sufficient material may be removed to
relieve the unusual pressure upon the frames; a process that b
continued as long as the conditions demand. The above scheme
is employed at the Ontario mine. Park City, Utah, and in the
Never Sweat mine, Butte, Mont., where a system of narrow
"square sets," with open lagging, placed outside of the timbers
of the large three-compartment working shafts, has been success-
fully employed to meet juat such conditions in swelling ground.
There are certain established principles connected with the use
andframingof mine timbers that should be borne in mind. Pressure
is best resisted in line with the grain of the wood rather than across
the grain, which maybe made clear by the following explanation:
Fios. 1-3.
Let Fig. 2 be a section of timber supporting upon end and
side the weight pressures representetl by the arrows a and b;a
acting in line with the grain of the piece, b at right angles to the
grain. As shown in Fig. 1 each individual grain or fiber of which
the block is composed resists the pres.-3ure o by the strength of
the combined fibers of the timber, or in other words by the full
strength of the timber itself. On the other hand, Fig. 3, the pres-
sure b acting across the grain is resisted by the power which binds
MINE TIMBERING
together the bundle of fibers that make up the piece, the weight
tending to crush them down one against the other until the shape
and strength of the timber are destroyed. The writer has himself
seen in Cralk's Colusa mine, Meaderville, Mont., 24 in. of square-
sawed yellow pine crushed down to a thickness of 8 in. by the
weight pressing upon its side, at right angles to the grain of the
wood, while the supporting post still retained its integrity.
In framing timbers the sets should be made with especial
reference to the direction of the pressure thrust.
In Fig. 4 let us suppose the pressure upon the frame comes
from the direction of the arrow a, in which instance it will be seen
(1
b ^.
Figs. 4 and 5. — Weight Pressure on Timbers.
that the full cross-section of the timber A is supported at either
end by the pieces B and D. This joint is without doubt an
excellent one when, and only when, the entire pressure upon the
frame comes from the direction a or c. The frame, however, is
likely to be subjected also to pressures from the directions band
d, to resist Which the timbers B and D offer only a portion of their
cross-sections while the remaining parts x y of the pieces tend to
split off from the larger portions, thereby weakening the timbers
by an amount equal to the sections a/ y' so removed. A similar
result from the pressure c might now cause the portion x zto
split off from C, in which event, there remaining, as against the
pressure 6, no shoulder upon C to support B in place, the timber
B would be forced from its position, causing the frame to collapse.
MINE TIMBERING 7
Therefore, for resisting pressure from two or more directions the
framing shown in Fig. 4 is not applicable.
The only satisfactory remedy for this inherent weakness of
square-shoulder framing is to make use of the mitered joint
or beveled hitch, as shown in Fig. 5. In this method, because of
the support afforded a timber by the miter of this joint, the pres-
sure from any of the directions a, 6, c, and d is resisted by the
strength of the full cross-section of the piece against which the
force acts. However, as shown in the piece C, the simple miter
is not in itself sufficient to sustain any considerable thrust without
a tendency to wedge apart the timbers B and Z), and thus destroy
the set. Without doubt the simplest and strongest joint obtain-
able is some combination of the square-shouldered tenon with
the miter or beveled hitch. This combination is shown in the
joints supporting the piece A. Here the full strength of the timber
is obtained, with no tendency to split or slip, and weight up to
near the point of crushing only serves to bind the set more firmly
together.
Heavy ground is supported by the heavier timbers; by sets
placed near together; and by sets strengthened by reinforcing
sets of timbers.
Round timbers are stronger than square-sawed pieces, in
which the grain of the wood has been cut and weakened by the
saw. Used in the mine, round timbers are less easy to handle
than are the squared; they are less easy to aline properly, and it
is impossible to reinforce satisfactorily sets framed from such
timbers by the usual false sets or pieces. The bark should in-
variably be removed from round timbers, as it collects moisture
and fungus, and thus hastens the decay of the wood. It also
prevents the pieces from becoming properly seasoned before they
enter the mine.
Timbering of Shafts, Stations, and Levels
Shafts. — Shafts are of two kinds, vertical and inclined.
The former is more frequently used in large operations, where
speed and convenience in hoisting are the prime necessity — par-
ticularly in connection with the more steeply inclined deposits,
and with flat ones and pockets lying entirely beneath the sur-
face.
MIXE TIMBERING
i-
-«?.
i.
-^
-->;
--
Fig, 6. — Three-piece Level S
J^.
-f- 1 0*-
d
FiQ. 7. — Four-piece Level £
MI.NE TIMBERING
10
MINE TIMBERING
1^^^^^^^
The usual size for single-compartment shafts, and for the hoisting
compartments of the larger shafts in metal mining, is from 4 to
6 ft. in the clear of the timbers; the com-
partment used to carry water-columns,
air- and steam-pipes, and ladders, is
frequently made larger in cross-section
than the working compartments. The
expense of sinking shafts and of keeping
them in repair in average ground in-
creases rapidly beyond a certain size;
it is therefore considered good practice
to make the shafts as small as possible,
keeping in view the work to be carried
on through them.
Inclined Shafts. — Inclined shafts are
used largely during the preliminary stages
of development in veins, and other out-
cropping deposits that dip below the
horizontal at angles too small to allow
of the economical use of vertical shafts.
Similar methods of timbering both classes
of shafts are in use, although at times
the timbering of inclined shafts ap-
proaches more nearly to that employed
in supporting the level workings; as
when application is made of the three-
piece and four-piece level sets to in-
clines (Figs. 6 and 7). The single stull
piece, with head board, is often used in
the mountains when the hanging wall or
top rock is of such strength as to require
little support.
When the three-piece level set is em-
ployed the cap is usually lengthened,
and the top of each post fits into gains
cut near the ends of the cap. Where a
sill piece is desirable the sill is framed in
the same manner as the cap, and the
posts act as dividers. (See Fig. 7.) In
such use technically the posts become end
-5^
-.9.8-
X.
.V
.-8-f 1^
I-Lj
J
Fig. 9. — Three-compart-
ment Shaft Set.
MINE TIMBERING
11
plates, the cap and sill side plates, while posts when used are
placed lengthwise of the shaft as distance pieces to separate
the sets. (See Fig. 8.)
A two-compartment shaft is constructed by placing a third
post or girt in position at or near the center of the set in much
the same manner as are located the end posts or plates.
1(
J(
?f
111
* ■»!*
n^Aiii^ai
H<!tf>t4W
>».ti
1
1
Fia. 10. — Three-compartment Shaft Serr.
I b I
L .
1
M ,M
\'t— ■■"
.r
1 1
U
W1
□II
FiQ. II. — Details o
3 FOI-R-
B Set.
The three-compartment shaft is similarly constructed by
locating two such girts at their proper position, the tenons of the
girts being V-shaped. (See Figs. 8, 9, and 10.) Behind or back
of the side plates, and in line with the end plates and girts, the
12
MINE TIMBERING
set is tightly blocked and wedged in place. Pole or plank lagging
is used where it is necessary to prevent falls of loose rock from
the walls and sides of the shaft. Skip-ways are carried by the
sill piece or bottom side plate. Guides also are attached to
the end plates and center girts when safety devices are used upon
the ore-skips.
FiQ. 12. — Station for Inclixed Shaft.
Other methods of framing the four-piece set, as applied to
the inclined shaft, differ from the above framing in minor details,
and at the same time allow of the use of the full width of the
MINE TIMBERING
13
shaft. (See Fig. 11.) The halved system of framing, as explained
under vertical shafts, is rarely used for the inclines, and then only
when posts are employed to form the complete square shaft set.
U
c=
-Z-J
73
Fio. 13. — Station for Inxlined Shaft.
Stations for Inclines. — The stations constructed for inclined
shafts are of two kinds, one being so arranged that the ore cars
dump directly into the hoisting skip, held in position just beneath
(Fig. 12), while in the other a 25- to 75-ton ore bin is placed
14
MIXE TIMBERING
beDeath the station and above the shaft, from which bin the ore
is drawn into the skip for hobting to the surface at intervals.
This station, while requiring more excavating to construct, is by
far the most economical in the end, as the skip can be run entirely
independently of the trammers or carmen. (See Fig. 13.)
Fia, 14, — Straioht-edob
t
'
m
,
m
!fi't
/f
m
»■
FiQs. 15 A
i. — Stiiaight-edoe and Ph'mb-lise.
AUnement of Incline Sets. — Probably the simplest method of
alining the .•side plates of inclined-shaft sets, in order to get them
in line one with another, is by the use of the combined straight-
edge and plumb-bob.
MINE TIMBERING
15
A straight-edge is made of a length greater by a foot or so
than the distance between two seta. From the side opposite the
true edge is built up a frame, one piece of which is so set that a
plumb-line attached at its upper end will hang vertically along a
fixed line, marked upon it, when the straight-edge coincides with
the true inclination of the shaft, and at the same time simulta-
neously rests upon three bottom plates. To prevent the plumb-
line from swinging too freely it is confined at its lower end within
comparatively small limits by a cleat attached to the upright
piece. (See Fig. 14.) The straight-edge alone is used to locate
nn
EH
EH
nn
nn
m
m
a '
t-h'
in
\h
s
Flos. 17-20. — Ladders a
) HAt
the end plates evenly in line with each other. (Fig. 15.) When
the sets are placed they are bound in position by hanging hooks
or bolts (Fig, 20), as explained under vertical shafts, and when
so held are blocked and wedged firmly in place; the straight-edge,
16
MINE TIMBERING
aa above described, being employed to locate the sets in their
true position during this operation.
Vertical Shafts. — The timbering of shafts varies according to
the nature of the ground and the size of the shaft. Shafts sunk
in some localities require little if any timbering, while in other
places they are supported only by huge timbeiB that have been
framed with the utmost precision.
Cribbed Shaft Timbering. ~ In small shafts usually some
form of cribbing Is used. This system of sliaft timbering is
the simplest and often the cheapest in use, but it becomes
cumbersome and expensive in large shafts. As usually employed
it requires little framing, is easy to place, to repair or renpw,
and to keep properly alined, and its use enables the timber-
ing to be kept even with the bottom of the shaft in sinking,
if that be n
MINE TIMBERLNU 17
The simplest form of cribbing is that of poles, cut to
I required lengths and placed in pairs across each other, eitlier
I from above or below. Located in this manner it forms an
openwork lining to the shaft. Strips an nailed to the poles
I upon the inside corners keep the cribbing in position. (See
p. 21 and 21A.)
Fio. 23. — Cbibbsd Shaft Timbering wrrn Framku Set.
Cribbing is also formed fr<mi sawed timbers of various
E dimensions, the most simple method being that in which planks
tof the required lengths are placed around the shaft, upon
L edge, and resting upon similar sets below or supporting similar
18 MINE TIMBERING
sets above. These sets are made to resist the outside pressure,
usually, by so placing the two shorter or end pieces that they
will hold apart the two longer side pieces, the former in their turn
being held in their position by corner strips b within, and nailed
up and down the shaft to the side pieces. (See Figs. 22 and 22A.)
While the method of timbering is extremely simple it is un-
satisfactory, and good mining practice makes use of the framed
set as being stronger and in every way better. The basis of this
system is some form of the tenon and mortise, whereby the ends
of the two timbers forming a joint are framed with both a tenon
and what might be called an open mortise, the mortise of one
piece engaging the tenon of the other and vice versay to the end
that each piece supports or keys its mate in place. See Fig.
23, a, 6, and c, which show the more simple forms of this method
of cribbing, the latter c being excellent for the reason that it
causes the edges of the planks on the sides to break joint with
the edges of the end planks in a way to stiffen the shaft and
prevent the sets from moving horizontally one upon another.
The methods of framing planks for these styles of cribbing are
shown in Fig. 23, d and e.
Halved Framing for Shaft Sets. — A development of the tenon
and mortise framing of joints is of almost universal application
in advanced methods of supporting vertical shafts. This method
is applied to the cribbed system as shown in Fig. 24, a, ^, 6,
and B, The method of framing the pieces for openwork cribbing
is shown in Fig. 24, a, and for tight cribbing. Fig. 24, 6.
Fig. 24 B also shows the framing of the opening from the
shaft to the levels. False timbers or struts are used temporarily
to hold the sides of the shaft intact while this opening is being
framed into the level, or the framing can be placed before the
planks are removed from the cribbing. A stronger and more
satisfactory frame, however, is obtained by the combined beveled
hitch and halved joint. The most satisfactory use of this com-
bination is that in which the top and bottom of the side plates
are made to break joint with top and bottom of the end plates.
(See Fig. 25.) Details of this framing are given in Fig. 25, a and 6,
while the method of placing the timbers is shown in the isometric
perspectives A and B.
Compartments are formed by cutting the side plates to receive
a center girt that is framed very similarly to the end plates.
MliNE TIMBERING
FioB. 24 AND 25. — Halved Framing fob Shaft Sara,
20 MINE TIMBERING
The tight cribbing has been used for large shafts in heavy
ground. On the Comstock lode, Virginia City, Nev., several of
the important shafts were timbered with a solid cribbing of
14-in. pieces.
Square-Set Shaft Timbers. — In the square-«et system, as
applied to the timbering of vertical shafts, the heavier timbers
of a cross-section of 6 in. and upward are employed. A set
consists of the side and end pieces, with posts used to separate
the horizontal frames. In the larger shafts divisional timbers,
called girts, are used to separate the compartments. The side
and end pieces are called wall plates, for the reason that they
frame the sides or walls of the shaft. The longer pair of plates
are designated as side wall plates — usually called side plates —
and the shorter pair as end wall plates, or end plates. Shafts of
a single compartment are characterized as one-compartment
shafts; and those which are divided by inner struts or girts into
two, three, and four divisions, as two-, three-, and four-compart-
ment shafts. It is doubtful if shafts larger than with four
compartments can be successfully operated in deep mining, unless
in exceptional cases. The framing of the various sized shafts is
very similar, differing only in details that will be explained later.
One-Compartment Shafts. — The timbering of a one-com-
partment shaft consists of two side plates, a, two end plates, b,
and four posts, c, which technically make a single set, successive
sets being used to the bottom of the shaft to support the sides,
and a lining of plank or lagging, d, is employed to prevent falls
of loose material into the opening. (See Fig. 26.) For the
wall plates the halved method of joint framing is employed, and
at the same time a hitch or square shoulder one inch deep is cut
in the tenon as a support for the post. This halving of the tim-
bers, if used alone, greatly weakens them, and the beveled hitch
is framed from their inner faces so that their full strength may
1)0 brought to the support of the shafts. (Fig. 26, z.) The
dimensions of the set are such that the plates when fixed in posi-
tion are separated 5 ft. from center to center, the practice being
to increase the size of the timbers in heavy ground rather than to
place the frames nearer together.
In framing the sets the utmost care is taken that the meas-
urements shall be exact, and that the timbers shall be cut true
to the line, especially for all important working shafts, large and
MINE TIMBERING
21
small. A center line is laid of! upon the inside faces of the plates
and the measurements for tenons, mortises and miters are taken
i^^ I -T I
^
a
d'
a
\.
I I l~~" I I
Twoofthla A
Top
Vtew
^^
eJi
Front
Vtow
h
y
-•^1^
Bottom
Vtow
Vtow
Twoofthla b
Top
Vtow
t
-eif^
H
Front
Vtow
s
X —
4V-
Bottom
Vtow
b,
-J
P
^
-^0^
tdl
Buk
Vtow \
Twoofthla C
»'.'
X
Fio. 26. — TiMBERixo OF A OxE-coMPARTMENT Shaft. Details.
MINE TIMBERING
from this line. The faces of the
tenons and shoulders are made at
right angles to, or parallel with,
and measured from the face of the
plate. These precautions are neces-
? sary because of variations in the
dimensions of timbers. The halved
tenons of each side plate occupy
the lower portion of that timber,
those of the end plates the upper
part, 80 that when in place the side
plates support the end plates by
their tenons. See Fig. 27, a, show-
ing the isometric perspective of this
shaft.
Locating Shaft Sds. — When a
shaft is to be sunk from a sur-
face too level to furnish possi-
I bilities for the disposal of the waste
material coming up from below, it
is necessary to elevate the top or
collar of the shaft above the
surface of the ground. This is
accomplished by building up a
cribwork of rough timbers to the
desired hight by placing logs of
sufficient length in layers by fours
or more across each other, with the
shaft opening in the center. This
cribbing is reinforced by waste filled
in against it, and with this as a
backing the shaft sets are located
in position and blocked securely
against the cribbing.
It also happens at times that the
top material in which a shaft _i3 to
be sunk is too loose to support the
sets by simple blocking. In this ca.se
the tenons at both ends of the side
plates are made to extend beyond
MINE TIMBERING
23
the limits of the shaft, and these extensions are bolted to cross
timbers above or rest upon such timbers as a support, the latter
being of a length sufficient to bear upon the ground to either
side of the shaft, and thus support its weight until it sliall
have entered rock firm enough to afford secure support to
the sets by blocking and wedging in the usual manner. (See Fig.
28, a and b.)
Fig. 28. — Method of Supporting Shaft Sets.
The process by which shaft sets are located and fixed in posi-
tion as integral parts of the shaft is as follows: The side plates of
the set to be put in place are swung to the set above by hanging
hooks or bolts, which arc made usually of 0.875-in. round iron,
hooked at one end and threaded at the other as far as may be
necessary. (See Fig. 20.) These hooks are used in pairs, the
length of each being about 4 in. greater than one-half the hight
MINE
of each set from outside to outside of the wall plates, measured
vertically. Thus, with plates of 12-in. cross-section in a 5-ft.
set, the length of each hook would be about 3 ft. 4 in., with the
bolt end threaded for 6 to 8 in. These bolts are the simplest
and most easily manipulated de%-ice yet constructed for hanging
a set in place. Holes are bored through each side plate, two
at S.'ced points near either end, to receive the bolts, one hole at
each end being used to hang the plates to the set above while the
other holes are intended for the next succeeding set. Cast-iron
washers are used between the plate and nut to give bearing to
the latter when binding the sets together. The bolts having been
located in the plates, the hooks attached to the loose timbers
are caught upon the hooks of the set above, the end plates are
put into place, their tenons resting upon the tenons of the side
plates, the posts are set in the hitches cut to receive them, and
the nuts are screwed down until the frame is tightly bound to the
set above. If this upper set is properly level, and the framing
of all the parts correctly done, the center line marked upon the
new set must be level. Blocks x are placed on the two sides of
each corner in line with each plate, between wall-rock and frame,
and wedges are driven to tighten the set in its proper position.
(See Figs. 26 and 27.) The back of each plate carries a strip
nailed thereto, and resting upon this as a ledge for support is
placed the plank lagging or lining of the set. Filling is stowed
behind the lagging, as the planks are put in position, sufficient to
prevent movement of the surrounding ground that would be
likely to throw the shaft out of plumb. The same process is
repeated as the sinking progresses to the bottom or sump of the
shaft. In dangerous ground the practice is not to remove the
bolts after the sets have been located, and it is well in any case
to leave them in place for several .sets from the bottom of the
shaft, in order to bind the frames firmly together at this point.
AtinemeiU of Vertical Shafts. — Various methods of alining
the timbers of vertical shafts are in use, the moat satisfactory
probably being the combination straight-edge and plumb-bob,
A double straight-edge of a length sufficient to extend over three
wall plates in pasit ion —-about 11 ft. for 5-ft. sets — is made,
near the center of which is attached a plumb-line of a length of
about 4 ft, A hole is cut in the straight-edge near its bottom
end, in which the bob may swing freely, wlule a cleat attached
MINE TIMBERING
25
just above this point serves to confine the line so that it is quickly
located at the center mark, and a line is drawn upon the flat
eide of the piece parallel to the true edge, with which mark the
plumb-line must coincide when the true edge is exactly vertical.
(See Fig. 16.)
The set, having been bound to the one above, and blocked
to its approximate position, is then alined truly with the two
sets above by means of the straight-edge (Fig. 15) and by the
combined straight-edge and plumb-line (Fig. 16), and is brought
to its exact position vertically, the wedges being driven first at
one side and then the other until the set is in place. Usually
the sets are alined first at the side, the side plates first at one
end and then at the other being brought into position by the
wedges, when the process is repeated with the end plates in
order to aline the ends of the shaft. Should it be a shaft of two
or more compartments the side plates are alined by blocks and
wedges in line with the divisional girts separating the compart-
ments after the corners of the shaft liave been brought to their
places in the same manner as has been described. If the timbers
are rightly framed the inner faces of the wall plates should exactly
coincide vertically with the inner faces of the sets above. The
frame having thus been brought into and fixed in its true position,
the lining is placed and the set is complete. (See Fig. 27.)
Repairing Shalts. — When, by reason of undue strain, weak-
ness develops in one or more of the timbers of a shaft, the faulty
pieces must be removed and replaced by new ones. Preliminary
to this work several sets, particularly those next above the point
at fault, are tightly bound together by the hanging bolts, If
posts only are to be replaced it may be accomplished by removing
the lagging adjacent, excavating enough ground from behind each
poet to allow of its being driven back from the shaft until it is
clear of the timbers, or it may be chopped out with little trouble.
The new poet is then placed in position from behind, being driven
or wedged into place and fitting into the hitch framed to receive
each post in the plates. When necessary to replace the wall
plates the lagging of the adjoining sets above and below is
removed, the blocks are knocked away and the posts taken out,
when the plates may be released and new ones put in place.
The posts are then returned to their position, the set b bound
to the plates above and below by bolts, blocked, wedged, and
26 MINE TIMBEEIXG
alined, lining ia put in, and the repairs are complete. It may
happen that the ground will not stand during this process, in
which case false timbers and lining must be used to hold the
walls of the shaft in place.
TimberiTig Shafts in Loose Ground. — ■ Shafts are frequently
sunk in ground that breaks away from the walls before a set can
be placed in position, and a quick process of lining the sides of
the excavation is necessary. A method of false lining, largely in
use throughout the West, keeps the loose earth from falling. It
consists of planks of desired lengths placed vertically, and so
blocked and wedged into position as to press each piece out-
wardly against the walls. The top end of the plank ia blocked
from the wall against the lagging of the last set placed in posi-
tion, reaching a foot or so above the wall plates of that set. The
plank is further blocked and wedged away from the wall-plates
themselves, the effect of this being to throw the foot of the piece
backward from the shaft against the side of the excavation, and
thus prevent the material from coming in. This lining is often
carried completely around the shaft. (See Fig. 29.)
Fig. 29. — Lin:\g fok tJHAtrs is Loose Ground.
Timbering Sltafls in Running Ground. — In soft running
ground, or loose ground too heavy to allow of placing the false
MIN'E TIMBERING
27
lining above described, a method of spiling is employed that is
practically identical with that used for dri\'ing levels through
similar material. The process consists of supporting the dan-
gerous ground l>eiieath the last set placed in position, by what
might be termed an enclosing and protecting shield of plank
spiling or forepoling, that Is, advanced downward from that set
piece by piece as the material ia excavated from within. The
spiling, a, sharpened at the foot, and often shod with iron at the
[ head, is driven with a sledge, one plank at a time being advanced
for a short dL'^tance as the material is withdrawn from before it.
The spiling is held in position by the set and the material through
which it is being forced, only enough of this being removed at a
time to allow it to be driven a short distance; otherwise the
isure from without may force the lining into the shaft. Each
I plank around the shaft ia driven successively one by one, until
I the entire shield has been advanced, when the process is repeated
J and continued until the shaft has been excavated to a depth
I BufEcient to allow of the placing of another set in position, the
1 Ijeing to advance the sliield by successive small stages during
\ the work.
The spiling is started at a considerable angle, but as it is driven
' downwanl it tends to approach nearer and nearer the vertical
until, when the new set has been permanently located, tail pieces
or bridges b are placed to hold the Iwttom of the planks in
position, and at the same time to furnish an opening between
the plates and the foot of the shield through which to drive the
spiling for the ne?ct succeeding set. These tail pieces may be
permanently left in place, or removed in order to allow the planks
to settle against the top of the spiling below, binding the latter
in place and making a closer lining. Ledge strips c may be
attached to the plates, and the usual close lining placed about
the shaft as additional security, and to keep from the shaft ma-
terial that otherwise might work in at the corners. The posts
prevent spiling from being placed vertically so as to form a
I continuous close lining, which difficulty may in a measure be
I overcome by diagonal spiling so placed as to cover these openings,
I whether they occnr at the sides or at the comers of the com-
I pBrtnient shafts. Where possible the sets should ije blocked and
I wedged to place in order that the shaft may be kept plumb, and
I the hanging hooks should always be retained in treacherous
MINE TIMBERING
ground. The above process is repeated successively until the
shaft has entered firm ground, when the usual methods of tim-
bering may be resorted to. {See Fig. 30.)
Fio. 30. — SPiusa in Bunnino Ground.
Two-Compartment Shafts. — In preliminary operations, in a
mine where pumping is necessary, two-compartment shafts are
employed, one of the divisions being given up to hoisting and the
other to pumping and laddei^. Both compartments are made
of the same size, the usual practice in the West being for each
division to be 4 ft. along the length of the shaft by 4 ft. 6 in.
across its width, hoisting cages being most frequently constructed
for operating in compartments of those dimensions. The tim-
bering of a shaft of this size is framed in a manner almost iden-
tical with that of the one-compartment shaft, with the exception
that the side plates are made longer, and that a divisional piece,
called a center girt, is made to fit by tenon and mortise across
the center of the side plates. Center posts are also used to
:i:--^e„,„,_ "'«««««„„
aJini,
/ Wift
.VG
29
' mine ■
'■■"■raM
OlOJT!
30 MINE TIMBERING
extensive hoisting appliances^ a third and larger compartment for
pumping is added to the two-compartment shaft, while the
smaller compartments are given up to hoisting. Because of the
jar and strain upon the timbers from winding, this work should
be done in the compartments that are supported by the solid
side plate, as they are more rigid and self-sustained.
Although three-compartment shafts are often enlargements
from two-compartment shafts, nevertheless most of the large
working shafts throughout the West are those of three compart-
ments that have been commenced and carried to the bottom as
such. Fig. 31 gives the isometric perspective of a shaft of this
type. This framing is such as obtains the greatest possible stiff-
ness and strength for the wall plates, and represents the most
advanced timbering in use. The arrangement is excellent. The
small cage for the use of the pumpmen, traveling closely against
one of the side plates to allow space at the opposite side of the
compartment for locating the water-column, air- and steam-pipes,
is hoisted by an independent engine, and the safety arrangement
for the ladders is carefully designed.
The sets are located in the same manner as are those of the
single-compartment shaft. The side plates are hung to the plates
above, the end plates are placed in position, the solid center girt
is fitted into the mortise cut to receive it in the center of the
solid side plate, the divisional girt is located at the joint between
the long and short side plates, the eight posts are placed, and
the set is tightly bound by the hanging bolts to the set above,
blocked, wedged and alined. The side plates are sometimes
made of a single piece, framed to receive two solid center girts,
which make the shaft more rigid. Long timbers of this kind are
difficult to handle in a shaft, and it is not always possible to use
them. Where possible they should be placed at the stations,
both above and below, in order to make the frame of the station
set as strong as possible, as shown in Fig. 31.
The principal reason for the almost invariable adoption of the
double-hoisting-compartment shaft in large operations through-
out the West is that of balancing the loads in winding. One of
the cables winds over, the other under, the same engine-shaft,
and when the two drums or reels are both clutched to the shaft
the weight of one cage and load acts in a measure to balance
the other, thus saving power.
MINE TIMBERING
31
Four-Compartment Shafts. — Four-compartment shafts, with
three hoisting divisions, may be divided into three classes, viz.:
the single-width shaft, largely used throughout the Witwatersrand
goldfields of South Africa; the "L" shaft, now practically aban-
doned for good reasons; and the double-width shaft, which it
would seem is likely to come into general use as being one pecul-
iarly adapted to the vast operations of extensive mining.
In the single-width four-compartment shaft the two end
hoisting compartments are employed for raising ore, and, on
occasion, for lowering timbers; the third is used in sinking and
by the pumpmen, and likewise for lowering timbers into the mine,
while the fourth compartment is given up to the pumps, the
water-columns, air- and other pipes, and to the ladders. The
framing of the timbers for this shaft is almost identical with that
for the three-compartment shaft, except that the divisions are
such that each section of the side plates supports two compart-
ments. (See Fig. 32.)
r
II L
4
3 L
: c
\ 1 ^
: c
\
L
Fig. 32. — Framing of Single-width, Four-compartment Shaft.
The double-width four-compartment shaft practically com-
prises two two-compartment shafts placed side by side, the end
plates being lengthened in order to form a double-width shaft.
Two of the end compartments are used for the hoisting of ore
and the lowering of men and timbers, one of the two remaining is
employed as a cageway for pumpmen and timbermen, with its
station cut on the opposite side of the shaft from that for the
hoisting divisions, while the other is given up to the uses of the
pump and for carrying the water-columns, air- and other pipes,
and ladders. See Fig. 33, giving the plan of the shaft, and a, 6, c
and d the method of framing the timbers, which is similar to that
for the three-compartment shaft, and Fig. 34, showing the iso-
metric perspective of the construction.
32
MINE TIMBERING
J
□
a
LJ
a
LJ
b
r-i
n
c
• 1
• •
c
P
LJ
b
d
r-i
"1
a
U
Two or this
a
•^l^
Top View
f^
wH
w 4^e' ^
«
_.4ie»_._
H
1
Front View V
^1*
f«-Mt*
k -4i«< 5
r^
--*'•'
-^
k„tH
Bottom View tH^
^th'
»• 1
u^a^
p
r— *4
^
Back View
Two of this
[»-M^
Top View
r
^U
Fix>iit View
i*Jfe^^
II
Bottom View ^'
-HO-Sf'
f-fiSET
View
^ One of this , ^ ,
Jg fop View
^
:qzv
to
^ 4V
\
Bide View
P
«-i»'-.
uAt
T.
]
~T] Two of this d
•^-/hiir:
a ^ / r-l side «
g^ Bottom View
V^ 4^<—
View
i^
^•1
i^ [] Bottom :^ View 3^
Fig. 33. — Framing of Double-width Four-compartment Shaft.
Plan and details.
34 MINE TIMBERING
bers are so long as to render their handling in the shaft difficult,
while at the same time the excavation is nearly square in cross-
section, and of a size to facilitate the breaking of ground, and
the placing of the frames in position. Furthermore, the bracing
received by the plates from the interior cross girts, both long and
short, greatly solidifies and strengthens the set. The great capac-
ity of this shaft, together with its compactness, strength, and
rigidity, and its accessibility for repair, renders it especially
adapted to extensive mining operations. As compared with the
three-compartment shaft this shaft requires the excavation of
but 450 cu. ft. more of material in each 100 ft. of its depth than
does the former.
Ladders. — The ladders that are placed in the man-ways of a
shaft, and in other inclined and vertical passageways throughout
a mine, are usually made in 5-, 10- and 15-ft. lengths or there-
abouts. (See Figs. 17, 18 and 19.) They consist of two sup-
porting 2x4-in. scantlings, placed parallel about 14 in. apart,
to which are fixed cross pieces or rungs at regular spaces of
about 10 in. The rungs may be of wood or iron, preferably the
latter, unless the mine waters are sufficiently acid to attack the
iron — which is often the case in the deep workings. The wooden
rungs are often simply spiked to the scantlings, or they may be
set into hitches cut in the edges of the side pieces, and nailed
firmly in place. Frequently the scantlings are bored, and turned
rungs are fitted into the holes, the ends of the rungs being wedged
to hold them in place. While this method makes an excellent
ladder, the holes weaken the scantlings materially, and, further-
more, it is almost impossible to replace a rung without destroying
the ladder. The most substantial ladder, and one easily repaired,
is the following: The inner face of each scantling is bored at the
required intervals to a depth of 1 in. in order to receive the ends
of 16-in. lengths of 0.75- or 0.875-in. common iron pipe, cut
exactly. At every fifth rung smaller holes, concentric with the
others, are bored entirely through the scantlings, through which
and through the lengths of pipe located at such points are passed
20-in. lengths of 0.75- or 0.875-in. round iron, threaded at the
ends to receive nuts. When the different rungs of the ladder
have been located in their places these nuts are tightened upon
washers fixed between them and the scantlings, binding the ladder
frame securely together. These rungs possess great strength,
MINE tlmherinti
35
while but little strength is lost to the scantlings, and the ladder ia
easily repaired.
Shaft Station Sets. — At various depths, usually at intervals
of 100 ft., levels are run from the shaft, to and through the inner
workings of the mine, and at such points stations or large rooms
are excavated in the walls of the shaft, and timbered to serve as
centers for the storage of material of all kinds, whether coming
from or to be distributed to the various working places. The
construction of these stations necessitates a change from the
usual shaft framing at such points, in order to obtain the needed
hight for an entrance from the shaft to the station. Should the
shaft have been carried below the point for a station, the obstruct-
ing wall plates at the entrance must be removed, together with
their girts, and the posts both above and below. The longer
posts, fitting into the gains framed in the plates, are then located,
and distance pieces for the walls and girts for the center of the
shaft — the same being tenoned to mortkes in the posts — are
placed in position, occupying that of the wall plates removed,
except that the station entrance is left free of such pieces. The
remaining sides of the shaft are then lined with the usual tight
lagging. See the isometric perspectives of the three- and four-
compartment shafts. (Figs. 31 and 34.) False pieces or temporary
Struts holding in place timbers to support the walls of the
eliaft during this operation are used when necessary.
Stations. — The ordinary working station is made of a width,
in the clear of its framing, of the two hoisting compartments, or
of a width which in enlarged at the pumping stations by an addi-
tional chamber usually equal in width to the length of the pump
compartment, for the accommodation of the pump; the usual
practice being In make the inner faces of the station seta aline
with those of the shaft timbers.
In hight the stations are made equal to that of the shaft
entrance, less the thickness of the flooring, but the roof is made
to slant downward from the second or third station set to the
end of the room. The length of the station varies with the
conditions, from 20 to 40 ft. being usual.
The timbering of stations consists of the four-piece level sets,
enlarged and placed at such distances apart as the nature of the
ground requires, usually from 5 to 10 ft. Distance pieces or girta
are used to hold the seta in position, this in connection with the
36 MINE TIMBERING
usual blocks and wedging. Ordinary plank lagging prevents the
fall of loose rock, and a flooring of 2- or 3-in. planking is laid, to
which is screwed a turning sheet of boiler plate, whereon ore cars
may be turned or slewed around. A sump tank to hold the
mine water that is to be pumped to the surface is framed and
placed beneath the pump division of the station.
In loose ground it is necessary to timber the station by a
system of loose spiling, analogous to the method explained in
driving levels through similar material.
Levels. — Levels include all those approximately horizontal
workings through which mine transportation to and from the
working places is carried on, and include adits, cross-cuts, and
Fig. 35. — Single-piece Set.
drifts. An adit, usually miscalled tunnel throughout the West,
is a horizontal tramway driven either within or from without the
ore deposit, and connecting the interior workings of the mine
with the surface, while an adit-level in contradistinction includes
only those portions which are contiguous to and immediately
connected with the adit, and are operated through it. A drift is
a horizontal opening driven longitudinally with and in the ore-
body, its function being to afford a means of communication along
the lode. A cross-cut is that part of a level which is driven laterally
across the country formation, or across the ore deposit to connect
one part of the mine with another. The methods of timbering these
various openings are identical, and will be treated under one head.
MINE TIMUEUINT.
37
The timbering of levels is accomplished by what is known as
I the single-piece, or the two-, three-, or four-piece set, depending
I upon whether one, two, three, or four timbers are employed.
I They are also known as the quarter, half, three-quarter and full
[ set. The pieces are known as the post, if approximately vertical,
I the stull if inclined, the cap or top piece, and the sill or bottom
I piece. Upon the latter rest the posts of the four-piece set, the
I sill being used to keep the feet of the posts of a set from being
] forced inward by exterior pressure, and also where the ground
[ beneath will not support the weight resting upon the set.
Fio. 30. — Two-piece Set.
Where the sides of a drift are sufficiently strong, when the
I deposit is of a width of not more than from 15 to 20 ft., a single
piece is frequently used. (See Fig. 35.) Should either of the
walls prove to be weak, this single piece is supported at either
end as shown in Fig. 36, forming what is called the two-piece set.
If both walla are too weak to support the single piece, or should
1 the deposit be of considerable width, posts are placed under both
I ends, somewhat as shown in Fig. 37, forming the three-piece set.
I This set is, however, usually made from framed timbers, either
[round or squared; the posts of the set being of equal length, and
ithe sets nearly or quite of equal size. These sets are held in position
f by distance pieces, either of poles sledged into position between
Kthe sets, or of squared timber, in which case the sets are framed
Ewith a hitch to recei%'e and support the ends of the piece. Poles
MIXE TIMBERING
used for this purpose are called "eprags," whOe the square pieces
are known as "girts." The framing of squared or round timbers
for this set is practically identical, but round timbers because of
Fio. 37. — Three-piece Set.
their unevenness usually require that a pattern shall be made as
an aid to aystenmtic framing. The three-piece set is usually
made of round timbers, with the posts set with a spread or slant
outward at the bottom as an aid to resist the outside pressure.
Fio. 38.
The feet of the posts are set into hitches or rests at the floor of
the level ; this also tends to strengthen the set against the inthrust.
(Fig. 38, a and b.)
The four-piece set is usually framed from squared timbers,
MINE TIMBERING
39
the posts being set upright, making the square set, or with a slant
outward as in the three-piece set. The set consists of the cap,
sill, and two posts, usually carefully framed. In adits the set is
often alined with considerable exactness, and when thus placed
the passage presents a pleasing appearance. In adits and cross-
cuts the posts are usually given a slant. Often, however, this set
becomes an integral part of the regular square-set system as
applied to the extraction of masses on the levels and in the stopes
of the large metal mines. (See Fig. 38, a, b and c.) The framing of
this set often becomes massive, especially in the heavier ground
of adits. A center post is often placed in position for forming
the double tramways. (Fig. 30.)
Fig. 39. — Four-piece Set.
The ground between the sets is held in place by lagging of
poles or sawed plank, which rests at either end upon the timbers.
Being of comparatively small strength a lining of this character
will yield to unusual pressure, and thus give evidence of incipient
crushing that would soon destroy the timbers if not attended to.
Timbering Levels in Loose Ground. — For this purpose the
process known as spiling or forepoling is employed, its use being
somewhat similar to that described under one-compartment shafts.
The spiling may be of sawed plank or of poles of the required
length, sharpened at the forward ends, and with their heads
protected by an iron shoe w^hen necessary. A set having been
fixed in position (see Fig. 40) a bridge y is placed upon the cap
supported by the blocks x at either end. Between this bridge
and the cap the spiling z is started, sloping upward at an angle.
40
MINE TIMBERISG
As it is driven forward, piece by piece, the material is picked
away from the point of each plank as it is forced ahead a short
distance at a time. In this manner the entire shield is advanced
through successive small stages until it has been driven forward
through about half the distance to its iinal position, when a tem-
porary false set, a, is located to support the spiling. The driving
is then continued until the shield has been advanced to its place.
The regular set is then fixed in position, a bridge is placed upon
its cap, and the false set removed, which allows the spiling to settle
upon the bridge. The same process is continued in excavating
for the succeeding sets while passing through similar material
until more solid ground is reached. When necessary the same
I-ooHE Ground.
process is also applied to the sides of the opening, bridging the
posts in the same manner as the cap b bridged and similarly
advancing the shield. In very soft ground it is sometimes neces-
sary to employ the same method in carrying the bottom of the
level forward. In very soft or running ground the edges of the
plank spiling must fit closely against each other, and at the same
time the face of the working is retained by breast boards held in
position by struts footing against the forward set. These boards
are advanced behind the forward edge of the shield, being re-
moved one at a time, and placed farther ahead as the material
is removed from in front of it, a longer strut being used to support
it in its new position.
MIKE TIMBERING
W
TlMBERIxa OF THE WoRKISG PlACE3 I?J A MiNE.
As regards the process of extracting the valuable materials
from their places of deposit there are in use many methods well
adapted to keeping the workings open under the varying condi-
tions. Of these the most simple are tliose employed in the
horizontal or bedded deposits, where often the overlying rocks
are of such strength as to require little support other than that
furnished by the occasional pillar of ground left in place for this
purpose. Even the material left in these pillars is sometimes
removed, and the roof allowed to fall, when it can be done
without injury to future operations.
Posls. — The method of supporting the roof
of horizontal deposits by posts or propa is
almost universally employe<i, and is the most
simple artificial means of keeping open the work-
ing places of mines of this character. These
posts are formeti of sections of trees of various
diameters and of lengths up to 20 ft. They
are placed in a vertical position, normal to the
roof and floor of the deposit, with a flat plank,
called a cap piece or head board, placed upon the
top of each prop to distribute the pressure evenly
Pmt and "Pon "'^ timber, and to give greater bearing
Head Buard. surface against the rock. (See Fig. 41.)
Cribs. — Another method employed is that of cribbing, or,
as it is sometimes called, penning. This consists of building up
a crib or pen from floor to roof of logs, jto^
laid in pairs or in greater numbers
across each other. These cribs may
be made solid if desired, but this is
not often done, for practice prefers to
make a single or double pen and fill
its interior with waste material, which
is usually at hand in underground
workings, and the use of which greatly ^
Gtrengthens the crib. (See Figs. 42
and 43.) The stowing of waste in underground excavations
from which the valuable materials have been extracted is often
resorted to and forms a solid filling that will, with comparatively
42
little subsidence, support any pressure. Waste filling is frequently
used in connection with and as adjunct to the various aystenia
of timbering employeil in supporting the walls of ore and other
deposits. It fornia the only i»ermanent and certain means of
retaining the walls of orebodies in approximately their original
position.
The metal mines of the West for the most part consist of de-
posits that dip Ijelow the horizontal at varying degrees up to the
vertical, the dip of the blanket veins and other bedded deposits
depending upon the uplift of the enclosing formations, while
that of the fissure veins follows the course of the fissures cutting
through the earth's crust. Contact veins may present the char-
acteristics of either of the above mentioned classes, and the
chambers or isolated pockets of valuable materials may follow
certain lines of deposit or be without regularity or regular form.
Fia 43 —Cm \
In size these different deposits vary from the deposits too small
to be successfully worked in a commercial way, to immense
masses of ore, the extraction of which brings into use all the
science of the miner and of mining. Some of the methods in use
for timbering these excavations, during and after the extraction
of the ores, are but the application of old methods to present use,
while other systems are dbtinctly modern, both in origin and
application.
Stulls. — Of the older methods there is principally and pri-
marily the stull system, which is but the application of the post
of the flat deposits to the use of the inclined veins. Stulls are
almost universally employed in raining the smaller veins, with or
without waste filling as an adjunct. They consist of sections of
trees, pine, fir, oak, or other substantial woods, round, and peeled
MINE TIMBERING
43
of their bark. These sections are of all lengths up to about
20 ft., as may be required at the points to be timbered, and in
diameter up to about 4 ft. The greater the diameter the greater
the strength of the timber. Length beyond certain limits de-
creases the power to resist pressure, as the piece is more liable
to bend or buckle under the weight.
Like the post the stull is placed
with a head board to distribute the
pressure, and to give greater bear-
ing surface to the stull in supporting
the hanging wall of the deposit,
while the foot of the stull is
trimmed and squared to fit more
closely into the "hitch" cut into
the foot-wall to prevent the timber
from slipping from its place. (See
Fig. 44.)
Unlike the post the stull is
not located in position in a line normal to the walls of the
deposit, but at an inclination thereto approximating at a certain
ratio to the dip of the vein, the angle of underlie of the stull
(see Figs. 44 and 50) being about one-fourth of the angle of
dip of the deposit, thus:
Fig. 44. — Stull.
Dip of Vein
Angle of Underlie
of Stull
Dip of Vein
Angle of Underlie
of Stull
10^
20
30
2J^
5
7i
40°
50
60
10°
12i
15
The reason for this underlie of the stull is that if the piece
were placed at right angles to the walls of the vein a slight move-
ment of the hanging wall would cause the stull to fall. Also the
stull usually carries the weight of waste filling above the levels,
and this it would be unable to do if placed perpendicular to the
wall, while this weight tends to wedge the piece more tightly
into place if placed at an angle above the perpendicular to the
walls.
Where the foot-wall of the vein is too weak to support the
stull in position a false stull is often placed to transpose the ver-
44
MINE TIMBERING
tical weight upon the foot of the stuU to a diagonal thrust against
the hanging wall, (See Fig. 45.)
In wide veins stulls are often rein-
forced, so as to enable them to bear
both the vertical weight of the waste
\ filling above and the side pressure of
'■■ the walls, by what is known as the
\ double-fituU method. This consists of
false stulU placed beneath the stuU
proper, the former being placed with
a foot-hitch, and the stull, supported
in its position by logs resting upon
Fig. 45. — Stoll and Falsb two OF more of the false stulls beneath
Stcll. to either side, footing against the foot-
wall without a hitch to receive it. This method is shown in
Fig. 46, a being the end view and b the plan.
Fia. 46. — DocBLE-BTiTLL Method.
In vertical or nearly vertical veins it is impossible to place
the stull in position with the usual underlie, and some method
MINE TIMBERING
45
is necessary that will change the vertical weight due to waste
above into a diagonal thrust against the walls. This is done as is
shown in Fig. 47, a by means of the saddle-back system of bracing,
Fio. 47. — Saddle Back and Arch.
and b by the arch with key-piece. This saddle back is sometimes
used, as in Fig. 48, to carry the weight of waste filling above,
but it is without value to resist side pressure.
Fio. 48. — Saddle Back.
Penning, — A method of timbering known as penning is some-
times employed in the inclined veins, and is nothing more than
the crib of the flat deposits applied to the incline. It consists
of cribs of logs built up from the foot-wall of the vein to the
hanging wall, which it supports. Occasional longer timbers are
46
MINE TIMBERING
used to tie the cribs together, and for the purjxise of forming
sills and caps for the passageways of the mine, as shown in Fig. 49.
This methtMi of using timbers for keeping open the working places
of a mine is expensive, and requires quantities of timbering, but
in connection with waste filling it is about as permanent aa any
method of timbering can be. It also has the advantage of a
certain flexibility without weakening during movement.
— Pbnninc.
Square Sets in Sloping. — This system of timbering is pecu-
liarly adapted to the extraction of ores occurring in large masses.
In fact, the size of the deposit matters little if waste filling be used
in connection with the sets. The method requires vast quantities
of timber, and the framing of the pieces is no small item of ex-
pense, but the handiness of the .sy.stem is so great, and its adap-
tability to all the needs nf mining operations in extnicting the
valuable materials from their places of deposit is such that it has
replaced many of the cheaper systems of timbering. Indeed, it
is a fact that its use in large operations is often found to be
cheaper in the end than are many of the supposedly more eco-
MIXE TIMBERING
47
nomical methods, and this in spite of the fact that the framing
of the sets involves no small item of outlay. Briefly, the system
consists in filling up the excavations resulting from the extraction
of ores with what might be termed open blocks or cells of timber
that may be added to and extended indefinitely in every direction,
lengthwise of the deposit, across it, and between the levels, while
the slope of the body matters little for the reason that, in following
the ores between their walls, sets may be extended laterally
Fia. 60, — Angle op Underue of Stulls.
outward from the main body of the timbering at any point of
the foot-wall, or left out when the slope of the hanging rock
encroaches upon the timbering.
The set is made up of posts, cap, and girt, the former being as
usual placed in an upright position, in line with the posts aI)ove
and below. The cap rests upon the top of the post, and is in-
variably placed across the deposit, the cap of one set becoming
in effect the sill of the set next above; while the girt, which like-
wise is set upon the post, is located along or longitudinally with
48 MINE TIMBERING
the run of the orebody. The sets are, in the best practice, framed
for a hight of 7 ft. in the clear of the timbers; the reason for this
being that this length obtains the full strength of the frame at
the same time that it saves timber in the mine, and leaves suffi-
cient hight for passage without inconvenience. This hight also
allows of placing the reinforcing sets in position, and still permits
passageway if necessary. Across the deposit the caps are made
Fia, 51, — Square Sets in Stopiso.
of a length such as will set the posts 5 ft. apart in the clear of
timbers, which gives room for working the airdrills in the breasts
of ore, and for other work at end points. Along the length of
the orebody the girts are made to separate the cross frames by
a distance of 4 ft. 6 in,, adding somewhat to the number of such
frames and thus giving greater resisting power to the sets against
thrust from the side, from which direction the maximum pres-
reusually acts against the timbers, (See Fig. 51.) In tiiis figure
the method of locating the sets is shown in isometric projection,
and also that of placing the different timbers of the system.
Usually a heading or drift is first run along the level, as near
to the center of the deposit as may be, although this is not essen-
tial, and along this excavation the sets are placed from which to
build up the more extended timbering. On the floor of this drift
are laid the two-post sill pieces, the sill girts are placed in posi-
tion as is shown in the figure, then the posts are located, and
upon them is placed a cap piece across the drift, while a girt
connects this cross frame with the last one placed in position.
The frame is now blocked and wedged against the top or back
of the drift, and the set is completed. Aa material is removed
from either side of this drift, one-post sills are laid upon the
floor of the excavation and penned to the two-post sills already
located, a sill girt is placed, the post set upon the framing fitted
to receive it, and cap and girt hold its top in position, It is
then blocked and wedged firmly against the ground above, and
also from the side. A 2-in. plank roofing is laid from cap to cap
above the set, which performs the functions of a floor for the
Bet next above as the timbering is carried up. When the foot-
wall of the deposit is reached, the sets are carried up along its
slope by means of the cap-sill, a timber which combines the
functions of the cap and the sill, also shown in position in the
figure. Upon these cap-sills as a foundation are built up a new
line of seta, and the process is carried on to any extent by repe-
tilion. Above the sill floor, as the ground is excavated, posts
are set into the gains formed by the framing of post, cap, and
girt beneath, and the timbera are continued upward, outward,
and lengthwise as far as may be necessary. The sets from one
level are carried up to those of the level above, when short sets
are placed in position to carry the weight of the upper framing.
Retnforcing Sets. — When the timbering t* carried into un-
usually heavy ground, or where it is forced to carry a great
weight, it is frequently necessary to reinforce the sets across the
deposits in line with the greatest pressure, and this is done by
what is known as the diagonal brace, the three-piece set, the full
or four-piece set, the "N" frame brace, the "N" frame set, and
the "X" frame brace. These are all shown in Fig. 51.
Ore Chutes. — In delivering the ore from the stopes above a
50
MIXE TIMBERING
level to that level so that it may be loaded into cars and carried
to the shaft for conveyance to the surface, a storage bin and
passageway combined b necessary, and this is obtained by lining
one of the sets as it is carried up from the level by a close lining of
2- or 3-in. planking, preferably the latter. These bins are desig-
nated as chutes, and the framing at the bottom of them wliereby
the ore is delivered into the cars is called the gate of the chute.
This is made by constructing an Inclined flooring, with sides,
that shall project beyond the side of the chute into the tramway
sufficiently far to allow the rock to fall from it into the car.
Cross timbers are placed across the chutes at varying hights of
about 30 ft. in order to break the fall of the rock so that it shall
not destroy the gate frame. In keeping the chutes near the
center of the deposit they are as often as is necessary offset
toward the floor wall on an incline from one line of sets to the
next lateral set on the floor above.
Waste Filling. — In average ground no system of timbering
will long sustain the walls of large excavations, and waste rock
from the vein and walls, especially the hanging wall, is employed
for filling up the spaces between the timbers in order to make a
solid filling that shall hold the ground in place. Passageways
are strongly reinforced, and the flooring is removed from the
different floors when waste is thrown into the excavation from
above.
Methods of Framing. — There are
several methods of framing the timbers
of square sets in order that they shall
come together from the six directions
in a manner best suited to the needs
of the occasion. Fig. 52 shows the
method of cutting the timbers in use
in the Anaconda mine, Butte, Mont.,
a giving the isometric perspective of
the post, cap, and girt as shown
separately, b showing their appearance
when joined. The Eureka method of
framing is shown in Fig. 53, and
— Anaconda Method. . - -i ^ ..l » i *
IS very similar to the Anaconda frame,
the latter having one more section cut from each side at
each end of the girt. Both of these methods are used for opposing
Fia.52.-
1^
MINK TIMBERING
51
from the sides of the veins, the caps abutting against
one another to secure the greatest strength from the tinibers;
but by transposing the timbers of this set, so
that tVie posts shall rest end on end upon one
another, vertical pressure may be beat resisted.
This is shown in the Burlingame frame (Fig,
•icv^ p->m-^ 54), a separated and b joined, which b the
|px^>^ Eurekii framing with the post of the latter
I ^■vX— -^ forming the girt of the former, the cap of
, Pio.53.— Eureka the Eureka the post of the former, and the girt
^^^^^f"- of the Eureka the cap of the former. Fig. 55
presents the Richmond frame, which is >Ol n^^
a strong but complicated and ex- (=^^^1 BuriiD«iui» f^;^!^
pensive joint in which the cap and <
post are framed from 12-in. timbers and "
the girt of 10-in. pieces. Usually the
Anaconda and Eureka frames are made
of 10-in. timbere, the reinforcing seta
ftcd solid waste filling being depended
upon to hold up the ground rather than
by increasing the cross-section of the
timber. Frequently, however, the upper
levels of a mine are supported by 8-in.
pieces, but this is infrequent at the deeper pj„ ^ _ b„rungame
levels. The Eureka framing is now used in Method,
some of the Anaconda mines as being
the simplest and cheapest method of
framing. Fig. 56 furnishes the details of
framing timbers for the Anaconda set.
The square-set system of timbering was
originated to meet the needs of the sit-
uation as developed in the workings of
the Ophir mine, on the Comstock lode,
Nevada, by Philip Deidesheimer.
Important details connected with
the methods of timbering herein de-
scribed, and other systems now in suc-
cessful operation among the metal mines
of this country, are excluded from this
Fk!.66. — RicBuovD Method, necessarily abridged article.
MISE TIMBERING
ilfti Li "•"
\i
■^•■-i.-r »-
H|fl 1
jr^'^ -r r' ^
••--"•'''t" «"">"*
D --
-»'-'^ Oosiil
^AH a -
m
,$z^:-,i:wzv^-— -—Jiii^i^
t^^^jTI
M U -
b^'r
V-»'-'"l Ol*.P»t8lll
HI
.B^K-rf ;,.-.■-.— -^i'.
■ ■ -r-W'-i
1 1 H - 1
i-j t=i
U L_,
r"'"*'-*'-^- :^^^i^
1 H -
P 1 1
Fio. 56. — Anaconda Mcthod of Fsamino. DetaiU.
MINE TIMBERING
BY THE SQUARE-SET SYSTEM AT ROSSLAND, B.C.
BY BERNARD MACDONALD
MINE TIMBERING BY THE SQUARE-SET SYSTEM AT
ROSSLAND, B.C.*
By Bernard MacDonald
In mining operations, when the ore extracted exceeds a width
of 12 or 15 ft., it has been found that the cheapest and only
effective method of timbering is by the square-set system.
The system may be generally described as a rectangular
skeleton framework of timbers, extending from wall to wall of
the vein as exhausted, the different members of which are so
framed as to stiffen and support each other, and equalize and
distribute local strains after the manner of a truss.
Historical
The square-set system of timbering was invented by Philip
Deidesheimer, while Superintendent of the Ophir mine, on the
Comstock lode, in 1860.
In Monograph IV of the United States Geological Survey,
*• Comstock Mining and Miners," the following reference is made,
which will be found interesting under this heading:
"At the 50-ft. level (of the Ophir mine) the vein of black
sulphurets was only 3 or 4 ft. thick, and could readily be
extracted through a drift along its line, propping up the walls
and roof, when necessary, by simple uprights and caps. As the
ledge descended, the sulphuret vein grew broader, until at a
depth of 175 ft. it was 65 ft. in width, and the miners were at a
loss how to proceed, for the ore was so soft and crumbling that
pillars could not be left to support the roof. They spliced timber
together to hold up the caving ground, but these jointed props
were too weak and illy supported to stand the pressure upon
them, and were constantly broken and thrown out of place.
* From Proceedings of Canadian Mining InstituUf 1903, Vol. 6.
55
56 MINE TIMBERING
The dilemma was a curious one. Surrounded by riches, they
were unable to carry them off.
"The company was at a loss what to do, but finally secured
the services of Philip Deidesheimer, of Georgetown, California,
who visited and inspected the treasure-lined stopes of the Ophir."
During Mr. Deidesheimer's engagement at the Ophir, all the
principles of square-set timbering were evolved under his imme-
diate supervision, and the wide and rich orebodies occurring in
that mine were successfully extracted without the loss of ore or
injury from caving by the use of this system. The system was
then used in all the mines on the Comstock lode, and subse-
quently in all metalliferous mines elsewhere where the orebodies
exceed a width of 15 ft., the extreme width that it is practical to
.timber by stulling.
The "square set" has undergone numerous modifications of
detail in dimensions and the framing of its members in the various
camps where it has since been used, owing mainly to local condi-
tions, the dip of the vein, and the character of the orebodies and
the enclosing rock.
Vein Characteristics at Rossland
In the Rossland mines, the ore deposits have widths ranging
up to 100 ft. or more, and lengths of several hundred feet along
the veins. The veins are sheer zone fissures, the vein-filling
consisting of country rock, which is now found replaced, and
cemented to various degrees of completeness by auriferous pyr-
rhotite and chalcopyrite.
The ore and the enclosing rock may be designated as extremely
hard, and the veins dip at angles of about 70 deg. These condi-
tions facilitate and simplify timbering, without, however, doing
away with its necessity.
Preliminary Work
In stoping out these deposits, the work is begun at the level
drives or drifts run in the vein, and continued upward in steps
or stopes.
The first work in opening up an ore shoot or deposit prepara-
tory to extraction consists of running drives or drifts through it
from the level stations at the shaft, which are generally cut at
MINE TIMBERING 57
distances of from 100 to 200 ft. in depth below each other. Such
drives may happen to be run along either wall of the vein, or
through the vein at any point or distance (usually varying) from
either wall.
These drives are considered as random bores, made longitu-
dinally through the vein to determine, in a general way, its
course or strike, and the behavior and characteristics of the ore
shoot. They serve, besides, as preliminary thoroughfares for the
traffic, drainage and ventilation necessary for the preparatory
work of stoping, to be hereafter described.
As generally run in the LeRoi vein, the drives have widths of
about 6 ft., and hights of about 8 ft., and require no timbering,
owing to their comparatively small size and the hardness of the
vein rock.
When it is decided to begin stoping on any new level, the first
work done is to excavate the ore along the drives from wall to
wall of the vein, making the excavation of sufficient hight to
receive the sill floor set of timbers, as the first series of square
sets on the level is called, and to leave a space of 2 or 3 ft.
over the set. This space serves to provide room for blocking
and wedging the timbers to place, and to receive a layer of old
timbers, which act as a cushion in preventing the possible breaking
of the timbers by the masses of rock that must be blasted down
on them, as the work of stoping out the ore above proceeds.
Sill Floor Construction
The sill floor is a framework, made of 10x10 -in. sawed
timbers, laid down on the working level in the orebody. They
serve as the sills or foundation timbers on which the square sets
are to be erected. It is, therefore, the first as well as the most
important part of the square-set system of timbering.
Figure 57 shows the sill floor as laid down and ready to receive
the sill floor set of timbers. The members of the sill floor
consist of three pieces: the stringer, or long sill; the spreader, or
short sill; and the butt spreader, or brace. These members, when
repeatedly laid in duplicate, will make up a sill floor to any
extent required by the size of the deposit.
The dimensions and details of the framing of these members
are also shown in the figure.
UI.N£ TDIB£KL\G
MINE TIMBERING
59
The long sill measures 15 ft. over all, anti is framed from a
16-ft. Umber, which alluwa 6 in. to be cut from either end to
square the piece and remove sun cracks.
The short sill, as framed, measures 5 ft. 4 in. in length, over
all, three of which may be cut from a 16-ft. timber, if it over-
measures a few inches, as it generally does, and the ends are
sound.
The butt sill or brace is framed of varying lengths to suit the
existing epace, which generally varies owing to local bulgings or
contractions of the vein. It is framed on one end exactly like
the short sill, while the other is cut square or beveled to fit or
butt against the wall-rock, from which it is wedged tightly to
place against the long sills.
A description of the method of framing the sill floor set of
timbers is not needed, as it will be fully comprehended by a
glance at the figure.
In laying the sill floor, the long sills are set ends abutting
flush against each other, and as nearly as possible parallel with
the general strike of the vein, ignoring any local bulging of the
walls.
The first sill is laid close and approximately parallel to the
foot-wall, in which position it is leveled and held by blocking or
butt braces; the other long sills are laid paralleling this one at
proper distances apart, that is, 5 ft. 4 in. between centers. The
cross sills fit on top of these, lying level with them, the ends being
halved in framing to rest into similar halvings in the long sills,
and to abut flush against each other and extend endwise from
wall to wall of the vein.
When the long sills reach as near the hanging wall of the
vein as desirable, they are braced from it by the butt spreaders
or by blocking, wedged tightly to bring all the members into
proper position. The philosophy of thb design of the sill floor
is as follows:
The long sill is made 15 ft. in length, bo as to better sustain
the superstructure of square seta erected on it when the ore upon
which it rests comes to be sloped away. For instance, when the
ore is being blasted from under the sill floorby the work of stoping
coming from the level below, and the blasting tears away a por-
tion of the ore upon which the sill floor rests, making an opening,
I as it generally does, of, say, 8x8 ft., the long sills would over-
60 MINE TIMBERING
reach sucli opening, and one or both ends would rest on the
solid rock beyond. Nor would the ahort sills drop away through
such opening, owing to the fact that they rest on the top of the
long sills, as previously described and shown in the figure.
Through the opening thus made in the ore, the portion of the
eill floor exposed would be supported by posts set on the timber
sets in the slope below. Thus the long sill operates to allow
the work of sloping out the ore upon which the sill floor rests
to be safely condiicteci, if such portions of the sill floor as become
exposed as the work proceeds are properly supported by posts
from the timber work underneath.
Timbers and MtrrHODS Used after Sill Floor is Laid
The first tier of square sets erected on the sill floor If known
as the "sill floor sets." The assemblage of the framed timbers
into square sets then proceeds upward, by floors, set over set,
vertically, pari passu as the work of sloping exhausts the vein.
The timber structure over any level is referred to in subdivisions
as the "sill floor sets," "first floor sets," "second floor sets,"
and so on until it reaches the level above and catches up and
supports the sill floor on that level.
This method of reference to the timbering aa it advances
MINE TIMBERING
61
carries with it the data for a general calculation of the portion
of the vein exhausted over a level, as each set of timbers in place
indicates that 9 ft. vertically and SJ ft. horizontally of the vein
are exhausted, 9 ft. being the bare hight and oj ft. the width of
space required for a set of timbers. And each square set in place
indicates tiiat 24 tons of vein matter have been extracted.
Aside from the sill floor, all the timbers employed in the
square-set system, except the planks for floorings and chutes, are
framed from round logs. These logs are preferably of red fir, it
being the strongest native timber, but pine, spruce and tamarack
may be used. When cut in the woods, the logs are peeleci and
-i
Fig. 59. — Woi
1 PV
N-r., B.C.
allowed to season for a period of from six to twelve months,
during which time they lose about one-third of their green weight,
which is a very important advantage in subsequent handling.
In diameter, they range from 12 to 20 in., but generally average
about 16 in., and are sawed in lengths of 16 ft. 6 in.
The logs may be framed by hand or with machine saws into
the various members of the square set, as follows, viz.: posts,
caps, girts or braces, and butt caps. Like the members of the
sill floor, these members may be duplicated to any extent required
by the size of the excavation to be timbered.
The posts as framed are 8 ft. 2 in. over all; the caps are 5 ft.
62 MINE TIMBERING
4 in., and the girts or braces are 5 ft.; the butt caps, like the butt
spreaders on the sill floor, are cut in varying lengths to suit such
spaces as may exist.
The details of framing the logs into members of the square
set are plainly shown in Figs. 57 to 63, and need no further
description. The philosophy of this method of framing the
timbers is that the cap pieces of the various sets form continuous
stringers of timbers running horizontally from wall to wall of the
vein, no matter what this distance may be. Such stringers oflfer
the end grain or greatest strength of the timbers to the walls,
from which the greatest strains are generated. The posts and
girts rigidly support the stringers thus formed of the several
cap pieces in true horizontal position, bearing on the joints from
right-angled directions, while the cap pieces and the girts support
the posts in true vertical position.
The whole framework forms a strong, rigid structure, capable
of indefinite extension upward and longitudinally as stoping
proceeds, allowing at the same time for any expansion and con-
traction in width to suit such irregular widths of the vein as may
occur.
Besides the functions of the various members of the square-
set system to support each other in the manner described, that
of the cap pieces is to receive directly and sustain the strains
coming from the walls of the exhausted deposit, while that of
the posts is to support the vertical weight coming from the un-
dercut ore deposit and the broken ore lying on the floors, but
strains coming from any direction are distributed over all the
members of the set.
The system possesses, to a considerable degree, the qualities
of a truss, and makes it possible to extract all the ore of any
deposit and effectually secure the enclosing walls from caving in.
When the framework comprising the sets is erected, a floor,
consisting of 3-in. plank, is spiked down on the caps of each
floor set. These are the working floors on which the miners
operate the machine drills, in the method shown in Fig. 58.
When the ore is dislodged from the vein by blasting, it falls on
these floors, where the waste or second-class ore may be sorted
out from the shipping ore. The shipping ore is shoveled into
chutes which are built of 4-in. plank spiked to the timber frame-
work and carried upward with the square sets, as shown in the
I
I
r
MINE TIMBERING 63
figures. The second-class ore, or waste sorted out, may be stored
temporarily or permanently in the framework of the timbering,
from whence it may be drawn off at any time through chutes,
ehould removal elsewhere be desired.
Figures 58 and 59 are ideal longitudinal and cross-sections
illustrating the method of timbering and the work of stoping as
it is carried on between the levels. Tlie original position of
the level drive, as already stated, fumiahes the point from which
the excavation of the vein matter for the sill floor is commenced.
The step method of excavating the ore is shown in Fig. 58,
where stoping is proceeding in double-headed steps, each step
excavating the ore from wall to wall and having a vertical hight
of 9 ft. in the clear, which allows of the erection of one floor of
timber sets, which in turn provides the scaffolding from which
the miners may attack the ore above.
In sloping out the ore on any level, the ordinary method is
to keep the sill floor at least 30 ft. in advance of the first floor,
and it about 30 ft. in advance of the second, and so on, as is shown
in Fig. 58. One machine drill, or generally two, in case the vein
ide, are assigned to work the two opposite headings of any
floor, going in opposite directions, working on each heading alter-
nately. When one face is drilled and blasted, the machine drills
are changed to the opposite face, and the shovelers pass the
broken rock into the chutes, or sort it, if sorting is required.
When the ore broken is thus removed from the face the timber
gang erects another unit of timber there, and the stope is again
in readiness for the machine drills, which have by this time
finished drilling on the opposite face.
Generally the step method of stoping proceeds in opposite
directions from a raise run through the orebody between the
levels, as shown in Fig. 59. The framed timbers are delivered bi
the stope by dropping them down thniugh this raise or hoisting
them from the level. Sometimes the framed ends of the timbers
are injured by dropping them through the raise, but as a rule no
material injury is done to them, while the time gained by this
method is a very important factor in cheapening the cost of
timbering, compared with hoisting piece by piece from the sill
floors underneath.
64 MINE TIMBERING
Per Tonnage Cost of Square-set Timbering
After the sill floor is laid and the framework started, a square
set, which is made up of one post, one cap, and the brace, consumes
18 ft. 6 in. running feet of logs.
The logs peeled and seasoned cut measuring 16 ft. 6 in. cost
$1.20 each delivered f.o.b. the cars at the works, or about 8c.
per running foot. Therefore, the 18 ft. 6 in. required for the set
would cost $1.48, or say $1.50, unloaded in the framing shed,
provided the logs are not cut to waste in framing, which may be
avoided with a little care and foresight.
The cost of framing the pieces comprising the set would be
about $0,553, when framed by hand labor, carpenters being paid
$3.50 per day of nine hours.
Cost Data per Square Set, Hand Framed
Material. — A log, measuring 16 ft. 6 in., costing $1.20, cuts
into two posts, or three caps, or three braces; therefore:
Material in one post costs $0.65.0
Material in one cap costs 0.43.0
Material in one brace costs 0.43.0
Total cost of material in one set is, say $1.50.0
Labor, — One carpenter (wages $3.50) frames per day:
About 21 posts, costing each $0.16.7
About 21 braces, costing each 0.16.7
About 16 caps, costing each 0.21.9
Total cost for framing $0.55.3
Total cost of labor and material in set $2.05.3
The details of cost of the individual members of the set framed
on the surface, ready to go into the mine, are therefore as follows:
, . , , I Material $0.65.0 1 ^^ q, _
1 post costs, for. ... I ^^^ 0.16.7 l^-^^-^
1 cap costs, for . .
1 brace costs, for.
Material ^..^.^ y«n 64 q
Labor --- rw.tH.a
Material
Labor
0.43.0 1
0.21.9 J
0.16.7 J*"-^^-
Making the total cost $2.05.3
The costs next attaching to the square set, or unit, of this
method of timbering are:
MIKE TmBERING
^
lowering into the mine appro si mate ly 80.10
Delivering to place reijuired approximately U, 10
Labor in erecting. approximately 1.50
Incidental material, such as blocks, wegdea. toola, naila, approximately 0.10
Cost of sill fli>or averaged over 11 seta between levels
100 ft. apart .approximately 0.1-5
8T95
These coets last given above may vary greatly, being in-
creased or decreased with the completeness of the faoilities for
handling the framed timbers; the cost of the several items as
stated may vary accordingly from time to time, but the total
will be about the average rost, and will closely approximate that
of carefully eupervised operations. Therefore, from the fore-
going it will be seen that the cost of the square set placed in the
mine will come down, as follows:
Total cost of lalxir and mal«rial, as above , , S2.0S.3
Labor and material when set is in place, as above. . . 1.95. tl
Total cost, say 14.00.0
When framed by machine saws, the cost of framing a square set
does not exceed 30c., including the cost of power, as against 55c. by
hand, a difference of 25c, per set. Therefore, if the framing is done
by macliinery, the cost of a set in place would be $3.75 as against
$4 as shown above when the framing is done by hand work.
The per tonnage cost for timbering by this method works out
as follows: The average space to be excavated for each square set
is 5.3 ft. wide by 5 ft. long, by 9 ft. in hight, or 240 cu. ft. The
Kossland ores, being heavily impregnated with iron and copper
pyrites, yield a ton of 2000 lb. for each 10 cu. ft. of ore in place;
therefore, from the 240 cu. ft. of vein required to be excavated
for a set of timbers, the yield will be 24 tons. If the timbers
were framed by hand the cost of timbering, so far as described,
would be about $0.17 per ton; if by machinery, $0.15.6, a differ-
ence of $0.01.4 per ton in favor of the machine-fnimed sets.
In addition to the costs above tabulated, there still remain
the costs of the chutes, floors, ladders, and railings necessary for
the convenience and safety of the miners and Ihe passage of ore
and supplies. These require, on an average, about 100 ft. of
lumber, board measure, per .square set, which, at $1 1 per 1000 ft.,
would add for the lumber $1.10, and for placing it, say $0.10. or
a total of $1.20 to each square set, which would then cost, in the
MINE TIMBERING
case of hand framing, S5.20, or a total cost of SO.21.6 per ton of
crude ore; and in the case of machine framing, S4.95, or a total
cost of $0.20.6 per ton of crude ore.
MINE TIMBERING 67
INCIDENTAL Costs
The cost of timbering, per too of ore shipped, would be greater
than the figures given above in proportion to the quantity of
waste or second-elass ore that would be sorted out from the
crude ore extracted.
In the Rossland mines about 20 per cent, of the ore mined
is sorted out and goes to the second-class ore dump to await
profitable treatment, expected to come in the future. Deducting
20 per cent, of the 24 tons of crude ore in a square set, there
would remain 19.20 tons as the shipping ore, against which the
total costs of the square set as above, $5.20 or $4.95 as the case
might be. would have to be charged. This would raise the per
tonnage costs on the ore shipped to about $0.27 and $0.26 re-
spectively.
Where there is a reasonable expectation that the second-class
ore will eventually pay a profit after suitable treatment, it would
be only fair to charge a pro rated cost of the timbering to it, and
the cost would then remain SO.20.6 and SO.21.6 per ton as above.
In eases where, on account of bad ground, angle bracing,
bulkheading, or cribbing and filling would be required, the per
tonnage cost would be still further increased, but to a compara-
tively small extent.
Limitations of the Squasb Set
The limit of the capacity of the square-set system as already
described, without any reinforcing devices to withstand the
pressure that may be exerted on it by the enclosing walls of an
orebody when that orebtxly is extracted, may be reached.
This limit depends on the nature of the walls enclosing the
deposit, and the extent of the excavation. If the wall-rocks are
Bolid and do not swell on exposure to the air and dip at a high
angle, the orebody may be extracted between levels, say 100 ft.
apart and for a length of 200 or 300 ft. along the vein, and the
pressure likely to be exerted by the walls will be sustained by the
ekeleton square set without reinforcement of any kind.
If, however, the vein dips at a low angle, and the wall-rocks
are decomposed, or of a talcose or serpentine character, and
disposed to swell, the pressure that might be exerted on the
' timbers, when even a comparatively small excavation of the
68 MINE TIMBERING
orebody has been made, may cause them to crush, "jack-knife,"
or collapse, allowing the waII-ro<?ka to cave in and close up the
stope. When the members of the square set become squeezed
out of the truly riglit-angled position which they should occupy,
their capacity to resist wall pressure or strains from any direction
is practically nil.
When, owing to wall pressure or imperfect erection of the
sets, "jack-knifing" of the square sets results, the cave-in which
sooner or later will follow, with disastrous consequences, may be
prevented by either bulk-heading, cribbing, or filling the skeleton
framework of the timbers.
The cost of the foregoing methods of reinforcement, which
are the only practical ones that can be successfully used in bad
ground, cannot be given with any general degree of accuracy, as
that is so much affected by the local conditions in each case.
A general idea of what the cost is likely to be may be gleaned
from the description following:
Reinforcement Methods
Angle bracing. — If, after the square sets are properly erected
in place, the members manifest an inclination to swing out of
the right-angled positions they originally occupied to each other,
this tendency may be arrested and prevented by a system of
angle bracing. This consists of placing diagonal braces made
of round or square timber on the sill floor and against the foot
of the posts, and leaning the heads so they will fit snugly against
the top of the posts underneath the caps or girts, as the ca;e may
be, of the next adjacent set. The head of this diagonal brace
should lean in the direction from which the pressure comes.
This method is illustrated in Fig. 62.
Cribbing. — When the square sets manifest a stronger ten-
dency to swing than in the case referred to, the collapse threatened
may be prevented by crib work. This consists of crossing alter-
nate layers of round or square timbers of any convenient size
between the posts of the seta until the space between the sill and
cap is filled, as shown in Fig. 63. This crib work may extend
from wall to wall through two or more rows of sets if required,
and the spaces between the sets thus cribbed may be filled with
waste rock, but this is called "filling," and will be referred to
under that heading below.
MI.VE TIMBERIXG
70 MINE TIMBERING
Bulkhcading. — This method of reinforcement consists of
placing timbers closely together in much the same way as the
crib work above referred to, and wedging them tightly between
cap and sill.
Filling, — This method consists of filling the spaces between
the members of the square set with any material such as waste
rock, earth or sand. When the filling is done it is retained within
proper bounds, and the necessary passageways are kept open
through the timbers by building crib work around them as de-
scribed.
Waste rock for filling purposes is generally secured from the
development or dead-work that is being prosecuted in other
sections of the mine, but where a large quantity is required, it is
often found necessary to mine it specially for that purpose, or
draw it from the waste dumps on the surface. About 8 cu. yd.
of material are required to fill the vacant space of the frame of a
square set, and the cost of such filling will be the cost of obtaining
and placing such material, together with the crib work required
to retain it within proper bounds.
General Remarks
The square-set system of timbering is used successfully and
exclusively in all mines where large deposits of metalliferous ores
occur.
Where favorable conditions, such as railway transportation
and a moderate supply of timber, exist, it is comparatively cheap.
If care is taken in the construction of this system in the mine, it
ensures that all the ore existing may be extracted without injury
to the workman or the mine. Round logs or sawed timbers of
any dimension, ranging from 8 in. upwards, may be used, but
the sizes are governed by the economic conditions and mining
requirements.
In the mines of Rossland, the round logs or timbers used for
the square sets cost $1.20 for each log 16.5 ft. in length f.o.b.
the framing shed at the mine. These logs are cut in the state
of Washington, and delivered over the Spokane Falls and Northern
Railway on flat cars, over distances ranging from 45 to 75 miles,
each flat car being loaded on an average with 60 logs. The
unloading at the framing shed is done in a few minutes by cutting
MINE TIMBERING 71
off the retaining standards on the flat cars, and allowing the
logs to roll off on the storage platform.
Of course, where wagon transportation is required from the
railway terminus, the expense will be correspondingly increased.
In every mining camp there will be more or less variation in
the method of framing, and in the cost of the square sets in place,
also in the tonnage of ore to be extracted from the space occupied
by each square set.
Where the dip of the vein is at a flat angle or the walls are
bad, shorter posts than those described herein will probably be
more advantageous; the more vertical the dip of the ore deposit,
the longer the posts may be, and vice versa.
Where sawed lumber is comparatively cheap, 3-in. plank is
preferable to lagging poles for floors, on account of the better
floor it offers for shoveling, and the fact that it may be removed
and re-used.
MINING AND TIMBERING
IN LARGE OREBODIES IN BRITISH COLUMBIA AND
MICHIGAN
BY NORMAN W. PARLEE
METHODS OF MINING AND TIMBERING IN LARGE ORE-
BODIES IN BRITISH COLUMBIA AND MICHIGAN*
By Norman W. Parlee
The method of mining to be adopted in any particular mine
depends upon a number of important considerations. Among
these may be mentioned the size and attitude of the orebody or
deposit, the hardness and rigidity of the ore and adjacent rock,
the quantity and quality of timber available and its cost, the
price of labor, and the value of the product to be mined. Gen-
erally speaking, if a narrow vein is to be worked, stull timbers
are used, the limit being a width of about 15 ft. As the vein
widens beyond this, stulls are out of the question, and another
system must be adopted. The method then employed may be
the square-set system, or a filling method, except in case of soft
ore, when a caving system may be followed. There are a great
many modifications of all these systems to suit circumstances
and conditions, and it is the intention in this paper to describe
and discuss them as carried out in those mines in which the
writer has worked, and in which he has become more or less
familiar with the methods in successful operation.
The names of the mines treated, and location, are as follows:
Le Roi mine Rossland, B.C.
Old Ironsides Phoenix, B.C.
Baltic mine Baltic, Mich. /
Atlantic mine Atlantic, Mich.
Bamum mine Ishpeming, Mich.
Section 16 Ispheming, Mich.
Soft Ore Hematite Ishpeming, Mich.
Queen mine Negaunee, Mich.
In nearly all these mines the methods used apply principally
to mass mining in large bodies of ore. The one exception is the
Atlantic mine, which has a narrow deposit, and is mined entirely
by the old-fashioned stull method.
> From Transactions of Canadian Society of Civil Engineers, Vol. 18, 1903.
75
MINE TIMBERING
Le Roi Mine, Rossland, B.C.
In this mine there are one or more veins or ore shoots of
varying width and carrying the minerals pyrrhofite. chalcopyrite
and iron pyrites, and mixed with these more or less disseminated
gold. It is the gold, however, that affords the principal value
of the ore, and without it there would be no Rossland. The
vein is of a pockety nature and some of the pockets are of very
large size. The dip is about 70 deg., and an incline shaft was
sunk at about this slope. As depth was attained it was found
that the vein pitched a little steeper, and the shaft was given a
steeper pitch also, thus forming what is called a "knuckle" in
the shaft. This knuckle aftenA'ards became a source of consid-
erable trouble, because, at high speeds, the skip was liable to
leave the track.
At intervals of 100 ft. drifts were run on the lead, and the
deposits thus opened up. The first shaft had three compartments
timbered with the ordinary square shaft sets. Sinking was car-
ried on with three shifts of miners working eight hours each, and
the rock broken was hoisted to the level above with a bucket
and air hoist. As the shaft became deeper the ore and rock
were hoisted by skips, run on the balanced principle. A pentice
of about 15 ft. of rock was always left in the shaft at each level,
and served as a protection to the shaft men working below. It
was located under the two hoisting compartments, and connec-
tion was made below by a passage at the side. Each drift was
usually excavated before being timbered.
At each level, drifts were run on the vein in the ordinary
manner, dimensions being 6x9 ft. In the earlier workings the
tracks were laid very poorly, and were often the cause of a great
deal of trouble and delay, when a large output was desired. But
as time pas.'^ed improvements in this, and many other respects,
were inaugurated, and the tracks were laid to a grade of from
7 to 10 in. per 100 ft. Track laying is a very important matter
in the economy of a mine, and a good track will always pay for
itself many times over. The tracks should not only be good,
but there should be plenty of them, placed so that they will
be close to the rock to be removed. In drifts movable lengths
of 8 to 10 ft. should be used. This saves shoveling to a long
distance, by placing them in position as soon as there is room,
MINE TIMBERING ti
and enables the mucker to work to advantage, until there is
sufficient space for the ordinary 16- to 20-ft. rails. The rails are
laid on 4x6-in. ties, 3 ft. in length, and placed about 4 ft. apart,
the rails weighing 16 and 20 lb. to the yard. The waste rock
encountered in development was trammed to the shaft and sent
ElaTsUao ol Slop*
-Stull TiUBERiNa, Le Roi Mine.
to the surface, though now most of it is filled into the stopes of
the upper levels.
When the miners began to stope on any level, an upright
post was rigged, and the holes pointed upward and backward.
On a narrow part of the vein a cross bar was often employed.
78 MINE TIMBERING
which enabled the muckers to tram beneath from another part
of the level, while drilling operations were being prosecuted.
Whenever convenient, however, the miners prefer to rig upright,
as they can drill more advantageously from that position. As
they climbed higher on the vein, hitches were cut in the foot-wall,
and stulls were put in from foot- to hanging wall. One end was
fitted into the hitch, and the other end cut with such a bevel
that it fitted against the hanging wall, which had been previously
faced if necessary. (See Fig. 65.) The greater the weight coming
on the stull, the more securely it would remain in place. These
stulls were placed tightly in position, and wedged if necessary or
possible. If there was any liability of their being knocked out
by blasting, a hitch was also cut in the hanging wall. Stulls
were used to form floors to work from at intervals of nearly
20 ft., and such a distance apart horizontally that the lagging
placed upon them would not be broken by the blasts above.
They were also put up against any bad ground that required them.
The lagging used on the stulls consisted of round poles, and
plank chutes were run up the stope at convenient intervals.
An idea of the stope and chutes may be gathered from Figs.
64 and 66. A cross bar and stage is shown in Fig. 64, but usually
most of the work is done from the broken ore resting on the stulls,
and an upright post is rigged, either on this ore or on benches
on the foot-wall.
But where the orebody widened, stulls could not be used.
Here the stope was started by enlarging the drift to the total
width of the deposit, and a face obtained right across the vein.
In one case the width varied from 40 to 80 ft., and, as a back or
roof of this size would be dangerous to work under without some
support, the timber had to be quite close to the face. When the
muck was removed mud-sills were laid down, upon which the sill
posts were erected. These sills were carefully placed, and tamped
with fine dirt. They were braced apart by cross ties, and had a
length of 10 ft. 8 in., or two sets. The framing and manner of
laying them is shown in Fig. 67. At first the sill floors were not
planked over, but later it was seen that a plank floor was eco-
nomical to shovel from, as often there would be rock tumbling
down, or breaking through from the floors above.
On one level in the Le Roi, the 700-ft. level, there were no
fewer than eight machines working at the same breast simulta-
MINE TIMBERING '9
neously. This meant that the rate of advance was very rapid,
and difficulty was experienced in keeping the timber close enough
to the face. Two parallel tracks were laid to remove the ore,
one along the foot-wall side and one along the hanging wall side,
and a lai^e gang of muckers and timbermen became necessary.
When the sills had been laid down square sets were erected upon
them, and securely braced or spragged. Spragging a set of
timber requires considerable experience on the part of the tim-
berman. Spragga are pieces of round lagging, cut square at each
end and of varying length, and placed between the ground and
m
a
^
a
ffl
H
Fio, G7. — Mui>-BiLLS AND TiES, Lb Roi Mike.
the cape or ties, as the case may be, and securely wedged. They
serve to keep the sets rigidly in their proper position, and thus
prevent them from falling down during concussion after blasting.
The details of the square sets are shown in Fig. 68. These
were at one time framed by hand, but now a framing machine
does the work. The sets are shown in position in Fig. 69. This
ia a view of a section across a rather narrow part of the vein.
One post on the foot -wall is placed in a special manner to avoid
the necessity of cutting a large hitch in the rock, which is very
hard. A hitch is often made when it can be cut without too
much trouble. On the hanging side an extension cap ia shown,
80
MINE TIMBERING
no hitch or support being made for the end of it. The top " butt "
cap on the hanging side is supported at the end by a heavy pole
instead of a post. The plank floor, lagging and spraggs are
shown at the top.
The posts used in the Le Roi ranged from 12 to 24 in. in diam-
eter, the caps 12 to 15 in., and the collar braces or ties somewhat
smaller. In the old days it was the custom to cover the caps
Cap
^i^.
- -0-
Collar Brace
Joint Across Vein
"T="
^^
o
Poet
BUI Post
Fig. 68. — Details of Square Sets, Le Roi Mine.
with round lagging, 16 ft. long and up to 7 in. in diameter. They
thus reached over three sets, but were difficult and awkward to
handle, on account of their length. After several years of this
inconvenience it was decided to cut them so they would reach
only two sets. The lagging was then brought to the mine in
lengths of 20 ft., and they were sawed in half on the surface.
A double tier of lagging was used, one tier being laid on the caps
and the other at right angles to them. Still later in the history
MINE TIMBERING
81
of the mine 3-in. planks in 5-ft. lengths were laid on the caps,
and a few rough holes placed on top of them, to prevent the
plank being broken by the blasts. These planks were spiked
with one spike in each end, and served to stififen the timber
considerably.
When the excavation on the level had advanced a reasonable
distance, say about 60 ft., another floor was started on top of
the timber. Overhand stoping now commenced and rock or ore
was broken much more readily than on the sill floor, as it had a
better chance to break, there being more free surfaces. Holes
Fig. 69. — Square Sets in Position, Le Roi Mine.
were drilled in a face about 7 or 8 ft. in hight, and placed so as
to bring the ore down to the best advantage, viz., enough holes
were drilled and enough powder used to break the ore to con-
venient size for economical handling. If it were broken too fine
it would take too long to shovel into chutes, while if it came down
in the form of large boulders it was necessary to blast. The
sizes most conveniently handled were lumps weighing from 25 to
50 lb., which could be rapidly and easily thrown or pulled into
chutes. The holes were generally drilled in the direction of the
vein or orebody, and not across it, the depth being about 7 ft.
At each set-up the miners moved across the face from foot to
82
MINE TIMBERING
banging, or vice versa, as the case might be. In this way the
muckers cleaned out the broken ore behind, and, as soon as there
was room, the timbermen proceeded to put up the timber.
To get out the ore, chutes were built in every other set, or
Figs. 70-72. — Views op Chute, Lb Roi Mine.
every third set at most. The bed pieces were made of 8xl0-in.
timbers, placed at proper slope for the rock to roll down, one end
being on the collar brace, and the other supported by a cross
piece inserted between the posts, and high enough to enable the
one-ton ore cars to pass beneath. Figs. 70 and 72 show a front
MINE TIMBERING
83
and side view of a chute respectively. The chute door or gate
consisted of a semicircular sheet-iron plate, with suitable stiffen-
ing to prevent deformation, and a lever attached by which to
operate it. By means of these chutes proi^erly made, and with
dry ore, the car could be filled in a very few seconds.
As more floors were constructed above, the chutes were car-
ried up the full size of a set, by spiking plank 8 ft. 8 in. in length
on the caps and collar brace.s. To bring them closer to the ore,
as in a large stope, the chutes were expanded to take in two, .
three, and even four or five sets. (See Fig. 71.) The chute
planks were all placed vertically, and where it became necessary
a bottom of short lagging was made for the rock coming from
above to fall upon. A stiffening was made for the chute planka
by a cross brace between the posts, half-way up and well spiked.
In a wide stope, two rows of chutes and two lines of track were
constructed. By this means the muckers were enabled to get
the ore into the chutes without being compelled to tlirow it far,
or to use wheelbarrows or any other device.
While any level was being developed a winze was sunk from
the level above to provide ventilation. These winzes were always
located in the slopes, and provided a sort of chimney by which
the smoke had a chance to escape. They were also used as an
easy route by which timber could be lowered to the upper floors,
and later, when the ore had been all removed, or nearly so, waste
rock was run in through them to fill up the stope.
As more and more floors were attacked and carried forward,
more faces were worked simultaneously. Care had to be exer-
cised in regard to approaching too near the front line of timber.
The blasts might jar the timber, and possibly cause it to throw
forward a few inches, even if they would not kncK'k it down.
When square sets have been disarranged in this manner, it is a
very difficult matter to foree them back into position again.
I have had occasion, as a timbernian. to use jack-screws in
cases of this kind, and to spend considerable time on work
which, with a little more caution on the part of the miners or the
management, would have been unnecessary. One machine at a
face and one machine at every other floor appeared to be a good
method. This allowed the men of the timber gang to put up a
line or two of timber on the intermediate floors, and they were
not interfering with either the muckers or miners.
84
MINE TIMBERING
An idea of the method of attack in a stope may be gathered
from Fig. 73. In this view, however, I have unfortunately
shown the limit of advance on each floor rather than the actual
working condition. Aa illustrated in the diagram it would be
necessary to carry the lower faces ahead to allow a chance to
work on the upper ones.
As the floors became more numerous and farther and farther
away from the winzes, some method had to be adopted to get the
timber into the stopes more easily, quickly and economically.
An excellent plan was introduced in the Le Roi in the large stope
on the 700-ft. level. A track was laid the full length of the stope
Fig 73 — Cbneril Schfmf of Stope Le Roi Mine
on the first floor abo\e the level up out of the way of the tram-
ming tracki and a truck carrymg a small air hoLstmg engine
placed on it From the drum of this hoist a manila rope was
carried up a special timber chute, over a pulley on an upper
floor, and then down the chute to the level below Here the
timber was attached with a hook and half hitch, and hoisted to
any floor desired. An idea of this arrangement may be gathered
from Fig. 73, in which one timber chute is shown beside an ore
chute. The timber chutes were made of 2-in. planks, spiked to
the collar braeeii, and inclined with the vein. They were erected
every 80 ft. or less, and were convenient for hobting drills and
MINE TIMBERING
85
machines, as well as timber. The timbers could be readily dragged
to any place desired by means of the " come-alongs," which were
a pair of hooks attached to the center of a small pipe 3J ft. ia
length. A man on each end of this pipe could drag a post any-
where over the floor.
The ore was not Borted in the mine, but sent to the surface to
be treated there. It was trammed to the shaft and dumped into
large pockets from which the skips were loaded. The tracks at
the shaft were laid directly over the pockets, and the ore was
dumped from the car between the rails, or at one side of them.
These pockets were capable of holding a good many tons, bo tbat,
if anything happened to the hoisting apparatus, the trammers
could still work away, and fill the pockets. In the new shaft,
which was put through by means of raises from each level, pockets
were made with a capacity of about 200 tons.
From this somewhat detailed description it will be seen that
a great deal of timber is iised in this mine. The timber is not
used merely to hold up the hanging wall and roof, but principally
to furnish a convenient method of reaching all the ore, and to
prevent loose slabs and boulders from dropping on those who
must work beneath. The workings are kept closely timbered,
and thus liability of accident is reduced. No staging is needed
in rigging machines, the muckers have a good floor to shovel
from, and chutes are handy and convenient, more so than could
possibly be the case in any other mining method.
By this system all the ore is taken out between levels. The
Bills of one level are caught up from beneath, and timber connec-
tions made with the level below.
When a stope or level is worked out the only timber saved is
the rough lagging and plank flooring, which is readily torn up
and used again. Waste rock from development work in other
parts of the mine Is dumped down, and the old stope gradually
filled up. This rock is brought up from the lower levels on
cages in the new fi\e-compartment shaft. No great attempt is
made, however, to fill the stopes.
Old Ibonsides Mine, Phoenix, B.C.
In this mine and the adjacent Knob Hill, we have a still
wider and larger orebody than at any point in the I^ Roi. Not
86
only IS the deposit of immeiise size, but the grmde of the ore is
much lower, neee^itating a much lower cost of extraction, in
order to mine it at a profit. To accomplish this a large output
is essential, and cheap and rapid means of handling it, from
breaking the ore down untfl it finally reaches the smdter.
The ore is mined in three ways in these deposits:
(1) By open cuts,
(2) By the milling or "glory hole'' method, and
(3) By the 'ordinary overhand st oping with the use of square
sets.
The open cut was on a level with the railroad track, and a
tramway was built with an incline to enable a smaU hoist to bring
the ore up high enough to dump into the railroad cars. This is
quite an ordinary method and needs no fiuther comment, the
ore being broken down in the usual way. Later, however, when
a considerable excavation had been made, a steam shovel was
used, which handled rock of much larger dimensions. Boulders
too large to go into the bucket were picked up by means of a
chain. They were loaded either directly into the shipping cars,
when the ore was crushed at the smelter, or into small wooden
cars, and taken to the crusher first by horses, and at the present
time by a small locomotive. Three steam shovels are now at
work for this comjmny in their low-grade orebodies, and they will
tend greatly towards solving the problem of decreasing the cost,
and, at the same time, largely increasing the shipments.
The milling or "gIor>' hole^' method also applies more par-
ticularly to the Knob Hill than to the Old Ironsides Mine. It
consists essentially in driving a tunnel into the deposit to be
excavated, as low as can be conveniently worked without the
sides caving in, and then a raise to connect with the surface.
At the bottom of the raise a very substantial chute is constructed
from which the ore can be readily withdrawn into cars. Opera-
tions then begin on the surface and the ore is milled or broken
down, being blasted into the raise. Suitable faces and benches
are soon established, and a better command obtained of the size
of the rock going down the chute or raise. Very deep holes are
drilled and very heavy blasts set off, thus breaking the ore quite
rapidly and economically. The benches are arranged in such a
manner that a great amount of the rock rolls down into the chute,
which is always partially filled, without much handling.
MINE TIMBERING
S7
The advantnges of this method are as follows; practically no
expense for timber; no bad air to work in and hence no time
lost; few drill holes needed and comparatively little powder used;
the ore handled mostly by gravity.
The disadvantage is that there is a limit to the depth at
NT, Old Ironsides Mink.
which the ore can be excavated, because of the caving or falling
in of the sides.
On the deeper levels of the mine the usual method of under-
ground development was carried out. The system of mining tlie
ore was very similar to that in vogue in the I^ Roi, which has
been already described. The timbers, however, were stouter,
and the method of lagging was different. In arranging the lagging
88
MINE TIMBERING
the object was to place it in such a way that the broken ore could
be rolled into the chutes with the least possible amount of shov-
eling. To accomplish this, lagging about 10 ft. long was laid on
the caps, close together, and, if the poles were weak, perhaps a
double layer. A space two sets square had the poles laid parallel,
and the adjacent squares were poled at right angles to these.
The caps and collar braces were of the same dimensions, hence it
did not matter which way the lagging was arranged. In this way
the poles had a good support at both ends, because they reached
well over two 5-ft. sets. When it was desired to remove the
muck, all that was necessary was to move a pole so that the ore
could drop through. As it rolled down, with the aid of a pick
or bar, another and another pole could be rolled from beneath it.
In this manner the writer has rolled into the chute 40 or 50 tons
in four or five hours. Any very large boulders, of course, were
smashed with a sledge hammer. Fig. 75 is meant to show the
arrangement of the lagging. It is a plan of the floor immediately
under the ore to be mined, while Fig. 74 is an elevation of the same.
Fias. 76 AND 77. — Chute Aruanqement, Old Ironsides Mine.
A special method of chute building was adopted here. Above
the first floor they were built in the shape of a long trough-like
MINE TIMBERING 89
V running from one brace down and across to the next. Poles
were used for this work, and spiked securely to the square sets.
Figs. 76 and 77 show the arrangement of the chutes in elevation
and plan. At convenient intervals an outlet was made, and
between the chute gates the ore was allowed to pile up a little.
The ore ivas trammed to the shaft in ordinary one-ton cars, and
hoisted to the surface on a cage through a vertical shaft.
It will thus be seen from this brief account that a very easy
and economical method of removing the ore was in vogue at the
Old Ironsides.
Baltic Mine, Baltic, Mich.
The method adopted in the Baltic is peculiar to this mine,
and is not used, as far as I am aware, at any other mine
in the copper country. It is a simple system of walling up each
tramway with waste rock, thereby keeping a roadway open, and
filling in above with the gangue and country rock, as convenient.
In this way the expense of putting in timber is minimized, which
is offset by the walling and filling. The method is only appli-
cable when the vein carries waste, or when waste rock la easily
and cheaply obtainable.
The material mined is native copper, which occurs in a vein
of lava rock both as "shot copper" of varying size scattered
throughout the rock, and as "mass copper," which is solid copper
of more or less irregular shape. The pitch of the vein is about
70 to 72 deg., and the width varies from 20 to 50 ft. Parts of
the vein are more or less barren of copper, and this rock, called
"poor rock," is picked out by the "copper pickers," and forms a
good part of the filling.
The vein was oiiened up by shafts and drifts, and when stoplng
began, the drifts were widened out to the full width of the vein.
After the copper rock was cleaned out from the face, the poor
rock was taken back in carB, and shoveled to one side. When
the "wallers" had enough rock to start on they began and walled
it up on each side of the track, leaving a space of 7 ft. for a tram-
way The walls were made about 7 ft. high, and heavy stull
limbers laid on them as caps. These caps were placed about
3 ft. apart and covered with cedar lagging, so that no rock could
come through. (See Fig. 78.)
IQXE TDIBERIXG
At intervals of about 40 ft. spaces were left for chutes on one
side of the track. They were built up with rock and had a timber
margin for planks to be spiked to. In the bottom of the chute
flatted hemlock timbers were laid, and a hea\y sheet-tron {date
Fig. 78. — Method of Walling up, Baltic SIixe.
was fastened to them with drive bolts. The bottom of the chute
was made flat because very large boulders were handled in it.
For a gate a spout was used, one end of which was raised and
lowered by means of a long, stout lever. The copper rock thrown
Fig 79 — Method
, Baltic Mine
into the cl ute was pulled out I y the trammers mto two-fi
taken to the shaft and dumped directly mto the skips
WIen the work had progressed far enough on the
Ie\el overhead stipin? began above the cape and v.i
station
ills, by
MINE TIMBERING
91
drilling with machines and blasting in the usual manner. The
rock broken down was picked over by the cojiper pickers, the
copper rock being thrown into the chutes, and the poor rock
thrown back to fill up the excavation. As more and more filling
accumulated, the chutes were carried upward in the form of a
hole 5 ft. square, by means of heaA-y cribbing flatted at the ends
and spiked. (See Fig. 79.) Sometimes the pickers needed wheel-
barrows to get the rock into the chute or "mill."
In sloping, a gootl breast was carried along, and heavy holes
drilled, since no damage could be done by hea\'y blasts, though
it was not advisable to shatter the roof too much. As the room
grew in hight the back got farther and farther away from the
filling. This necessitated the use of long posts for the machines
and staging for the miners to work from. The idea, of course,
was to work as much aa possible from the top of the broken
rock, but aa there were 100 ft. between levels, and not a very
high percentage of poor rock, it became necessary to cut out the
foot- or the hanging wall to fill in, and thus reach the back. This
should always be done after the copper rock has been picked out,
as otherwise much poor rock would be mixed with it. An
attempt is made to convey an idea of the atope in Fig. 80.
bTopB Baltic Mine
This method is <>uppo3ed to take out practically all the ore
and the only u^e made of timber is to crib the chutes and co^er
the tracks. The ^ein rock is quite tough and with a slight
arch in the middle of the roof, there is comparatively little danger
from overhead. The greatest difficulty to be encountered will
be in making connections between levels. Here the filling from
92
MINE TIMBERING
the level above will run down and mix with the copper rock
below. Taken altogether, however, this is an excellent method
of mining, and has given the Baltic people satisfaction up to the
present time.
Atlantic Mine, Atlantic, Mich.
The Atlantic vein is similar to the Baltic, though it only
averages about 15 ft. in width, and it does not carry so much
copper. This rock is not picked over, but the total product
Fia. 81. — Stull Timbering, Atlantic Mine.
mined goes to the stamp mill. Thus no filling can be obtained
from the rock broken and, the vein being narrow, stulls can be
used.
When the levels have been opened up the miners take con-
tracts to stope out the pay rock. Each contract includes a part
of the vein 99 ft. in len^rth and extending between levels, which
are about 85 or 90 ft. apart, and tlie price is paid on a basis of
at least a widtli of 15 ft. The contractors first nm a drift to the
end of their ground and commence st oping, taking out enough
rock to put in the stulls to protect the level for tramming.
These stulls are very heavy, about 20 ft. or more long, and
placed in hitches cut in the walls. They are inclined at an angle
MINE TIMBERING 93
of about 70 deg. to the horizontal, thereby leaving roi>m for &
track between the stuUs and the hanging walla. (See Fig, 81.)
At the same time they were quite steep to prevent them taking
up more weight than they could safely bear. They are covered
with lagging, which prevents the muck from coming down on
the track. When this line of stulle is finished, etoping is com-
menced higher on the vein, The miners keep rigging up on the
rock they break and it is trammed out from below when they
are crowded for head room. In this way they are always close
to the back, and work to the best advantage. They work up to
within 15 ft. of the level above, and then, as the rock is withdrawn,
the timbermen place stulls wherever they are nealed to support
the hanging, and make it safe for the muckers below. The pillars
left constitute the fioor of each level.
This method furnishes one of the cheapest and best methods
of getting out stamp rock in the copirer country. The width of
the vein, its regularity and pitch or dip, make this a peculiarly
valuable method to the Atlantic Company. Without it the mine
would probably be operated at a loss, as the copper values do
not exceed 25 lb. per ton of rock.
Coming now to the iron country of Michigan we find a some-
what different order of things. Here we do not have the ores in
regular well-defined veins, as is the case in the copper country.
On the contrary, the ore occurs in blankets or deposits of more
or leas irregular shape, and the sustaining power of the adjacent
rock is a far more uncertain quantity. The ore itself varies a
great deal, some being soft and capable of caving, while much is
hard, and a caving system could not be adopted, Some again
is intermediate between hard and soft ore, and a combination of
a caving system with some other method becomes a necessity.
Barnum Mine, Ishpemi.vg, Mich.
This is a hard ore mine producing a hard hematite. The
system of mining is simple and inexpensive, although about
one-third of the ore is left for pillai3. The levels are from 40 to
50 ft. apart, and after being driven, raises are run up to the
level above at convenient intervals. When the raises are com-
pleted, the mineiB be^in at the top and mill the ore down the
raise in a maimer similar to the "glory-hole" method already
94
MINE TIMBERING
described, except that the work is, of course, underground. They
work from convenient benches and gradually cut out lai^ge cham-
bers. Care must be exercised in scaling any loose rock from the
roof while the men are close to it, because when they get lower
down the roof will be out of reach. Wherever necessary, pillars
are left 22 ft. square, one being as nearly as possible directly
above the one below. Machines and tripods are employed, and
the rate of drilling is slow, varying from 4 ft. to 15 ft. of hole
per shift. The ore is also hard to break, and a 50-per cent,
dynamite is used. There are no pockets in the mine, and the
cars are hoisted to the surface by a single-compartment shaft.
As the method at the Bamum is so simple, little more need be
said; suffice it to say that the method is very wasteful of ore,
because such a large percentage of it is left in the mine.
Level
^y////////y//////y//A
■ p^?^^^?^^^^52^
yy/y^///yy//y///^^^^^ vy^////
%^/////yy///////A^^^ w////yy^//////yy///J^ —
Level
Fig. 82. — Stopes and Pillars.
Section 16 Mine, Ishpeming, Mich.
The ore from this mine was also fairly hard and a similar
method of mining was adopted. Levels were run from the shaft
to the orebody at intervals of about 60 ft., and a drift run along
the foot- or hanging wall as desired. From this drift raises were
driven every 50 ft. to the level above, thus making a passage for
timber and ore. At 15 ft. below the upper level the raise was
enlarged into a stope or room, and made of such a size that it
would be safe to work in, dividing pillars being left on each side.
The ore was thus removed down to the level below, and pillars
were left extending across the orebody.
When the rooms had all been excavated in this manner the
robbing of the pillars began. The pillars were usually 25 ft.
through, and they were undercut on one side to a distance of
MINE TIMBERING
95
about 9 ft., and right across the vein. The timbermen then
built cribs of timber 8 ft. square in this space, and as many as
they had room for, leaving a space of 3 ft. between them for a
passage. These cribs were built right up to the back, wedged
down and filled with rock. (See Fig. 83.)
Bobbing and Filling
Tramway Set
Fia. 83. — Filling System, Section 16 Mine.
The next step was to undercut another 9 ft. and treat it with
timber cribs and rock in a precisely similar manner. Finally the
last portion of the pillar was removed and cribbed, and the pillar
rested now entirely on the crib supports. The stopes on either
side of the pillar were then filled with loose rock to the level of the
top of the cribs, and also in between them, a passageway, of
course, being left for tramming.
The pillar having been undercut to a hight of about 8 ft.,
another slice is removed in much the same manner, at a higher
level. Mills become a necessity in order to let the ore down
through the rock filling, and these are made of round poles and
placed at convenient intervals. As the pillar is attacked at a
96 MINE TIMBERING
higher point the work proceeds on the top of the filling, hence
by this method it is possible to remove practically all the ore.
The filling used is obtained from two sources: part is furnished
by the ordinary development work, and the remainder is ob-
tained from the dump of a neighboring mine. It is loaded into
railroad cars, and dumped directly down a raise for that purpose.
This raise is tapped where desired by a rough chute, and the rock
trammed in small dump cars running on tracks laid on the filling.
These tracks are readily moved laterally, so that the rock is
conveyed to the place desired without very much shoveling being
required.
In parts of the mine where the orebody is of such nature that
ore pillars are not necessary, a method of overhand stoping is
prosecuted. This operation is followed directly by the filling,
the ore being mined out and the excavation filled with waste
rock. Where the roof is not good, cribs are built on the filling to
support it.
Again, in other parts of the mine, filling is not used, but the
ore is mined from each level upwards, and the regular squarenset
timber erected.
The methods of mining at this mine are therefore somewhat
special and varied. The cause of this variation is due to the
fact that the orebody changes from place to place in hardness,
width, and accessibility. In some parts of the mine it is hard
to introduce the filling, while in others it is a cheap and efficient
adjunct in extracting the ore. Wherever used it forms a com-
pact and satisfactory substitute for timber, which, to perform
the same duty, would be quite expensive.
Soft Ore Hematite Mine, Ishpeming, Mich.
Here we have a mine which was formerly covered by Lake
Angeline, a body of water of about 100 acres in extent, and
50 ft. deep in the deepest part. The water was pumped out by
means of powerful pumps, and the lake bed became compara-
tively dry. On the margin of the old lake shafts were sunk,
and the mining of the large deposits of soft ore was begun. The
ore, being a soft red hematite, was very easy to break down, but it
was impossible to have large chambers excavated, because of its
MINE TIMBERING
97
heavy Eettling nature. As the soft ore caved so readily, a caving
system of mining was soon inaugurated.
Haulage ways were, aa far as possible, made in solid rock.
Then raises were driven to the top of the ore deposit, at intervals
of from 60 to 100 ft., and cribbed with two compartments, one
for a ladder road and the olher for ore. Sub-levels were also
made to facilitate operations. The ore was loaded into oars
holding about 2i tons, which were attached to a " bull-dog," and
taken to the shaft in trains of six or seven. The bull-dog was
jMrt^o^nA....
Fio. 84. — CAnNO System, Soft Ore Hematttb Mine.
Operated by a cable, each end of which passed around a drum
run by corapreased air. One engine was located at the simft
and the other at the end of the haulage way. At the shaft the
cars dumped directly into the skip, and were moved up to, and
away from, the shaft by hand. The idea of the bull-dog is to
facilitate coupling, the cars being connected to the buil-dog
instead of directly to the cable.
When the chutes were completed a "top-slicing" scheme was
b^:un. AdriftSxS ft. was driven parallel with the deposit, and
timbered with square sets. Thes? sets consisted of legs and caps
98 MINE TIMBERING
as shown in Fig. 84, and were placed 4 ft. apart. At the raise it
was important to have rather stout timber, because here the tim-
ber was expected to stand the longest, and was therefore sub-
jected to most pressure. Farther from the raise or chute the
timber was much smaller, 6 to 12 in., and the caps were covered
with light lagging. The caps, as a rule, were a few inches larger
in diameter than the legs.
The second step in top-slicing is to begin at the farthest end
of the drift and cross-cut to both foot- and hanging walls. These
drifts are also 8x8 ft. and are driven parallel, and one after
another, until the whole area is excavated, that around the
chute being taken out last. The same procedure is followed on
the opposite side of the chute. The floor is then all lagged over
to prevent mud, gravel, etc., from mixing with the ore when
subsidence takes place. The legs of the sets are blasted out and
the overlying burden is lowered, as a consequence, all over the
area in question.
Mining below this is now done by the real caving system.
The miners drop down 12 or 15 ft., depending on the hardness
of the ore, and run a drift as before. Side rooms are run to
foot- and hanging walls, and when these are reached the most
remote sets are blasted, and the roof is caved in. By working as
they retreat practically all the ore is removed from beneath the
lagging above, only one set usually being blasted at a time.
Sometimes several rooms are worked out before caving, but it is
unsafe to leave them for any length of time. It is deemed ad-
visable to finish one room before beginning another. In this
manner a whole slice is taken out, and overlying debris or "gob**
is lowered once more. Then a drop is made for another and
another slice, until the bottom of the deposit is reached.
Contrary to what might be expected this is a comparatively
safe method of mining. The men work near the back all the time,
and, should there be any danger, warning is given by the gradual
crushing of the timber. No large rooms are excavated at any
one time, and there is practically no danger from this source.
The system is also cheap, comparatively little timber is used,
and even that is of an inferior order. Very little powder is neces-
sary, and there is not much drilling done. Holes are drilled with
machines, augurs, or hammer and drill, as the particular hardness
of the ore may make advisable. The cost of mining is low, and
MINE TIMBERING 99
t contraiita run at $4.50 for an 8x8-tt. drift per foot of advance.
I The miuers make from $55 to $60 per mouth after deducting all
[- expenses for powder, cape, fuse and candles.
QuEEX Mine, Negaunee, Mich.
In the Queen mine, as its name implies, we have a fine example
of systematic iron mining. The orebody is larpe and fairly regular
and lenda itself particularly well to methodical development. The
ore ia not very hard, and it ia not soft enough to cave, as in the
Hematite, A special method has been adopted and seems to
answer the purpose very well. The system in vogue starts out aa
a square-set system and develops a caving system as the work
proceeds.
The orebody is in the shape of a lens, and dips to the north
at an angle of 38 deg., and also pitches to the west at 45 deg.
Six shafts have been sunk, the first three on the eastern side
being now worked out. From the shaft a well laid out system
of haulage ways has been driven, special attention being given
to prevent interference of cars with timber, and vice versa. The
timber can be handled on one line of tracks often at right angles
to the haulage tunnels. The main ore drift has been double
tracked, and an endlesa cable picks up the loaded cars of ore aa
desired, and takes them to the ahaft. The cable ia operated by
an engine at the aliaft with a special device to keep up uniform
tension. The care are attached to the cable, which is always
moving, by hand, and are detached automatically when they
reach the shaft. They are dumped into pockets and sent back
by the cable on the other track. The expense of operating this
haulage system is only J cent per ton,
Coming now to the mining system proper, we find a face of
3 aeta wide or 25 ft. carried forward, and timbered with good
Bubstantial square-set timber. Then parallel to this another sim-
ilar face is driven, but with a pillar 5 acts, or 40 ft., left between.
Cross-cuts are also nm. blocking out the pillars into squares.
(For elevation and plan of stojies and pillars see Figs. 85 and 86.)
At the aame time these faces are being worked on the level,
another and another slice is stoped out and timbered above. In
this way the orebody is honeycombed to the top of the de]Hj6it,
pillars and rooms alternating throughout the level.
826240 A
100
MIKE TIMBERING
After the ore has been excavated in tliis manner the work of
taking out the pillars and ca\ing begins A raise 8x8 ft. b
now run up through the center of the pillar and timbered with
the usual seta Thus between the center set and the timber
in the rooma outside there is a distance of two sets The top of
the pillar is taken out to the depth of one set and caps of double
length are used to connect the center with the outside sets. This
f^
.-T
-
^^r^
--
-^™s^-^i!5^-js^-.-.. '^
■:^
=
p u
„
X
1 ■■
_
Vert cat Section through A B
~
=
=
p,„.- 1
=
^
^
P
~^
*
1
il
=
=
^
=
J
u
u
L
1
_
1
^
^
=
FlQB. 85 A
— Stopbs and Piu^rs, Qobev Mine.
is done on the four sides, and the top heavily lagged. The ore
is then worked downward, using the long caps at each step, but
without lagging. The material of the pillar is readily broken up
and sent down the chutes in the outside sets; in fact, it is the
most rapid method of breaking ore in the mine.
When the pillars have all been robbed the tracks are taken
MINE TIMBERING 101
up, a flooring of poles is laid, except where there is a rock floor,
and every second leg is blasted out, thus bringing down the whole
mass of timbers as well as the roof.
A system called ■■scramming" is used to mine on the level
below. The level is divided into 50-ft. squares, and in each a
raise 4x9 ft., in two compartments, is run up to the lagging
above, the levels being 85 ft. apart. Starting 9 ft. down, a drift
is driven from the raise 25 ft. each way, and timbered with light
sets. The ore is shoveled directly into the chute or a wheel-
barrow is used. A second drift ia nin beside the first, though
not always, and the bottom is lagged over. Then the legs are
blasted, and the overlying debris caved, as in the Hematite mine.
The process is repeated until the 2500 sq. ft. is lowered 9 ft.
The miners now drop once more, and repeat the operation, and
so work down to the level.
While work is progressing in the drift the timbers begin to
crack, which is a good sign, because it shows that the mass above
is slowly settling. If the timbers do not shi)W that they are
supporting great weight the debris has become "hung up," and
is liable to come down at any moment. Seeing this the miners
either blast it down, or get out of the place. When the timbers
Bhnw pressure the workmen are safe, as the mingled rock and
timbers settle very slowly, an inch or bo a day.
This method of scramming is also used in new workings, under
gravel, sand , or loose rock. In that case great pits are formed on
the surface immediately above.
In the foregoing description of these several mining methods,
little attempt has been made to go info the minute details of the
various schemes presented. The systems taken up represent the
actual practice, in their most essential features, of underground
work in western America, outside of coal mining. Much more
, might be said in regard to many matters connected with them,
\ such as their comparative expen.se, the percentage of ore recov-
ered, their suitability to general conditions, etc. To go farther
! into these matters would make the paper unduly long. No
[ nferences have been consulted, as I have gathered all the data
I at first hand.
During the diacussioti nf his paper Mr. Parlee said that in
I connecting up timber between levels, it was considered gtHid
102 MINE TIMBERING
practice to have sills of the level below, in the sme vertical
plane with those above, surveyed and laid down accordingly,
but in carrying up the sets 100 ft. it was almost impossible to
go up straight enough to have post match with post properly.
They would come either one side or the other of the vertical
plane and be out of plumb perhaps a foot or two. Unless they
could meet the upper sets exactly, it did not really matter whether
the sills below were surveyed or not, except to get the general
direction of the timber. The sills of the upper level were caught
up by the cross timbers, reaching two or three sills. Little
attempt was made to have posts of lower sets directly under
posts of upper sets. Bulkheads were often used and the rock
must be blasted out carefully and not too fast.
Mr. Parlee also said that the squarenset system was used
wherever the ore was too hard to cave without it. It was not
the intention in the paper to discuss all the methods used in
each mine, but only those especially valuable. Different methods
might be used under different conditions.
The chairman remarked that what Mr. Parlee had said about
the impracticability of exactly connecting the timbering of ad-
joining levels held true in all parts of the mining world. The
theory was that posts in successive levels should come under one
another, and in certain mines that he had visited more or less
successful attempts had been made to do this, but in most cases
the method described by Mr. Parlee had to be adopted. As
he had said, the main thing was to see that the vertical
lines were kept true and that the timber was put in substantially.
Sometimes comparatively heavy bulkheads were used. It was,
of course, possible to survey with sufficient accuracy to have the
posts placed perfectly plumb and in line, but this was too trouble-
some, and it was still more troublesome to erect great masses of
sets exactly in line and plumb, especially when, as was frequently
the case, there was movement going on in the orebody or hanging
wall.
MINE TIMBERING
IN SECTION 16 OF THE LAKE SUPERIOR MINING
COMPANY, MICHIGAN
BY C. ST. G. CAMPBELL
MINE TIMBERING IN SECTION 16 OF THE LAKE
SUPERIOR MINING COMPANY, MICHIGAN*
By C. St. G. Campbell
In the following paper it will be necessary to depart some-
what from the subject proper and give a brief description of the
location of the mine, the method of mining the ore, the manage-
ment, etc.
Section 16 is essentially a hard ore iron mine, situated three-
quarters of a mile from Ishpeming, a town fifteen miles from
Marquette, on the south shore of Lake Superior.
The mine is worked chiefly for hard ore, there being three
large lenses, each of a different grade, according to the percent-
ages of iron and phosphorus contained. There are also two
** pockets" of soft ore, which is locally knowm as "hematite," but
after mining these pockets for some time, it w^as found that the
ore was too high in phosphorus to compete with the soft ores of
the surrounding mines. So, for the present, at least, the mining
of it has ceased.
The hard ore is found w^ith a foot-wall of decomposed diorite,
resembling soapstone, and a hanging wall of quartzite or jasper.
A great dike of diorite cuts across the deposit and makes the
formation somewhat irregular. The three lenses dip at an aver-
age of 70 deg. with the horizontal. They have an east to west
strike and vary very much in their dimensions, ranging from
10 to 700 ft. long. The dimensions of the so-called "south
vein '^ have not yet been determined, as it reaches below present
operations.
The method of extracting this hard ore is as follows: At
intervals of 60 ft., levels are run out from the vertical or hoisting
shaft until the ore is reached. A tunnel is cut along the length
of the lens, clinging to either hanging wall or foot-wall as the
* From Tran8<iction8 oj Canadian Society of Civil Engineers^ Vol. 18, 1903.
105
106
MINE TIMBERING
case may be. Raises are then made every 50 ft. to the above
level, or nearly so, a back of 15 ft. being left to make tramming
safe. Through this back a small hole is cut to let down timber,
also for the purposes of ventilation, etc. When first cut, these
raises are 9 ft. in diameter and are afterwards widened until
the dividing pillar is as thin as is consistent with safety, say 15 ft.
in the average.
The next step is, in many ways, modified by the width of the
lens, but it suffices to say that the stope is carried across the
Plans of and and xodi Lerels to X.eft
and Rigfatctf Hoisting Shaft Respectively.
acu ar DvrMiea
M to lOS tM
oTtiuM
Shift H<^ I
(lacllMd)
BonnlBryof PittalnuKudLakcliuBillMlIlM^
Fig. 87. — Section 16 Mine.
Projection of 2d and 10th levels. The leveb are 370 ft. apart.
width of the vein, the shift boss using his own discretion as to
the method employed. Finally, however, the stopes or raises
are filled up with rock, leaving a timber tunnel for the passage of
trams on the level below. Mills are also built and rock filled in
around them, a process which will be described more fully later.
The pillars are then mined out and their places filled in with
rock. In this way all the ore is secured.
The hematite, so called, is mined by the "square-set" system,
which consists of taking out slice after slice of the ore, the length
and breadth of the pocket, and in its place putting timber in the
form of skeleton cubes, the sides of which measure 8 ft.
These cubes or square sets, aa they are called, are put in one at
a time, just enough ore being taken out to allow the erection of
a single square set. The pocket is worked from bottom upward,
thus securing the advantage of gravity for the removal of the
ore. All the ore is sent down by means of improvised chutes
made of lagging.
The mine is at present 850 ft. deep and the shaft is still being
sunk to tap the south vein. There are at present 13 levels,
12 of wiiich open on to the shaft. The 4th. 5th, 6th. 7th and
8th levels have all been mined out even to the pillars. On the
lower levels, tunneling and raising are being carried on. while on
the first three levels the "robbing of the pillars'' is not yet
completed.
There are two other shafts, besides the one above mentioned.
These are used for ventilation and shooting down the rock used
for filling. These shafts, one of which is inclined, reach only to
the second level. From there on, the rock is sent to the lower
leveb by means of mills.
For the most part, the "hard ore" justifies its name and is
hard and compact, but occasionally it is of a slaty structure or
full of cracks and fissures. In such places it is necessary to use
drift sets, I^imilar protection is also necessary when drifting
through decomposed diorite. locally known as " soajistone."
The proposition which the timberman has to handle now
having been outlined, the respective applications of the different
methods will be taken up in detail.
The timber is obtained, for the most part, from lumber camps,
the farthest not being more than 20 miles from the mine. This
timber is taken to the mine by rail and stocked near the main
shaft. .Second-class logs are used, knots and slight crookedness
not being objectionable. The logs, cut into either 5i-, 8-, 10- or
16-ft. lengths, are lowered into the mine by means of chains
attached to the bottom of the skip. The timbermen land them
at the level station below with the aid of a rope, ship them on
to a tram and take them to a timber-dock, where they remain
until required. Between the hours of twelve and one on the
day shift the miners are on the surface for hmch, and advantage
is taken of this fact to lower tinil>er. In consequence the limber-
i below and take out timber, thus postponing their
108 MINE TIMBERING
!une& M- one hour. Hemlock and white pine are used for the
aa-iit riin in the large timbering. Cedar is used for lagging.
Tw j^pcdia is at present experimenting on hard wood. Squared
rjttwr 2? used only in the shaft and under certain special condi-
ricns eisew'bere. In other places not only is timber used round,
but iio with the bark on. The life of a "stick" is very uncer-
taio. iewoding upon the nature of the wood, the stress to which
i 2> scbjihrted. and the temperature, hence the moisture. On
tJ» r^i iad Mh le\-ek, immediately above the pumps, which are
«m :ie ^h level, the timber lasts only five months, after which
i ii i^ciice easy to force the point of a candlestick six inches into
rhir wvxxl with the hand. This is exceptional, however. The
;sv«ci^ 5» ^^f timl^r in the mine is said to be ten years. The
rimi-vr i? often crushed by the settling of ground, but there is
ifctir ^iabSfW to life in this, owing to the slowness of settling.
Shaft Timbering
XV S9«<)^^ <^f sinking the hoisting shaft is somewhat similar
H/ 5?Ufc: v< »fein^ a square set. A rectangular hole is stoped
MW9 w * ^^^ ^^f ^^ ^^^ ^ving a width of 10 ft. and a length
^ "S ^ *»^* '^" ^^^ ^^^'^ ^ ^^ ^^P ^ double square set, 8x8x 16 ft.
^is ^^^^ ^^ ^ sus[x*ndeil from the one above by means of
It "'54 'Vn weviireil into place and lagged between the
HM^ i^i ^"^'^ ^ "^^ ^^^^^ ^ ^^^^^" ^^^^^ another 8 ft. and another
v.. ,--4-\^ ^^ i^avtxi and United to the bottom of the former,
^ V V siv.KiVsi .Hud timlH^ring proceeds. The timber in the
^v -s»\' -s trv>m 12 to IS in. in diameter. Ever\^ time an
.* -'^-w <^^vs v-4 ft.> is made, the small shaft pump is
; N V 3=2^"^ viistamv. so keeping within the 27-ft. practical
^"!!|** ^ \jv^^;> ^ tht^n Umxl inside tlie square sets with 8x8-in.
; ^ -^ivrs. IS ft. K^t^» plai*t\l cK>se to one another verti-
s^tuv^v^ -^^^^ ^^ ^^^^^^^ ^ lv\.liko character. In each set and
'^****^ ^". V ^"^^5^ ^'^ ^"^' ''^*^^" ^^"^^ placeil cross pieces to which
:^H*ii> ^^^ '^.^^j ;hx:svUNidiui: the shaft into four compartments.
>^a«iv r\^ ^-^^ ^^^^ ^^^^^^ ^ ^^^, ^^ ^j^^^ ^.^^^ ^^^ ^1^^ ^^j ^j^^ ^^^1 ^j.^
^^/'*^*'''\.\Vw.<! x^J'^l*^ ^^^^^ *^»d o.'m{Xirtments are used for
'»«^r V ^ i^^vJvl^r \\5^>*^^ V^*"*' rlC vVn.)
**^ ^^^ ^*^^'^ *^ "'^'^'^ ^"^'^^^ • "' ^ '"' square and 5 ft.
no
MINE TIMBERING
liigh, slide in runners which consist of four 8x8-in. beams, two
at each side of the skip. These are placed vertically 6 in. apart.
Until lately much trouble has been experienced from water in
the shaft. With a view to stopping thb water downpour, troughs
or garlands have been arranged to carry the water into pumps at
depths of 190 and 680 ft. This has proved very effective.
The rock shafts are very much simpler in construction, being
merely lined with rough unbarked logs built up like a crib. It is
usual to hoist to the surface all rock from the stopes at the bottom
of the mine and send it down again to the levels where the pillars
are being robbed. Obviously this supply of rock would be insuffi-
cient. Hence carloads of loose rock are brought from the No. 1
hard ore mine and dumped down one or other of the shafts as
required.
Drift Sets
In running through soapstone on the 2d, 9th and lower
levels, the back and sides of the tunnel are so weak that they
Fio. 89. — tiiDE Elevation- of Deuft Set, Section 10 Mine.
have to be supported. This is done by means of "drift sets."
Two trestles, 5 ft. apart, each consisting of two legs and a cap,
MINE TIMBERING
111
with a covering of poles resting on the caps, constitute for the
main part what ia known as the "drift set." The caps are
chopped flat at the ends so as to set firmly on the legs. The
pairs of legs are kept apart by studdles, which are poles 4 ft.
6 in. long and 4 in. in diameter, set close under the caps and at
right angles to them. (See Fig. 89.) The legs are firmly spragged
against the wall, and spaces between the legs lagged on the rock
side. The lagging is nailed to the legs horizontally, one above
the other, and the loose rock ia piled in behind the partition so
formed. The covering poles used are from 4 to 5 in. in diameter.
These are laid lengthways, the ends of the poles in one direction
of a set rcstmg on a cap, and m the other direction resting on
the ends of the poles of the precedmg set By means of small
pieces of timber the back is caught up and wedged tightly. (See
Fig. 90.) If the pressure is likely to be great, owmg to caving in
Fio. 00. — E.ND View or Driit Set, Section 16 Mine
of the sides of the tunnel, the legs are set wider apart at the
bottom to ensure greater stability. At each end of a line of
drift sets slanting props or " rakers " are propped against the
l^s to keep the whole steady when the blasts go off. (See
Fig. 91.)
• • .»
MINE TIMBERIXG
V -
MV-v^
::u.e -viatp -^ i>n<ist5 of tour vertical legs arranged in
M.-Tv tiv ■: t- >mic s ft. liiirh. The legs of two opposite
-:> M.:i-irv <e!: jjpe leid ti»mher by caps, which rest on
■ ■^'^
v.«
i^
r
\ , v-A. ^JCvTrrN Id Mine.
. V \
I I « « « ■ I
>*-•*•
>• '\
, * -■ ■ \
. (
r , r <:v:e< are held together,
'■. .\< :.: '-.Ls t'ii5e S to 10 in.
" 'i ■•. vl:i/t^ :i lirtle lower tlian
-\ 'r:.j:e .:.:in;erer^ of 18 and
\. ■ <i- :> i'oven?il with 4-in.
• . -• •— :■ \vn on top of the
''■..■.."^ V -^ ■'• ' -' - < — .^^•■: <«■"-«■ -r.'.y w/.en tirsr built and
* "•.> r;':\\-:'< ':' ' - ;• ■.>: "v - ■ -^r >t::<. Vot the sake of
sTv^::^-;; .■:\,: v\ :\' .•■•;.-% '">- -:i:v<^ ' a^ >: V^ ,^: :i <(7u;ire set alwavs
iv:^o :/.o /:\-;s. 1: '"v >'. ;v :> :'..•. ~!\ -Aiie :i::i hiirh. chutes are
bv.:!: in <,^ r'.u: o;-i-i\ v^r.?^ ;> :Vv: * v :-.\o .^^!:;mr.s of sots. Twice
arro:v.:^:s linvt^ l^^v:: iv.:;do :v^ :v.ir.o :ho :::in.l ore hv this system,
but without success.
Mri.i.s
In raising up along the lens the hanginsr wall is often loose,
great masses sometimes breaking off, anil, in consequence, it is
to prop the loose ground up by means of stulls. (See
MING TIMBERING
IHg. 92.) A stull is a single stick of timber varying in size ac
cording to the stress In which it is subjected. The distance i
Fio. 93. — Sruua, Section 16 Mine.
measured from foot-wall to hanging wall and the stull cut a cor-
responding length. A socket b made for the end of the stull on
the foot-wall by scooping out a shallow hole. The stull is then
driven into place and fixed tightly by means of wedges. For
obvious reasons, every endeavor is made to have the greatest
stress along the line of the prop, though in some ca^es ttua is not
at all possible. {See Fig. 93.)
Fig. 93. — Stull, Section 16 Mine.
In the raises on the 13th level, it is impossible to set up ma-
chines, owing to the narrowness of the lens and the steepness
of the dip, except as follows: Two stulls are erected within 7 ft.
of the breast on either side of the raise (8 ft. apart). On the top
side, poles are laid halfway up to the hanging and then ore is
pulled down behind these poles until a horizontal surface is
114 MINE TIMBERING
obtained. On this surface, which is about 6 ft. wide by 9 ft. long,
the machine is set up. (See Fig. 94.) This is called a bench,
and is used for 16 ft. of advance stoping, after which another one
is built above it in the same manner. It b found expedient to
remove the lower ones as soon as the top ones are built, to give
free passage for ore.
Fia. 94. — ■ Method op Settino up Macitinis.
Great difficulty is experienced in getting timber up into the
raises. Owing to oversight, all the tackles are too short, so the
logs have to be carried up the slope by the timbermen, who hold
the log under one arm and use the other to pull themselves up.
It is quite customary to do this for 30 ft. before the tackle comes
into play.
TiMBKR Pillars, or Cribs
The duty of a timber pillar is to hold up ground. It serves
the same purpose as a vertical stull, only on a much larger scale.
The pillar is made of rough imbarked logs, 8 ft. in length and
anything from 6 in. to 2 ft. in diameter, according to the weight
the pillar is to bear.
A pair of such logs, 7 ft. apart parallel to each other, are laid
directly under the "bad ground," and on top of these are laid
two more at right angles to the first two, the same distance apart
and parallel to each other. Again on top of these are laid two
more in the same way. The pillar is thus gradually built up to
the back and eventually wedged down tightly by lagging and
MINE TIMBERING
115
Bmall pieces of wood. Considerable ex[)erience is required lo
make a tight fit, owing to the unevenness of the ground and
tlie tendency for the whole to shift. All the pillars are inspected
every day by the timber boss to guard against any such failure.
In laying one cross piece on top of another there is great tendency
to roll; in consequence, notches or "joggles," as they are called,
are cut in the lower log, into which the upper one fits. It is not
usual to cut them more than 3 in. deep.
Wooden pillars are used nearly altogether in the robbing of
the ore pillars in between the stopes. These ore pillaiH are about
25 ft. through from stope to slope. A space is cut out of the
pillar, about 9 ft. through and the width of the lens, if the
same be narrow, and 8 ft. high. As many pillars as can lie are
built in this space, 3 ft. always being left between them for
walking roads, Sometimes, instead of making two pillars of the
foregoing dimensions, one long pillar is made 16x8 ft, The
inside of the timber pillar is now filled with loose rock. This
rock steadies the pillar and takes the bulk of the weight when
the back settles. The long pieces are called "edgers" and the
shorter ones "cross pieces." Wiien these pillars are securely
wedged against the back, the machines are set to work again
and a space similar to the first is mined out and treated with
pillars. This process is carried on the width of the vein and
breadth of the ore pillar until all the ore in the latter rests on
timber. The stopes on either side are now filled with loose rock
to the level of the top of the timl)er pillars, likewise the spaces
in Ixttween the pillars, and the process of mining out and tim-
bering procecfls as before, the timber pillars having as their floor
tlie tope of pillare of the slice below. The level of the rock in
the stopes is kept up to the bottom of the timber pillars.
Doc lis
The purpose of a "dock" is to hold back rock. It is used
where loose rock is pouring down upon the track and so stopping
the trams; likewLse in filling the stojies, as before mentioned.
The dock is a simple cribwork like the timlier pillar. Rock
is dumped inside and then the running rock is allowed to hank up
against it. The double length 16 ft. is more usual than the
eiiigle in docks. To save timber and labor the inside edgers are
116
MINE TIMBERING
sometimes done away with, the ends of the cross pieces resting
on the outer edger and on the sloping pile of rock. As the work
progresses, a couple of men shovel down rock and thus keep the
level of the rock up to the required bight for the croes pieces to
rest upon. (See Fig. 95.)
Fia 95 — DocTKS
In filling the stope a tunnel must be left for the trams hence
on both sides of the track dorks are built to a hight of 8 ft and
are filled with ro<k in and Ijehind A double lajer of cohering
poles, 4 in. in diameter is 1 iid across from one dock to the other
and the whole is filled over with rock. It is considered advisable
to leave ample space overhead in the timnel, because the pillars
sink sometimes 3 ft. or more, owing to the settling of the
rock filling. It is found that the hanging wall side settles much
faster than the foot-wall side.
The spaces between the logs are stopped up with "filling
pieces," to prevent the rook from coming out into the tunnel.
Mills are used in robbing the pillars, to convey to the level
below the ore which is mined. A mill might be called the con-
verse of a timber pillar. It is cribwork built up like the other,
but is not filled with rock. Instead, the mill is covered with
cedar lagging on the outside and filled around with rock.
The mill is built in the same relative position to the tunnel
** the dock. As the ore is taken out above, it is dumped into the
I^H mill, com
MINE TIMBERING
117
FiQ 06 — HuxB
mill, coming out into a tram in the tunnel by means of :
chute.
The mills are made either single or double, being 5 ft. 4 in. by
5 ft. 4 in., or 5 ft. 4 in. by 10 ft. The latter is the more usual form,
one compartment being used for a. ladder n»ad, the other to
dump rock down.
Filling pieces are used in the partition
of the double mill to prevent rock from -,-,-— .-sb-J^stL/^'*'"
coming into the ladder-road. (See Fig.
96.) There is an enormoua wear and tear
on the mills, due to the falling ore, hence
the soundest timber is used. Hemlock ia
preferred, owing to its toughness.
The life of a mill is very uncertain
On an average, a mill lasts three months
when it is worked night and day for six
days each week. What then happens is
that the pieces of ore cut through the
cribbing pieces, attacking all sides of
the mill impartially. To repair a mill it is lined with }-in
4 ft.x6 — in, iron plates for 20 ft. downand then with 3-m planka
The wear and tear depends upon the hight of the mill the kind
of timber and the nature of the ore. The diameter of the pieces
of timber is from 10 to 18 in.
It is customary to give an inclination of 15 deg. to the vertical
in the mill, in order to break the fall of the ore and so save the
bottom boards of the chute, and, incidentaliy, insure safety for
trammers.
Chutes
The chutes that empty the mills are 2 ft. wide at the smaller
end, widening out to 4 ft. and covering all the floor space of the
mill. They have an inclination of 45 deg., the mouth is 4 ft. 6 in.
from the track and protnides 1 ft. into the tunnel. All chutes
are made of 3x8-in. planks. Spaces are cut out of the cribbing
pieces of the mill to permit the chutes to be made. Chunks of
ore. 8 in, or lees in diameter, can get through the chute; anything
larger than this sticks and has to be "block-holed," This is to
be avoided, because the blasting soon destroys both mill and
chute. (See Fig. 97.) In the case of the square chute, the ore
lis
MINE TIMBERING
is never allowed to fall directly into the chute from any hjght
over 8 ft,, as will be seen, the inclined lagging in each set acting
as a sort of chute.
The ore is kept back by means of boards fitting into slita in
the sides of the chute. Sometimea it is hard to send these planks
into place and so complications arise,
Fig. 97. — A Typical Miu. Cuuie.
Notice the extra cross piece for the double mill; also the pike and trum bar
beside the track.
Stag INC!
When it is necessary to take ore off the back of a high stope,
the drilling machine has to be raised within a few feet of the
place to be mined. This is done by means of staging. A stage
consists of three ladders, each at the apex of an equilateral triangle
of 5-ft. side. The ladders are inclined outward and are wedged
against the back. Planks are then placed on the nmgs of the
ladders, so as to make a platform. Tlie machine is then set up
on this platform. At the best it is a very shaky affair and cannot
be carried to any great hight, 15 ft. being considered a very good
hight for the platform of such a stage.
MINE TIMBERING 119
Ladders and Sollars
In this mine the ladders all have an inclination. This incli-
nation tends to make climbing much easier and safer. The poles
of the ladders are made of 3x5-in. white oak scantling. The
rungs or "staves" are either of white oak or iron, the former
being 1 J in. in diameter, the latter } in. in diameter. Under the
calked boots of the miners they are soon worn through and are
in many cases left too long for safety.
The shaft ladders are in sections of 20 ft. The sollars are 15 ft.
apart, with a hole in each large enough for a man to get through
with ease. The end of the ladder protrudes through the hole.
The ladders in other parts of the mine, in the other raises,
for instance, are much longer, and are made by bolting together
two or more 20-ft. lengths with scantling, on the outside. The
ladders are always spragged securely to prevent shaking.
The sollars are a great means of safety and prevent many
serious accidents, especially in the shaft, where it is now impos-
sible to fall more than 20 ft., in the ladder road, that is to say.
Miscellaneous
The timber-gang in full force is eleven strong, counting the
boss. Below is a classification of the men in the mine.
$2.50 per diem.
Captain $4.50 per diem. (?)
Shift-bosses
Timber-lx)8ses
Bam boss $2.30 per diem.
Timbermen $1.85 to $2.00 per diem.
Miners $2.10 per diem.
Helpers to miners $1.85 per diem.
Contract shaftmen (Paid per foot of shaft sunk.)
Ore trimmers
Rock trimmers
Pumpmen
Track-layers
Skip tender
Track cleaner
$1.85 per diem.
Amount of wages not
ascertained.
The tools of the timber-gang are few. The following is a list
of their whole outfit :
Wax candles 5 per day of 10 hours.
Two saws hand and cross-cut.
Axes one per man (used also as hammers).
120 MINE TIMBERING
Spikes various sises (1-12 in. kmg).
Ropes various sixes.
Chain 8 ft. long.
Timber truck.
Log pike.
The foregoing informatiou was obtained at Section 16 mine
last summer. The figures given are, to the best of my knowledge,
accurate. However/ the character of the mine is such that rules
of thumb are few and far between. When a problem presents
itself, it is solved according to the ideas of the particular shift-
boss in chaige, subject to the approval of the captain, who makes
his rounds every morning.
OTHER CONTRIBUTIONS
THE FRAMING OF RECTANGULAR SHAFT SETS
BY WILBUR E. SANDERS
SQUARE-SET PRACTICE AT BINGHAM, UTAH
BY LOUIS S. GATES
SQUARE-SET TIMBERING AT BINGHAM, UTAH
BY CLAUDE T. RICE
MINE TIMBERING AT LAKE SUPERIOR
BY W. R. CRANE
TIMBER AND TIMBERING IN THE COEUR D'ALENE
BY J. H. BATCHELLER
TIMBERING AT THE CHILLAGOE MINES, QUEENSLAND
BY T. J. GREENWAY
TIMBERING IN TASMANIA
BY MARK IRELAND
THE FRAMING OF RECTANGULAR SHAFT SETS*
By Wilbur E. Sanders
The support most frequently employed for preserving the
integrity of vertical and inclined shafts consists of a rectangular
frame of timber, the parts of which, proportioned to any required
dimensions, are so fitted together at the joints as to form a con-
nection that will weaken the timbers forming the "set" or frame
in the least possible degree. Many methods of framing the joints
have been employed and many forms of joints used, but those
described below are now almost universally accepted as affording
the greatest possible strength while being at the same time of
comparatively simple construction. Their present general use
may be said to represent a survival of the fittest. (See Fig. 98.)
The connecting joints between the different timbers that are
assembled to form the shaft set are made up of various shapes
of the tenon and mortise, the gain and the miter, used either
singly or in combination, which are the basis of all joint framing,
however much they may vary from their simple forms when
employed as shoulders, squared or beveled; and all other con-
trivances whatsoever for bringing together from two or more
directions the parts of the set and properly connecting them at
such points. In general it may be assumed that the pressure
thrust is directed from without inward toward the center of the
shaft, and it is for the purpose of opposing or resisting this pres-
sure that the shaft set is designed. This hypothesis, however,
is true only in part; for through causes that are sometimes known,
but often are unknown, the action of this inward pressure becomes
deflected from a normal direction to one that bears upon the
frame at a divergent angle, and this is especially true with regard
to inclined shafts in certain formations. In such cases the
remedy is usually applied whenever it may be necessary, subse-
quent to the timbering of the shaft.
» From Engineering and Mining Journal^ March 10, 1904, Vol. 77.
123
124
MINE TIMBERING
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MINE TIMBERING
125
The several parts of shaft seta are named with regard to their
position relative to the shaft. Primarily the frame consists of
the timbers of the rectangiilur set proper, together with those
distance pieces, called "posts," which retain it in position at a
required distance from the adjacent sets above and below. The
rectangular set of the frame is made up of jointed tiniVjers that
are known as "plates." While all of the plates of a set are
properly wall plates, yet there is a distinction usually made in
that the longer pair, those paralleling the greater axis of the
shaft, are named " wall plates " in contradistinction to the shorter
pair which are in line with, or parallel to, tlie shorter axis of the
shaft, and which are known as "end plates," or briefly "ends."
This designation ia now generally applied to the plates of both
the vertical and inclined shafts, although it is probable that the
name originated in connection with the timbering of the latter,
in which the longer timbers of the set, the one supporting the
hanging wall and that supporting the foot-wall of the working,
naturally were called wall plates, and this significance of the term
was finally extended to comprehend the similar longer plates of
vertical shafts as well.
The above are parts belonging to the simple rectangular set
of the single or one-compartment shaft, but the cross-eectional
area of larger shafts is usually divided, for purposes of traffic,
ventilation, and the accommodation of mining appliances, into
two or more compartments separated from one another by divi-
sional girts or "centers." In sinking through firm ground the
bottom of the shaft is frequently excavated for a considerable
distance ahead of, or below, the timber supports, in order that
ample space may Ite afforded for the placing of the shaft seta,
and to remove the timbers thereof from any possibility of being
shattered or displaced by heavy blasts beneath. This allows the
use of undivided full-length wall plates. In some ground, how-
ever, this is not permissible, and the material surrounding the
shaft, through which it is being driven, may be of such texture
as will make it imperative that the timbering shall closely follow,
if indeed it does not crowd, the excavation of the working. Under
such conditions the use of full-length wall plates is impossible,
and therefore it is necessary to divide or "splice" such timbers
that they may be brought into position. The girts act as distance
pieces between the plates in order to preserve the width of the
126 MINE TIMBERING
shaft. At the points of division of the wall plates, at the splices,
the girts are known as "splice centers," while those used to
separate the compartments, at such other points of the wall
plates as are not spliced but solid, receive the simple designation
of "centers."
Such being briefly a description of the different parts that
are assembled together to form the rectangular shaft set, I will
proceed to discuss the methods whereby the timbers are cut and
framed in order that they may properly and truly join together
and fit exactly at the joints. (See Fig. 99.) I will assume that
they are of the desired length, and that they are square-sawed to
the required cross-sectional area; but in the latter instance they
are certain to vary slightly from the exact dimensions and often
may be more or less twisted. One side or face, therefore, is se-
lected — the most perfect and even one — if there should be
marked imperfections, and this face is taken as a basis of opera-
tions.
It is necessary in the first place that this face shall be true,
that is, without bend or twist as regards both its length and its
breadth. Care in this particular is essential, as it determines the
exactness with which the timber shall fit its companion pieces at
their common joints in the assembled set; and therefore, upon a
perfect plane throughout, or by means of it, depends in large
measure the perfection of the set itself. Where extreme precision
is required, the selected face is worked to straight-edges, sighting
from one to another until at proper points the face has been
worked to line with the assumed plane which is shown when the
edges of the straight-edges are brought to coincide; bends and
twists are removed locally wherever it may be necessary to frame
a joint. In the process of framing many prefer to select for this
face the one that will be the top or uppermost side of the timber
when in its place in the set, and to take all lines, measurements
and angles with regard to it; but for sufficient reasons I believe
that the basis of all framing should preferably be that which will
become the interior face of the piece when the parts shall have
been assembled.
Upon this face a center or base line is marked from end to
end, either by means of a straight-edge or the chalked line, and
all measurements lengthwise along the timber are laid off with
reference to this line, as also are those crosswise lines which
MINE TIMBERING
127
locate and outline the shapes of the joints to be framed upon
the selected face, the relative positions thereof having been
established by the measurements. This base line represents a
line at which, should a second imaginary plane be passed length-
wise through the center of the timber at right angles to the
Bvvel
'B«lT«d-teDOO
K
Bplic«-c«uttr Joint ^ ***** .
BalTed-MooB
END PLATE Tw« tkw
Ual'
CENTER Om ft«
^
SPLICE CENTER OMtkM
^
H
Fio. 99. — Laying out and Framing Rectangular Shaft Set.
plane of the selected face, it would cut or coincide with the latter
throughout its length; and this line of coincidence of the two
planes we have fixed upon the face of the timber by marking,
so that we may employ it as a basis for the laying out and framing
of the joints. (Fig. 99, A and B.)
128 MINE TIMBERING
Backward from this face to required distances there are laid
off tenons, mortises, gains and miters that go to make up the
joints which will allow the different parts of the set to be brought
together into one complete and perfectly connected whole.
(Fig. 99 C.) By thus taking all measurements from the base line
toward the top or bottom part of the timber, and by projecting
the points and lines thus established backward from its selected
inner face towards its outer face or back, all troubles due to
twists or variations in the size or shape of the pieces going to
make up a properly framed set may be overcome; and the joints
thus framed will be in their correct relative positions, exact in
size and shape, and they will join accurately with those of the
other connecting parts of the set. It is needless to say that
exactness in the fitting together of the joints cannot be expected
unless all necessary precision has been employed in their framing.
The joints that must be framed in the construction of a set
are: those at the comers of a shaft, which connect the wall plates
and the end plates at their ends; those connecting the centers
and splice centers with the wall plates at the division of the
compartments; and, where it is required or used, the "boxing"
of the ends of the posts into the frame in order to insure that
they shall retain their proper positions. The framing of the
wall plates and the methods of cutting their joints are shown in
Fig. 99 D and E; that of the end plates, Fig. 99 F; of the
centers, Fig. 99 G; and that for the splice center in Fig. 99 H.
The wall plates and end plates are joined together at right
angles to each other by a combination of the tenon and miter,
or "bevel," as the latter is usuall}^ designated. The thickness of
the tenon is just half that of the plate, the measurements therefor
being taken from the center or base line on which is formed one
face of the tenons, their lengths being equal to the widths of the
mating tenons of the joints. The wall plates invariably have
their tenons at the bottom half of the pieces that they may
support the end plates while the set is being placed in position
in the shaft, the tenons of the end plates on the contrary being
framed at the upper half of the ends in order that they may rest
upon and be supported by those of the wall plates when the parts
are assembled. This halving the timbers in framing tenon for the
purpose of support removes just one-half of their cross-section
and thereby weakens the pieces at such points proportionally.
MINE TIMBERING 129
This difficulty is overcome by the use of a half right-angled
miter, of 45 deg., which is framed from the face of the timber
backward usually to a depth of one inch; or, in otlier words,
the piece is so beveled that this milered face will coincide
with and abut against a similar miter that is framed upon the
companion piece, both being placed in the same relative position
within the joint. By means of this construction of the comer
joints of a shaft set it is brought about that the full cross-sei'tion
of one plate engages the full cross-section of its companion plate
at their common end, at which point the two pieces are at right
angles to each other, and thereby it is assured that the full strength
of one of the timbers supports and is supported by the full strength
of the other.
In the case of the simple divisional girts or centers, instead
of tenoning through the width of the wall plates at the joints,
as do the ends and splice centers, they are connected therewith
by a short V-shaped tenon that is mortised into a corresponding
gain framed into the inner face of the wall plates at desired
points, the tenon being narrower at the bottom than at the top
in order that it may not fall or be forced out of its position.
(Fig. 99 G.) The shoulders of this tenon should be constructed
of a width sufficient to engage the face of the plate, whereby it
may afford support to the full size of that timber. The simple
center with some form of the V-tenon is employed for the pur-
pose of dividing the cross-sectional area of a shaft into com-
partments, save only at points where the wall plates are spliced
in order to shorten them so that they may be brought to position
in confined quartern.
Whenever it Iwcomes necessary to shorten the wall plates,
the timbers are so cut that the splice will coincide with the length-
is ise center tine of one of the cross girts or centers that divide the
shaft into one or more compartments. Generally, in the three-
compartment shaft, which has been taken as a type for the
reason that the framing of all of the diflerent joints employe*! in
shaft sets may be shown in simple detail, this cutting in two or
splicing of the wall plates is made to center between the pump
compartment and one of the hoisting compartments. The upper
halves of the wall plates at such points are removed to a width
that is somewhat less than the thickness of the splice-center
, there to be placed, in order that the shoulders extending beyond
130 MINE TIMBERING
the sides of the engaging tenon of the center may furnish support
against side pressure to the full cross-sectional area, and therefore
to the full strength of the plates themselves. (Fig. 99 E and H.)
The posts are not framed, although they should be cut with
precision and their ends properly shaped so that they may come
truly to position and that the effects resulting from any twist of
the timber may be removed. Almost invariably throughout the
metal mines of the western United States gains are framed into
plates and centers of the set into which the ends of the posts are
boxed, the shoulders of these gains being employed to support
the posts in place against the inward thrust of outside pressure.
(See Figs. 98 and 99.) On the other hand, the general practice
throughout the eastern portion of the country, in metal and
coal mining, is to do away with this boxing of the posts, to frame
no gains for their reception, but to set them flush with the top
and bottom faces of the set, and to depend upon the tightness
with which the assembled parts are blocked and wedged into
position for retaining them in their places.
In practice certain variations of these several joints are em-
ployed, oftentimes to advantage, but the above discussion is
intended to describe the practical methods of framing the typical
rectangular shaft set.
SQUARE-SET PRACTICE AT BINGHAM, UTAH*
By Louis S. Cates
Bingham, situated in Salt Lake county, Utah, about twenty-
five miles south of Salt Lake City, has become one of the largest
low-grade copper camps in the West. The ore occurs in large
shoots varying from 50 to 200 ft. in width, from 100 to 300 ft. in
length, and in some cases proving to be continuous in depth
for over 600 ft. These chambers or shoots in most cases have
a well-defined foot-wall of quartzite and a hanging of lime-
stone, although some have been found imbedded entirely in the
lime. There is no well-defined dip to these bodies as with the
veins, and they are found varying in dip from the horizontal to
the vertical.
The ore is heavy, running about 9 cu. ft. to the ton, and carries
on an average 25 to 30 per cent, iron, 20 to 25 per cent, silica,
2 to 5 per cent, copper, $1 to tS gold, and 1 to 4 oz. silver. In
mining this ore great care is exercised, for it is not uniform in
texture, changing in a very few feet from hard compact sulphide
to a soft disintegrated silicious ore, which, imless caught up, wdll
run and cause a cave. The large size of the orebodies, the vari-
able texture of the heavy ore, and the added disadvantage of
having a heavy hanging wall, have made it necessary for the
square-set system to be universally used in mining the large
shoots.
The larger companies use finished Oregon pine timber which
is framed before shipment, while the smaller ones frame their
timber at the mine.
The sills are framed from 6xl0-in. timber cut 5 ft. long, dapped
1 in. on each end and cut in 4.5 in. in order to support one-
half of the posts on each end, as shown in Figs. 100 and 101.
Occasionally, where long caps are used in order to leave out a
* From Engineering and Mining JoumcU, August 25, 1904, Vol. 78.
131
MINE TIMBERINQ
MINE TIMBERING
133
post in the sets, so that a curve may be made in the track, a
long 10-ft. aiU is used. Posts are cut from 9xlO-in. timber, 6 ft.
8 in. over all, and are framed on one end only, the base setting
into the sills 1 in., and the top having a tenon 1 in. long and
6x7.5 in. The caps are framed on both ends, as shown in the
sketches, from lOxlO-in. timber, and since they are framed down
into the posts 1 in. it is evident that the sets are 5-ft. centers on
the sill and 7 ft. 4-in. centers in elevation. The braces are made
Fig. 102. — TRANSVEReE Sectiu.v
from 6xl0-in. timber cut 4 ft, 4.5 in. and framed as shown in the
sketch. For lagging, 2x8-in. lumber is used; any heavier than
that is too strong, for it does not bend enough in event of great
weight being exerted, nor give auSicient warning of impending
danger.
The size and extent of the shoot having been determined,
there are two methods of opening up the stopes dependent upon
the character and dip of the orebody and the heaviness of the
banging wall. The preferable method, illustrated by Fig. 102,
134 MINE TIMBERING
is used where the hanging wall is firm and the ore solid, allowing
large chambers to be opened up without danger of excessive
pressure being exerted which would cave the stope. A definite
level having been determined, the sills are laid for the first set
at right angles to the general strike of the shoot. The sills are
only 5 ft*, long, for in most cases it is inexpedient to open enough
ground ahead of the timber to lay longer sills. The sills in place
and tamped down, a floor of single lagging is laid and the four
posts erected. The caps are placed on the posts in the same
relative position as the sills below, and braces are framed to fit
the top of post and cap, thereby completing the square set; no
braces or girders are used to keep the posts on the sills, but in
their stead the floor lagging is laid from sill to sill, and a notch
is cut in the lagging next to the post which acts as a foot brace
and prevents any lateral motion of the post on the sill. A double
floor of lagging is placed on the caps and braces and the set blocked
securely, completing the first set of the stope.
This, first set having been placed in one of the drifts, as near
the center of the orebody as practicable, a row of lead sets is now
started running longitudinally through the orebody; after this
has been done, or the sets have been carried ahead four or five
sets, another row of wing sets is started on one side of the lead
sets, running parallel and adjoining them. The sill floor is opened
up in this manner until four or five rows of sets have been carried
along before stoping on the floors is begun. This method has
been found more economical, for after once getting the lead sets
through, there is an excellent opportunity to slice the ore off
by simply starting another row of wing sets, and it affords more
place for the machines to work than the second method.
The sill floor once opened up sufficiently, the first floor is
opened up exactly as the sill, by driving a row of lead sets over
the lead sets on the sill floor. Care is always taken to have the
sill floor at least two and preferably four rows of sets wider
than the first floor, thereby making it easy to keep the broken
ore on the floors. The second and upper floors are then carried
up, the object being to carry the lead sets right up to the middle
of the body, thereby relieving the weight on the sill floor by
resolving the downward pressure of the orebody into two com-
ponents, a horizontal one resisted by caps and braces, and a verti-
cal component resisted by posts. The stope then should resemble
MINE TIMBERING
135
a pyramid of blocks, with each lower layer extending one or two
blocks beyond the next higher. After the lead seta have been
carried up in this manner the floors are opened out by continual
slicing until the walls are reached.
The second method, illustrated by Fig, 103, is used where
the hanging wall is very heavy and there would be great danger
Fio. 103. — Transverse Shction
of a cave were the firet method used, and especially where the
nature and extent of the orebody is not known. In this case,
as in the first, sills and cape are placed at right angles to the
general strike of the shoot, but instead of starting at the center
of the body the firet set is placed as near the hanging wall aa
possible and the lead sets driven along the hanging. This row
being driven ahead, a second row is started adjoining and parallel
136
MINE TIMBERING
to the first. After two rows have beea driven, stoping is begun
immediately by starting a row of seta directly over the second
Bill row and carried up by auccessive floors until the hanging
wall is reached; when this is done, another row is driven on the
sill floor and the sets carried up to the hanging wall. The stope
ia continued in this manner until worked out or it ia advisable
to cave it and start a new one.
Fio. 104. — Shoi
The double advantage of this method is manifest. First,
there ia always a solid breast of ore on one side of the stope, which
greatly relieves the pressure on the timbers; second, should the
stope cave in unexpectedly, only the ore on the floors and in the
chutes is lost, for a new stope can l>e opened up by driving a row
of sets on the sill floor, right next to the caved stope. and then
carrying them up to the hanging as before. On approaching
MINE TIMBERINQ 137
the hunging wall it is evident thiit it is not always possible to
remove all the ore and catch the hanging wall up with full sets.
In such cases short sets are used.
Formerly, when a short set was used, the post nearest the
hanging was cut the desired length, and the post in the full set,
into which the small set was framed, was cut the same length.
The cap and braces were placed as in a regular set, then in order
to complete the full set two small posts were framed into the small
set. This scheme took a lot of time and weakened the posts
of the full set.
In order to overcome this disadvantage, a method illustrated
by Fig. 104 is usetl. A glance at this sketch shows that the post
of the short set is placed in the usual position on the cap below,
but instead of cutting the post in the full set in two, the tenon
on the cap is cut off. allowing the cap to butt right up to the post.
The cap is spiked to the post to hold it in position, and a piece
of 2x8-in. lagging resting on the cap below is also spiked to the
post and forms the support. To prevent lateral motion of the
cape on the lagging, two pieces of 2xS-in. lagging are nailed to-
gether and spiked in position to be used as a brace on the end
where the tenon is cut off, thereby holding the cap as securely
as necessary. This method is simple and equally as etEcient
as t he former, as it answers all the requirements.
When mining on the foot-wall, ground posts and butt caps or
butt braces are used, depending on the steepness of the foot-
wall. These methods are shown in Fig. 105, When the foot-
wall is very steep, a piece of lOxlO-in. timber is framed on one
end as a cap or brace, as the case may be, to fit into the full set,
the top is cut 1 in. deep and 9x10 in. to fit the posts, and the
sides 1.25 in. deep by 6x10 in., or 1.25x9x10 in. to fit the brace or
cap, and cut long enough to fit the hitch which is cut into the foot-
wall, deep enough to make the butt cap or brace secure.
In cases where the foot-wall slopes off so much that it is im-
possible to place the butt cap, so that it is resting on solid ground
at the point where the post is placed on it, the butt cap is framed
as before, except that the bottom is cut 1 in. deep by 9x10 in. to
hold a post which affords the necessary support under the post
which is placed above on the cap. Frequently spreaders of lag-
ging are placed, extending from the base of the ground post to
the post of the full set, to hold it in position.
138
MINE TIMBERING
When a post shows signs of weakness, instead of putting in a
false set to strengthen it, angle braces are used. For example,
a post on the sill floor shows signs of weakness; the angle braces
are framed to fit between the top of the post directly over the
weakened one and its cap, and extend diagonally downward
to fit between the cap and the foot of the posts on each side. In
aM
>^s
M
>'■ 'i 'i:
w
Avi
IV
'l '■ 'l 'l ' i
M
3c=r:
■ ' ■
w
iM^
II
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.1 1 . 1. 3:
X^lL,
f'xSV
V
^
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7/
/
ft.
/
FiQ. 105. — Butt Cap and Ground Post.
this manner the load is distributed between two posts, and thus
has the advantage over false sets, especially on the sill floor, of
not decreasing the head room.
Economy is evident in all workings. For often, in shooting,
a cap or brace is shot down on the post, injuring the tenon; in-
stead of a new piece of timber being put in, the old one is knocked
back in position, and a piece of lagging spiked to the side of each
post upon which the injured member rests, reaching to the sill,
or, if on the floors, a cap, thus forming a support on each end
MINE TIMBERING 139
and relieving the pressure on the broken tenon and keeping the
injured timber in place.
In blocking the sets down, care is used to see that the timber-
men always put the blocking as nearly as possible over the posts
and never near the center of the brace or cap, on account of the
leverage exerted on the timber, should the set take weight. When
shooting, especially in hard ground, the timbers are faced with
old lagging, and double floors are used to prevent large boulders
breaking through the floors.
When much waste is broken in stoping, it is not run over the
dump, but, instead, certain sets are lagged up to the hanging wall
and the waste thrown in to be used as filling, making columns
which greatly aid in holding back the ground. When a stope
has been worked out, floors, pipes, ladders and everjrthing mov-
able are taken out and 1-in. holes bored in nearly all of the posts
in the sill floor; powder is inserted and the whole round is shot
by a battery, caving the stope.
SQUARE-SET TIMBERING AT BINGHAM, UTAH »
By Claude T. Rice
At present square-set timbering is mainly used in mining the
orebodies at Bingham Canon, Utah. As the orebodies are mainly
replacement deposits in the limestone along mineralizing fissures,
the walls of the orebodies are generally strong except where the
limestone has been shattered by faulting. Because of this strength
of wall, complete filling of the stopes with waste, such as is the
practice at Butte, Mont., where in some of the squarenset stopes
the filling or "gob" is kept within two floors of the roof of the
stope, is not required.
Mining Methods
Consequently the orebodies of Bingham are mined without
much waste filling, thus resembling the open square-set stopes
of some of the Leadville mines w^here the ores also occur in lime-
stone. Whenever a stope shows signs of a "taking weight" a
few square sets are lagged and waste is dumped into this pen,
forming a waste-filled bulkhead which helps materially to steady
the stope. These "pen" bulkheads work so satisfactorily that I
failed to see any wooden bulkheads such as are used in some of
the Boston & Montana mines at Butte.
The chutes are simply plank-lagged square sets with occa-
sional offsets to break the fall. Owing to the softness of these
sulphide ores there is no excessive amount of cutting of the
lining of the chutes, and consequently neither "bricked" chutes
nor the open staggered chutes which characterized the open
square-set stopes of the Homestake mine, at Lead, S. D., are
necessary. Two-inch planks are used for floors in the stopes.
Owing to the strength of the ore and the little tendency it has
to scale off, the roof sets of the stope generally do not have to
* From Engineering and Mining Journal, Nov. 3, 1906, Vol. 82.
140
MINE TIMBERING 141
be lagged, another feature which makes the timbering and mining
cost in Bingham Canon square-set stopes much less than at
Butte, Montana.
The Squabe-Set System
However, the mine managers at Bingham have not been
quite satisfied with these advantages, but have designed, in order
to save timber, a specially framed square set, which, at least as
Fio. 106.
PtnpecUnVlfw
SUtVIa,
- Details of Square-bbt Tiuberino.
far as my experience indicates, is' peculiar to these mines. This
system was first used at the Highland Boy mine of the Utah
Consolidated and has later been adopted at the near-by Boston
Consolidated mine. It has proved so satisfactory that the same
framing of square sets is used at the Cactus mine at Newhouse,
Utah, which like the Boston Consolidated is under the control of
Samuel Newhouse.
On the Comstock lode the original square sets were framed
as designed by Philip Deidesheimer, with the horns of the posts
142 MINE TIMBERING
butting against those of the posts below. This framing is still
retained in the few square sets used at present on the Comstock.
Whether the downward pressure there is greater than the side
pressure, as the framing would indicate, I do not know, but I
could not help noticing this feature of the framing of the original
square sets, which to me at least is unique; for although I have
worked in many mines, and visited many more, in which square-
set timbering is used, I have not seen elsewhere this feature of
butting the posts against each other.
Peculiarities op the Bingham Practice
At Bingham Canon the sets are designed to offer the greatest
resistance to side pressure and so the horns of the caps are caused
to butt against each other, the cap being 10x10 in. square.
In this butting of the caps there is nothing unusual, but in the
posts we have the unique feature of a piece rectangular in section
instead of square, the post being 10 in. wide in the direction of
the girts and 9 in. wide cap-ways, thus saving an inch in the
cross-section of the posts. Moreover, the posts have a bottom
and a top end, for they are "bald" at the bottom and have only
a 1-in. horn on top. ^ In consequence of this framing of the post,
the top mortise made up by the assembling of the caps and girts
differs from the bottom mortise, and so there is a top side and
bottom side to the caps and girts. This at first confuses the
green timber man used to caps without a bottom or top side,
but of course this is no valid objection to this square set. Nat-
urally, it is necessary to have a tenon on the top end of the post
on which to rest the caps and girts. As the bottom of the post
rests on the caps and girts it does not need to be framed, but it
seems to me that it would be just as well to have the top and
the bottom ends of the posts similarly framed with horns, for
then there would be no such complicated arrangement of framing
as the present design demands in the caps and girts. True, that
would cause an extra pass of the post in the framer, but it would
avoid the special framing of a cap only on the top side of the
girt. If the similar framing of both ends of the post were adopted
the girt would be a plain GxlO-in. timber resembling the girt
used by F. A. Heinze at the Cora-Rock Island mine at Butte,
Mont., where (if my memory be correct) the girts are plain,
MINE TIMBERING 143
8x10 in., and the posts are 10x10 in. with horns on both ends, and
the caps are 10x10 in. butting up against one another.
Criticism op the System
This making of the girt only 6x10 in. in cross-section ap-
pears to be a step in the right direction; for the purpose of
the girt or tie, or, as it is better called in some camps, the brace,
is mainly to resist the side movement of the caps and is not to
resist any great inward pressure in the stope as is the function
of the cap. Consequently the girt does not have to be as strong
as the cap. In my opinion it is a waste of timber to make the
girts equal in cross-section to the caps.
Another feature that strikes me as worthy of consideration is
the fact that although the vertical distance in the clear between
the caps and the posts is 6 ft. 5 in., the distance in the clear cap-
ways and girt-ways in the sets is only a little over 4 ft. It might
be possible to increase this distance, and effect still more economy
in the timbering without endangering the stope, but this last
matter of course is a point for men well acquainted with the
ground to decide, and undoubtedlyit has been given much thought
by the Highland Boy management, which is noted for its high
efficiency. I mentioned the point only because of the striking
difference in these dimensions, which the managements of these
mines have thought necessary. The only drawback to the girt
being as narrow as 6 in. is the ease with which a floor can be
torn up by a heavy blast in the stope, unless the floor is tightly
wedged in place, for it has only a 3-in. hold when laid cap-
ways. But this, of course, is a very small drawback.
All these timbers are framed at the mills in Oregon and
Washington, and are shipped ready to go into the stopes.
The arrangement of the sets is shown in Fig. 106.
Owing to the fact that the dimensions were scaled to the
timbers themselves and not taken from a drawing, there may be
some slight mistakes (even J in.) in some of the dimensions, but
the dimensions of the sets are in the main correct.
MINE TIMBERING AT LAKE SUPERIOR ^
By W. R. Crane
Much timbering is done in the copper mines of northern
Michigan, although in many of them the use of timber is confined
almost exclusively to the shafts, pillars being depended upon for
support of the hanging wall in the stopes. The problem of
support of workings several thousand feet distant, vertically,
below the surface is becoming more difficult of solution with the
lapse of time, owing to the rapidly increasing area of workings
only partially supported, and to a less extent to the collapse of
the supports, pillars, or timber in the upper levels. The enormous
loads thrown upon the hanging walls of large open stopes, which
are supported by pillars or timbers of only a very small propor-
tionate part of the total area exposed, must ultimately cause
their disintegration, which, when it occurs, may start a move-
ment that may be very slight, yet the results would be difficult
to conjecture.
Where portions of the vein filling are left for support of hanging
wall, the idea is to remove ultimately as much of it as possible
before it collapses and before any fall of roof would interfere
with the operations carried on below. No systematic attempt
has been made to rob pillars, except in the filling system, in which
case those left standing and finally removed are the floor or chain
pillars. That none too large pillars are left for the support of
the hanging wall is evidenced by the rapid breaking up of such
unmined portions, and that, too, in the course of but a few years.
Timbering may be used as an auxiliary to pillars, and alone,
even, as temporary support, and is in fart employed extensively
both ways. Probably mine support by timbering is carried on
most extensively and systematically in the Calumet and Hecla
and the Tamarack mines, which are among the largest and deepest
in the district. It would seem, after the disturbances which have
» From Engineering and Mining Journal^ Nov. 10, 1906, Vol. 82.
144
MINE TIMBERING
145
recently occurred m several nf the mines of this district, that
ultimately filling of t!ie stopes with waste must be the solution
of the problem of support. No attempt is made in this connection
to give details of all of the forms of timbering employed, but
rather to make note of only a few typical forms which have come
under our observation.
TiMBEHiNO IN Shafts
The method of sinking practically all of the shafts through
the surface materials, which are usually sands and gravels, b by
drop shafts, consisting of frames and
Btnddles forming sets, to which ad-
ditions can be made indefinitely. These
sets, when securely bound together by
bolts and inclosed in a sheathing of
lagging, maintain the shape and aline-
ment of the shaft and keep out any
quicksand that might enter otherwise.
Below the point where the surface
materials terminate, and where the
shafts enter solid rock, often no
timbering is necessarj', for a time at
least, the excavation being self-sup-
porting.
The arrangement of the timbering
used in self-supporting excavations is
shown in Fig. 107. The long sleepers,
running transversely with the shaft,
are set in hitches cut in the sides of L .
the shaft, and are carefully alined
with the finished portion. Timbering
in this manner is done in reverse order
to shaft sinking, i.e., is carried on from
below upward, the object being to fa-
cilitate matters. Timljers are placed Fio. 107.-
up to the rock pentice, which is left
. as a protection to the operations in the shaft below, and
liwhen it is removed, only a few pieces of timber remain to be put
a place to complete the support of the tracks, ladders, etc. The
146
MINE TIMBERING
alinement of sleepers placed in this manner is rendered consid-
erably more difficult than if carried downward continuously frouGi
the finished shaft above, the work of alinement having to be
carried on through the small sinking shaft and to a point 100 ft.
below the end of the working portion.
\w;//\V\U'<^n^)>^>sn\V):.
Fig. 108. — Level Timbering and Square Setting.
1. Sill
2. Foot Knee
3. Hanging Knee
4. Post
5. Stull
6. Filler
7. Starter
8. Hanging Post
9. Center Post
10. Studdle
11. Leg
12. Double Ender
13. Lagging
14. Bottom Wall Plate
15. Wall Plate
16. Blocking
17. Stull
18. Post or Strut
19. Flat Cap
20. Props
The sleepers having been placed and securely wedged in
position, the ties are next put in jx)sition, being set alternately
with ends overlapping. The sleepers are 12x12 in. by 17 ft.
8 in. and are spaced 8 ft. apart, center to center. There are six
7x8-in. or 7xlO-in. ties placed between two adjacent sleepers.
A partition 4 ft. high separates the hoisting compartments from
the manway, which is 4 ft. wide. Posts (10x10 in.), set be-
tween the foot- and hanging w^alls, support the 2-in. planking
of the partition, which serves as a protection against falling rock
MINE TIMBERING 147
to men passing up and down in the manway. Wooden ladders
are fastened to the sleepers as shown in Fig. 107.
On the up-shaft side of the sleepers are fastened planks, which
extend from the top of the sleepers to the bottom of the shaft
excavation, thus dividing that portion of the shaft flush with the
tops of the sleepers and ties into sections or pockets, as it were,
by the plank dams. These sections are filled with fine mine
dirt, the placing of the dirt being accomplished by a small skip
of about two tons capacity, which is provided with a small gate
at the lower part of the rear end. A load of dirt is hoisted to
the point in the shaft desired and the gate is opened by simply
unlatching it, when the dirt runs out and is spread largely by
gravity.
Concrete Lining
When the shaft excavation is not self-supporting, the framing
employed in the quicksand and other surface materials, or similar
forms, is resorted to, usually, however, without lagging. Aside
from timbering, concrete linings are occasionally employed, which
reach from the surface to bed rock, with which connection is
made, thus effectively shutting off the water that is often en-
countered in large quantities in the loose surface accumulations
of gravel and sand. Concrete is also used in the rock excavation
of shafts, where it serves as support for the tracks, being built
either in transverse ties or longitudinal stringers for the rails to
rest upon and be fastened to by long bolts passing through plates
in the body of the structure. •
Timbering in Drifts and Stopes
In the workings, i.e., levels and stopes, timbering takes the
form of stulls and square sets, and all imaginable combinations
of the two. In the deeper levels of the Tamarack mines, stulls,
both in the form of individual members and in groups of three
or four, set close together (commonly known as batteries of
stulls), are extensively employed. The batteries are spaced from
8 to 10 ft. apart and may be used in combination with individual
stulls. Stull timbers range in size from 1 to 4 ft. in diameter.
They are carefully measured and cut on the surface, and then
carried below and set normal to the lode, being wedged fast.
148
MINE TIMBERING
♦
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1
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t
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T
or
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1
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o
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n
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en
MINE TIMBERING 149
The arrangement of timbers employed in levels, which serves
as a basis for the building of square sets in stopes, is shown in
Fig. 108. Further, square setting may be stopped at any time
and the face of the timbering covered with lagging as shown.
One form of square-set joining is shown in Fig. 109. The forms
of the individual members are shown in three projections each,
from A to G, while in H is shown a combination of A, B and C
(a joint for a standard set), and in I are grouped F and G and a
form of C. The arrangement of timbers shown in H is a plan of
the joint at A, Fig. 108, while in I is shown a plan of the joint B.
The blind double ender D is used with B and C in joint at C,
In H and I the dotted lines represent the members above and
below the plane of the plan given, always similar, but not neces-
sarily vertical.
Timber caps, or wall pieces, usually rough round logs, are
also employed, being supported by pack walls built along the
lines of the levels. A lagging of rough poles is placed on the
caps and waste rock piled on these in turn. Levels are thus
formed and maintained in the Baltic and Trimountain mines,
where filling methods are employed; often as much as 30 to 50
ft. of waste filling may rest upon the caps.
Timber as a means of support for the mines has a wide range
of usefulness in this district and will always be an important
factor in mining regardless of the methods employed.
TIMBER AND TIMBERING IN THE COEUR
D'ALENE »
By J. H. Batcheller
The timber principally used is fir and tamarack. Bull pine,
in large sticks, seems to mildew and rot too rapidly for good
service, though in the form of planks, spiling, track ties and
wedges it does well enough. Fir and tamarack seem to resist
decay equally well, even in old workings. There is, however, one
limitation to the use of tamarack: it bears end pressure well, but
is too brittle to give good service under any side or transverse
stress. Because of this failing, tamarack is rarely sawed into
square timbers, such as caps, ties, etc., but it is cut into posts,
stulls, helpers, angle braces, sprags, poles, chute cribbing and
chute lining. Fir not only serves for all of the above, but is also
cut into sills, caps, ties, and plates.
In a general way, there are four different principles recognized
as making for economy in timbering: first, the utilization of
all the products from cutting the raw material; second, the use
of simple, framed joints; third, the adapting of the size and
number of timbers used to the duty required; and, fourth, the
use of a uniform system of timbering throughout the mines.
The saving under the first head is accomplished in the follow-
ing way: The trimmings made in squaring timbers are cut into
5-ft. lengths called "slabs/' which are used in covering square
sets under bulkheads, and in cribbing waste-fillings. The ends
of large round timbers — too short for squaring into cap)s, ties,
or collar braces — down to about 2.5 ft. in length, are framed
with a top tenon 4x4x7 in. long (Fig. 110) on one end and
left flat on the other. They are used for foot-wall stope-set
posts (Figs. 115 and 116). Ends shorter than 2.5 ft. are cut
into wedges.
» From Engineering and Mining Journal, Sept. 15, 22, 29, 1904, Vol. 78.
150
MINE TIMBERING
151
The planks — 2, 3 and 4 in. thick — are purchased ready
cut. The 2-in. planks are used in chutes, flooring, and as
Bpreader boards in tunnel sets. Three-inch pisnks, 5 ft.
long, are employed for flooring and short chutes. Three- and
4-in. planks 8 and 10 ft. long are used in temporary slide chutes
in newly started slopes, before they are cut out high enough for
permanent cribbed chutes. The lagging is split cedar, 5 ft.
long, and used in bulkheads (Figs. 113, 114 and 115], waste cribs,
'w
mm
PUaolUulUud
Fics. UQ-114. — SaUARE^ET TlMBBIta.
and as temporary sprags and blocks, around newly erected square
sets. The economy of material is almost perfect. A given stick
of round timber will yield but little to go into the refuse pile, as
the series of useful articles runs from quadniple ties 19 ft. S in.
by 8 ft, 10 in., down to short chute cribbing 3 ft. 10 in. long
by 4 in. diameter.
Under the second principle governing economy, a system of
framing has been worked out to conform with the idea, first,
that the less the end of a timber ie f ut to make a joint, the stronger
the joint; and, second, that all joints are a source of weakness.
152
UINE TIMBERING
Simple joints not only economize material, but cost less in framing
and in labor of erecting. Under the first, note the framed ends of
the aqua re-eet timbers (Fi^. 110. Ill, 112 and 115), of the tunnel-
^set timbers (Figs. 118 and 119), and of the shaft set limbers
(Figs. 120 and 121).
In the framing of square sets there are several advantages in
having the top tenon of the post longer tlian the bottom one.
This arrangement leaves only a shallow hole, the bottom of which
is easily reached with the fingers, to be cleaned out of the joint
to make ready for sloping a new post. At the top end, the longer
tenon not only gives a better hold on the newly placed cap and
tie, but also gives a better chance to block the post itself to the
FiQ n->
-■mjiahe-bet Timbers.
ground. The straight tunnel-set timbers have no framing what-
ever save only the shallow notch cut on the inside of Ihe posts.
at the top. This serves merely as a shoulder on which the spreader
board can rest. In the battered seta, the under side of the cap
Ls notched at the ends, to leave a portion in the center for a
spreader to the posts; then the ends are beveled merely enough
to give the square ends of the posts a firm seat. In both styles
of sets, the full cross-section strength of the posts is retained.
The loss of strength to the cap of a battered set, from notching
the under side at the ends, is partially made up by its ha\-ing
less distance to span than the straight -fiet cap. The inclined-
shaft sets are of far greater strength, under this system of fram-
ing, than under the vertical-shaft system, where the plates are
MINE TIMBERWG
153
joined ^ith half-splice tenons. This method is possible in in-
clined shafts, where the end plates carry but little side pressure,
and it gives full cross-section strength to the timbers holding
the wail plates.
In recognizing that all joints are a source of weakness, note
the use of double, triple, and quadruple ties (Tigs. 116 and 117).
At first thought, it might seem that this point does not concern
the matter of "simple framed joints," However, as there is a
154
MINE TIMBERING
limit to the length and size of timbers that can be used, there
will have to be many joints. By using long ties, the joints where
they are supported by helpers are the simplest and strongest for
s
a
i^
e*« •"
e\ 8"
BATTERED TUNNEL SET
rJ^.
Ml
.^
-__!__
STRAIGHT TUNNEL SET
OCALE
■ ■■■■I
12 FMt
Fig. 118. — B.\ttered axd Straight Tunnel Sets.
the work, as they are merely butt-end bearings. Owing to the
limited .^ize of the drawing, no full-length quadruple tie is shown
in Fig.*<. 116 and 117. They are, however, extensively used on
MINE TIMBERIKO
155
the sill and second floors of stopes. Above the serond sets in &
stope, they become impracticable because their length makes
them too difficult to handle. Triple ties can be used in many
places for three or four sets up, but at last they, too, are dis-
carded when it becomes too difficult to get them into place.
Double ties can be turned anywhere, and are used wherever
possible.
The third principle — that of adapting the size and the
number nf timbers to be used, to the duty required — is illus-
trated in every feature of the methods of timbering, and consti-
tutes one of the most important points of economy. The term
"duty" must be understood to mean not only the amount of
immediate weight a timber must hold, but also the probable
future weight and length of time it will be desired to hold. Note
(Figs, 116and 117) how the light stope sets are used like stagings
to work on, while the weight of the ground is carried principally
by the waste filling. Where the ground gets too heavy for the
stope seta alone, the small, inex[)ensive, unframed helpere and
angle braces are put in alongside of the square-set posts to give
local relief, sufficient to serve until filling is completed around
these places. On the top floors, wherever suspicious pieces of
ground threaten to fall in large masses, big stulls, sometimes
footed against the timbers, and sometimes on the filling, are put
I in temporarily until the ground is taken down and square sets
f erected.
Two sizes of helpers are used: Center helpers, 8 to 10 in. butt
L diameter; and side helpers, 6 to 8 in. diameter. Center helpers
156
MIXE TIMBERING
are placed under the long tiea, in the positions where framed
posts would come, if the seta were of short length. Side helpers
are put next to framed posts to hold up the failing ends of caps
and ties. Angle braces are put in to prevent the seta from
"riding" (or leaning). The tops and bottoms of the posts,
against which they are set, must have either tenons or sprags to
hold against the side thrust. This merely means that angle
braces do no good if placed against the flat-bottomed helpers
unless the latter are strongly held from being pushed out of
position. Sometimes two angle braces are put in to lean against
e:
31
30
,-1 -■-■ 1
1
i
PLAN
•
m
.-.
3, .-..■
^
"s
i
'3
ELEVATION
i.j !..;
;J
MPAitTUE.vT Shaft.
each other, like a triangular truss, fo take the place of a post, or
center helper (Figs. 116 and 122). In this case the object ia to
take all possible weight from above the center of a drift and
transfer it to the sides. .\11 angle braces, stulls and helpers are
sawed to measure at the time of erection, and are cut to drive
home tight. They are always put in butt-end up, as it has been
found they do not split lengthwise as readily that way as with
the small end up.
The use of long ties — when the ground docs not break too
short to he opened up sufficiently — offers a number of advan-
tages. Not only does it save one, two, or three framed posts^
MINE TIMBERING
respectively — as the ties are double, triple, nr quadruple length
— but also just twice the number of caps as posts (that is, two
caps for each post). Further, there is a saving in size of the
limbera put in the place of the posts. The strength of a 9-in.
center helper is greater than the transverse st.rength of the
SxlO-in. tie on top, for the latter will almost invariably break
first, or mash down, or turn over, before the helper fails. This is
a saving of two inches in the diameter of the timber, for framed
posts, on an average, are never less than 11 in. in diameter when
„ ,.-. „■ ^
-.
a
'9
2
•i
7
1 .,.,.
•i
T
1
ELEVATION
t
Fig. 121. — F
round, and they are. of course, cut from still larger timber when
squared to 10x10 in. In place of the two caps saved where
each center helper goes, small sprags or girts are put in and
driven tight.
Besides the matter of economy, the long ties have the advan-
tage of greater strength. Where a tie extends over the top of a
helper, all the top fibers of the timlier lend their tensile strength
to the others in the span, which is not the case where a joint
occurs. The use of long ties has also a marked tendency to
1.58
mXE TUBERIXG
Btiffea the atoipt timben. sod nukes it exaer to bold than all in
l^oml condition tSI fiOing is completed. The MiTwotsec a€ saSoi-
iof the Mope timbeis amouma to a ^nat deal vfaoe cribfaed
ehutes come up emy four aet«, frma me end of the stope to the
other, paiaDel with the pitirh of the oreshoot. As ties are alvsTs
placed aertJBB the stope — from foot to banging — the rfantes
come ap between them. The slope of a rhnte oftai neceasilates
the mnoval of a cap, thus greatly weakening the j«nXs ot tbe
two sets on eitber side. H o w ev er, where long ties aie toed on
either side, at tbe point where a chute r rn r rn a set. thefe are no
caps in the way, and the girt« are moved mcnly enougb to giw
clearance.
- \soLE Braces
The Rystem of using double drift lets (Figs 116 117 and 124),
at points where long life and power to bear great weight are
desired, w another important feature in the timbering practice.
Thcwc HetH are usually put up only where a drift or a station is
to Ite kept open for a long while under a filled stope. As the
ontttidc poHlH and cap in no way affect the inner set, the single
ftet undergoes no break or change where it joins or leaves the
double portion.
The use of a uniform system of timbering permits of a saving
not only in material, but also in labor. All stope, drift, adit, and
shaft sets, and etulls holding filling, are put in 5 ft. apart — center
to center. Flooring planks, slabs, lagging and poles are cut a
bare inch short of 5 ft. long; so tliat they can be used equally
MINE TIMBERING
159
well in all parts of the mine. Another, though minor point, is
that the caps and ties are of the same cross-section; therefore, if
required, a cap can always be framed from a tie. The uniformity
of system lessens the amount of dimension stuff necessary to hold
in stock, and saves many minor delays to the timber gangs
underground.
The foregoing remarks cover some of the details of the methods,
but are concerned mostly with their economic side. There is,
however, an equal or larger number of points that are of great
importance to the efficiency of all timbering. Attention can best
1 PmI
Fig. 123. — Standard Stope Set.
be called to some of these in connection with a running comment
on the accompanying figures.
On comparing Figs. 110-114, 116, 117 and 123 with Figs.
115 and 122, it will be noticed that the latter show round
stope-set posts, while in the former they are shown square.
They were drawn square purely as a matter of convenience, and,
furthermore, though not especially common, posts 10x10 in.
square occasionally come in from the sawmill. The average size
is 1 1 in. butt diameter. This does not occasion any loss in strength
to the square sets. The cross-section area of the lOxlO-in.
stick is only 100 sq. in., as against 95 sq. in. cross-section of the
11-in. round post. Examination of the details of the bearing
••v^t/xx '£ •»pi i3ti '.jet gukkt tia: m. i. Ils^ir-a^ •.
'u^ vaL 's-.-v^ ;',. *•'_ n... tat -Oiii Tft I* stL JL "Tilt ■;
For fill [/rit'-i i'Jil fnirfKiff^ llic fto-sq. in. cross-fief t ion of Ihe
ll-in. f«int. (tiv(« iiM Kmul w;rvifc; as the 'JG-i^f\. in. useful bearing
fiirffn^n <if Hk; lOxlO-iii. \xif1. There l« yet another ad\-an-
(;.(;'', U-njii(« Ihf; wotjornif.'il oti« alreu'ly pointed out. Of the
two ciw'K, th<! pmijil ixift, thoiiith smaller, will invariably l)e the
(■I rori(r»:r, iMrr-niiH; it. i>o>iM*h(w Jill the f^trenpth of the original
oiitHi'h; fil«;rH of the lijnl«T, wliile tlic >iq»areiJ post is weakened
by htivinif thorn cut.
Tl:(; (iK'iKw jfivcri alKivn nhow that the ties ha\-e 50 per cent,
trj'irr; hciiriiiif r^iirfHcc on the jHwtH than the cap!!. This fact
MISE TIMBERING 161
indicates clearly the reason why bulkJieads should always be
Btarted from the ties rather than across the caps. In the details
of a bulkhead (Figs. 113, 114 and 115), observe that the planks
from which it starts are laid across the ties. In erecting, the
lagging is cribbed up till there is not room for more, then blocks
are put in and wedged as tight as it is possible to strike them.
Owing to their inconvenient position, it is often impossible to
jamb the whole bulkhead tight by means of the top wedges
alone. To accomplish this, wedges are driven in at the four
comers below, over the planks, and the whole structure is keyed
up tight. This is of prime importance, for the bulkhead is
needed, not only to hold the ground from slacking away, but in
steadying the square sets from swinging when shots are fired
near by. It is also important that all newly erected timbers
should be tightly blocked and spragged from the ends to the
ground; likewise all flat-bottomed posts and helpers, wherever
they may be in danger of being shot out. It is only by holding
all timbers rigid tliat stope sets can be held from " riding." When
once "riding" starts, it is not only difficult but expensive to
stop.
The foundation planks of a bulkhead are usually cut with a
saw, 5 in. back from ejich end, .5 in. deep, on the sides that overlie
the cape; so that when a new poet is to be erected on top of one
of those by the bulkhead, one blow from an ax will knock off
the 6x5-in. block, and make room, without chopping the
grit-covered planks, for the foot of the post. As the cedar lag-
ging is softer than the wood in the planks and timbers, the con-
dition of a bulkhead always gives first warning, by its state of
compression, of the square sets taking any excessive weight.
Though not shown in the drawing, slabs are frequently used
across the ties, between the foundation planks, to serve as a
covering to the seta. These slabs never carry any of the weight,
but merely keep small rocks from sloughing off on the men below.
Bulkhead material can be used over and over, till too badly
crushed and broken to bear weight. After tliat it — and all
other useless truck — is thrown inio the waste fillings. Where
long ties are used, bulkheads are built in exactly the same man-
ner, in units; only two, three or four are erected to correspond
Kith the length of the tie.
Figures 116 and 117 show some features of interest. After
162 MINE TIMBERING
the timbers around and above the tunnel sets were well secured
by filling, the direction of the sets was changed from having
the ties point perpendicularly to the direction of the adit and
the strike of the vein till the ties lay parallel with the axis of the
ore shoot. The pitch of the orebodies rarely coincides with the
dip of the foot-wall. Most commonly it lies at some oblique
angle. Where the erection of angle sets begins, it is sometimes
necessary to use horizontal braces or sprags, from the straight
(the original) sets, diagonally or comerwise through the angle sets
over to the foot-wall. This diagonal bracing ceases naturally
when the original straight sets are worked out against the hanging
wall of the stope; and the connection between the two classes of
sets is held by filling.
The particular advantage of turning the sets lies in the pos-
sibility of keeping the chutes always along in the stope, and
those that start in the stope at the sill floor can be carried clear
up to the level above. If the sets were continued as begun,
perpendicular to the strike, the chutes at one end of the sill
floor would soon run into barren ground above the ore shoot,
while at the other end the stope would soon reach diagonally up
and beyond the last chute started in ore on the level. From this
level, on this side, it would then become necessary to run raises
through barren ground in order to get chutes up to the stope
for ore. There would be no way to avoid the condition, for the
ore chutes could not well be made small enough to turn diagonally
up through the stope sets without their being too small for any
service.
Two sizes are used, known as foot -wall and hanging wall
chutes. The former are 4 ft. high by 3 ft. wide in the clear
inside, and the latter 3x3 ft. inside. The chute cribbing is
round and varies from 4 to 10 in. in diameter. The ends are
sawed so as to leave a flat tenon 5 in. long by 3, 4, or 5 in. thick,
according to the diameter of the stick. (Fig. 119.) With a
5-in. tenon on each end, and the inside clearance of 3 and 4 ft.
respectively, the cribbing measure is 3 ft. 10 in. and 4 ft. 10 in.
The inside clearance between stope posts and ties is practically
4 ft. 2 in., so there is ample room in which to build chutes and
make the turn necessary where the angle sets start away from
the straight sets. Manways are made in exactly the same way
as the foot -wall chutes, 4x3 ft., hut are always built entirely
MINE TIMBERING 163
separate from them on the foot-wall. The hanging wall chutes
are made as branches of the foot-wall, so that all the ore can be
handled from one gangway.
Sometimes stopes are started from the sill floor in a slightly
different manner from that indicated in Figs. 116 and 117. Sill-
floor posts S.5 ft. in the clear, with flat bottom and a 4x4
x7-in, top tenon, are used. On top of these regular stope-ties
and cape are placed. Pillars of cribbed filling are put in to hold
the stope above, and a heavy covering floor is laid over the
gangways and stations left open between the pillars. On top of
the pillars and heavy flooring are laid the stope sills proper, for
the regular 7-ft. square-set posts, entirely independent of the
sill floor below. When this procedure is followed, the single
tunnel set is usually enough, and the cap is braced by means of
an extension or heavy sprag put in against the end from a hitch
cut in the foot-wall.
However a stope may be timbered above, it is always started
on good sills. These are covered with stout poles to hold the
filling against the time when the ore in the floor will be taken
out by stoping from a level below.
In closing the comments directe<l solely to stope timbering,
there are some interesting points worthy of comparison between
the 7-ft. clear sets used in the Bunker Hill and Sullivan Com-
pany's mines, and the 6-ft. clear sets u.sed by some other mining
companies. It must be remembered that in each case the thick-
ness of the flooring plunks must be deducted from these measure-
ments, which leaves these sets with 6 ft. 9 in. walking room, as
against 5 ft. 9 in. in the clear for the others. The longer posts
give greater efficiency to the working powers of the men in the
stope. For example, only an exceptionally tall man would be
unable to walk erect, with timl^ers or steel on his shoulders, in a
6 ft. 9-in. clearance. Furthermore, angle braces frequently have
to be put in where a passageway is being used to reach a chute.
A 7-in. angle brace put in across a 7-ft. square set, still leaves
room for a man to nm the average sized iron wheelbarrow under
it; while the same timber between G-ft. posts would stop the way.
As a matter of economy, the longer posts are desirable. It
would take only 41 posts 7 ft. 10 in. long to gain a vertical bight
' of 321 ft. 2 in. against 47 posts 6 ft. 10 in. for the same distance.
[ This means a total saving of 6 long posts, or of one 7 ft. 10-in.
164 MINE TIMBERIXG
poet in every 53 ft. 8 in. In a stope of given hight, there is not,
of couree, any saving in the number of feet of timber put in ver-
tically, but the use of the longer posts saves the cost of one com-
plete floor for the whole stope — caps, ties, general nuiteri^.
and labor — in every 53 ft. 8 in. vertical.
Figure 118 needs but little comment. The battered tunnel
sets are the cheaper, both in material and in the amount of
ground necessary to be broken out. The posts are frequently
given more batter, where the ground is softer and has more side
weight. The drawing represents the minimum amount.
Since they are not put up on sills, battered sets are not used
in places where the floor will be worked out from below. The
straight tunnel sets have top and bottom spreader boards spiked
to the caps and sills. There are several sizes used in the mines,
varying slightly in the hight of the posts as well as in the dimen-
sions of the timbers. The choice of a given size is governed by
the place where the sets are wanted, and the duty they must
fulfil. Double tunnel sets are made by placing an extra laiige
straight set outside of the ordinary single set. Figures 116, 117.
and 118 show the double sets, and 7-ft. square sets erected side
by side from the same floor. The principal point is that tunnel
sets of any style should always be made, as nearly as possible,
free and independent of the stone sets; so that any settling or
swinging of the latter will not affect the gangway.
The inclined shaft sets shown in Figs. 120 and 121 have already
received comment. Where the inclination is not too great, the
V tenon and mortise joint can be omitted, and then a two-com-
partment shaft set becomes nothing more than a two-compart-
ment tunnel set, on a slope instead of horizontal. This latter
method of timbering is successfully used in one 45-degree shaft.
The limits governing its general use would be the amount of side
pressure the end plates would have to carry, and also the increas-
ing difficulty of erecting as the slope becomes greater; since there
would be no V tenons and mortises to hold the end plates from
dropping out while the set was being blocked and wedged.
Figures 125 and 126 show the general arrangement of the
timbers at shaft stations on levels. The dotted lines in Fig. 126
show the chutes cut in the rock, just outside the shaft covering,
connecting the places where the cars are dumped at the station
with the chutes in the bottom compartments of the shaft.
MINE TIMBERING
165
Figures 127 and 131 show some points in detail that are quite
common in use. Figure 127 shows how segments should be
framed to support a long station cap, when the load is uniformly
distributed along the cap. The plane of the joints should be so
cut as to bisect the angle formed by the intersection of the two
Fro. 125. — Two-coHPABTMEST Shaft Station.
adjacent segments. This practically gives them the same shape
and carrying strength as an arch. Figure 130 shows at a glance
how the framing should not be done. The center segment would
not carry any load, but would act merely as a spreader. Further-
more, the vertical side segments would carry but little weight,
while the sloping side segments would thrust almost entirely out-
166
MINE TDIBERIXG
ward. Figure 129 shows the manner of holding up stope timbers
so that a post can be cut off. There is no opportunity for choice
as to how the top ends of the sloping segments should be framed,
but at the bottom ends a method is shown which is better than
in Fig. 130, though not as good as in Fig. 127. The only advan-
tage of this method in Fig. 129 is that the vertical side s^ments
do not have to be as large timbers as in the others. For the
sake of simplicity in the drawings, it is not indicated that the
posts of sets must be held against the side thrust of the s^ments
by fillings or sprags.
Horizontal Section on A-B
Fig. 126. — Four-compartmext Shaft Set.
Figure 131 shows the details of the framing of two angle
braces put in from one floor up to the tie or cap of the set above,
to hold a load concentrated at one point. It is similar to the
method shown in Figs. 116 and 122, save that in this case the
timber supported nms across the direction of the angle braces.
In these cases no sprags or cribbed fillings are necessary to hold
the side posts, for the thrust is resisted by the bottom tenons.
Figure 128 shows how a tunnel may be widened, say to make
room for a double track, without discarding all the timbers in
place. This method, however, cannot be used unless the con-
MINE TIMBERING
167
dition of the ground is favorable, for there is the weakness of
two joints on that side, instead of one. In good ground, the
short side post may even be safely dispensed with, and a hitch
can be cut in the foot-wall for the bottom end of the sloping
segment.
Slight mention has been made of stull timbering. It is a
large and important part of the work, though there are but few
details that seem to lend themselves to description. Neverthe-
less, it calls for as much, if not greater, skill and judgment on
SCALE
1 t S 4 ft fHl
Figs. 127-131. — Details of Framing.
the part of the timberman to point his stulls and balance the
ground to the best advantage, as in any other work. A few
features are shown in Figs. 132 and 133. It is always preferable
to build the chutes on the foot, not only to get all the steepness
of grade possible, but also because it is more convenient for load-
ing cars when the level is run on a bench cut in the foot-wall. It
is desirable to run a level thus, in order that it may be left intact
when the next stope from below comes through the ore left in
the bottom. Sometimes, when the stope is not too high and
MINE TIMBERINO
the elope is sufficiently eteep, no cnbbed chute is built at all.
In this case the broken rock runs down over the foot-wall in a
passage kept open between two rows of stulls, lagged and filled
on the outside. Figure 133 shows a cribbed manway built up
into the stope alongside of the ore chute.
Before closing these notes on timbering in the Bunker Hill
and Sullivan mines, some figures of costs in regard to square-set
timbering will Ijo of interest. Exclusive of the initial cost of
material and freight, the total cost of sqiiare-set posts, caps, and
ties, deliveretl at the mouth of the mine, is as follows: posts,
12.5c.; caijs and ties, 10c. each. These figures include not only
MINE TIMBERING 169
the framing, but also the cost of unloading timber from the ears
at the sawmill, the cutting and squaring, and delivery at the
mine.
The center dimensions of a standard set are 7 ft. 10 in. by 5x5 ft.,
giving a contents of 195.75 cu. ft. Assume, for an example, that
a set is being put up in ore carrying 20 per cent, galena (about
17.3 per cent, lead) with a heavy quartzite gangue. The specific
gravities would be, approximately, galena 7.5, gangue 3.3; and
under these conditions it would take about 8.61 cu. ft. of ore in
place (unbroken) to make a ton. This would give 22.74 tons
for the contents of one square set. There are parts of 12 timbers
in each set — four posts, four caps and four ties (see Fig. 123),
but only one-fourth of each of these can be charged to a single
set. This would be equivalent to one post, one cap and one tie,
at a total cost, for outside handling and framing, of 32.5c. per set,
or 1.429c. per ton.
Especial attention is called to the fact that all of the accom-
panying figures are made from timbers actually in place.
In concluding, I wish to express my thanks to Mr. Stanley A.
Easton, manager, and to Mr. T. H. Simmonds, superintendent,
of the Bunker Hill and Sullivan Mining and Concentrating Com-
pany for the assistance they gave me in gathering information.
TIMBERING AT THE CHILLAGOE MINES,
QUEENSLAND ^
By T. J. Greenway
In working the Chillagoe mines, in northern Queensland, the
conditions are such as render necessary the adoption of some
method of square-set timbering which will permit of the use of
the stunted and twisted local timber without the aid of a saw-
mill. After experimenting with various methods of cutting and
framing round timber, I devised and adopted the method de-
'/MlnmRato
Ooantenank
//ScrevB
.'/„ Iron Plate
' f Stud
^\
SUid
Square Template with Spirit Level
ior Gaging Post Tensions
Angle Template for Gaging
Caps and Stretchers
o,
o
Hi
y_^t^ws^^^
r»a^ " Mirgj^^^TT^"'^^"^^-^-
Tenon
--4-
tsr—
-x-r*iH
--6 7H
POST
Side View
Figs. 134-137. — Templates and Posts.
scribed hereafter, which has now been in successful use for two
years.
The square sets are made up of the usual members, namely,
posts, caps and stretchers. The shape of the posts is shown in
Figs. 135 and 137, and the shaj^e of the caps and stretchers,
which are alike in every respect, is shown in Fig. 138. All are
* From Engineering and Mining Journal, March 16, 1905, Vol. 79.
170
MINE TIMBERING
171
cut from rough-hewn logs which are delivered at the various
mines by timber-getters in accordance with a specification re-
quiring that the logs shall have a clear minimum length of 6 ft.
6 in., ami a minimum diameter of 10 in. The heavier logs are
selected for making the posts, and the lighter ones are used for
making the caps and stretchers.
rmnmrn
CAP OK STRETCHER
mm
CAP OR STRETCHEB,
The various set members are cut to the required shapes and
dimensions by a simple method of sawing and adzing the logs,
accurate measuring, centering, etc., being attained by using the
miter box and the angle and square templates shown in Figs. 134,
136, and 139.
A post is made by fixing a selected log in the miter box (by
means of wooden wedges) with one rough end projecting out of
the squared end of the miter box. This rough end is then cut
off flush with the end of the miter box, and the other rough end
bi cut off to a lenglh determined by the transverse gage cut in
the miter box. The post, after lia\ing i>een thus ciit square and
true to the required length, is taken out of the miter box and
firmly fixed in a suitable saw and frame, and the ends are then
shaped into square tenons by sawing and adzing them to dimcn-
* sions which are gaged and squared by means of the square tem-
plate with its accompanying spirit level.
172
MINE TIMBERING
30
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MINE TIMBERING
173
Fio. 140. — Method of Framing Pobts, Caps, and Stretchers.
174 MINE TIMBERING
A cap or stretcher is made by fixing a log in the miter box,
and cutting it to the length and shape determined by the miter
cuts. It is then removed to a sawing frame, and the beveled
ends are shaped into miter tenons by sawing and adzing them to
the required dimensions, which are determined by means of the
angle template.
The manner of framing the posts, caps and stretchers together
underground is clearly shown in Fig. 140.
With this method of cutting and framing, the use of rough
log timber for square-set timbering presents no difficulties. As
need scarcely be said, such timber is, weight by weight, much
cheaper and stronger than sawed timber, and it can be used in
remote districts where sawed timber is practically unobtainable.
In the Chillagoe district the logs are delivered at the mines at a
cost of from 6c. to 8c. per running foot, and the cost of converting
them into posts, caps or stretchers is 4c. per running foot.
TIMBERING IN TASMANIA ^
By Mark Ireland
The orebody being worked at the Mount Rex tin mine, Ben
Lomond, Tasmania, is about 100 ft. in length by 70 ft. in width.
A face of 15 ft. is stoped over the whole level at one operation,
this hight standing without any timber.
Double lines of logs, 20 ft. in length, and from 10 in. to 1 ft.
thick at the small end, are laid longitudinally, butt to butt,
and breaking joint from end to end of the orebody; they are at
10-ft. centers from wall to wall. The starting logs are single for
the first 10 ft., and their ends are hitched into the solid rock.
These are called "runners," and are the logs which are picked up
as the level underneath Is worked up. The double layer gives a
better chance of picking up. Logs are then laid from the center
of the orebody and at right angles to the runners, the ends being
hitched into the walls.
A space, 7 ft. wide, is left open right through the center of
the orebody, and a similar space through from the cross-cut lead-
ing to the shaft. The cross logs are spiked down, 4 ft. apart,
to the runners. Decking, of small spars from 3 to 6 in. thick, is
then laid down. Timber cribs, or "pig-styes,'' are next built up,
4 ft. wide, on each side of the open spaces previously referred to,
forming a skeleton drive.
The pig-styes are constructed as follows: Two logs are laid
parallel, 4 ft. apart, and upon them, in notches at the ends and
the middle, three cross sills are laid, two more logs are laid uix)n
them in turn, and so on imtil 7 ft. high in the clear Is obtained.
In the spaces between the logs, waste rock is filled in as fast as
built. Strong caps, 12- to 14-in. timber, are then laid 4 ft. apart
across from pig-stye to pig-stye. Decking is laid over these caps
as on the level. Chutes and traveling ways are then built, and
» From Engineering and Mining Journal^ July 22, 1905, Vol. 80.
176 MINE TIMBERING
the level is ready for filling with waste, which is sent down from
the surface.
This method is strong, and very cheap as compared with
square sets. But little dressing is required, only an ax, saw and
auger being required; any rough, but fairly straight, timber will
do. An additional advantage is that no blasting, however heavy,
can injure it.
INDEX
PAGE
Adit-level 4,36
Adits, definition of 36
Alinement of inclined-shaft sets 14
Anaconda mine, Butte, Mont.. . 50
Angle braces 68, 156
Atlantic mine, Atlantic, Mich. . 75, 92
Baltic mine, Baltic, Mich 89, 149
Bamum mine, Ishpeming, Mich. 93
Batcheller, J. H 150
Battered tunnel sets 164
Ben Lomond, Tasmania 175
Benches for machines 114
Bingham Canon 141, 142
Bingham, Utah 131, 140
Boston and Montana mines,
Butte, Mont 140
Boston Consolidated mine 141
British Columbia, mining and
timbering in 75
Bulkheads 70, 140, 161
Bunker Hill and Sullivan Co.'s
mines 163, 168, 169
Burlingame method 51
Butte, Mont 140, 141, 142
Cactus mine, Newhouse, Utah. . 141
Calumet and Hecla mines 144
Camp»)ell, C. St. G 105
Cates, lx)uis S 131
Chillagoe mines. Queensland. . . . 170
Chutes, 49, 82, ^,88.90. 117,140, 162
Comstock lode, Virginia City,
Nev 20, 51, 55, 56, 141, 142
Concrete lining 147
Copper, method of mining 89
PAGE
Cora-Rock Island mine, Butte,
Mont 142
Cost of timbering 64, 168, 174
Cralk's Colusa mine, Meaderville,
Mont 6
Crane, W. R 144
Creeping ground 5
Cribs 16, 41, 68, 114, 175
Cross-cut, definition of 36
Deidesheimer, Phihp. .51,55, 56, 141
Docks 115
Drift, definition of 36
Drift sets 110
Easton, Stanley A 169
Eureka method of framing. . . .50, 51
False sets 7
Filling, waste 5, 42, 50, 70, 96
Forepoling 39
Four-compartment shafts 31
Four-piece set 10, 12, 38
Framing, methods of 50
Framing rectangular shaft sets . . 123
Georgetown, California 56
Girts 38
Glory-hole method 86, 93
Greenway, T. J 170
Halved framing for shaft sets. . 13, 18
Hanging hooks 15, 23
Haulage ways 97, 99
Heinzse, F. A 142
Hemat ite mine, Ishpeming, Mich. 96
177
178
INDEX
PAGE
Highland Boy mine 141, 143
Homestake mine, Lead, S.D.. . . 140
Inclined shafts 10
stations for 13
Ireland, Mark 175
Iron mining 99, 105
Ishpeming, Mich 105
Knob Hill mine, Phoenix, B.C. . 85
Labor in Section 16 mine 1 19
Ladders 34, 119
Lagging 5, 12, 80, 87, 151
Lake Superior, mine timbering
at 144
Lake Superior Mining Co., Mich. 105
Le Roi mine, Rossland, B.C. . . 57, 76
Lead, S.D 140
Leadville mines 140
Levels, timbering of 7, 36, 37
Loose ground, timbering in . 26, 39, 1 12
MacDonald, B 55
Machines, method of setting up . 113
Michigan 75
Millingmethod 86
Mills 116
Miter box, use of, in framing ... 171
Mount Rex tin mine, Tasmania 175
Mud-sills 78
Never Sweat mine, Butte, Mont. 5
Newhouse, Samuel 141
Ncwhouse, Utah 141
Old Ironsides mine, Phoenix,
B.C 85
One-compartment shafts 20
Ontario mine, Park City, Utah. 5
Open-cut method 86
Ophir mine, Nevada 51, 55, 56
Ore chutes 49
Ore-skips 12
Parlee, N.W.
Penning . . .
..75, 101, 102
41, 45
PAGE
Phoenix, B.C 85
Pig-styes 175
Pillars 94, 99, 144
Plank lagging 12
Plumb-bob 14, 24
Pole lagging 12
Pressure on timbers 5
Queen mine, Negaunee, Mich.. . 99
Queensland 170
Rectangular shaft sets, frammg. 123
Reinforcing sets 49
Repairing shafts 25
Rice, Claude T 140
Richmond method 51
Rossland, B.C., mines.. 55, 56, 67,
70,76
Round timbers 7
Running ground, timbering in. . 26
Sanders, W. E 3, 123
Scramming 101
Section 16 mine, Ishpeming,
Mich 94, 105
Shaft sets, locating 22
rectangular 123
repairing 25
Shaft station sets 35
Shaft timbering 108
Shafts, concrete lining in 147
timl)ering of 7, 145
tinil)ering in loose ground 26
timl)ering in running
ground 26
Sill-floor construction 57, 60
Simmonds. T. H 1G9
Single-compart nient shafts 10
Single-piece set 37
Skip-ways 12
Soft Ore Hematite mine, Ish-
peming, Mich 96
Sollars 119
Spiling 27, 39
Spnigging 38, 79
Square-sawed tinil)er 7
Square set, limitations of 67
INDEX
179
PAGE
Square set, shaft timbers 20
system 106
timbering, cost of . . 65
Square sets, in Section 16 mine. 112
in stoping 46
in s^'elling ground . 5
reinforcement meth-
ods 68
Square-shoulder framing 6
Staging 118
Stations 35
for inclined shafts 13
shaft sets for 35
timbering of 7
Step method of excavating .... 63
Straight edge 14, 24, 126
Stulls 10, 42, 78, 92, 112
Swelling ground 5
Tamarack mines 144, 147
Tasmania 175
Three-compartment shafts . . 5, 1 1 , 29
Three-piece set 10, 37
Timber and timl^ring in the
Ck)eur d'Alene 150
Timber, best kinds to use 150
chutes 84
pillars 114
Timbering, cost of 64, 168
cribbed shaft 16
four-compartment
shafts 31
in drifts and stopes . . 147
PAGE
Timbering, levels in loose
ground 39
principles of econ-
omy in 150
shafts 20, 108, 145
in loose ground 26
in running
ground ... 26
stations 35
three-compartment
shafts 29
two-compartment
shafts 28
Tools used in Section 16 mine. . 119
Top-slicing 98
Track laying 76
Trimountain mine 149
Tunnel 36
Two-compartment shafts ... .11, 28
Two-piece set 37
Utah Consolidated 141
Vertical shafts 7, 16
alinement of . . . 24
Wages in Section 16 mine 119
Walling-up system 89
Waste filling 5, 42, 50, 70, 96
Weight pressure on timl^ers. ... 5
Winzes 83
Witwatersrand goldfields 31
Working places, timbering 41
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