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ROCK

EXCAVATING
AND BLASTING

By
J. J. COSGROVE

Author of

"PRINCIPLES AND PRACTICE OF PLUMBING"
"SEWAGE PURIFICATION AND DISPOSAL"

"HISTORY OF SANITATION"

"WROUGHT PIPE DRAINAGE SYSTEMS"

"PLUMBING ESTIMATES AND CONTRACTS"

"DESIGN OF THE TURKISH BATH"

'SANITARY REFRIGERATION AND ICE-MAKING"

"SANITATION AND HYGIENE"

Published by

Rational 3?trc proofing Company

Pittsburgh, U. S. A.

PREFACE

HIS work was called forth by a real
and urgent demand for a book that
would help the young engineer, the
superintendent, the rockman and
miner to understand the mysteries
of explosives; how to handle them; and how to
get the best results in the various kinds of rock
excavating.

It is a well-known fact that schools of engineer-
ing teach the design of engineering works, but
not their construction. A few strokes of the
pen show how a tunnel is to be driven through a
mountain, but there is nothing shown on the
drawings or taught in school, that will point out
how the work is to be accomplished. This part is
left for the contracting engineer to work out for
himself, and the young engineer in charge of
the work, if he has had no previous experience,
must pick it up as he goes along from the rock-
men in charge of the blasting.

As most of the graduates of engineering col-
leges follow the contruction branch of their call-
ing, and in the course of their work are soon put
in charge of rock excavating, either open-cut
work, tunnel driving or shaft-sinking, this work
will be found invaluable to them as well as in the
class room, and in the hands of anyone interested
in quarrying or blasting rocks or other hard ma-
terials.

It is believed that by following the text a person

wholly unfamiliar with blasting and explosives
could intelligently superintend rock excavating or
do it himself. Text and illustrations show how
to drill bore holes to get different results; how
to charge the bore holes ; how to drive a tunnel ;
how to sink a shaft ; blasting in quarry- work and
open-cut excavating; care, handling and storage
of explosives ; and the tools and machines required
in rock excavating.

A copy of this book should be found on the
shelves of every library. It will also be found
invaluable at mines and quarries, in the class room
of engineering colleges, and in the offices of en-
gineers, architects and contractors.

J. J. COSGROVE.

Philadelphia, Pa., September, 1913.

PUBLISHERS' NOTE

HIS is an age of vocational training. The
old system of apprenticeship having passed
away left a lack of skilled workers without
which no nation can be truly prosperous.
Schools and colleges have been established
to supply this lack of technical training,
but schools and colleges can help only those
who come to their doors, thirsting for knowledge.

The great host of workers, however, the very back-
bone of the industrial Commonwealth, are left to shift for
themselves, and carve out of the hard rocks of experience
their own futures and fortunes. Such a system injures
not only the worker, but the employer and State as well;
and within recent years large industrial concerns have
turned their attention toward providing vocational training
for all those interested in their calling.

Railroads not only have traveling instructors and
courses of study for the trainmen, but some of them have
schools for apprentices in their shops; and most of the
railroads do not stop at that, but reach out to help the
farmers, manufacturers and tradesmen along their lines to
produce bigger crops, increase their output, and in every
way improve their methods and make greater profit.

Manufacturers of type-setting machines maintain free
schools to teach the care and operation of their machines.
Manufacturers of plumbing and heating goods have text-
books and free publications of an educational nature pre-
pared, to help and instruct those connected with their call-
ing; and all along the line is found the same awakening
to the importance, the duty, and the benefit of a like course.
In keeping with the spirit of the times, we, as the
pioneer manufacturers of fire-proofing materials for build-
ings, and the largest manufacturers in the world of
NATCO hollow tile building blocks, have accepted the re-
sponsibility thus imposed upon us, to do our share towards
furnishing reliable and readily-available information re-
garding all phases of building construction. In carrying
out this undertaking our monthly magazine, BUILDING
PROGRESS, was started, and the work, "Rock Excav-
ating and Blasting," first appeared in its pages as a serial
article. The value of the information contained in the
series prompted us to put it out in more enduring form,
suitable for ready reference; and this we do just as it left
the author's hands, without one word of advertising any-
where in the book.

NATIONAL FIRE-PROOFING COMPANY,

Pittsburgh, Pa.

TABLE OF CONTENTS

eg? <ty

PAGE

FORCE AND DIRECTION OF A BLAST 1

SINKING SHAFTS THROUGH ROCK 17

TUNNEL DRIVING 23

ROCK- DRILLING TOOLS AND MACHINERY 35

OPERATING DRILLING MACHINES 45

ROCK-DRILL BITS OF STEEL 51

HAMMER DRILLS 69

STONE CHANNELERS 75

POWDER 91

CHARGING DRILL HOLES WITH POWDER 107

DYNAMITE 117

METHOD OF THAWING DYNAMITE 127

DETONATORS FOR EXPLODING CHARGES 147

FIRING BLASTS BY ELECTRICITY 157

HANDLING AND STORING EXPLOSIVES . . 173

LIST OF TABLES

TABLE. PAGE

I. Size of Drill Holes ........................ 12

II. Weights and Specifications of Rock Drills ____ 38

III. Weights and Specifications of Rock Drills ____ 56

IV. Air Required to Run Rock Drills ........... 64

V. Factors for Various Altitudes and Pressures. . 66

VI. Capacities of Hammer Drills ............... 70

VII. Specifications of Stone Channelers ........... 85

VIII. Specifications of Channeling-Machine Steels... 87

IX. Size of Drill Holes for Different Weights of

Explosives ............................. 105

X. Size, Number and Weights of Tamping Bags. . 116

XI. Sizes and Weights of Dynamite Cartridges. . . . 123

XII. Sizes of Blasting Caps .................... 148

XIII. Name and Use of Fuses . . 152

LIST OF ILLUSTRATIONS

FIG. PAGE

1. Hole Made by "Grip" Shot .................. 2

2. Inclination of Drill Hole for "Grip" Shot ..... 3

3. Effect of Blast in Rock Having Two Free Faces 5

4. Effect when Charge is Equal Distance from Two

Free Faces ............................... 6

5. Showing Terms Used in Blasting .............. 8

6. Bench Work in a Quarry .................... 9

7. A "Chambered" Drill Hole .................... 11

8. Effect .of Multiple Blasts .................... 13

9. Rock Removed by Multiple Blast .............. 15

10. Arrangement of Drill Holes in Shaft Sinking. . 18

11. Deep Drill Holes for Shaft Sinking ........... 20

12. Rock Drilling in Small Tunnel— Soft Rock ..... 24

13. Diagram of Drill Holes in Tunnel— Soft Rock. . . 25

14. Drill Holes for Small Tunnel in Hard Rock ..... 26

15. Drill Holes Near Fissures or Faults ......... 29

16. Method of Working Large Tunnel ........... 31

17. Rock Drill on Tripod ....................... 36

18. Rock Drill on Quarry Bar .................... 40

19. Mining Column or Shaft Bar ................. 42

20. Sand Pump ................................. 47

21. Perspective View of Rock-Drill Steel .......... 52

22. Drill Steel for Hard Rock .................... 52

23. Drill Steel for Soft Rock ..................... 53

24. Length of Rib on Drill for Soft Rock .......... 53

25. Cutting Edge on Drill Steel for Soft Rock ...... 54

26. "X" Bit Drill Steel .......................... 55

27. A Swage ................................... 62

28. A "Sow" .................................... 62

29. Cross-Shaped Dolly .......................... 62

30. X-shaped Dolly .............................. 62

31. A Flatter ................................... 62

32. Spreader ..................... 62

33. Swage for Anvil 62

34. Swage for Hammer 62

35. Hammer Drill 72

36. Steel for Hammer Drill 73

37. Method of Using Hammer Drill 74

38. Simplex Channeling Machine 77

39. Duplex Channeling Machine 79

40. Channeler Steels for Marble 81

41. Three-piece Gang Drill Steels for Channeler... 81

42. Gang Drill Steels for Channeling Slate 81

43. Z-Shaped Channeling Steel for Fissured Rock. . . 81

44. Channeled Walls of Chicago Drainage Canal 82

45. Quarrying Dimension Stone with Channeler. ... 83

46. Group of "A" Powders 93

47. Group of "B" Powders 94

48. Method of Charging Drill Hole 110

49. Cartridge of Dynamite 123

50. Kettle for Thawing Dynamite 128

51. Thawing-Box for Dynamite 130

52. Thawing-House for Dynamite 133

53. Steam or Water-Heated Thawing-House 138

54. Dynamite Tray 140

55. Blasting Cap 148

56. Coil of Fuse 151

57. Fuse Attached to Blasting Cap 152

58. Blasting Cap in Dynamite Cartridge 153

59. Fuse Attached to Side of Cartridge 154

60. Fuse Primed for Lighting 155

61. Lampwick Primer for Fuse 156

62. Section of Electric Fuse 158

63. Waterproof Fuse for Submarine Work 159

64. Electric Fuse Attached to Cartridge 160

65. Two Electric Fuses in One Drill Hole 161

66. Two-Wire Circuit for Multiple Blasts 162

67. Three- Wire Circuit for Multiple Blasting 163

68. Joint for Electric Wires 164

69. Two-Post Blasting Machine 166

70. Three-Post Blasting Machine 167

71. Portable Dynamite Magazine 176

72. Detail of Portable Magazine .178

ROCK

EXCAVATING
AND BLASTING

PART I.

DRILL HOLES

* *
CHAPTER I.

FORCE AND DIRECTION OF A BLAST.

IRECTION OF A BLAST.— There is a
popular belief that different explo-
sives behave differently when fired,
some expending their forces down-
wards, others sidewise, while still
others have a lifting, or upheaving, direction.
Nothing, however, could be further from the
truth. All explosions of blasting agents of what-
ever composition follow the line of least resist-
ance, although more or less execution is done
along the line of greatest resistance. For ex-
ample, if a heavy charge of an explosive be fired
close to a stone slab standing on edge along the

Rock Excavating and Blasting

side of the charge, the slab would be shattered.
It would likewise be shattered if it were below
the charge or above it at the time of firing.
While the direction of a blast cannot be changed,
different effects can- be produced by the use of
different explosives, or by varying the charge, as
will be explained later.

The form of cavity produced when a single
charge of explosives is fired in a vertical drill hole

is shown in Fig. 1.
Following the line
of least resistance,
the blast would pro-
duce a cone-shaped
cavity, the size of
the cavity depending
upon the strength
and size of the
charge. If the
strength of the explosive or the size of charge
were not sufficient to dislodge a large amount of
rock, still the cone shape would be adhered to,
only the cone in that case would be smaller,
for instance, that shown by the dotted lines. In
case too small a charge or too weak an explosive
were used, a blowout would occur, carrying with
it a small cone-shaped fragment from near the
mouth of the drill hole. In that case the blast
would act just as a charge of powder in a gun —
it would simply blow out the tamping.

INCLINATION OF DRILL HOLES. — A vertical posi-

Fig. 1.
Hole Made by "Grip" Shot.

Rock Excavating and Blasting

tion is the worst position in which a drill hole
can be made for a key-hole or cut-out blast, for
the reason that there is only one free face for
the force of the blast to break, as the downward
and side pressures are opposed by solid rock.
Action and reaction being equal but opposite, it
follows that in a cavity made by firing a charge
of explosive in a vertical drill hole, the resultant
of all the forces would be along the line of the
drill hole, or from the apex of the cone to the
center of the base, which would represent the line
of least resistance. That being true, a better
method is to drill the hole at an angle as shown
in Fig. 2. This brings the drill hole away from
the line of least resistance and gives an enlarged
free face for the explosive to act upon, with the
result that there is less danger of a "blow out,"
and greater amount of rock will be dislodged.

The limiting inclination of the drill hole is
45 degrees with the free face. With a hole of less

inclination less
rock will be
broken and the
amount will
grow less as
the hole ap-
proaches the
free face, until,
if discharged
at the surface,

Fig. 2.
Inclination of Drill Hole for "Grip" Shot.

the result would be practically zero.

This inclination of a drill hole is important to
3

Rock Excavating and Blasting

keep in mind, for it is the starting point for all
plane surfaces. In the starting of an excavation
for a cellar, for instance, beginning at the center
a grip shot of this description could be fired;
then with this cavity to work from the drills
could be started radiating in all directions, using
the surface for one free face, and the cavity for
another, and inclining the drill in whatever direc-
tion necessary to get the best result.

FREE FACES IN BLASTING. — The more free
faces exposed in the rock to be removed the more
easily can it be blasted. This is particularly im-
portant where the rock taken out is to be used
for building purposes, for it can be taken out
without shattering it to the same extent that
would follow blasting with only one free face.
Further, the cost is kept down considerably by
the greater ease of quarrying from rock having
two or more free surfaces.

The effect of a blast in rock having two free
faces is shown in Fig. 3. If the charge were
placed where shown in the illustration and the
top were the only free face exposed the blast
would remove the rock from a cone indicated by
the triangle a b c. If, on the other hand, the top
were solid rock and the side face free the cone
removed by the blast would be represented by
the triangle a b d. In this case, however, both
the top and side faces are free, and the rock re-
moved by the blast may be indicated by the dotted
lines which almost parallel the solid line c b d.
It will be noticed that, with two faces exposed, the

Rock Excavating and Blasting

blast will remove practically twice the quantity
of rock that would be displaced with only one
face free — that is, it will if the charge is of the
right size and located equally distant from both
faces, so that the bounding surface of the two
craters that would be formed by different blasts

Fig. 3.
Effect of Blast in Rock Having Two Free Faces.

in single face explosions will be along the line a b.
If the charge were located as shown in Fig. 4 at
unequal distances from the faces of rock, the
charge acting on each face separately would
break the cones a b c and d b e, respectively, the
wedge-shaped piece indicated by shaded lines not

Rock Excavating and Blasting

being included in either. When the two faces are
exposed, however, part of the force of the blast
is used to break down the rock in this wedge-
shaped piece, and the crater actually broken out
is that bounded by the dotted lines / b g.

It will be observed that in figuring the rock
removed by a charge the cone-shaped crater

f ' - c

Fig. 4.
Effect when Charge is Unequal Distance from Two Free Faces.

formed by a single drill-hole blast is used as a
base, and from this the amount of rock that can
be broken down by a single shot is calculated or,
rather, judged. The greater the number of free
faces the greater the amount of rock that can be
broken down by a single shot, or, in other words,
a smaller charge can be used to break down a

Rock Excavating and Blasting

certain amount of material when there are two
or more faces exposed than when there is only
one free face; but the amount of rock loosened
will not be proportional to the number of free
faces.

In drilling for a blast, where two or more free
faces are exposed, it may be taken as a rule that
the longest line of resistance, or the distance back
from any one of the free faces, should not be
greater than one and a half times the shortest
line, or line of least resistance, if the maximum
effect of the explosion is to be obtained. Further,
it is better, if possible, to so place the charge
that the shortest line, or line of least resistance,
will be horizontal and the longest line vertical,
so that the weight of rock loosened by the blast
will help break down the mass.

TERMS USED IN BLASTING. — The terms, or
names, used in quarry work and blasting can be
readily understood by a reference to Fig. 5, which
shows a bench, or open ledge, of rock having two
free faces, one the top surface and the other the
front face. It will be noticed that the new face
of the bench of rock is some distance back of the
bore hole, a certain amount of rock being loosened
from that place at each blast. The "burden of
rock" is the mass loosened or broken down by the
charge, while the line of least resistance in this
case is the shortest distance from the center of
the charge of explosive to a free face.

In open-cut work the best and most economical
7

Rock Excavating and Blasting

plan is to break the rock into regular benches.
This rule holds true whether quarrying for the
stone itself or simply breaking out the rock to
remove it. When broken into regular benches
the condition 'of the rock can be carefully ob-
served, the subsequent bore holes can be more
intelligently placed and the machine drills can be
more easily set up and handled.

Fig. 5.
Showing Terms Used in Blasting.

In Fig. 6 can be seen regular bench work in a
quarry, with men at work with "Plug" drills,
cutting plug and feather holes for splitting out
the blocks. The smooth deck space on the several
benches show clearly how much easier this rock
would be to work upon than a space of similar
size broken into irregular surfaces.

Rock Excavating and Blasting

DIAMETER AND DEPTH OF DRILL HOLES. — There
is an intimate relation between the diameter and
depth of a drill hole used in blasting. The drill
hole should not be filled more than half full of
the explosive, while as a general rule the charge
should be about twelve times as long as the diam-
eter of the bore hole at the bottom. For instance,
a bore hole 2 inches in diameter at the bottom
would have a charge of about 24 inches in length.
The diameter of the bore hole should likewise be
proportioned to the line of least resistance, for
if a drill hole of small diameter be carried down
too deep in the rock, or too far from the free
face, the charge will fail to break down the mass
and a blow-out shot will result. Ordinarily a
hole sufficiently large can be made by using a
larger drill than the ordinary when the drill hole
is to be extended to unusual depths. This in-
creased diameter of the hole, which by doubling
the diameter quadruples the charge it will accom-
modate, will suffice for ordinary blasting opera-
tion. Sometimes, however, in quarry work, pre-
paring sites for buildings, in side cuts of earth-
work, railroad and other engineering works, drill
holes twenty feet or more — sometimes as much
as sixty feet — in depth are made and hollowed
out at the bottom to form a chamber or pocket,
into which several kegs of powder or other explo-
sive are introduced to charge for the breaking-
down blast. This form of drill hole is shown in
Fig. 7. The chamber is made by first drilling a
hole to the required depth, then exploding a stick

Rock Excavating and Blasting

of dynamite at the bottom of the drill hole, with
little or no tamping.

This operation can be repeated with increased
charges until a chamber of the right size is ob-
tained. A caution that must be observed, how-
ever, in this method of working, is never to put
the powder or dynamite in the chamber until the
rock has cooled to its normal temperature. Any
attempt to charge the hole immediately after a
chambering or squibbing blast might lead to a
disastrous explosion.

In large operations, like the blowing up of Hell
Gate, New York, a chamber is excavated in the
rock at the required point,
or place, and a tunnel con-
structed leading into the
chamber, so it can be charg-
ed with kegs and bags of
powder or other explosives,
ready for the blast. In
ordinary building and
engineering construction,
however, the drill hole, or
drill hole and chamber, are
about all that will be neces-
sary in the way of a pocket
to hold the charge.

Experience shows that Fig. 7.

drill holes having diameters A "Chambered" DHH Hole,
varying from three-quarters of an inch to iy%
inches are the best for hard rock, if charged with
the strongest high explosives. For soft rock, on

Rock Excavating and Blasting

the other hand, charges of weaker explosives are
best, and they should be in drill holes l!/2 to 2i/£
inches in diameter.

The depth of drill holes will generally vary
with the character of the rock. As low as 4 feet
and as high as 12 feet are not extremes, while
depths of from 5 to 7 feet would probably be
considered the average in built-up districts where
great care must be exercised.

The line of least resistance may be proportioned
to the size and diameter of the bore hole, accord-
ing to Table I.

TABLE I.
Size of Drill Holes.

Diameter of Drill Hole

\Y± inches

inches

1% inches

f Line of least resistance .

. 3K feet

feet

5 feet

\ Depth of drill hole . . .

. 3K feet

feet

5 feet

f Line of least resistance . ,

, 3% feet

feet

6 feet

1 Depth of drill hole . . .

. 5% feet

A feet

9 feet

f Line of least resistance

5 feet

feet

7 feet

I Depth of drill hole

10 feet

feet

14 feet

According to this table shallow bore holes are
made of a depth equal to the line of least resist-
ance; medium depth drill holes are one and one-
half times the length of the line of least resist-
ance; while for deep holes, 10 feet or more, the
line of least resistance is only half of the depth.
In open-cut work in outlying districts, however,
the practice is generally followed of drilling the
holes one and one-half times the length of the
line of least resistance. For instance, in work on

Rock Excavating and Blasting

the Chicago Drainage Canal the holes were drilled
12 feet deep and back 8 feet from the face of
the bench.

EFFECT OF MULTIPLE BLASTS. — A greater mass
of rock can be dislodged by firing two or more
blasts simultaneously than would be broken down
by firing the same shots independently. This
greater effectiveness of the multiple blasts can
be seen by referring to Fig. 8. If the blasts a and

Fig. 8.
Effect of Multiple Blasts.

b were touched off separately, they would break
out, approximately, the amount of material shown
by the triangles in which they are situated, leav-
ing the inverted triangular mass of rock c intact ;
while if these two charges were exploded simul-
taneously, they would blow out not only the two
triangular masses of rock, as when exploded

Rock Excavating and Blasting

separately, but they would dislodge the mass of
rock represented by c as well.

In order to get the maximum results in the case
of multiple blasts, the drill holes must be approxi-
mately right, or right if possible. In the case
represented by Fig. 8 the distance between the
drill holes a and b should not be more than twice
the distance they are back from the face of the
rock. Naturally the distance would have to be
varied to suit the character of the rock, being
less in soft than in hard materials. In average
strong rock the holes would be spaced from one
and one-half to two times the distance back from
the free face; for moderately strong rock from
one to one and one-half times, and for weak rock
the distance apart should not exceed the line of
least resistance. Unfortunately, there is no mid-
dle ground between theory and practice in the
formulation of rules as to the form of cavity and
amount of material dislodged by a shot or multi-
plicity of shots; consequently, the quantities
given can only be approximate, and used compar-
atively as a guide. Experience, which comes only
with time, is the only safe guide. An experienced
quarryman or miner will study the character of
the rock, so as to take advantage of slip, cleavage
and dip of the rock, and be able to place his holes
at such angles as to get the maximum effects and
avoid blow-out shots.

In working on hard rock, it is well, when possi-
ble, to get hard-rock quarrymen or workmen who
have had experience on hard rock; while for

Rock Excavating and Blasting

soft rock, workmen with experience on soft rock
are to be preferred. However, the superintend-
ent must often work with the labor available, and
it is then his knowledge of rock excavating will
be invaluable.

The effect of multiple blasts is still further
shown in Fig. 9. In this example three holes
are drilled close together, and each charged with
a shot that if fired separately would not break

- -. -*-- IT !!

Fig. 9.
Rock Removed by Multiple Biast.

down the wall of rock between it and the free
vertical face. By firing three charges together,
however, all that mass of rock bounded by the
lines will be displaced. This method of blasting
will be found useful in many cases, and by means
of it greater masses of rock can be removed with
smaller drill holes than would be possible were
it not for the combined effect of the several
charges. To secure the effect of a multiple blast

Rock Excavating and Blasting (%^ffii)

however, the charges must all be fired simultan-
eously, not one after the other in close succession.
When explosions follow one another, even with
but a fraction of a second between blasts, the
effect is lost, for the blow of an explosion is almost
instantaneous. After the first shock the rock be-
comes shattered sufficiently to reduce the pressure,
and with shots following one another, the force
of one blast is liable to be spent before another
comes into action. Electric firing of blasts is the
only way in which the charges can be exploded
simultaneously. No matter how experienced and
careful a rock-man may be, he cannot time fuses
so the charges will all fire together. Differences
of a little in length ; slower or quicker burning of
some of the fuses, or delay of some of the fuses
in taking fire will all contribute more or less to
the scattering of shots.

CHAPTER II.

SINKING SHAFTS THROUGH ROCK.

RILL HOLES IN SHAFT SINKING. —
There is considerable latitude al-
lowed the quarryman in the placing
of drill holes for shaft sinking and
tunnel driving, but whatever their
arrangement, they all are based on the principle
that there is but one free face in that class of
work, and to get the best results two faces must
be exposed. In order to get two free faces, key
holes, or cut holes, are drilled and fired in order
to blow out a portion of the rock, and the work-
men then arrange the drill holes to take advantage
of this cavity. It is not necessary to actually
drill and blast those cut holes first, for the effect
of the blast being known, the key holes can be
drilled at the time all the other holes are drilled,
then they can be fired first to make a second free
face for the other blasts.

The location of drill holes for shaft sinking and
tunnel driving is practically the same. The key
holes may be arranged in a circular form to take
out a cone of rock, and the drill holes arranged

Rock Excavating and Blasting

in concentric circles outside of this cone, or the
key holes may be arranged in straight lines to
take out a wedge-shaped core of rock. One
method of arranging drill holes for shaft sinking
through a white limestone is shown in Fig. 10.
The approximate dimensions are given on this

Fig. 10.
Arrangement of Drill Holes in Shaft Sinking.

illustration as a guide to the judgment in arrang-
ing drill holes and spacing them in similar work.
The rows of drill holes are numbered 1, 2, 3 and
4 for convenience in reference. The depth of the
cut was 6 feet, and the dimensions of the shaft

Rock Excavating and Blasting

20 by 20 feet, one-half only of which is shown.
In sinking a shaft of this kind, the holes would
all be drilled in one shift. The rows of holes
2, 3 and 4 would then be protected so they would
not fill with dirt; the double rows of holes 1-1
be charged with the explosives, and the charges
fired simultaneously. This would cut or blow out
its wedge-shaped mass of rock bounded by the
lines of drill holes at the sides and the free face
on the top. The removal of this wedge of rock
exposes two free faces on each side of the cavity,
and the double row of holes 2-2 would then be
charged and fired. After the rock from this blast
had been cleared away the double rows of holes
3-3 would in like manner be charged and fired,
and after clearing out the rock dislodged by the
blast the squaring-up rows of holes 4-4 would
be fired.

After the first level of the shaft has been blasted
and the rock removed, the experience gained
ought to show whether a different arrangement
of the drill holes or a heavier or weaker charge
of explosive were necessary.

The object is, of course, to remove all the rock
necessary, so holes will not have to be hand-drilled
for squaring-up purposes, and at the same time
to use charges of explosive of only sufficient
strength to remove the rock at each blast without
shattering the side wails of the shaft or blowing
the removed material to atoms.

It will be noticed that the squaring-up drill
holes, 4-4, are slanted so as to bring them a little

Rock Excavating and Blasting

outside of the plumb line of the shaft. This is
because the drill operator cannot place his
machine close enough to the shaft wall to drill a
truly perpendicular hole, and, in order to take

Fig. U.
Deep Drill Holes for Shaft Sinking.

out enough rock so as not to necessitate subse-
quent cutting and blasting, the drill hole is put
in at a slight angle to bring the bottom of the
charge of explosive outside of the plumb line of

Rock Excavating and Blasting

the shaft, or the side line of the tunnel, as the
case may be.

In this example the cut is a shallow one, only 6
feet of material being removed for each cycle of
operations. In the method shown in Fig. 11,
eleven feet of the same material can be removed
by one cycle of operations. In working accord-
ing to this plan of shaft sinking, the primary rows
of cut-out holes, 1-1, are drilled as in the preced-
ing case, but reaching to a depth of 6 feet only.
Secondary rows of cut-out holes, 2-2, are then
drilled, meeting at a depth of 11 feet from the
surface, and the ordinary rows of blast holes, 3-3
and 4-4, together with the squaring-up rows of
holes, 5-5, are next drilled.

After protecting all the other holes, the double
row of cut-out holes, 1-1, are charged, fired and
the rock cleared away.

Having two free faces for part of the depth,
the double row of secondary cut-out holes, 2-2,
are then charged and fired and the rock cleared
away.

There are now two free faces for the remain-
ing blasts to operate on, and the rows of drill
holes are charged and fired in their consecutive
orders, 3-3, 4-4 and 5-5, each battery of charges
in the like double rows being fired simultaneously
to get the maximum effect of the shots. In shaft
sinking there are two operations besides the drill-
ing and blasting which must be considered. As
the shaft goes deeper and deeper, more and more
water will seep into it, just as it would in a well,

Rock Excavating and Blasting

and provision must be made to pump out this
water as fast as it accumulates. Sometimes, in
high places, this is a simple matter, while in other
localities in low-lying land pumps must be kept
constantly at work to maintain the shaft in work-
ing condition.

A hoist must be rigged up, too, with which to
remove the rock loosened by blasting. Ordinarily
there is but little danger of rock from the walls
falling into the shaft on top of the workmen, pro-
vided they inspect the walls closely as the shaft is
deepened, and see that no loose pieces of stone are
left hanging to the walls, to be jarred out of place
later on.

CHAPTER III.

TUNNEL DRIVING.

RILL HOLES FOR TUNNEL DRIVING IN
SOFT ROCK. — In driving tunnels
about the same system of drilling
would be followed as for shaft sink-
ing. The methods previously ex-
plained would be found quite satisfactory for a
medium sized tunnel, while that shown in Fig 12
may be successfully followed for small tunnel
driving in medium hard rock. It will be noticed
in this system of drilling that three drill holes
are bored in a circle, or so as to form a triangle,
and the other holes are drilled around the edge
of the tunnel close to the sides. The center tri-
angle holes are drilled toward a central point
about 6 feet below the face of the rock. These
three holes form the key holes, or cut holes,
which are to be charged and fired first, the other
holes then being charged after the rock has been
cleared away, and the charges fired simultane-
ously.

In this illustration, on account of the small size
of the tunnel, only one row of holes is drilled out-

Rock Excavatiid Blasting

side of the cut holes. In a large tunnel, however,
if this method were used, two, three or more rows
of holes would be drilled, according to the size
of the operation and the quality of the rock.

In one respect, the drill holes for tunnel work
differ slightly from the system of drill holes used
for shaft sinking. In the case of tunnel driving

Fig. 12.
Rock Drilling in Small Tunnel. Soft Rock.

in soft or shaly materials, the drill holes are not
spaced uniformly. This can be easily seen by re-
ferring to Fig. 13, which is a diagram showing
the location and surface arrangement of drill
holes in the tunnel illustrated in Fig. 12. It will
be observed that there are more drill holes in the
bottom half of the diagram than in the top half.
Beginning with the bottom row, there are three

Rock Excavating and Blasting

holes, as against two holes in the top row; while
the second row from the bottom has four holes to
three holes in the third row. The reason for this
is, gravity helps to bring down the mass of rock
from the roof of the tunnel, wrhile the rock from
the bottom of the tunnel must be shattered and

Fig. 13.
Diagram of Drill Holes in Tunnel. Soft Rock.

torn away in spite of the resistance it encounters
and the weight of rock above. The moment soft
rock or shaly material is shattered along the roof
of the tunnel, it falls by its own weight, therefore
a greater amount of rock can be torn loose by a
blast than if in the bottom of the tunnel, where

Rock Excavating and Blasting

the shot has not only to rend the rock, but lift
it as well.

Further, the roof of the tunnel does not want
to be shattered too much by numerous or large
blasts, or masses of rock might be loosened and
hang suspended without being noticed, until a

Fig. 14.
Drill Holes for Small Tunnel in Hard Rock.

subsequent jar detaches it and allows it to fall
to the floor, endangering the lives of the work-
men. For these reasons, it is better to use only
enough explosive and as many drill holes in the
upper half of the tunnel as will remove the right
amount of rock, without subsequent hand drilling.

Rock Excavating and Blasting

In blasting, according to this system, the holes
a a a would first be charged and fired. Next the
holes b b, and finally the finishing holes c c. Some
quarrymen fill the holes b b and c c simultane-
ously. It is better though to fire holes b b first
and remove the rock before charging.

In drilling the cut holes, the practice differs
among quarrymen. Some rockmen drill the holes
so they will not meet, with the view of making
a wide end to the cavity broken out by the blast.
Other quarrymen, on the other hand, drill the cut-
out holes so they meet at a common point. Where
drill holes meet in that manner they form an en-
larged chamber in which a large quantity of pow-
der can be placed, consequently, a more effective
blast can be had than from single drill holes.

DRILL HOLES FOR TUNNELING IN HARD ROCK.—
A system of drilling for tunneling through hard
rock is shown in Fig. 14. This system does not
differ much from the one for soft rock and shaly
formations, other than having a greater number
of drill holes. In this case there are, first, four
cut-out holes, 1-1, to blast out a cone-shaped cav-
ity. Next, there are four enlarging holes, 2-2, for
the purpose of enlarging the cavity and giving a
larger free surface to work upon. Last comes
the row of holes around the sides of the tunnel.
The four holes numbered 1 would be charged and
fired at one time. After the rock removed by the
blast had been cleared away, the holes numbered
2 would be charged and fired. Next, after having

Rock Excavating and Blasting

cleared away the loose rock, the drill holes num-
bered 3 along the roof and sides of the tunnel
would be charged and fired, and finally the row
of drill holes along the floor of the tunnel would
be charged and fired. The drill holes 3 and 4 are
fired simultaneously by some quarrymen, but bet-
ter results will be obtained by firing the number
3 holes and follow with the number 4.

The foregoing illustrations of drilling for blast-
ing cannot be accepted as the proper system to
use in all cases, but only as fair averages, show-
ing the principles of rock excavation. Differ-
ences in the hardness of rock, veins of harder or
softer material crossing the shaft or tunnel, fis-
sures or faults in the strata would all necessitate
changes from the order shown, and the experi-
ence of the rockmen must be the guide in such
cases. No rules can be given that will be applic-
able to every case, and no illustrations can pos-
sibly show the right thing to do every time. At
best, the principles are all that can be successfully
taught in any line. Experience must improve
that knowledge to make it of practical value. For
example, in extremely large tunnel work the up-
per part of the tunnel would be driven as explain-
ed in the foregoing paragraphs, and the lower
portion worked in benches similar to open-cut or
quarry work.

DRILLING NEAR FAULTS OR FISSURES. — A meth-
od of drilling rock in a shaft or tunnel where there
is a fault, fissure, slip in the rock or a semi-free

Rock Excavating and Blasting

face of any kind is shown in Fig. 15. The usual
cut-holes in the center of the face are omitted,
and instead side cuts, or drillings, are made in
the heading, in the direction of the slope or fis-
sure. Care must be exercised, however, not to

Fig. 15.
Drill Holes Near Fissures or Faults.

drill through the rock into the fissure or too close
to its face, or when the blast is touched off a part
or most of its force, depending upon the size and
openness of the rock, will be expended without
doing any good. In this method of drilling, two
holes, 1-1, are the cut-holes. They are not ex-

(g^jfr Rock Excavating and Blasting &/j^)

tended clear down to the bottom of the cut,
but only a sufficient distance to dislodge a large
enough wedge of rock to give a large free sur-
face for the subsequent blasts to work upon. The
rest of the drill holes are carried the full depth
of the cut, which, in this method, would perhaps
not exceed 4 feet, at about the angles shown in
the illustration. In blasting they would be fired
in volleys, according to the way they are num-
bered.

In the first volley the charges in holes 1-1 would
be fired. After the rock had been cleared away,
holes 2-2 would be charged, and fired simultane-
ously. When the rock from that blast had been
removed, holes 3-3 would be charged and fired;
and, finally, the squaring holes, 4-4, would be
loaded and fired.

In some rock formations a thin seam of soft or
rotten stone, or soft coal, from 4 inches to 12
inches thick, is encountered. Where such is the
case, the soft material can be cut out with a pick,
blown out with a small shot or otherwise removed
for a distance of 4 to 6 feet, thus forming an un-
dercut which gives a large, free surface and dou-
ble face to work upon. Under such conditions
cut holes can be omitted, and the shot placed in
the best position to bring down the greatest
amount of material, according to principles prev-
iously explained for blasting where two free faces
are exposed.

DRIVING LARGE TUNNELS. — In Fig. 16 is shown
the way a large tunnel is driven, the work being

Rock E:x ating and Blasting

Rock Excavating and Blasting

done in two operations, driving the heading and
blasting the bench. The heading is driven by
drilling the breast of the rock and blasting it the
same as for a small tunnel. Indeed, this part of
the operation may be considered as driving a small
tunnel. This takes out only part of the material
that must be removed, however, and the second
operation which is in the nature of enlarging the
opening first made, consists of blasting out the
bench, a process which is carried on in much the
same manner as would be done in open-cut work,
only smaller charges of explosive are used.

In order to condense the principle features of
tunnel driving into a one-page illustration, the
drawing is made out of proportion. In the first
place, the heading and bench would not be so
close together. In very large operations the
heading and bench are so far apart that working
on one does not interfere with work on the other.
Again, the bench is generally deeper in propor-
tion than the heading, a condition which is re-
versed in the illustration.

In large tunnel operations, instead of one rock-
man operating a drill in the heading, two, and
sometimes three work simultaneously with power
drills mounted on mining columns ; and instead of
starting operations at one side of a hill or moun-
tain and driving through to the opposite side,
the tunnel is started at both ends at the same
time, and the workmen meet with the tunnel in
the middle of the mound they are driving through.

Back of the bench is the "muck-heap," as the

Rock Excavating and Blasting

material loosened by the blast is called, and the
workmen engaged in removing the "muck" from
the working are known as "muckers."

No support or lining is shown in the illustra-
tion, as the operations of rock blasting and ex-
cavating only are intended to be shown. How-
ever, as the heading progresses, props or posts
are put up to support the roof of the tunnel, and
prevent rock loosened by the blasting from crush-
ing down on the workmen. After the bench is
blasted, the tunnel is lined, either with temporary
or permanent lining; and when permanently
lined, the space between the masonry lining and
the rock walls of the tunnel is flushed full of con-
crete or grout. During the driving of a tunnel,
particularly through wet or seamy ground, pro-
vision must be made to take care of the seepage
which in some cases is considerable. Indeed, in
limestone localities, underground streams are
often encountered when driving tunnels below the
hydraulic gradient.

Between the dangers of falling roof ; of prema-
ture blasts; accidents to the storage magazine;
gas ; fumes from the explosives and poor air gen-
erally of the underground workings, it requires
the most watchful care on the part of those in
charge to prevent damage, injury or death to
those in their care. As soon as the heading is
driven a short distance, the roof should be held
up with good stout props. Then, as the bench
work follows the heading and props have to be
removed to make way for- the workmen, the roof

Rock Excavating and Blasting

back of the bench must be supported until the
lining, temporary or permanent, is in place.

The removing of the rock blasted out of the
tunnel is no small task, and a clear runway must
be maintained for the tracks and the muck cars
which take the rock out of the tunnel. In the
case of large tunnels driven in mountains or hills,
the muck is carted out on dump cars, and de-
posited in muck heaps at convenient points. In
driving tunnels under the streets of cities, how-
ever, the disposal of the rock removed sometimes
is a problem in itself. Some of it can be disposed
of for building purposes, but getting it to the sur-
face and carting it away without interfering too
much with the ordinary traffic is one of the prob-
lems that must be considered.

PART II.

ROCK-DRILLING TOOLS AND
MACHINERY.

sft? ty
CHAPTER IV.

HAND AND AIR DRILLS.

OCK DRILL ON TRIPOD. — Hand drill-
ing of rock, with sledge and chisel
bar or drill steel, of course every-
body is familiar with, but under
present-day conditions economy of
time and labor will not tolerate that old-time
method, which has been supplanted, so far as
large operations are concerned, by rock drills
operated by power.

The commonest types of power drills, and the
ones most extensively used, in general engineering
work are the reciprocating, or striking, machines,
operated either by steam or by compressed air.
A rock drill of this type, mounted on an adjust-
able tripod is shown in Fig. 17. The legs of
the tripod on which this machine is mounted are

(^^jfr Rock Excavating and Blasting (tffi&

provided with universal joints, so they can be
adjusted to the uneven surface common to all
operations, and are weighted with heavy castings
to hold the machine firmly in place, and prevent

Fig. 17.

Rock Drill on Tripod.
36

Rock Excavating and Blasting

it being raised from the surface every time the
drill strikes the rock at the bottom of the hole.

Rock drills are made in various sizes, with
lengths of stroke ranging all the way from 4
inches to 8 inches, and that will drill holes of
diameters ranging from %-inch up to 6 inches.

Further, a machine of this type will drill holes
from 1 inch to 32 feet in depth, while larger ma-
chines of similar type have been successfully and
economically used to drill holes 50 to 60 feet deep,
and ranging in size from 6 inches at the top to
? inches at the bottom.

In drilling with a power drill only a certain
depth of hole can be drilled, depending on the
length of feed of the machine, when the feed must
be readjusted, a longer drill fitted in the chuck,
and the hole extended down as far as the feed
will permit, when the operation of readjusting
must be repeated until the hole is carried to its
final depth. Twelve inches is the length of feed,
or depth that can be drilled without changing
steels, for the smallest machines, and from that
minimum the length of feed is gradually increased
in the various sizes until the maximum, 30 inches,
is reached.

In holes that are drilled to a considerable depth
different sizes of steels are used, the diameter be-
coming smaller as the holes grow deeper, so there
will be no binding of the drill steel in the holes.
The length of stroke, length of feed, depth of
hole a machine will drill, diameter of hole, num-
ber of drill steels required to drill the maximum

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Rock Excavating and Blasting

depth, as well as a lot of other information re-
garding these drills, can be found in Table II.

The drill steel is kept well down in the hole it
has formed by means of the feed screw shown at
the top in the illustration, and the steam or air
supply may be attached either to the right or left
side of the machine. In this case it is connected
to the right side by means of a flexible tubing
wound with wire, and the supply of steam or air
is controlled by a stop cock convenient to the op-
erator's hand. In ordering rock drills the order
should state whether steam or compressed air is
to be used. Drills are always supplied with pack-
ings for steam unless air is specified as the motive
power.

ROCK DRILL ON QUARRY BAR. — The rock drill
on quarry bar is practically the same as the ordi-
nary rock drill, the principal difference being the
mounting. For plug and feather work in quar-
ries, channeling or any other kind of drilling
where it is necessary to have the holes in a line
and parallel with one another, the quarry bar is
used. A mounting of this description may be
seen in Fig. 18. Once this bar has been properly
set up and secured in place, the drill can be moved
along from place to place, drilling holes as close
together or as wide apart as the operator pleases.
Holes can be drilled so close together, in fact,
that they form almost a continuous channel, and
can be used for channeling by breaking out the
core or partition between the holes by means of a
special broaching bit. Large blocks of stone can

Rock Excavating and Blasting

likewise be taken out of the quarry, without
breaking or shattering, by the plug and feather
method — that is, a series of holes are drilled in a
row and a break is made along the line of holes
by means of wedges.

Quarry bars of this type are made in lengths
of 8, 10 and 12 feet, and the carriage is so con-
structed that it can be easily and quickly moved
along the bar, thus changing the position of the
drill without loss of time, as would occur with
the tripod mounting. The quarry bar is fre-
quently used for channeling in engineering and
architectural works where the nature of the rock
prevents the use of channeling machines.

ROCK DRILL ON MINING COLUMN. — Both the
drill mounted on the tripod and that on the quarry
bar are designed for cutting or drilling holes
downward, either vertically or at slight angles
from the vertical. In driving tunnels, mining
and similar works it is necessary to have a drill
that can be pointed in any direction, up or down,
or straight overhead. In the mining column
shown in Fig. .19 we have such a machine. These
columns are made in several lengths, to suit dif-
ferent heights of drifts, and are secured in place
by tightening the jack screws at the bottom to
jam the top of the column tight against the roof
of the tunnel if set upright, or against the side
of the working if set on side. The usual length
of column is 6 feet, with the jack screws drawn in.

The drill is perfectly adjustable when mounted
on one of these columns, as it may be swung tc

Rock Excavating and Blasting

drill in any direction. It may also be moved up
or down on the column, and as a further adjust-
ment may be revolved in the saddle. In fact,
there is no position in which the drill cannot be
set up.

In using a column, wood blocking should al-
ways be placed at the ends to give an even bind-
ing surface.

Rock drills are operated by compressed air for
all mine and tunnel work, and air is also replacing
steam to a constantly increasing extent for quar-
rying and other work above ground. The mount-
ing principally employed for the former purposes
is the mining column or shaft bar, while tripods,
quarry bars, etc., are used on the latter work.
The operation of columns is, therefore, described
using air, and the operation of tripods with the
instructions for running when using steam. In-
structions regarding the setting up and operat-
ing of steam and compressed-air drills, furnished
by the manufacturers from their extensive expe-
rience, are given in the following chapter. In
operating a rock drill, no matter what its mount-
ing may be, it is necessary to so handle the ma-
chine that the drill steel will not bind or stick in
the drill hole. There is not so much danger of
this in drill holes which point down, for the rota-
tion of the drill steel will keep the hole large
enough and in sufficient alignment, particularly
when the drill steel is properly made with the
right gauge of wings or vanes. As the hole to be
drilled varies from the vertical to the overhead

Rock Excavating and Blasting

angle, however, the liability of the drill steel stick-
ing increases. This is because the dust and chip-
pings fall to the lower side of the drill hole, there-
by protecting the lower side, and forcing the drill
steel against the upper part of the hole all the
time. The result of this is, the hole describes
more or less of an arc as the depth increases, and
to compensate for this upward movement, the
drill must be lowered on its mountings from time
to time.

The inclination or tendency of a drill steel to
curve the hole upward can be checked to a great
extent by keeping the hole free from dust and
chippings. In horizontal holes and those with
but a slight upward tilt, a wire with hook on end
will enable the operator to rake the cuttings out.

CHAPTER V.

OPERATING DRILLING MACHINES.

UNNING WITH COMPRESSED Am —
SETTING UP AND STARTING.— In set-
ting up a mining column or shaft
bar it is well to set the jackscrews
on a solid block of hardwood. In
drifting always set the jackscrews parallel with
the direction of the tunnel. Run the jackscrews
back as far as possible, set the column or bar in
position, and place blocks or wedges tightly be-
tween the top plate and the rock. Draw up on
the jackscrews, and as the drill is started keep
tightening the screws until the column or bar is
secure. In a drift or tunnel the columns should
be as long as possible, so that resetting of the col-
umn when the bottom holes are reached may be
avoided. The mounting being in place, fasten the
machine rigidly to it. The connections to the
mounting should always be firm and tight, as the
slipping of a clamp or saddle will make the drill
"fitcher," or stick, frequently causing the loss of a
hole. Always blow out the hose before connect-

Rock Excavating and Blasting

ing it to the drill. Before starting, the rock should
be squared off where the hole is to be put.

DRY HOLES. — Start the drill slowly and on a
short stroke. In drilling dry holes, or those at a
small angle above the horizontal, it should be
remembered that such holes have a tendency to
turn upward, due to the accumulation of cuttings
on the lower side, which tends to raise the drill
bit at each stroke. It is well to start the hole a
little below the desired angle, and it is often
necessary to lower the drill on the column in
order to keep the steel from binding in the top
of the hole. Care should be taken that the
cuttings are continually running out of a dry hole
while drilling. If allowed to accumulate in the
hole they tend to pack behind the bit, and often
cause difficulty and loss of time in getting the
steel out, as well as reducing the progress of the
drilling. The flow of the cuttings in a flat or
horizontal hole may be assisted by means of a
long wire picker. If the cuttings stop running,
close the throttle until the drill reciprocates slow-
ly, then crank the drill backwards out of the hole
the full length of the feed screw. This clears
away the cuttings from behind the bit, leaving the
hole free for further drilling. The tendency of
cuttings to pack in the hole increases in damp
ground, and especial care should be used in this
case. Steels should be dry when inserted in the
hole, for if a wet steel be put into a dry hole the
dust adheres to it and clogs it.

Rock Excavating and Blasting

DOWN HOLES. — In drilling down holes or those
at any angle below the horizontal, care
should be used to feed water at such a
rate that there will be a continual dash
of mud out of the hole. If too much
water is used the hole will fill up, and
the dashing will be prevented, quickly
resulting in a clogged or mudded hole.
If too little water is used the drill wastes
most of its energy in stirring up the
heavy mud in the bottom of the hole.
Deep holes should be cleaned with a sand
pump, similar to that shown in Fig 20,
or spoon at each change of steel, and if
the hole becomes mudded the cleaning
must be done frequently.

LUBRICATION. — When starting up new
air drills use a lubricant consisting of
one pint of cylinder oil to one-fourth
pound of flake graphite, applying one
tablespoonful of lubricant for each
5-foot hole during the first ten shifts
drilled. After this use a good grade of
drill oil, one tablespoonful for each
10-foot hole drilled. Do not use a heavy
grade of oil with air drills, as such oil
freezes readily and retards the machine.

RUNNING WITH STEAM.

SETTING UP AND STARTING. — What-
ever the mounting, it must be firmly se-

Rock Excavati n g a . n d B 1 a s t i n g

cured. If the drill is mounted on a tripod or
quarry bar set the mounting in the desired posi-
tion and then "spot" a small hole in the rock with
a hand drill for each leg, and place the weights
on the- legs. Where the rock is so soft that the
jar of the machine causes the legs to cut into
the stone, and thereby throws the drill out of
line with the hole, it is necessary to put a wooden
block under each leg. An iron plate, with a
hole in it for the leg, should be screwed on
each block. Where compressed air is used the
drill will start at once, but with steam it will
take a few minutes for the machine to become
equally heated.

Do not strike the steam chest or any other part
of the drill, or loosen any bolt or side rod, for
when the steam chest or cylinder becomes suffi-
ciently heated the drill will start. Start the drill
slowly and on a short stroke, as noted above.

LUBRICATION. — The general instructions for
putting in upper (or dry) and down (or wet)
holes with air drills apply also to those run by
steam.

When starting a steam machine which has been
shut down some time do not oil until the water is
all out of it, then oil often and in small quantities
through the oiler which is furnished with each
machine. Also oil the drill through the hole in
the top head. Use a good grade of cylinder oil
when running with steam.

Rock Excavating and Blasting

GENERAL SUGGESTIONS.

In soft ground in both wet and dry holes the
drill may cut into the rock faster than it can
throw the cuttings out of the hole, causing mud-
ding or clogging. In these cases always throttle
the air to reduce the hardness of the blow and use
the longest possible stroke.

When the drill strikes a cavity or seam in the
rock crank the machine down to a short stroke,
until the bit has started in the next ledge. Do
not keep the machine running if the piston stops
rotating, or if the drill stops cutting. If a tripod
leg has worked low, causing the steel to bind in
the hole, straighten it up. If a column arm is too
high let it down, or vice versa.

Keep the drill steel running freely in the hole
by making such changes in the position of the drill
on its mounting as may be required, making these
changes as soon as the steel begins to bind. Do
not wait until the hole has become crooked. Avoid
running with crooked steels or shanks. Have the
steel tight in the chuck or it will rapidly wear the
chuck bushing, which causes the drill to run out
of center, and results in excessive friction and
wearing of the bit on the sides of the hole.

ADJUSTMENTS. — In starting a new drill care
should be taken that all adjustments on the drill
are tight and secure, and they should be kept so
at all times. The exhaust pipe should be screwed
in with a wrench and made tight. Otherwise it

Rock Excavating and Blasting

will jar loose, wearing or stripping the threads so
that when next screwed tight it may partially
choke the exhaust passage. The steam-chest
plugs, or buffers, should be screwed in as far as
they will go and the check nuts which hold them
in place then made tight. After running for a
few hours, slack off the check nuts and tighten
the plugs again. These buffers do not form any
means of adjustment, but merely afford access to
the valve.

CHAPTER VI.

ROCK DRILL BITS OR STEELS.

OCR DRILL STEELS. — Too much em-
phasis cannot be placed on the im-
portance of using suitable drill
steels with rock drills. The bits
must be properly formed, sharpened
and tempered for the work in hand, and must be
of the right gauge, or the drilling machine can-
not operate to advantage.

A typical rock drill steel is shown in perspective
in Fig 21. Other drill steels differ from this only
in the length of the ribs or wings, the angle of
the cutting edge and the angles at which the
wings cross each other.

Experience in the manufacture and use of
drilling machines shows that it will prove
economical to secure the best blacksmith obtain-
able to care for the drill steels. If bits of the
right temper, shape and sharpness are always on
hand the drills will be able to work constantly
to the best advantage, whereas delays to the drills
mean losses in efficiency to the whole plant.

For general mining and quarrying purposes
the ordinary cross-bit is recommended. The
proportions of the bit, as to length and thickness

Rock Excavating and Blasting

of the wings or ribs, are indicated in the accom-
panying illustrations. Figs. 22 and 23 are bits
for hard, non-gritty rock, and are alike
except for the different angles shown on
the cutting edges. Fig. 22 shows about
the highest angle to which the cutting
edge can be made without danger of break-
ing. The angle shown on the cutting edge
in Fig. 23 is one of many which may be
used under different con-
ditions without any other
change in the bit. In
cutting hard and medium
hard rock, sharp drills
and a wide-open throttle
may be used to good ad-
vantage, and the hole will
not ordinarily clog with
mud, as the amount of
rock loosened by each
blow is so little that it is pefspect-
at once mixed into slush lot Rock
by the water in the hole.Drin
The sharp rebound of the drill
when striking hard rock, to-
gether with the positive recovery
of the machine, quickly gets rid
of this slush. If the same bits
steel for Hard and drill are run on an open
Rock. throttle in soft or even medium-

soft ground the hole soon becomes clogged. The
reason for this is that while the hole remains the

Rock Excavating and Blasting

same diameter and the amount of water for mud-
ding purposes is, therefore, the same, the steel
chips out three or four times as much dust at each
blow as it does in hard rock. The rate of cutting

: | should, therefore, be reduced

in order to keep the drill
working at maximum effi-
ciency. The speed may be
regulated by throttling the air
or steam, but this reduces the
rapidity of action of the drill,

Fig. 23.

Drill Steel for Soft
Rock.

so that it does not always mix
into slush the dust caused,
even at the slower speed. The
recoil of the steel from soft
rock is also considerably less.
In soft rock duller bits should
be used, like that shown in
Fig. 23. The angle of the cut-
ting edge may be even duller
than this, sometimes almost
square on the end, in order to

Fig. 24.

Length of Rib on Drill
lor Soft Rock.

Rock Excavating and Blasting

secure good results. In connection with the above
subject it is well to bear in mind the length of
the wings or ribs for different kinds of work.
Figs. 22 and 23 show extreme lengths for very
hard rock, intended to give strength and hold the
gauge as long as it is necessary. Figs. 24 and 25

show shorter ribs, which
give the bit more clear-
ance and make it more
tL___J desirable for general

"T \~IM~~7 purposes. Under ordin-
ary conditions its ability
to mix mud is much
greater than that of the
long bit like Fig. 22. For
drilling dry holes in tun-
nel headings or else-
where, the bit with short
ribs has less tendency to
allow the hole to draw
up. The wings are five-
eighths of an inch thick,
for the size shown in
Figs. 22 to 25, and should never be less than that
for this size of bit and steel. They should be
the same thickness throughout to allow free
return of the cuttings. If gauge less than 2*4
inches is desired make the bit correspondingly
shorter.

In seamy ground the bit shown in Fig. 26
will occasionally work satisfactorily when a
cross bit would not prevent a "rifled" hole, since

Fig. 25.

Cutting Edge on Drill Steel
for Soft Rock.

Rock Excavating and Blasting

bit strikes only half as often as the "+"
bit in a given spot. Flat or chisel bits are not
recommended, since their reaming qualities are
poor, and while cutting faster than the + bit
under some conditions they are very hard on the
machine. It is important to keep
the wings square at the corners, as
this permits the gauge of the hole
to be properly maintained. Do not
use a set of steels after the gauge
has begun to wear. The time and
trouble taken in securing fresh
steel amount to little in comparison
with the delay caused by trying to
work down a hole with steel that
is constantly sticking, to say noth-
ing of the wear and tear on the
machine. Blacksmiths should take
pains to furnish bits made exactly
to the required gauge. A little
neglect in this particular causes
much trouble and loss of time with
the drill.

On any rock on which the cut-
ting edges are not dulled upon the
first hole a system should be de-
vised by the foreman or superintendent to de-
termine how much each bit will do without too
much "hammer help." The improvement will be
very pronounced.

SIZE AND WEIGHTS OF DRILL STEELS. — In Table
III will be found the number of drill steels used

Fig. 26.
X Bit Drill Steel

Rock Excavatila,nd Blasting

TABLE III.

Weights and Specifications of Drill Steels.

For Drill "UA"-2 inches- Feed 12 Inches

(Size of Shank, % in. 3% in.)

Name of Each
Part

Regular
Size of Gauge
Inches

Length Steel
Will Cut

Sizes of
Steel
Inches

Weight in
Pounds

Starter

1 ft. 0 in.

2d length .

2 ft. 0 in.

3d length

3 ft. 0 in.

4th length . .

4 ft. 0 in.

iy>

5th length .

5 ft. 0 in.

For Drill "US"-2^ Inches-Feed 15 Inches

(Size of Shank, % in. x 4 in.)

Name of Each
Part

Regular
Size of Gauge
Inches

Length Steel
Will Cut

Size of
Steel
Inches

Weight in
Pounds

Starter . . .

1 ft. 3 in.

2d length . .

2 ft. 6 in.

3d length . .

iy>

3 ft. 9 in.

4th length .

5 ft. 0 in.

5th length

6 ft. 3 in.

For Drill "UR"-2K Inches-Feed 20 Inches

(Size of Shank, % in. x 4K in.)

Name of Each
Part

Regular
Size of Gauge
Inches

Length Steel
Will Cut

Size of
Steel
Inches

Weight in
Pounds

Starter

1 ft. 8 in.

2d length .

3 ft. 4 in.

3d length .

5 ft. 0 in.

4th length .

6 ft. 8 in.

5th length .

8 ft. 4 in.

Rock Excavating and Blasting

TABLE III. — Continued.
Weights and Specifications of Drill Steels.

For Drills "UC" and "UC11-2M Inches-Feed 24 Inches

(Size of Shank, 1 in. x 4% in.)

Name of Each
Part

Regular
Size of Gauge
Inches

Length Steel
Will Cut

Sizes of
Steel
Inches

Weight in
Pounds

Starter . . .

2 ft. 0 in.

2d length . .

4 ft. 0 in.

3d length . .

6 ft. 0 in.

4th length . .

8 ft. 0 in.

5th length . .

10 ft. 0 in.

6th length . .

12 ft. 0 in.

For Drill "UD"-3 Inches-Feed 24 Inches

For Drills "UE2" and "UE11"-3K Inches-Feed 24 Inches

For Drills "UF2" and "UF11"— 3M Inches— Feed 24 Inches

(Size of Shank, 1% in. x 4% in.

Name of Each
Part

Regular
Size of Gauge
Inches

Length Steel
Will Cut

Sizes of
Steel
Inches

Weight in
Pounds

Starter

2 ft. 0 in.

\y*

2d length . .

4 ft. 0 in.

3d length . .

6 ft. 0 in.

4th length .

8 ft. 0 in.

5th length .

10 ft. 0 in.

6th length .

12 ft. 0 in.

7th length .

14 ft. 0 in.

8th length .

16 ft. 0 in.

9th length .

18 ft. 0 in.

10th length .

20 ft. 0 in.

Rock Excavating and Blasting

TABLE III. — Continued.
Weights and Specifications of Drill Steels.

For Drills "UH" and "UH11"— 3% Inches— Feed 30 Inches

(Size of Shank, 1% in. x 5^ in.)

Name of Each
Part

Regular
Size of Gauge
Inches

Length Steel
Will Cut

Size of
Steel
Inches

Weight in
Pounds

Starter

2 ft. 6 in.

2d length .

5 ft. 0 in.

3d length .

7 ft. 0 in.

4th length .

10 ft. 0 in.

5th length

12 ft. 6 in.

6th length .

15 ft. 0 in.

7th length .

17 ft. 6 in.

8th length .

20 ft. 0 in.

9th length .

22 ft. 6 in.

103

10th length

25 ft. 0 in.

114

llth length

27 ft. 6 in.

125

For Drill "UH"— 3% Inches- Feed 24 Inches

(Size of Shank, I1/ in x 5% in.)

Name of Each
Part

Regular
Size of Gauge
Inches

Length Steel
Will Cut

Size of
Steel
Inches

Weight in
Pounds

Starter

2 ft. 0 in.

2d length . .

4 ft. 0 in.

3d length

6 ft. 0 in.

4th length

8 ft. 0 in.

5th length

10 ft. 0 in.

6th length

12 ft. 0 in.

7th length .

14 ft. 0 in.

8th length

16 ft. 0 in.

9th length .

18 ft. 0 in.

10th length

20 ft. 0 in.

Rock Excavating and Blasting

TABLE III.— Continued.
Weights and Specifications of Drill Steels.

For Drill "UK"- 4^ Inches— Feed 30 Inches

(Size of Shank, 1% in. x 6 in.)

Name of Each
Part

Regular
Size of Gauge
Inches

Length Steel
Will Cut

Size of
Steel
Inches

Weight in
Pounds

Starter

2 ft. 6 in.

2d length .

5 ft. 0 in.

3d length .

7 ft. 6 in.

4th length

10 ft. 0 in.

5th length

12 ft. 6 in.

6th length

15 ft. 0 in.

107

7th length

17 ft. 6 in.

123

8th length

20 ft. 0 in.

140

9th length

22 ft. 6 in.

156

10th length

25 ft. 0 in.

174

llth length

27 ft. 6 in.

190

12th length

30 ft. 0 in.

206

13th length

32 ft. 6 in.

222

14th length .

35 ft. 0 in.

238

For Drill "UL"— 5 Inches- Feed 30 Inches

(Size of Shank, 1% in. x 6& in.)

Name of Each
Part

Regular
Size of Gauge
Inches

Length Steel
Will Cut

Size of
Steel
Inches

Weight in
Pounds

Starter . . .

2 ft. 0 in.

2d length .

4 ft. 6 in.

3d length . .

7 ft. 0 in.

4th length .

9 ft. 6 in.

5th length .

12 ft. 0 in.

6th length .

14 ft. 6 in.

7th length .

17 ft. 0 in.

114

8th length .

19 ft. 6 in.

131

9th length .

22 ft. 0 in.

148

10th length .

24 ft. 6 in.

165

llth length .

27 ft. 0 in.

182

12th length .

29 ft. 6 in.

200

13th length

32 ft. 0 in.

217

14th length

34 ft. 6 in.

234

15th length .

37 ft. 0 in.

251

16th length .

39 ft. 6 in.

268

Rock Excavating and Blasting

with Sullivan machines of various sizes, the
lengths, weights, etc. The letters at the top of
each table refer to the size of the rock drill, so
that full information can be had by referring
back to Table II. For instance, the "UA" size,
by referring to Table II, will be found to have a
cylinder 2 inches in diameter with 4i/2-inch
stroke and length of feed of 12 inches, together
with all necessary data as to sizes of steam or air
inlets and outlets, and all other information about
the machine.

In column two the regular size of gauge in
inches refers to the size of the cutting head in
end of the bit.

It will be noticed that the size of the gauge, or,
in other words, the size of the drill head, decreases
in size with each length added. For instance, in
the last size of drill listed in this table, the ma-
chine starts off with a drill that will make a hole
four inches in diameter, and each time the drill is
changed and lengthened the size of the bit is de-
creased one-eighth inch in diameter, so that at a
depth of 39 feet 6 inches it is drilling a hole only
2 inches in diameter. The object of thus decreas-
ing the size of drill at each change of the drill
steels is to prevent the drill from binding, as
would be the case if the attempt were made to use
a steel with the same size bit throughout the en-
tire depth of the hole.

It might be well to state here that for ordinary
building construction it will seldom be necessary
to use a machine that will drill deeper than 8 feet

Rock Excavating and Blasting

4 inches. For large engineering works the large
size drills may be used, but for ordinary opera-
tions the smaller sizes will be found to give satis-
factory results.

Drills 30 feet in length and over are generally
made in two parts for convenience in shipping and
handling, but can be had in one piece when so de-
sired.

BLACKSMITHS' TOOLS FOR FORGING
DRILL STEELS.

The special tools required by a blacksmith for
keeping the drill steels in condition are shown in
the following eight illustrations: Fig. 27 is a
swage for forming the wings of the drill steel,
Fig. 28 is a "sow" for gauging the wings, Fig.
29 is a cross-shaped "dolly" for shaping the cut-
ting end of the drill steels, Fig. 30 is an X-shaped
dolly for the same purpose, Fig. 31 is a flatter,
Fig. 32 is a spreader, Fig. 33 is a drill shank
swage for anvil and Fig. 34 is a similar swage for
a hammer.

AIR REQUIRED FOR DRILLING MACHINES.

The type of air compressor used to furnish air
for the machine drills will depend to a great ex-
tent upon whether the work is of a permanent
or temporary nature. For rock drilling in quar-
ries naturally a power plant will be required, and
a stationary air compressor, permanently mounted

Rock Excavating and Blasting

62.

Rock Excavating and Blasting

on a solid base, would be preferable. For tem-
porary work in building construction, unless the
operation is a particularly large one, a portable
boiler when steam is to be used, or a boiler, engine
and air compressor when air is to be used, will
be found the more convenient.

The size of the compressor required will depend
upon the number of drills that are to be operated,
which in turn determine the amount of free air,
that is, atmospheric air, which must be compress-
ed to the required pressure. Seventy-five pounds
is a common pressure to supply air to the drills,
and in Table IV can be found the number of cubic
feet of free air required to run from one to forty
drills.

Allowance has been made in the table for the
difference between piston displacement and actual
delivery, so that no further deduction need be
made from the compressor capacities stated in
catalogue. The figures represent the require-
ments of drills under ordinary working condi-
tions. When a practice is made of drilling deep
holes, or where special conditions render the work
unusually severe, more air will be necessary. It
is, therefore, wise in purchasing an air compres-
sor to allow for such contingencies, and many con-
tractors, quarrymen and mine managers of expe-
rience invariably install a compressor capable of
furnishing 20 or 25 per cent, more air than their
machines require.

Rock Excavating and Blasting

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Rock Excavating and Blasting

The figures given in Table IV are for air at 75
pounds pressure at sea level. The modern ten-
dency in rock drill practice is toward higher pres-
sures, and the present standard is near 90 pounds.
For estimating the air consumption of drills at any
required pressure or altitude the factors of mul-
tiplication given in Table V will be found conven-
ient.

These tables are used in the following manner.
Suppose, for instance, instead of 75 pounds pres-
sure, the drill is to operate under a pressure of
only 60 pounds, and at sea level. In column 2,
Table IV, it will be seen that a single drill requires
55 cubic feet of free air to operate at 75 pounds of
pressure. According to the factors for various
altitudes and pressures given in Table V, how-
ever, it would require only .83 per cent, of 55, or,
.83 X 55 = 45.65 cubic feet of air per minute.

Suppose, however, that instead of being at sea
level the rock drill was to be used in excavating
on the top or side of a mountain at an elevation of
6,000 feet above the level of the sea. In that case,
instead of a factor of .83 it will require 1.03 times
as much air to operate the drill under a pressure
of 60 pounds as it would to operate the same drill
at sea level under a pressure of 75 pounds. At
sea level and at 75 pounds pressure the drill re-
quires 55 cubic feet of free air, therefore at an
altitude of 6,000 feet and under 60 pounds pres-
sure it would require 55 X 1.03 = 56.65 cubic feet
of free air per minute.

Rock Excavating and Blasting

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Rock Excavating and Blasting

Take another example. Instead of running the
rock drill with air at 75 pounds pressure, suppose
100 pounds pressure be used. In that case 1.28
times as much free air would be required as when
the machine is operated under the lower pressure
of 75 pounds per square inch — 1.28 X 75 = 96
cubic feet of free air per minute. When the power
plant and compressor are located at considerable
distance from the workings, an additional allow-
ance of say 15 per cent, should be made for the
loss of head due to friction of the pipes, and the
loss of volume due to condensation or contraction.
Compressing air heats it so that it expands and
occupies more space than it would if compressed
without heat; and this air when in the storage
tank and being conducted through pipes to the
several machines, in cold climates or during cold
weather, has its temperature reduced and shrinks
or contracts correspondingly in volume, condens-
ing, perhaps, to a less volume, relatively, than
when in the free state.

It is false economy to try to operate with an
inadequate supply of air, so to remedy this state
of affairs it is well to have a compressor with a
capacity of from 25% to 40% greater than that
actually required. This makes the plant more
elastic likewise, enabling more machines to be run
at one time than was originally planned, a condi-
tion which is sometimes necessary.

On large machines, like stone channelers, it has
been found economical to use re-heaters for heat-
ing the air before it is used in the machine. The

Rock Excavating and Blasting

re-heaters not only increase the volume of air,
thereby increasing the supply to the machine, but
it also keeps the moisture in the air from freezing
in the exhaust ports, an occurrence which is liable
if the air is not heated, for the air on expansion,
when released from the cylinders of the channeler
has a refrigerating effect, just the opposite of the
heating effect due to compression. It is the cool-
ing effect of expansion which causes the exhaust
ports of machines operated by compressed air to
freeze, and, of course, the higher the pressure of
the air, the greater the cooling effect of expansion.

CHAPTER VII

HAMMER DRILLS.

* *

N blasting work, a charge of explosive
generally throws out or breaks down
blocks of rock too large and heavy
for removal. When such is the case,
"pop" holes must be drilled in them,
and the rocks broken up into convenient sizes for
handling by blasting them with small charges of
explosives. Hand drilling was formerly employed
for this purpose, but machine hammer drills, op-
erated by one man, and using compressed air, are
now generally used.

Hammer drills are handy not alone for breaking
up boulders and large rock fragments, but will be
found convenient for cutting hitches in rock walls
to receive timbers, and for trimming the walls,
roof or floor of tunnels, shafts or cellar excava-
tions. They can likewise be used to good advan-
tage in excavating rock in narrow sewer or water
trenches, where light weight, compactness and
rapidity of setting .up go a long way toward re-
ducing the cost of the work.

Rock Excavating and Blasting

Hammer drills are made in two sizes. The
small size weighs 25 pounds and is for drilling
holes up to 3 feet in depth, and large enough for
ys-inch powder. The large drill weighs 35 pounds
and will drill holes 3 feet deep and large enough
for 1%-inch powder.

The characteristic feature of the hammer drill
is that the cutting edge of the steel rests against
the rock all the time, and is forced into it by the
repeated blows of the piston, which is independent
or detached from the drill steel, and is driven rap-
idly back and forth in the cylinder.

The weights, dimensions and capacity of Sulli-
van hammer drills can be found in Table VI.

TABLE VI.

Capacities of Hammer Drills.

Class of Drill

DB-15

DB-19

Depths to which holes may be drilled
(inches) ...
Maximum diameter of holes (inches) .
Weight of drill in pounds ....
Size of hose required (inches)
Size of shanks, inches (shank is hex-
agonal)

IK
25
7-16

%x3

2
35

lx3K

For the classes of work for which they are used
the hammer drill has important advantages in its
light weight, the ease and rapidity with which
it can be set up and handled, its high drilling
speed and economy of power.

These machines or tools are so light they can be
handled readily by one man, and as no tripod,
column or other mounting is required no time is

Rock Excavating and Blasting

lost in setting up or in removing the drills from
one point to another.

They are so light and compact that they can be
carried wherever a man can go, and in narrow
trench work the openings need be driven only
wide enough to permit a man to enter. Holes
may be drilled at any point, at any angle, or in
any direction.

Some idea of the capacity of these hammer
drills may be obtained from past performances.
In oolitic limestone of varying hardness, very ir-
regular, full of mud pockets and often covered
with water, twelve of the smaller hammer drills
each averaged forty holes 18 inches deep per shift
of 10 hours. The best record was 100 holes 18
inches deep or 150 feet of drilling, while 36 holes
3% feet deep were drilled by one tool in seven
hours. Hammer drills are now being used to a
considerable extent in mine work for drifting,
owing to the time saved after a shot. The driller
can put in his upper holes from the top of the
muck pile while the mucker is at work loading out
the heaps. The lifters are then put in last after
the muck has all been removed. The great ad-
vantage in using hammer drills for work of this
class lies in the fact that no time is lost in muck-
ing for the "set-up" as in the case of piston drills,
or in mounting the drills afterwards on the bars
or columns.

Rock Excavating and Blasting

"Plug" and "foot hole" drills of the hammer
type are made in two sizes for drilling "plug" and
"foot holes."

The smaller hammer is for drilling holes up to
6 inches in depth, and the larger one for holes
up to 12 inches in depth. A hammer drill of this
type, which differs but slightly from those just
described, is shown in Fig.
35. This tool employs solid
steels or bits, while the
larger size uses hollow drill
steels. The solid steel,
shown in the illustration,
is rotated by a hand wrench
shown sticking out to the
left of the drill steel, and
the hole is kept free from
dust by exhaust air
from the drill, which
is directed into it by the
blower hose shown, con-
necting the exhaust port to
the flange, near the end of
the drill steel. When start-
ing a hole the valve is open-
ed, exhausting into the at-
mosphere, to avoid the an-
noyance of flying stone Fig. 35.
dust. After the hole is

started a small amount of exhaust air is allowed
to flow into the hole. As the hole is deepened
more and more exhaust air is deflected into the

Rock Excavating and Blasting

opening, all being used in this way if desired.
This will keep the bit free from dust and dirt,
even in broken, wet and seaming ground.

A solid drill steel, such as is used in a
hammer drill for drilling "pop" holes for
breaking up boulders and rock fragments,
is shown in Fig. 36, and the method of
using the hammer drill is shown in Fig.
37.

Some idea of the capaci-
ties of the "plug" and

Steel for' Hammer "foot hole" drills Can be

Dri11- gained from the following

statement of what they have accomplished.
In Barre granite the "foot hole" drill op-
erating with air pressure of 100 pounds
drilled a 1^-inch hole 6 inches deep in one
minute, while the "plug" drill, operating
under the same conditions, has put in 160
holes %-inch diameter and 3 inches deep
in one hour. Of course, the work one of
these hammer drills will accomplish will
depend upon the character and quality of
the rock, the skill of the workman hand-
ling it, and the air pressure supplied at
the valve. The foregoing statement of what they
have already accomplished, however, ought to
serve as a guide to what they can do, keeping in
mind, of course, the fact that rock varies so that
it is seldom the same in any two cases, and the
difference in quality, fissures, etc., must be taken
into consideration.

Excavating and Blasting

Fig. 37.
Method of Using Hammer Drill.

CHAPTER VIII.

STONE CHANNELERS.

0 work on rock excavating would be
complete without some reference to
stone channelers for engineering
and architectural works. For over
forty years machines of this kind
have been used in quarry work, and for many
years engineers have considered channeling ma-
chines indispensable when rock has to be cut
away for canals, locks, wheel pits, railroad cuts
or similar excavations. More recently still they
have been used in architectural works, the new
Pennsylvania Station in New York City and the
sub-grade terminal yards of the New York Cen-
tral Railroad at Forty-second street being notable
examples.

The channeling machine has advantages of
economy and utility for certain classes of work
which put them in a class by themselves. For
instance, the smooth, straight, solid walls cut by
a channeler are better in many ways than the
jagged wall left after drilling and blasting.

The channeler cuts exactly to the surveyed line
of the work, a matter which is difficult to accom-

Rock Excavating and Blasting

plish when the wall is made by drilling and blast-
ing. In the latter case too much rock is removed
at some points and the cavities so formed must
be filled with concrete or masonry. At other points
projections are left which must be trimmed off to
the survey line. A further advantage lies in the
fact that the cut made by a channeler affords an
additional free face for the powder used in blast-
ing to act against, thereby making the blasting
easier and reducing the amount of explosive
needed.

The wall left by the channeler and the rock back
of the channeled face remain as solid as the rock
strata themselves, since they are not weakened
or shattered by explosives.

Under many conditions a blasted wall needs to
be sloped away from the line of excavation, in
order to prevent slides, thereby making necessary
a large amount of extra blasting. Oftentimes
rock-blasted walls must have retaining walls to
prevent rock falls or slips, and they are greatly
affected by weather, water freezing in the crevices
caused by the shattering effect of the explosive
and heaving the loose particles out of place. Chan-
neled walls, on the other hand, are but little af-
fected by weather and will stand without deterior-
ation for an indefinite length of time.

Finally, in thickly built-up districts, where it
is necessary to excavate rock close to the foun-
dations of existing structures, channeling around
the sides of the excavation close to the buildings
is desirable, as it completely isolates the rock in-

Rock Excavating and Blasting

Fig. 38.
Simplex Channeling Machine.

Rock Excavating and Blasting

side of the cellar space, which can then be drilled
and blasted without damaging the foundations of
the near-by buildings.

The usefulness of channelers is limited to the
softer kinds of rock, and cannot successfully be
used for channeling trap rock, granite or hard
gneiss. They can be successfully and economically
employed, though, on marble, sandstone, lime-
stone, slate, soapstone and for the softer gneisses,
such as that underlying New York City, also the
softer porphyries and granites.

SIMPLEX CHANNELING MACHINES. — A Sullivan
direct-acting simplex channeling machine, mount-
ed on a movable truck, together with a boiler for
furnishing steam, is shown in Fig. 38. The truck
runs on steel rails, which keep the machine in
alignment for the channel it is cutting, and at the
same time permits it to be easily moved from one
position to another. The channel-cutting drill
steels are shown extending below the level of the
rails. These drill steels are in groups of five,
working so close together that the holes they make
run together into one continuous slot.

After the gang drills have cut a groove to the
required depth the machine is moved along so
that the next set of holes will form a continuation
of the slot already made. The cutting or chopping
engine which operates the drill steels is raised or
lowered on its standard by means of a feed screw,
in a manner similar to that employed for the ordi-
nary tripod-mounted rock drill. Machines of this

Rock Excavating and Blasting

-
si

Rock Excavating and Blasting

type can be used to cut not only vertically, but
likewise at any angle up to 23 degrees.

DUPLEX CHANNELING MACHINES. — A duplex
channeling machine of the same make as the sim-
plex machine is shown in Fig. 39. With this chan-
neler two sets of gang drills are used, so that
double the amount of groove is being cut at one
time that is possible with a simplex machine.
Further, this channeler is designed to cut grooves
at various angles, and although shown in the il-
lustration set up ready to channel a vertical
groove, by adjusting the mounting frame on the
round bar seen in the foreground the chisels can
be tilted to any desired angle up to 39 degrees, and
by means of special braces can be adjusted to cut
angles as high as 90 degrees from the vertical.
In other words, the machine has a range of from
vertical, or straight down, to a horizontal position.

Duplex channeling machines can be had with
or without air reheaters. The one shown in the
illustration is without a reheater, although there
are conditions under which it is of great advan-
tage to have the air reheated before delivering it
to the engine.

DRILL STEELS FOR CHANNELING MACHINES. —
The drill steels used for channeling are consid-
erably different from those used in ordinary rock
drilling machines, and, in fact, differ from one
another according to the character of the rock
they are to be used upon. A five-piece gang of

Rock Excavating and Blasting

steels suitable for working marble is shown in
Fig. 40. The illustration shows clearly the way
the drills are sharpened and set in relation to one
another.

A three-piece gang of drill steels for a chan-
neling machine working in crystallized and other
limestone is shown in Fig. 41.

A gang drill of three pieces for channeling slate
is shown in Fig. 42, which also illustrates the
way the steels are set in relation to one another.

Fig. 44.
Channeled Walls of Chicago Drainage Canal.

In Fig. 43 we have a solid Z-shaped bit, or drill
steel, which has been adopted by the manufac-
turers and is recommended by them for engineer-
ing and architectural works, particularly where
the cuttings are deep and the rock is broken or
fissured.

Rock Excavating and Blasting

ILLUSTRATIONS OF CHANNELED WORK. — Some
idea of the appearance of channeled walls can be
obtained from the accompanying illustration, Fig.
44, which shows a curve in the Chicago drainage
channel, which was channeled out of the solid
Joliet limestone.

No other illustration perhaps would convey such
a good understanding of what can be accomplish-
ed by a channeling machine as this solid bank of
rock rising perpendicularly from the water and
presenting smooth walls, free from pockets or
projections to impede the flow of water.

Another view which shows how dimension rocks
can be taken out of a quarry for building purposes
is shown in Fig. 45. Two channeling machines
may be seen in the background making the ver-
tical cuts, while the free face of the bench of rock
shows the smooth surface of the cut, made by the
channeling bits.

The sizes, weights and specifications of Sullivan
stone channels can be found in Table VII.

AIR REHEATERS. — When channelers are to be op-
erated by air power the use of a reheater is strong-
ly advised. A saving of from 15 to 25 per cent,
in power may be attained by reheating the com-
pressed air before it is used in the channeler en-
gine, and freezing at the exhaust is also prevented
by this means.

SPECIFICATION OF STEEL FOR CHANNELING MA-
CHINES.— As has already been pointed out, the
type of drill steels varies with the work it is to

vi Rock Excavating and Blasting $/

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Rock Excavating and Blasting

do and the machine with which it will be used.
In Table VIII will be found full information on
the subject, pointing out the kind of drill steel,
length, dimensions, number used in a gang and
other information for different kinds of work.

CAPACITIES OF CHANNELING MACHINES. — For
large engineering and architectural works chan-
nelers are made which will successfully cut to a
depth of 16 feet. For ordinary practice, however,
a depth of from 9 to 12 feet is about all that will
be required. After taking out rock to the 9, 12
or 16-foot level the channeler can be lowered to
the next bench and another depth channeled.

The cutting speed of channeling machines var-
ies within wide limits, depending upon the hard-
ness of the stone, freedom from fissures or other
irregularities, and to a considerable extent the
skill of the operator. Instead of giving averages
of various machines it is considered better to give
the actual performances of the several machines
listed in Table VII, as furnished by the manufac-
turer, so that the actual capacity of any of the
machines listed can be judged. The class letters,
Z, Y, etc., refer to the sizes and specifications of
channeling machines.

At Brandon, Vt., a "61/2" channeler has aver-
aged 1,485 feet per month, and a "Z" 1,677 feet
for twelve consecutive months. This is the hard-
est marble in the State. At West Rutland a "6i/2"
channeler has cut 2,652, 2,649, 2,287 and 2,449
square feet in four consecutive months, or about
100 feet per ten-hour day.

Rock Excavating and Blasting

B &

> "

s i

^3 C^

1
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3

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X X

to
X

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'5^

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3-piece
gang

5-piece
gang

3-piece
gang

5-piece
gang

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a? -8

Kind of Work

Usual Quarry ar

Limestone

N. Y. Sandstone
Marble. Hard
Sandstone

t
i

t
3

•

Broken Rock,
Contract Worfc

Ohio Sandston

Limestone, Slat
Marble and Soaps

H^q

».

fcH

Rock Excavating and Blasting

The double-head machine will cut from 40 to 50
per cent, more than this. In Georgia marble 220
square feet have been channeled in 7y% hours with
a double-head "6i/2" channeler. In the Tennessee
district, where single-head channels are the stand-
ard, 80 feet per day is considered a fair average
for a season's channeling, taking into account de-
lays and other loss of time. A good day's work
will often run as high as 115 or even 140 feet per
day.

In the Indiana Bedford oolitic limestone the
"Class Y" channeler will cut from 200 to 350
square feet in opening up a quarry, when the
stone is rough and uneven. In developed quarries
the improved machines will cut from 400 to 700
feet, depending on the length of runs and the even-
ness of the stone. In the Carthage, Mo., district,
where the stone is much harder, 125 to 150 feet
is the limit of the "Y" machine's capacity, when
operating with 140 pounds boiler pressure. In
Joliet limestone a record of forty consecutive
shifts, made with one "Y" channeler, on the tur-
bine-wheel pits for the drainage-canal power
house, in 1905, showed an average per ten-hour
shift of 210 feet, with a high run of 382 feet in
twelve hours.

In the Batesville, Ark., field, where the crys-
tallized limestone is hard and close grained, the
"Z" machine, with boiler attached, makes an av-
erage of 130 feet per day, and has cut as high as
250 feet on a test run. The "Z" in the tough
sandstone found at the "Soo," using a "Z" bit,

Rock Excavating and Blasting

and putting in cuts from 9 to 12 feet deep, aver-
aged from 60 to 75 feet under usual conditions,
but when given long runs was able to make 150
feet in a day. In channeling gneiss, which is prac-
tically a soft granite formation, in New York
City, the "Y-S" channeler, with air reheater, aver-
aged from 60 to 75 feet per day of eight hours.

The "VX" machine, in channeling Vermont or
Pennsylvania slate, operating on a steam pres-
sure of 100 pounds, will cut, month in and month
out, 60 to 75 feet per day, and under favorable
conditions will run as high as 100 to 125 feet.
The soft soapstone in which the "6i/2" and "VX"
channelers are used in Virginia is cut at the rate
of 150 to 250 feet with the "VX," and from 175
to 350 feet with the "61/2" machine, depending
upon the hardness of the veins. In engineering
and architectural works, to judge the comparative
cost of channeling along the outer boundry of
an excavation, and removing the rock along the
same line of survey by means of rock drills and
blasting, the cost of a retaining wall, when neces-
sary, must be added to the cost of removing the
rock by blasting. A retaining wall, or other
means, must often be employed to face the rough
surface of a cut made by explosives, while no
such work is necessary along a channeled wall.

Where a wall has been channeled, the undis-
turbed rock alongside of the cut is as strong and
firm as before channeling. When explosives are
used, on the other hand, for a distance back from
the face of the wall the rock is more or less shat-

Rock Excavating and Blasting

tered, the extent of the shattering depending to a
great extent on the care with which the work
was done, and the skill of the rock-men.

At its best a blasted wall presents a rough,
jagged surface, which for some purposes is ob-
jectionable and possesses economic disadvantages.
For instance, flumes, mill races, canals, and chan-
nels of all kinds will conduct a greater amount of
water, size for size, under the same head, when
the walls are channeled, for they then present
less frictional resistance to the flow of water
through them.

Again, with a channeling machine rock can be
excavated right to the surveyed line, and the cut
is as smooth as the surface of a masonry wall.
To work right to the line with drilling machine
and explosives is not so easy a task, and when
completed, if well done, is perhaps no cheaper
than the channeled wall.

PART III.

EXPLOSIVES USED IN BLASTING

•$9 <$?

CHAPTER IX.
POWDER.

HERE are many different kinds of
explosives used for different pur-
poses, such as mining, army and
navy, hunting, quarrying and in en-
gineering works. For mining where
there is danger of gas, flameless or safety explo-
sives are used. For army and navy uses smoke-
less powders are used, while the various explo-
sives so employed are sub-divided into different
grades and classes. For the purpose of rock ex-
cavating, however, the consideration of explosives
can be confined to blasting powders and dyna-
mites, those being the two kinds of explosives
commonly used.

HIGH EXPLOSIVES AND Low EXPLOSIVES. — Ex-
plosives are classified in practice as high explo-
sives and low explosives, and this classification

Rock Excavating and Blast ing

separates the materials into blasting powder and
dynamite.

Blasting powder is classed as a "low explosive"
because it is exploded by a spark, flame or other
means of generating a sufficiently high tempera-
ture, whereas "high explosives" are detonated by
the powerful shock of a blasting cap or electric
fuse. Low explosives, or blasting powders, are
slower in action than high explosives of the dyna-
mite group, and, consequently, are less likely to
shatter the material blasted.

COMPOSITION OF BLASTING POWDERS. — All pow-
ders of the nitrate group, whether gunpowder or
blasting powder, are frequently referred to as
black powder. Gunpowder, the most familiar type
of powder, consists of an intimate mechanical mix-
ture of potassium nitrate, charcoal and sulphur
in the following proportions by weight :

Parts
Potassium nitrate ....................... 75

Charcoal ............................... 15

Suphur ................................ 10

Total .............................. 100

Ordinary blasting powder contains the same
constituents as gunpowder, but in different pro-
portions.

The composition of blasting powder averages as
follows, different manufacturers using slightly dif-
ferent proportions:

Rock Excavating and Blasting

Parts Parts Parts
Potassium or sodium nitrate . . 65 76 66

Sulphur 20 14 11

Charcoal . 15 10 23

Totals ; 100 100

100

There are two grades of blasting powders made,
which are classed by the DuPont Company as

Fig. 46.
Group of '.'A" Powders.

"A" and "B." The "A" powders are made of
saltpetre and the "B" powders of nitrate of soda.
Both are made in several standard granulations,
or sizes of grains, as shown in Fig. 46, which il-
lustrates the several granulations of "A" powders,
listed, according to their letters, C, F, FF, etc.
The lower the letter in the alphabet the coarser
the grain of the powder, and the greater the num-

Rock Excavating and Blasting

ber of letters used to designate a grade the finer
is the powder.

The various granulations of "B" powder can be
seen in Fig. 47.

Fig. 47.

Group of "B" Powders.
94

Rock Excavating and Blasting

An important fact about powders to bear in
mind is that the finer the granulations the quicker
the powder will act, consequently the more shat-
tering the effect on the material blasted. "A"
powders and "B" powders are both made either
glazed (polished) or unglazed. Glazed or polished
blasting powder withstands dampness or moisture
better than unglazed, and will run more freely,
therefore more of it can be put in a bore hole or
pocket of given size. On the other hand, glazed
blasting powder gives off a little more smoke than
unglazed powder. Blasting powder will not give
the best results unless the drill hole in which it is
charged is carefully and compactly tamped to a
depth sufficient to prevent a blowout. Further-
more, it is quickly affected by moisture, both in
storage and in use, and care must always be taken
to keep it dry. It cannot be used to advantage in
wet works.

"A," or saltpetre, blasting powder is somewhat
stronger and quicker in action than "B" blasting
powder. It also withstands moisture better. It
is used principally in marble or other dimension
stone quarries, where conditions are such that
"B," or nitrate of soda, blasting powder would not
be sufficiently strong to give satisfactory results,
and where high explosives would shatter the ma-
terial too much.

"B," or nitrate of soda, blasting powder is very
slow in action and is used in coal mines where gas
and coal dust are not met with in sufficient quan-
tities to cause dangerous explosions. It is so slow

Rock Excavating and Blasting* &etf®

in its action that it lifts and pushes the coal out
in large lumps and breaks it up but little if prop-
erly used. Granulations from FF to CCC are gen-
erally used in coal blasting, although FFF is some-
times necessary for hard coal.

The finer granulations of blasting powder, also
a mixed granulation known as "railroad powder,"
is commonly used for engineering, architectural
and other open-cut work, where the material is not
particularly hard. "Railroad" blasting powder is
a mixture of all the granulations of B powder
from F or FF to FFF inclusive, for which reason
it is possible to get a greater weight of it in a
given space, as the smaller grades fill the spaces
between the larger grains. This makes a mixed
powder especially valuable in large blasts, where
it is desired to shake down a large amount of
material for removal by means of steam shovels.

PROPERTIES OF BLASTING POWDERS. — As black
powder is a deflagrating, not a detonating, explo-
sive, its quickness depends upon its rate of burn-
ing. By a deflagrating explosive is meant an ex-
plosive that does its work by an extremely quick
burning of its ingredients to form gases, in differ-
entiation from those explosives known as "high
explosives," which are instantaneously converted
into gases by means of a blasting cap or electric
fuse. The "B" blasting powders are slower in
their action than the corresponding sizes of "A"
blasting powders, consequently do not seem to be
so "strong." The "B" blasting powders are recom-

Rock Excavating and Blasting

mended wherever a particularly slow powder is
required, such as blasting coal, particularly bit-
uminous coal, earth, soft or rotten rock, etc.

Although both grades of black powder are
ruined by contact with water the "A" blasting
powders are less susceptible to the moisture of
the atmosphere than the "B" blasting powders.
If necessarily exposed to damp air, or stored in a
damp place, the "A" blasting powders will retain
their qualities for a considerably longer time, and
should, therefore, be used in tropical climates
where the air is heavily charged with moisture,
or wherever the powder in storage or in use is to
be exposed to unusual climatic conditions.

As has already been mentioned, black powder
is a deflagrating explosive, and its quickness can
be varied by changing its rate of burning. A
certain number of large grains present less sur-
face for ignition than an equal weight of smaller
grains; thus the smaller-grained black powders
burn faster and are quicker in their action than
larger-grained powder of the same quality.

For blasting in any soft material, such as rotten
or soft stone, where the material is wanted broken
down in large fragments, a coarse-grained powder
should be used. Where the material is hard, or
where it is to be broken up fine, a fine-grained
powder should be used. In either case an equal
amount of material will be removed, but in the
latter instance the rock will be shattered into
finer fragments.

Hard-pressed powders and glazed powders
97

Rock Excavating and Blasting

burn slower than soft-pressed powders of the
same grade or unglazed powders. Also hard
pressed and glazed powders are not affected by
moisture as readily as soft-pressed or unglazed
powders. Again, on account of the greater
density of the hard-pressed grades of black
powder, and on account of the smooth polish
on glazed powders, these grades will pack closer
in bore holes and cartridges, consequently give a
greater explosive force, bulk for bulk, than the
soft-pressed powders or the unglazed powders.
Therefore, in the selection of a suitable powder
for any particular work these several properties
must be taken into consideration.

INITIAL FORCE OF EXPLOSIONS. — The potassium
nitrate in a powder furnishes the oxygen for the
combustion of the carbon and sulphur, which re-
sults in the production of a large volume of heated
gas. It is the pressure of this large volume of
gas which disrupts the rock in which it is liber-
ated, consequently the greater the volume of the
gas produced and the tighter it is confined the
greater is the rending or shattering force.

After a blast has taken place the solid residue
remaining occupies about one-third of the original
volume or space, while powder exploded under
conditions similar to those in practice yields from
175 to 200 volumes of gas at ordinary temperature
and atmosphere pressure. The solid products re-
sulting from the explosion occupying slightly more
than one-third of the original volume of the ex-

Rock Excavating and Blasting

plosive, and the gaseous products somewhat less
than two-thirds, gives the relative volume of gases
with respect to the actual volume of the hole they
occupy as from 260 to 300 volumes. But we have
been assuming that the expansion of the gas took
place at ordinary temperature. As a matter of
fact, however, there would be a great increase in
temperature due to the explosion, and the volume
of gas resulting would be many times more than
300, depending upon the nature of the explosive
used.

The temperature of combustion for most of the
explosives varies from 5,000 degrees Fahrenheit
to 6,000 degrees Fahrenheit. In blasting coal
with black powder the temperature of explosion
does not much exceed 2,000 degrees Fahrenheit,
owing to the slow combustion of the powder and
the yielding nature of the coal, which shatters be-
fore the maximum pressure can be reached. This
gives in coal blasting an expansion of about five
times the gas produced, due to the heat of the
explosion.

If, then, the relative volume of gas produced in
powder blasting is 300 volumes, and the expansion
due to heat equals five times, the blasting volume,
pent up in that part of a drill hole originally
occupied by the charge of powder, would be
300X5=1,500 volumes of gas.

High explosives, on the other hand, produce
When exploded about 1,300 volumes of gas at
ordinary temperature, or about 16,000 volumes
at the temperature of combustion, giving a vol-

>\ Rock Excavating and Blasting

ume ten times greater than that of powder. This
is possible on account of the quicker action of
high explosives, which evolves the gases and
raises them in temperature before fissures in the
rock have time to open.

Powder used in rock blasting, on account of
the greater resistance of the rock, will create a
greater volume than in coal blasting. In practice
it can be assumed that under ordinary condi-
tions low explosives are capable of 1,500 expan-
sions in blasting coal, about 2,000 in blasting
rock, while high explosives are capable of about
16,000 expansions under similar conditions.

The initial force of an explosion, or the press-
ure exerted at the instant the explosion takes
place, is proportional to the number of expansions
of which the explosives are capable, and is equal
to the atmospheric pressure multiplied by the
number of expansions.

Example: With the atmospheric pressure 14.7
pounds per square inch, and blasting powder de-
veloping 2,000 expansions in rock blasting, what
will be the initial force of an explosion in tons
per square inch?

2,000
Solution : - " =U'7 tons per Sq" in*

MECHANICAL WORK OF AN EXPLOSION. — Theo-
retically, as pointed out in the preceding para-
graph, the mechanical work of which an explosive
is capable is estimated by multiplying the volume
of gas produced in the explosion by the pressure

100

Rock Excavating and Blasting

of the atmosphere. In practice, however, the
theoretical amount of work can never be realized.
Further, the factors or conditions affecting the
force of an explosion are so varied that seldom
can exactly similar results be obtained from
blasts fired apparently under similar conditions.

The stored energy of an explosive is only partly
converted into mechanical work in blasting, some
of the heat of combustion being lost by conduction
in the material enclosing the explosive. In case
the drill hole is damp or wet or the rock cold it
will decrease the available heat produced by the
discharge and the power of the explosive. Further,
slips, joints, cleavage planes and loose tamping
affect the blast, as do also the texture and struct-
ure of the rock, so that the work to be done by
a blast cannot be calculated definitely beforehand.

AMOUNT OF EXPLOSIVE REQUIRED. — As the ob-
ject of blasting is merely to shatter and dislodge
the rock so that it can be easily removed, only
enough explosive should be used to do the work.
When fragments are thrown more than a few
yards by a blast, it is generally evidence that too
large a charge of explosive was used. Unfor-
tunately, there is no rule that will apply in every
case as to the amount of powder necessary to use
in blasting. There is, however, a method and
formula by means of which the approximate
amount of explosive to be used may be judged,
and the effect produced by such a charge will
serve as a guide to the quarryman in determining
whether to increase or decrease the amount.

101

Rock Excavating and Blasting

In starting work on a new operation select a
homogeneous rock bench about 2 feet wide and 3
feet high, and in the bench, far enough apart so
they will not affect one another by opening up
seams when blasted, drill several holes 3 feet deep,
and of the standard diameter corresponding to
the depth.

The holes are to be drilled 2 feet back from the
face of the bench, thus giving a line of least re-
sistance of 2 feet, to a depth of 3 feet, which is
the right proportion.

Charge these several holes with different
weights of the explosive to be used, beginning
with a quantity too small to affect rupture, and
increasing by regular amounts to a charge which
will be more than sufficient. Explode all these
charges separately, one at a time, and select as
a coefficient for the formula the amount of explo-
sive producing the desired effect.

The coefficient for future work where the line
of least resistance varies can then be found by
means of the following rule :

Rule. — To find the coefficient for rock blasting
divide the effective charge of explosion used in
the trial holes by the cube of the line of least
resistance. The quotient will be the coefficient to
be used in determining the amount of powder to
be used.

Expressed as a formula:
P

— = C
R*
102

Rock Excavating and Blasting

In which

P =weight of powder in pounds and decimals
of pounds.

R3=cube of line of least resistance in feet and
decimals of a foot.

C ^coefficient for use in determining amount
of powder required.

Example. — What is the coefficient required for
determining the amount of powder to be used, in
subsequent blasts with greater lines of least re-
sistance, when in the trial blasts, with a line of
least resistance of 2 feet, the powder used was
1-3 pound?

Solution. — Substituting in the formula the
values given,

1-3 pound=.33 pounds, and 23=2x2X2=8; then
P .33

— = — = .04125
R3 8

Having determined the coefficient, it may be
used to find the charge of explosive required by
the following rule :

Rule. — To find the charge of explosive required
for blasting rock, multiply the cube of the line
of least resistance in feet by the coefficient de-
termined by trial blasts.

Expressed as a formula :

RS x C = B
in which

R3— cube of line of least resistance.

C = coefficient obtained as explained above.

B = charge of explosive required.
103

>\ Rock Excavating and Blasting

Example. — What weight of powder will be re-
quired to blast rock in which the line of least re-
sistance is 8 feet, and the coefficient .04125?

Solution.— R3 = 8X8X8 = 512. Coefficient =
.04125. Substituting these volumes in the form-
ula:

R3 C = 512 X .04125 = 21.12 pounds of pow-
der. (Answer.)

In the foregoing example it must be remem-
bered all the qualities were assumed, so that the
result obtained in the answer does not necessarily
represent the quantity that would be found in the
application of the rule and formula in practice.
The example is given and worked out to show how
the rule and formula are applied. The main thing
is to find the right coefficient, for naturally this
will vary with the kind and quality of the rock, a
larger charge being required for granite than
would be needed for limestone or sandstone, while
at the same time a smaller charge would be re-
quired for a soft granite than for a hard one,
which would occasion different coefficients for
these various materials.

The quantity of explosive determined in the
foregoing manner is for rock with two free faces.
In blasting where three free faces are exposed
only two-thirds of the calculated charge need be
used. In blasting where four faces are exposed
only one-half the calculated amount need be em-
ployed. When five faces only two-fifths the
amount, and when all six sides, as in the case of
large blocks, are exposed only one-quarter of the
calculated charge will be required.

104

Rock Excavating and Blasting

When the quantity of explosive to use has been
determined the size of drill hole that will hold
the amount, while at the same time occupying in
the bore hole a depth or distance equal to only
twelve times the diameter, can be found in Table
IX. This table was compiled from the formula

C = .3396gd3
in which

C = weight of charge of explosive in pounds.

g = specified gravity of explosive.

d = diameter of hole in inches.

TABLE IX.
Size of Drill Holes for Different Weights of Explosives.

Name of Explosive

Specified
Gravity
of Ex-
plosive
G

Diameter of Holes in Inches

lX/8

1000
1120
1160
1.550
1.550
1.600

.143
.160
• 166
.222
.222
-229

.228
-258
264
352
352
363

•340
380
.394
526
.526
543

480
.541
561
-749
.749
773

•664
.742
.769
1.027
1027
1060

•880
.988
1-024
1-367
1-367
1060

Ardeer powder
Blasting gelatine
Gelatine dynamite

Name of Explosive

Specified
Gravity
of Ex-
plosive
G

Diameter of Holes in Inches

Blasting powder- • •
Carbonite
Ardeer powder
Blasting gelatine . . -
Gelatine dynamite . .

1.000
1.120
1160
1-550
1.550
1600

1148
1.280
1330
1-775
1-775
1833

1.459
1-630
1-690
2256
2.256
2.329

1-822
2036
2160
2819
2819
2910

2-240
2-505
2597
3467
3.467
3579

2720
3-040
3-151
4-211
4.211
4347

3872
4-328
4488
5.991
5991
6.184

5-312
5-936
6.152
8218
8218
8-480

*Daw.

105

Rock Excavating and Blasting

It will be observed that a 2-inch drill hole will
hold only 2.720 pounds of blasting powder when
properly charged, but that by changing from 2
inch to 21/2 inch that charge can be almost
doubled. The table does not give the size of hole
for larger drill than 2y% inches, which corresponds
to a charge of blasting powder of 5.3 pounds.
This is a sufficiently large charge for ordinary
building practice, although in large engineering
works away from habitations as high as twenty
pounds in a bore hole are used, and from 18 to
20 of such charges fired simultaneously. In works
of that size it is found that in soft rock like lime-
stone about two cubic yards of rock can be ex-
cavated for each lineal foot of hole drilled, and
that each % pounds of powder brings down about
one cubic yard of rock.

When a blast is fired the workmen can judge
whether or not there has been enough, too much
or the right amount of explosive used. If the
right amount of explosive is used there will be a
deep boom and the rock will not be thrown with
great force for any distance nor will it be badly
shattered. If there was too much powder used
there will be a sharp report and the blast will
throw the rock a considerable distance, shattering
it badly. If not enough explosive is used, of
course, the rock will not be broken down in the
right-sized fragments, as it should be. If too
small a charge is used to break the rock the tamp-
ing will be blown out from the drill hole, just as
a bullet is shot from a gun.

106

CHAPTER X.

CHARGING DRILL HOLES WITH POWDER.

ARTRIDGES AND TAMPING MATER-
IAL. — In open-cut work where the
drill holes are dry and slope down-
ward from the mouth, blasting pow-
der can be poured into the hoie and
tamped. If the hole is sloped upward, however,
the powder cannot be poured in loose, but must
first be enclosed in cartridges, which are usually
cylinders of Manila paper, and these cartridges
can be tamped into the drill hole. In damp holes,
likewise, the powder should be confined in cart-
ridges to prevent it from losing its effectiveness
by becoming damp or wet. Bore holes under-
ground should never be loaded with loose powder
on account of the danger of dust from the powder
coming in contact with lights and carrying the
flames to the main body of powder, thus causing
an explosion.

The cartridges for use in blasting can be made
by rolling paper around a wooden cartridge bar
of a slightly smaller diameter than the drill hole.
The loose edges of the paper are stuck down by

107

Rock Excavating and Blasting

means of miner's soap, one end of the paper is
folded over to close the end of the cartridge, and
the stick when removed leaves a paper cylinder.
When the cylinder is filled with powder, the cart-
ridge is completed by folding down the other
end.

A uniform and compact tamping is essential
with the use of black powder. For tamping black
powder the material used should be free from
small pieces of stone or other hard substances
which might produce sparks or damage the fuse,
consequently stone dust and coal dust are not con-
sidered suitable tamping, although for want of
better materials they are sometimes used. The
best material for tamping is moist clay. In holes
having anything but a downward slant the tamp-
ing material is best wrapped in short paper cart-
ridges. When loose powder is used a wad of
paper should be tamped between the powder and
the wet clay.

In tamping, if the hole is dry, the cartridges
may be tamped hard enough to break the paper
so the powder will pack close and fill all crevices —
for the closer the powder is packed in the hole
the greater will be the effect produced by the
blast. If the hole is drilled in seamy rock a ball
of clay may first be put into the hole and a bar
driven into it to spread out and fill the seams
and crevices. If these crevices are not filled the
gases formed by the explosion will escape through
them and part of the force of the blast will be
lost. In wet drill holes the cartridges should be

108

Rock Excavating and Blasting

well coated with miner's soap and the filling not
tamped hard enough to break the paper.

DEPTH OF TAMPING. — In deep drill holes it is
never necessary to tamp the hole full, only suffi-
cient tamping being necessary to prevent a blow-
out or to prevent yielding before the full force of
the explosion is reached. With dynamite and
other high explosives which develop their full
power instantaneously, less tamping is required
than with powder, for the reason that with the
high explosives the shock is delivered on the sides
of the chamber with sufficient force to burst the
rock before it has time to affect the tamping.
With high explosives very light tampings are
sometimes used, as, for instance, filling the drill
hole with water or filling the hole a few inches
with sand or fine dirt, while for powder blasting
considerable tamping must be used, the depth of
tamping depending on the diameter of hole. For
1-inch holes the very least tamping that will hold
is 17 inches ; in a 2-inch hole, 18 inches of tamping ;
and in a 3-inch hole not less than 20 inches ol
tamping. These values are the minimum, it must
be remembered, and in actual practice not less
than 2 feet should be used for any size, while
even deeper tampings will prove safer.

METHOD OF CHARGING A DRILL HOLE. — In Fig.
48 is shown how a drill hole is charged with pow-
der, tamped and made ready to fire with a fuse.
The fuse, it will be noticed, is extended to the

109

Rock Excavating and Blasting"

center of the powder cartridge and where it leaves
the top end of the cartridge is offset to one side
of the drill hole to make way for the tamping.
The tamping bar has a groove at one side so it
will not cut or strip the fuse, or needle when a

Fig. 48.
Method of Charging Drill Hole.

110

Rock Excavating and Blasting

squib needle is used, and at the same time will
tamp the filling well around the fuse or needle.
Tamping rods having metal parts should never be
used on account of the danger of striking sparks
when tamping. When loose powder is poured in
the hole it is of the greatest importance to use a
wooden tamping rod, as an iron rod coming in
contact with stone or pyrites is liable to spark and
cause a premature explosion. Whenever a metal
tamping rod is used, it should be either copper or
brass, never iron or steel.

In filling the drill hole the tamping is put in
and tamped little by little, the first few inches
being rammed hard and the remainder only pack-
ed sufficiently tight to keep its shape and leave
open the needle hole when a squibbing needle is
used.

SQUIBBING. — Charging with a needle and fir-
ing by means of a squib is practised rather ex-
tensively, particularly in mines, but the operation
is rather dangerous and requires careful manipu-
lation. In this method a rod of metal called a
needle, about 14 inch in diameter and pointed at
one end, is placed along the side of the bore hole,
the powder placed in position, pressed down, the
hole tamped and the needle carefully withdrawn.
When the powder is in a cartridge, the cartridge
is first inserted in the bore hole and the needle
then placed in position, with the point piercing the
cartridge a few inches. The withdrawal of the
needle then leaves a channel down one side of the

111

Rock Excavating and Blasting

tamping and into the center of the powder in the
cartridge, into which the squib is inserted.

A squib is a small paper tube or straw that is
filled with a quick powder and has a slow match
attached to one end. The burning of the slow
match gives the workman time to get away after
lighting it and before the flame reaches the pow-
der. When this quick powder in the paper tube
is fired it shoots like a rocket back into the blast-
ing powder through the hole in the tamping left
by the withdrawal of the needle.

In squib firing a metal needle is required, but
this metal should be copper or some alloy like
brass. It should never be of iron or steel for the
same reason given for not using a steel or iron
tamping rod.

USES FOR POWDERS AND DYNAMITES. — Black
powders are generally favored for use in coal
mines, building-stone quarries or other places
where the material is to be taken out without too
much shattering. Also for blasting in soft ma-
terials where all classes of high explosives are too
quick in their action to utilize their entire
strength. The great advantage of powder in these
classes of work is that it exerts a strong push
upon the material to be removed, not a quick,
sharp, shattering blow, characteristic of high ex-
plosives.

It must be remembered, however, that dynamite
is now made in nine or ten different grades, some
slow acting, others quick acting, some full

112

Rock Excavating and Blasting

strength, others of less strength, so that dynamite
can be used for almost every purpose that black
powder is suitable for, and for many purposes
for which powder would be unfit.

TESTS OF BLASTING POWDER. — The only tests of
gunpowder that need be made by workmen or the
superintendent on the premises are some simple
ones to determine whether or not the powder is
dry and in good, usable condition. If the powder
has absorbed moisture enough to make it wet or
damp, it should not be used until dried. One way
to test for moisture is to rub the grains of powder
on a piece of clean white paper. If the paper be-
comes blackened the powder is moist, while if not
discolored no moisture is present.

Another method is the ignition test. If a small
quantity of good, dry powder is ignited on a sheet
of dry paper it will flash up instantly without
burning the paper or discoloring it to any great
extent. Burning of the paper usually indicates
the presence of moisture. Black spots left on
the paper after flashing the powder indicate an
excess of charcoal or an imperfect mixing of the
ingredients, usually the former, as with the ma-
chinery used in making powder the ingredients
are well mixed together. Yellow spots on the
paper indicate an excess of sulphur in the powder.

These tests at their best, while simple and easily
made, give only a rough approximate idea of the
quality or condition of the powder. At all events,
if sufficient heat must be applied to the powder

113

Rock Excavating and Blasting

in testing to ignite the paper, it is pretty conclu-
sive evidence that the powder is damp and not fit
for use without drying.

DRYING BLASTING POWDER. — Don't use wet
blasting powder. If the powder is only damp it
can be dried, thereby making it suitable for use.
The only way to dry damp blasting powder is to
spread it out in the hot sun on a dry day and in
a protected place where the wind cannot blow it
away. The powder must be spread out in a thin
layer and on a platform raised from the ground
so it cannot absorb moisture as it is given off.

Powder should never be dried on a stove or
near a fire, whether in the powder keg or loose,
as there is liable to be a flash or explosion if it
becomes overheated. The best way is to avoid the
use of blasting powder if there is danger of it
becoming damp or wet, and use a suitable grade
of dynamite.

HANDLING BLASTING POWDER UNDERGROUND. —
Too great care cannot be exercised in the handling
of blasting powder underground in tunnels or
shafts. Underground bore holes should never be
loaded with powder unless the powder is made up
into cartridges. The cartridges had better be
made up in daylight on the surface and carried
down in that way. Under no condition should a
light, unless a safety lamp, be permitted near an
open keg of powder, and if necessary to make up
powder cartridges underground the light should

114

Rock Excavating and Blasting

be kept well away from the powder and to the
windward side of it. If the light were on the
"lee" side of the keg, powder dust from the loading
might communicate with the light, thereby carry-
ing the flame to the main body of the powder and
exploding it. This is the reason that loose pow-
der should not be used for charging bore holes
underground. Trails of powder spilled on the
ground or powder dust in the air might lead to
a premature blast or an explosion of the powder
in the keg.

TAMPING BAGS. — No bore hole can be properly
charged with loose powder unless the bore hole
points down. In tunnel driving and other inside
and outside work, however, many of the drill
holes point upward, and to properly charge them
with powder the powder must first be made up
in the form of a cartridge. In tamping bore holes
that point upward it is likewise practically im-
possible to get loose material to stay in the hole
as it should, and in practice tamping bags are
made to hold the tamping material. Tamping
bags and cartridges are made in the same way
and same size and may be made by the workman
himself as previously explained, or can be had
with other blasting supplies.

The size, weight and other information about
stock tamping bags can be found in Table X.

Blasting powder weighs approximately the
same as water, which is 29.2 cubic inches to the
pound. For convenience in calculating, 30 cubic

115

Rock Excavating and Blasting

TABLE X.
Size, Number and Weights of Tamping Bags.

Size

Size in

Number

Shipping
Weight

Approximate
Weight One

Number

Inches

in Bale

per

Powder Bag

Bale

Will Hold

1 x8

5 M

32 Pounds

3 Ounces

IK x8

5 M

IK xlO

5 M

!Kxl2

5 M

IK x8

5 M

IKxlO

5 M

!Kxl2

5 M

IK x 16

5 M

105

inches of powder is often assumed as weighing
a pound. This gives to a cubic inch of powder an
approximate weight of .53 ounces. These figures
are, of course, only approximate, as the weight of
powder in bulk depends on the size of the grains
and how closely the grains are packed. The in-
dividual grains themselves likewise differ in
weight, varying in specific gravity from 1.5 to
1.85.

116

CHAPTER XL

HIGH EXPLOSIVES.

DYNAMITE.

ITROGLYCERINE.— There are a
number of high explosives used for
different purposes, but so far as or-
dinary rock blasting is concerned
dynamite and blasting gelatine are
the only ones that need be considered in detail.
It will be well, however, to explain the nature of
nitroglycerine, as this will help to a better under-
standing of the nature of dynamite, while gun
cotton will also be considered as one of the active
principles in all blasting gelatines.

Nitroglycerine is a mixture of nitric acid, sul-
phuric acid and glycerine. The glycerine used is
the pure glycerine of commerce, a heavy, oily
liquid resembling syrup and known as the sweet
principle of oils. It is obtained by the decomposi-
tion of vegetable or animal fats or fixed oils. In
the manufacture of nitroglycerine three parts of
strong nitric acid are mixed with five parts of
concentrated sulphuric acid, and after this mix-
ture, which has become heated by the process,

117

Rock Excavating and Blasting ^

cools off, 1 to 1.15 parts of glycerine are slowly
and gradually added, the mixture being stirred all
the while. In the manufacture of nitroglycerine
in dynamite mills, compressed air is generally
used for mixing the ingredients, and every pre-
caution is taken to prevent the mixture from heat-
ing.

After the nitroglycerine has been mixed it is
poured into five or six times its bulk of cold water,
where it sinks to the bottom as a heavy, oily liquid
of a yellowish tint. The color is due to impurities
in the ingredients, absolutely pure nitroglycerine
being clear and transparent.

PROPERTIES OF NITROGLYCERINE. — At ordinary
temperature nitroglycerine is an oily liquid, and
must be confined in a bottle or like receptacle. It
does not mix well with warm water, and seems
to be unaffected by cold water, which makes solid
explosives made of this mixture suitable for use in
damp places and under water.

Nitroglycerine has a sweet, pungent taste, is
an active poison, and produces in those unaccus-
tomed to handle it nausea, faintness and severe
headaches. Persons of a nervous temperament
are more easily affected than others, but become
accustomed to handling it without noticeable ef-
fect when made up into dynamite or like com-
pounds.

In the liquid state, when confined, nitroglycerine
is very sensitive and a slight concussion or jar
is liable to explode it. This unstability makes

118

^V>\ Rock Excavating and Blasting
^^^•••^^••^••^^^••••••••••^•^^••••••••••^^^^•^•^

nitroglycerine dangerous to store and handle, con-
sequently it is not used extensively in liquid con-
dition.

When frozen, nitroglycerine is less sensitive to
concussion than when in the liquid state, but it is
still dangerous to handle and the process of thaw-
ing is both difficult and dangerous. The explosive,
furthermore, loses some of its force after freezing,
so that all told little if anything is gained by
keeping it in the solid condition. Freshly made
nitroglycerine freezes at 55 degrees F., while puri-
fied nitroglycerine freezes to a white, crystalline
mass at 36 degrees F.

The firing point of nitroglycerine is 356 degrees
Fahrenheit, a comparatively low temperature,
equal only to that of steam under a pressure of
132 pounds per square inch, but it decomposes at
a lower heat. When unconfined, nitroglycerine
will burn, but a spark will not explode it, a con-
cussion or detonation being necessary to produce
an explosion.

Outside of shooting oil wells, blowing safes and
for a few purposes like that nitroglycerine is not
extensively used in its free state. Its interest to
us here lies in the fact that it is the active agent
in all forms of dynamite, really is still nitroglyce-
rine when made into dynamite, but is thus made
comparatively safe to store and handle.

DYNAMITE. — Dynamite is simply nitroglycerine
absorbed by some absorbent material called a
dope. If the dope is merely an absorbent for the

119

Rock Excavating and Bl a s t i n g

nitroglycerine and does not add anything to the
explosive character of the mixture it is said to be
inactive. If, on the other hand, the dope is of
such a material or composition that when the ex-
plosion takes place the dope also ignites or ex-
plodes, thereby adding to the force of the initial
explosion, the dope is said to be active. Strictly
speaking, the term dynamite is applied only to
those nitroglycerine explosives which have an in-
active dope, and special trade names are given
to those mixtures in which the dope is active.
Ordinary dynamite, also dynamites with active
bases, possess the advantages over nitroglycerine
not only that they are less sensitive and can there-
fore be more easily and safely handled, but they
can further be made in various degrees of
strength and put up in packages for convenient
handling.

DYNAMITE WITH AN INACTIVE BASE. — Dyna-
mites with inactive bases have been made with
such inert dopes as infusorial earth, magnesium
carbonate, sawdust and charcoal. Of all the fore-
going materials infusorial earth makes the best
dope, as this earth is very porous and when care-
fully prepared will absorb 75 per cent, of nitro-
glycerine. In America, however, very little dyna-
mite is made with infusorial earth, charcoal or
any of the other dopes enumerated above, for the
reason that cheaper dopes of equal safety can be
had in the form of wood pulp. The wood pulp is
usually mixed with sodium nitrate, which fur-

120

Rock Excavatin g and Blasting

nishes oxygen for burning the wood pulp when
the dynamite is exploded. When a silicious dope
like infusorial earth is used, on the other hand,
it is inert, acts merely as an absorbent, and leaves
a residue when the dynamite is exploded. Dyna-
mite having an inactive base and containing less
than 30 per cent, of nitroglycerine cannot be ex-
ploded.

DYNAMITE WITH AN ACTIVE BASE. — As ordin-
ary dynamite cannot be exploded when it contains
less than 30 per cent, of nitroglycerine, that is
the lowest possible amount that can be used, and
the force of the explosion cannot be regulated be-
low that limit. The force of an explosion from
that minimum limit upward, however, can be reg-
ulated by varying the amount of nitroglycerine
the dynamite contains. That is the reason or-
dinary dynamite is not suitable for blasting coal,
rock for building purposes, or for other purposes
where shattering is not desired, while at the same
time special dynamites with active bases can
sometimes be used for those purposes to good ad-
vantage.

If, instead of the inactive base, some combusti-
ble or explosive substance be used as an absorbing
dope and the proportion of nitroglycerine can be
reduced below 30 per cent., it will explode, and
the force of the explosion will be less than that
from the weakest common dynamite. On the
other hand, by retaining the same percentages of
nitroglycerine and using an active base the force

121

Rock Excavating and Blasting

of an explosion can be increased beyond that
which the nitroglycerine alone produces.

STRENGTH OF DYNAMITE. — The strength of all
high explosives is based on their execution, com-
paring them with ordinary dynamite of known
percentage. For instance, much of the dynamite
now sold has an active base, but is classed as an
ordinary dynamite so far as strength is concern-
ed. It is rated as 40, 50 and 60 per cent, dyna-
mite, but this does not mean it contains that per-
centage of nitroglycerine, but that it has an ex-
plosive force equal to 40, 50 or 60 per cent, com-
mon dynamite. Common dynamite, which is the
standard of comparison, is rated according to the
amount of nitroglycerine it actually contains, and
a 40 per cent, common dynamite means that it
possesses 40 per cent, of nitroglycerine.

The strength, or disruptive force, of special
dynamites is due to the active ingredients form-
ing the base as well as to the nitroglycerine.
These ingredients differ in the fumes they evolve,
water-resisting properties and resistance to
freezing — consequently it is necessary to use dif-
ferent grades for different works, a non-gas-
forming dynamite for tunnel or shaft work, a
frost-resisting brand for outdoor work and cold
weather, and a dynamite that will not be dam-
aged by water for blasting in wet places.

APPEARANCE OF DYNAMITE. — Dynamite looks
something like fine sawdust slightly dampened,
but varying in color from black, brown, yellow,

122

Rock Excavating and Blasting

gray to almost white, depending on the ingredi-
ents used for the dope. For use in blasting, dyna-
mite is made up into cartridges as shown in Fig-
ure 49. The cartridge wrappers are made of

Fig. 49.
Cartridge of Dynamite.

cylinders of paraffined brown paper, carefully
folded down or crimped at the ends so that none
of the contents can run out.

SIZE OF DYNAMITE CARTRIDGES. — Dynamite
cartridges are made of such diameters that they
will enter their complementary bore holes, if of
standard size, without forcing them. They are
made in sizes from % incn to 2 inches in diameter,
and in length of 8 inches. The standard stock
sizes and approximate weights of dynamite cart-
ridges can be found in Table XI.

TABLE XI.
Sizes and Weights of Dynamite Cartridges.

Diameter of Cartridge

Length of Cartridge

Approximate Weight
of Dynamite

% Inches

8 Inches

2 Ounces

1 Pound

123

@^\>\ Rock Excavating and Blasting

Dynamite is shipped in twenty-five and fifty-
pound wooden boxes, lined with paraffined paper
and packed with sawdust.

PROPERTIES OF DYNAMITE. — Dynamite is rather
plastic, which favors its being charged in a drill
hole. In spite of the fact that glycerine is an oil,
dynamite is not what would be called greasy. The
specific gravity of dynamite depends some on its
dope. Ordinarily, the specific gravity is about
1.15, which being heavier than water favors it
when used for submarine blasting. Dynamite has
the physical qualities of nitro-glycerine so far as
explosive power is concerned, and is equally poi-
sonous to those unaccustomed to handle it. Like
nitroglycerine, dynamite has a firing point of 356
degrees Fahrenheit, at which temperature it will
either burn or explode. If free from gas or pres-
sure it will burn, but if jarred, even when loose
and unconfined, may explode.

Ordinary dynamite freezes at a temperature
of about 43 degrees Fahrenheit and becomes in-
sensitive at from 45 to 50 degrees Fahrenheit.
When completely frozen dynamite is hard and
rigid. This condition is easily recognized, but it
requires a careful examination to determine
whether or not it is only partly frozen or chilled.
Dynamite will not do good work if chilled, and
when solidly frozen it is difficult or impossible to
explode it, or if it does explode the detonation at
best is only partial. Care should be taken, there-
fore, to see that the explosive is thoroughly thaw-

124

Rock Excavating and Blasting

ed in cold weather before using. It is dangerous
to cut, break or ram a frozen dynamite cartridge,
as part of the cartridge might be in a thawed con-
dition and the nitroglycerine crystals explode.

The sensitiveness of dynamite to blows or
shocks increases very rapidly with rise of temper-
ature, as would be expected, as that is a condition
common to nitroglycerine, from which it is made.

In the foregoing paragraphs the properties of
ordinary dynamite are pointed out. It will be
well for the quarryman to remember, however,
that there are special makes of high explosives
which differ greatly in behavior from ordinary
dynamite, while having the same explosive force.
Monobel and Judson powder R. R. P., for instance,
freeze at the same temperature as dynamite, but
if a suitable detonator be used they can be prop-
erly exploded even when frozen. The Arctic
brand of dynamite, on the other hand, does not
freeze at all, and the Red Cross grades do not
freeze until water freezes, at a temperature of 32
degrees Fahrenheit. It would follow from the
foregoing that high explosives differ widely in
their character, and it is of the greatest import-
ance to select a grade best adapted for the work
to be done. Besides the different conditions under
which various grades of dynamite can be used,
each kind of high explosive, except blasting gela-
tine, is made in different strengths, and each
strength is put up in cartridges of various diam-
eters, suitable for the different sizes of drill holes.
When engaged in rock excavating, whether min-

125

Rock Excavating and Blasting

ing, quarrying, tunneling or removing rock in con-
struction work, the superintendent in charge will
do well to secure from the various manufacturers
of explosives their catalogues and descriptive mat-
ter about the various brands of explosives they
make, and the purposes for which they are best
suited. Manufacturers of explosives, as well as
independent experimenters, are constantly at
work trying out new formulas, and as soon as the
demand arises for an explosive of any quality, the
demand is soon filled.

126

CHAPTER XII.

METHODS OF THAWING DYNAMITE.

HAWING FROZEN DYNAMITE. — Froz-
en dynamite will thaw out complete-
ly in a very short time if it is sub-
jected to a dry temperature of 80
degrees Fahrenheit and the cart-,
ridges so arranged that the heat can reach them
on all sides. Care should be exercised in this pro-
cess, however, to keep the temperature from ris-
ing higher than necessary, for every degree
through which the dynamite is heated brings it
that much nearer its firing point and makes it so
much more dangerous to handle. It is a danger-
ous practice to thaw frozen dynamite by passing
it through the flame of a candle, heating it in an
oven or holding it on a shovel before the open
fire, for, while dynamite will frequently burn in
the open and when unconfined, it very often ex-
plodes.

Convenience, safety and economy are all pro-
moted by having a suitable thawing kettle or as
many of them as are needed on an operation, for
blasting cannot be properly conducted in cold

127

Rock Excavating and Blasting

weather without some appliance for thawing the

explosives and keeping them thawed until they

are loaded into the bore holes. A thawing kettle,

specially designed for thaw-

ing dynamite cartridges, is

shown in Fig. 50. It is sim-

ply what is known in the

kitchen as a double boiler,

only much larger, being

made in two sizes, having

capacities respectively of

22 and 60 pounds of the ex-

plosive. The space between

the inner and outer kettles

is filled with hot water or

with cold water and placed

on a stove or on a fire to KettleFf0'r

heat, and when the water Dynamite.

has been raised to the right temperature the ket-

tle is packed in sawdust, the dynamite cartridges

placed in the inner compartment and a cloth of

some kind or other non-heat conducting material

placed over the top to keep in the heat.

The temperature to heat the water is a question
which must be considered when using a thawing
kettle. It must be remembered that a tempera-
ture of 80 degrees is all that is required to thaw
dynamite and keep it in that condition, while the
firing point is 356 degrees, or only 144 degrees
above the temperature of boiling water in an open
vessel. It must be still further remembered that
the higher the temperature of the dynamite the

128

Rock Ea

more unstable it is and the more likely to be de-
tonated by a slight shock. It is well, therefore,
to aim not to heat the cartridges to a higher tem-
perature than 100 degrees Fahrenheit. If a full
charge of 22 or 60 pounds of dynamite is to be
placed in a kettle and the dynamite is frozen, the
water may be raised to the boiling point, because
the heat required to raise the temperature of the
dynamite will lower the temperature of the water
until they will both be around 100 degrees Fah-
renheit. If only a small amount of dynamite is
to be thawed, on the other hand, or the dynamite
to go into the kettle is not frozen, merely chilled,
or being placed there to keep from freezing, then
the water should be heated only sufficient to per-.
form the work it has to do without raising the
temperature of the dynamite to a dangerous de-
gree.

Dynamite should never be thawed by exposing
it to steam or soaking it in hot water, as it will
lose some of its strength and the nitroglycerine
removed becomes a source of danger. For this
reason the water in a thawing kettle should never
be reheated by placing it over a fire or on a stove,
as nitroglycerine from the dynamite in the thaw-
ing compartment might have been extracted and
leaked through to the water compartment. When
necessary to replenish the heat in a thawing kettle,
add warm water from another vessel. In the
absence of a thawing kettle, burying dynamite in
a water-tight box in fresh manure which is giving
off heat is a safe and effective way to either thaw

129

Rock Excavating and Blasting

or keep in a plastic state dynamite cartridges.
The method requires considerable time, however;
a suitable manure pile is not always available and
it would seem more logical to get a thawing kettle
than a special water-tight box.

THAWING BOXES. — Fresh manure is a thawing
agent which is inexpensive, convenient, safe and

. 0

Fig. 51.
Thawing Box for Dynamite.

usually readily obtainable on all large blasting
operations where horses form part of the working
force or equipment. Manure is efficient, however,
only when it is fresh and will give off heat. It is
useless to take old manure in which no heat is

130

Rock Excavating an d Blasting

being given off by the fermentation taking place.
Time is another element in the thawing of dyna-
mite by means of manure, for it must be thawed
in large quantities, and the larger the quantity the
longer it will take. The dynamite cartridges must
not be allowed to come in contact with the manure,
as the moisture would draw more or less nitrogen
from the absorbent. It must be buried in the man-
ure, therefore, either in closed cases or in specially
designed boxes or magazines having walls lined
with manure. A box for thawing dynamite is
shown in Fig. 51, which will give an idea of how
to construct a thawing box for manure. If there
is a big heap of manure available, it may be buried
in the manure heap. If, on the other hand, man-
ure is not so plentiful, a hole or pit can be dug
in the ground a sufficient depth to permit a good,
deep lining of manure. The box is then placed in
the pit on top of the manure lining, and the sides
banked up to the level of the ground. The dyna-
mite cartridges in the cases, the tops of which
should be removed before placing them in the
thawing box, may now be placed in position, and
the cover placed, then the whole heaped up with
manure. In the course of time, a nice even tem-
perature will be generated inside of the thawing
box, and all of the dynamite will be thoroughly
thawed.

It is advisable to take the covers off the cases
before placing them in the thawing boxes, so that
sticks or cartridges of dynamite can be taken out
by simply removing the cover of the box, and

131

Rock Excavating and Blasting

without jarring or otherwise disturbing the dy-
namite. Removing the cover further gives more
of a chance for the heat to reach the interior of
the case.

The thawing box shown in the illustration is
made for just two cases of dynamite. They can
be made any size desired, however, just as well as
for two cases. The walls of the box are made of
2-inch planks, one side higher than the other, to
give a pitch to the cover. This pitch, together
with a layer of galvanized iron, sheds all moist-
ure from the box and keeps the contents dry. A
double-wall manure box may be used instead of a
single-wall box when desirable, the other box or
wall serving as the pit shown in the illustration.

A thawing box 22 by 34 inches will be found
large enough to hold two fifty-pound boxes of
dynamite, and will leave room all around them for
the heat to reach all sides. At the same time the
extra room will facilitate handling boxes or cases
when placing them in the thawing box or taking
them out.

Whether in storage or in a thawing box or
house, dynamite cartridges ought to be placed so
they will lay on their sides, not stand on their
ends, for if standing on their ends the nitroglycer-
ine is liable to ooze from the dope and collect in
the bottom of the receptacle.

THAWING HOUSES WITH MANURE-FILLED
WALLS. — In Fig. 52 is shown the construction of
a dynamite-thawing house with manure-filled

132

Rock Excavating and Blasting

walls. It is 8 by 10 feet outside dimensions, and
is 7 feet 6 inches high inside.

The house has walls 18 inches thick, filled with
fresh manure, and possesses a storage capacity

Fig. 52.
Thawing House for Dynamite.

of from 800 to 1,200 pounds of dynamite, taken
out of the cases and placed in a single layer on
the slatted shelves. This thawing house depends
for its heat entirely upon the stable manure which

133

Rock Excavating and Blasting

fills the walls. The length of time required to
thaw the stored dynamite, and the thickness of
the walls, are variable quantities and depend to a
great extent upon the severity of the climate and
the age of the manure.

With good, active manure giving off a large
quantity of heat, eighteen inches of manure will
be found sufficient for any ordinary locality. A
thawing house of this size and character is adapt-
ed to work requiring a large quantity of explosive,
but running through a period of one winter only,
or a few months of cold weather. However, by
removing some of the top boards from the walls
and replacing the old manure with a lot of fresh
manure each winter, such a thawing house can be
used indefinitely.

The class of materials used in construction can
be changed to suit any local conditions. For in-
stance, the illustration shows the roof covered
with galvanized sheet iron. It may be more con-
venient in some cases, however, to cover the roof
with tar paper or some other prepared roofing
material, while in some places the climatic con-
ditions or the short time for which the house is to
be used will permit the omission of any other
covering than the sheathing.

On the other hand, in some places it may be ad-
visable to cover the walls as well as the roof with
sheet metal or other like material.

This thawing house possesses one bad feature.
It is so arranged that it is necessary to enter to
get dynamite or place it on the shelves.

134

Rock Excavating and Blasting

As the house is both warm and convenient,
there will, therefore, be a probability of using it
as a place in which to make up the primers for the
blasts, unless regulations to the contrary are em-
phatically enforced.

STEAM THAWING HOUSE. — Permanent houses
for thawing dynamite are preferably heated with
exhaust steam or hot water. So far as the method
of construction is concerned, there is no difference
between the construction of a steam-heated thaw-
ing house and one heated with hot water, except
that when exhaust steam is used the supply is ob-
tained from the engine, or pump house, while,
when the thawing house is to be heated with hot
water, a special heater house will be required,
unless the boiler house already on the premises
happens to be so located that it can be used.

Exhaust steam is usually the most convenient
and inexpensive heat that can be used, for at the
majority of permanent works where explosives
are used there is an engine or pump, the exhaust
steam from which can be used at practically no
cost for the heat required in the coils of the
thawing house.

Live steam is dangerous to use, because of the
high temperatures of steam under pressure.
Eighty pounds is a comparatively low pressure for
steam driving an engine or pump, but at that com-
paratively low pressure steam has a temperature
of about 324 degrees Fahrenheit, while the dyna-
mite has a firing point of only 356 degrees Fah-

135

Rock Excavating and Blasting

renheit. At a pressure of only 131 pounds per
square inch, a pressure commonly carried in power
plants, the temperature of the steam is 356 de-
grees Fahrenheit, the firing point of dynamite. It
will be seen, therefore, how necessary it is not to
have live steam for thawing purposes, for if some
of the workmen were to carelessly, ignorantly or
recklessly attempt to thaw out sticks of dynamite
on the steam coils, as they sometimes do, there
would in all probability be an explosion if steam
of sufficient high pressure were being used.

It is well to keep a thermometer on the back
wall of the thawing house, in what ought to be the
hottest part of the interior, and have a double
glass window in front of this thermometer, so
the temperature of the interior can be determined
without opening the door and admitting cold air.
A damper should also be placed in the ventilation
flue to permit the regulation of the air circulating
through the house.

A thawing house suitable for the use of either
exhaust steam or hot water is shown in Fig. 53.
In this case, however, a heater house is incorpor-
ated, showing the method of connecting up the
water heater with the heater coils.

It will be noticed that the house cannot be en-
tered. On the contrary, the dynamite is placed on
and taken from wooden trays or drawers which
slide in and fill the compartments where they are
located. It follows that it is impossible to use
such a house as a place for priming cartridges or
doing other work of a like dangerous character.

136

?\ Rock Excavating and Blasting

137

Rock Excavating and Blasting

It ought to be needless to add that the thawing
house should always be kept locked and that only
one person should have possession or custody of
the key to the lock.

The heating coils for a thawing house must
never be placed in that portion of the building
where the trays are located, but must be installed
in a little lean-to attached to the thawing house,
and from where the heat from the coils can spread
to the tray racks. It is well to so construct the
lean-to that air will circulate freely through, in at
the bottom from the dynamite trays, up through
the heater coils, and out again at the top into the
thawing room. The amount of heating surface
required in the steam or hot water coils will have
to be worked out in each case. It will depend
upon the size of the building, the way it is built,
and the climate where the thawing house is to be
located. In severe climates, also where there is
a variable climate, it will be well to have the coils
in sections and controlled from the outside, so
that sections can be thrown into service, or cut
out as occasion requires. The aim is to keep the
interior of the thawing house and its contents at
a uniform temperature of about 80 degrees Fah-
renheit.

The walls of the house must be carefully looked
after, as they must be well insulated. Either sand
or sawdust may be used for this purpose when the
thawing house is in a protected place, out of dan-
ger of rifle shot. When there is a possibility of
the building being used as a target for rifle prac-

138

Rock Excavating and Blasting

tise by careless persons, however, it is better to
use sand for the filling material, the same as in
magazines for the storage of dynamite. The pre-
caution to use coarse, dry sand, but not coarse
gravel, should be observed here the same as in the
case of storage magazines, and for the same rea-
son.

The size of house to build will depend upon the
quantity of dynamite that is to be thawed. The
size is regulated to a great extent by the size of
trays. The trays are made 18 by 30 inches inside
measurement, by 5 inches deep, and are designed
to hold 50 pounds of dynamite each. Ten inches
space in height is allowed for each of the trays,
and a tier of five trays allowed to each compart-
ment. Two such tiers would make a thawing
house holding 500 pounds of dynamite, and if a
larger building is required, it can be increased in
units of 250 pounds each, making at the same
time a corresponding increase in the size of the
steam or hot water coils.

A dynamite tray for a thawing house is shown
in Fig. 54. The bottom of the tray is either slat-
ted or perforated, to allow the circulation of air.
When hot water is the heating medium used, the
heater house must be situated at a sufficiently low
level, so that there will be a rise of at least 1
inch in 10 feet in the pipe from the top of the
heater to the hot water coils in the leant-to of the
thawing house. If this grade is lacking there will
be no circulation of hot water, but steam will
form in the heater and make a rattling, snapping

139

^V*\ Rock Excavating and Blasting

sound. For safety sake the system must never
be a closed one, but must be open and provided
with an expansion tank to prevent the pressure
ever rising above that due to the head of water.
If the water were confined in a closed circuit, pres-
sure would be generated, and as the temperature
of boiling water and steam are the same under

» V,

I*T

WW »3

k\H fcM ttU kM M HI NX

i Ma M r\- ra

Dyr?&/7?/'fe Tray.

Fig. 54.

equal pressures, the water in a closed hot-water
system could be made as hot and, therefore, as
dangerous as steam in a direct steam system us-
ing high pressure. There would likewise be the
additional danger of a boiler explosion, with the
possible detonation of the dynamite. With an

140

Rock Excavating and Blasting

open system of hot water heating, on the other
hand, the temperature of the water can never rise
above 212 degrees in the heater, and would be
much less than that at the coils, so that the dan-
ger of overheating is thus minimized by using an
atmospheric system of hot water heating.

Distance of the heater house from the thawing
house is another condition that requires consid-
eration. A distance of from 30 to 50 feet has
been found the most satisfactory. Too close prox-
imity of the heater house to the thawing house,
that is, a distance of less than 30 feet, adds to the
fire risk, while too great a distance, that is, fur-
ther than 50 feet, increases the cost of construc-
tion and diminishes the economy of operation;
The aim should be, then, to strike the happy med-
ium between the two extremes.

The exposed piping, of course, must be well
insulated, or a frozen pipe and interrupted ser-
vice will result. The best of pipe covering is none
too good for this purpose, and non-combustible
covering material would be preferable to combus-
tible materials.

At permanent works, an inexpensive way to
keep dynamite from freezing is to store it in a
stone, concrete or brick vault below the surface of
the ground, and well below the frost line. The
roof can be tightly roofed over and banked with
earth or manure.

Perhaps no better advice could be given in this
chapter on dynamite than to incorporate the rules
to be observed in handling dynamite, sent out with

141

Rock Excavating and Blasting

each shipment of high explosives by the DuPont
Powder Company:

Never under any circumstances forget that it is
an explosive, and must be treated as such.

Do not store blasting caps or electric fuses near
dynamite. They are easily exploded, but by them-
selves do only local damage. If they are in the
vicinity of dynamite they might set it off and
cause great loss.

Do not carry or transport blasting caps or elec-
tric fuses together with dynamite.

Never expose dynamite to the direct rays of the
sun, a fire or hot stove. Never roast, toast or
bake it in any way.

Never put it on or in a stove or oven, on hot
steam pipes or on any hot metal.

Never fire into dynamite with a rifle or pistol,
either in or out of a magazine.

When a shot misses, never dig it out. Take
plenty of time before investigating.

Never use a metal tamping rod. Wood is the
only safe material.

Never attempt to use frozen dynamite. Thaw
it first.

Never store dynamite in a wet or damp place.

Never leave it in a field where stock can get at
it. Cattle like the taste of dynamite, but it would
probably make them sick.

All explosive material should be kept in a suit-
able dry place, under lock and key, and where chil-
dren or irresponsible persons cannot get at it.

142

Rock Excavating and Blasting

GUNCOTTON AND BLASTING GELATINE.

GUNCOTTON. — Guncotton is a highly explosive
compound prepared by treating cotton or other
cellulose materials with strong nitric and sul-
phuric acids. Ordinary cotton of commerce is the
cellulose material most commonly used for this
purpose.

Guncotton is highly inflammable, burning with-
out ash, but quietly unless under compression,
when it will explode. It is largely used as an in-
gredient in smokeless powder, but as an explosive
it has been largely superseded by dynamite.
When dry, guncotton is very sensitive and easily
exploded, but when wet with from 15 to 30 per
cent, of water it is insensitive to all ordinary
shocks. While in this condition, however, it may
be caused to detonate by detonating dry guncotton
in contact with it. The dry guncotton can be de-
tonated in a number of ways, but the surest and
most convenient is by means of a fuse of fulmi-
nate of mercury or a detonator of the same ma-
terial in a rubber sack in contact with the dry
guncotton.

Guncotton differs but little in appearance from
ordinary cotton, but it is harsher to the touch and
less flexible. It is insoluble in hot or cold water,
but it is readily soluble in many other liquids, not-
ably a mixture of ether and alcohol. Guncotton
by itself is not much used for rock blasting, but
it forms the base of a number of powerful pow-
ders, among which are "Tonite," consisting of

143

Rock Excavating and Blasting

guncotton 52.5 per cent, and barium nitrate 47.5 ;
and "Potentite," consisting of 66.2 per cent, of
guncotton and 33.8 per cent, of potassium nitrate.
Blasting gelatines are also made from guncotton
mixed with some solvent.

The explosive force of guncotton has been found
to be more than fifty times that of equal weights
of gunpowder.

BLASTING GELATINE. — Blasting gelatine is a
compound of guncotton and nitroglycerine in
which, strange to say, the qualities of both explo-
sives are so far modified that the resulting blast-
ing gelatine, while retaining nearly all of the ex-
plosive force of its true constituents, is made less
sensitive than either. It is probably the safest
of the high explosives, wTith the exception of wet
guncotton. Blasting gelatine is a yellowish brown,
jellylike mass, having a specific gravity of 1.6.
It does not absorb water, nor is it affected by
water, being only slightly affected at the surface
when immersed in water. This property makes
it more suitable than dynamite for use in wet
places, for under the action of water the nitro-
glycerine in dynamite has a tendency to exude.

When unconfined, blasting gelatine burns with
a hissing sound, but will not explode. When con-
fined it explodes at a tempreature of 399 degrees
Fahrenheit, which is 43 degrees above the firing
point of either nitroglycerine or dynamite. It
freezes at a temperature of 35 to 40 degrees Fah-
renheit, and when frozen is far more sensitive

144

Rock Excavating and Blasting

than when unfrozen, which makes it unsuitable
for extremely cold climates but rather suitable
for warm ones.

Closely allied to blasting gelatine are gelatine
dynamites, which are formed by absorbing blast-
ing gelatine in an active base in a similar manner
to making ordinary dynamite by absorbing nitro-
glycerine with a dope. Many of the dynamites of
commerce are really gelatine dynamites, they gen-
erally being packed, shipped, classed and other-
wise treated as dynamites. Different grades of
gelatine dynamites are made with a view of pro-
viding a suitable explosive for every known con-
dition. Among the advantages claimed for this
kind of high explosives are that the gases pro-
duced are less injurious, therefore in tunnel driv-
ing the drill runners and muckers can return to
their work with less loss of time and be in better
physical condition during the rest of their shift.
Gelatine dynamite is heavier, bulk for bulk, than
ordinary dynamite and consequently can be more
easily loaded in water. Being heavier allows a
shorter charge to be used, thereby saving the ex-
tra depth of drill hole. It is less affected by water,
which makes it more suitable for submarine work
and wet work, and being plastic it will stick in
upward drilled holes and not be jarred out by
other shots.

Among the gelatine dynamite group are the fol-
lowing well-known commercial brands: Hercules
gelatine, Atlas gelatine, Repawno gelatine, Giant
gelatine, ^Etna gelatine and Forate. All the ex-

145

Rock Excavating and Blasting

plosives of the dynamite group, that is the high
explosives such as guncotton, blasting gelatine and
gelatine dynamites, are handled and stored like
dynamite, and are generally classed as such. Gun-
cotton should be excepted from this list to a cer-
tain extent, for instead of keeping guncotton dry,
it is kept wet, as it is less liable to detonation while
in that condition. It is well for the quarryman
and miner to know the differences between the
various explosives, their peculiarities and proper-
ties, as this knowledge makes more safe, or less
dangerous, the handling of them.

146

CHAPTER XIII.

DETONATORS FOR EXPLODING CHARGES.

ULMINATE OF MERCURY.— Fulmin-
ate of mercury, one of the most
sensitive and violent explosives
known, and therefore one of the
most dangerous, is not used as a
blasting agent but merely as a detonator for ex-
ploding charges of other explosives. Fulminate
of mercury is in fact never handled except in very
small quantities. It is, however, almost indis-
pensable in work with other explosives, because
the shock resulting from its detonation has some
peculiar characteristics, not fully understood, by
reason of which it can detonate any high explo-
sive with which it is in contact. Moreover, the
flame from its detonation ignites and so explodes
blasting powder. Fulminate of mercury explodes
when heated to 305 degrees Fahrenheit.

DETONATORS OR BLASTING CAPS. — The most
common example of the use of fulminate of mer-
cury is in the percussion caps for ordinary shot-
gun shells, cartridges for rifles or revolvers, and

147

Rock Excavating and Blasting

such purposes. In rock blasting the blasting cap
shown in Fig. 55 is likewise charged with this sen-
sitive explosive, which is used in connection with
safety fuse to detonate high explosives. These

Fig. 55.
Blasting Cap.

caps are readily affected by moisture, and must be
kept perfectly dry until used. They are put up
in lots of 100 in tin boxes, and these tin boxes are
packed in wooden cases containing respectively
500, 1,000, 2,000, 3,000 and 5,000 blasting caps.
In Table XII can be found the trade name, mark-
ing and sizes of DuPont blasting caps.

TABLE XII.

Sizes of Blasting Caps.

Name and
Number of
Caps

Silver
Medal
No. 3

Gold
Medal
No. 4

Pont
No. 5

Du
Pont
No. 6

Du
Pont
No. 7

Du
Pont

No. 8

Color of
Box

Silver

Gold

Blue

Red

Brown

Green

Length of
Caps

1J4"

IK"

i*A"

Blasting caps must be kept perfectly dry, and
it is well not to take the detonators into a wet or
damp working until they are actually needed, as
they deteriorate rapidly underground or in a damp

148

Rock Excavating and Blasting

place. For example, according to some experi-
ments made in Leadville a number of years ago,
fresh caps which gave complete detonation, when
kept underground for twenty-four hours gave in-
complete detonation; after forty-eight hours un-
derground, they gave incomplete detonation with-
out red fumes. After seventy-two hours under-
ground, one of the caps exploded without detona-
tion, and finally, after being underground one
hundred and forty-four hours, or six days, prac-
tically a work week, the caps refused to explode.

The strength of the blasting caps should like-
wise be considered, for it is poor economy besides-
increasing the danger to use weak detonators. A
strong blasting cap will not only bring down from
10 per cent, to 25 per cent, more material when
used to detonate a charge of explosive than where
weakened caps are used, but there is less danger
of a strong cap missing fire and a missed shot is
not only a financial loss but a source of danger.
In the table of sizes of blasting caps the numbers
3, 4, 5, 6, 7 and 8 refer to the strength of the caps
— the higher the number, the higher the strength.
As different manufacturers use different amounts
of fulminate of mercury in the caps, only the ap-
proximate strengths can be given. What are
known as single-strength and double-strength caps
are not used in the United States. Triple-strength
caps, the weakest used here, contain from 41/2 to 5
grains of fulminate of mercury. Quadruple
strength contains from 6 to 7 grains; quintuple
strength, 8 to 9 grains; the next size, 10 to 11

149

Rock Excavating and Blasting

grains ; then come 12 to 15 grains, 19, 23 and 31
grains respectively.

MEANS OF FIRING EXPLOSIVES.

FIRING WITH FUSES. — Blasting powders may be
fired by means of squibs, fuses or safety fuses
with blasting caps, for blasting power explodes
upon being ignited, and any safe means that will
cause ignition may be used. High explosives, on
the other hand, must be detonated, and for this
purpose a safety fuse with blasting cap or an elec-
tric fuse or detonator must be used. Fuses defer
the time of explosion to allow the quarryman to
reach a place of safety before the blast takes place.
Once the fuse has been lighted, however, he has
no further control over the time of explosion than
that provided for in the length and make of fuse
used. With electric firing, on the contrary, every-
thing can be put in readiness and the time of fir-
ing deferred to suit the operator's convenience, a
simple pulling up or pushing down of the handle
of the blasting machine causing the explosion. It
will be seen that in electric blasting, therefore,
the time of the blast is completely under the oper-
ator's control, which makes this the safest means
of firing explosives.

DESCRIPTION OF A FUSE. — A fuse is a tube,
generally flexible, filled with an inflammable com-
pound, or, what is more commonly the case in
blasting, a cord or tape inflammable itself, or im-

150

Rock Excavating and Blasting

pregnated with an inflammable substance, usually
slow burning and intended to convey fire to an ex-
plosive or combustible mass, but so slowly as to
allow the escape of the person lighting it. While
fuses are generally made slow burning for rock
blasting, there are also made quick-acting fuses,
some of them almost instantaneous in their action.
It is well, therefore, to test a fuse before using it
by noting the rate of burning of a short piece.
The rate of burning of ordinary fuses varies from
18 inches to 4 feet per minute. For most pur-
poses a fuse with a rate of 2
feet per minute will be found
the most satisfactory.

Fuses are shipped in coils
as shown in Fig. 56. They are
rig. se. put up in cases of 500 feet,

1,000 feet, 2,000 feet, 3,000
feet, 4,000 feet, 5,000 feet, 6,000 feet, and in bar-
rels of 8,000 feet. It might seem needless to say
that fuses should be stored in a cool, dry place,
and out of contact with oil. The interior of the
place of storage should further be kept free from
sudden changes of temperature. Fuses are made
in a number of grades, depending upon the char-
acter of work for which they will be used. In
Table XIII will be found the several grades put
out by the DuPont Company and the uses for
which they are intended.

While certain grades of fuses can be depended
upon for very wet work, or even work under
water, they cannot be relied upon to give satis-

151

g} Rock Excavating and B lasting

factory results in submarine work or under any
depth of water. Blasting in this kind of work
should always be done by electricity, as in sub-
marine work the pressure might force water into
the cartridge or fuse, saturating them and render-
ing them useless.

TABLE XIII.
Name and Use of Fuses.

Dry Work or Damp
Work

Wet Work

Very Wet Work or
Work Under Water

Single Tape

Double Tape
Crescent
Reliable

Triple Tape
Stag

FIRING WITH FUSE AND CAP. — As was previ-
ously pointed out, blasting powder can be fired
by means of a fuse without the aid of a cap, but
for dynamite or other high explosive some form of

Fig. 57.
Fuse Attached to Blasting Cap.

detonator must be used, which in turn may be
fired by a fuse. To prepare the cap and fuse for
use, the fuse is cut off square across, never at an
angle, so fire cannot sputter out the side and ig-
nite the explosive before the cap has a chance to
detonate, and so the cap can be given a good hold

152

Rock Excavating and Blasting

when crimped onto the fuse. The cap is next
crimped onto the fuse as shown in Fig. 57, by
means of a pair of special crimping pliers or cap
crimpers. This crimping should never be done
by means of the teeth or by pounding the cap with
an iron bar, and care should be taken to crimp
the cap near the open end so that the fulminate
in the other end of the cap will not be disturbed,
for if the fulminate should happen to be tightly
pinched an explosion might result.

When the fuse is properly capped, next fold
back the paper from one end of the dynamite
cartridge and with a sharp stick like
a lead pencil but of just the right size
for the cap to slip into the opening
made, gently make a hole in the top
of the dynamite and in this hole push
the blasting cap, as shown in Fig. 58,
then tie the paper to the fuse, as shown
in the illustration. Instead of making
the hole parallel with the axis of the
dynamite catridge it can be made slant-
ing to one side, so the fuse will be along
one side of the bore hole and out of the
way of the tamping. Some rock-men
extend the hole down to the center of
the cartridge so that the detonation
will take place in the center of the Bla^jfng58cap
dynamite. It is a question, however, %a?g}5™elte
whether anything is gained by that method, while
carrying the fuse through a couple of inches of
the explosive is liable to ignite it, thereby causing

153

Rock Excavating and Blasting

deflagration of the cartridge instead of
detonation. In short cartridges it
would seem that the top method of
priming was the best, the only objec-

, tion being that the fuse is more or less
in the way and apt to be bent or in-

•F-use jured by the tamping.

In long cartridges, 18 inches and
'y thereabouts in length, if it is deemed
advisable to place the cap near the cen-
ter of the dynamite, the best way is to
run the fuse down the outside of the
cartridge and insert the cap through a
hole on the side which points down-
ward, as shown in Fig. 59. The fuse
must then be bound in place with
strings, as shown in the illustration, to

Fig. 59.

Fuse Attached prevent the cap being pulled out or
'cartridge!* otherwise displaced when placing the
cartridge in the bore hole and tamping
the drill hole for the blast.

All that is then necessary is to cut off the fuse,
allowing a sufficient length of time for the oper-
ator to get to a place of safety before the explo-
sion takes place. If a two-foot fuse is being
used, that is, a fuse that burns two feet per
minute, and it will take two minutes to reach a
point or place of safety, a fuse at least four feet
long over all should be used, while under some
conditions, such as a difficult place to get away
from, a greater length would prove safer. There
is no advantage gained by placing the blasting

154

Rock Excavating and Blasting

cap at the center of the dynamite cartridge, be-
cause the instant detonation takes place the shock
is communicated to the entire mass, so that wher-
ever the cap is all parts of the dynamite are
equally affected.

Some rock-men and miners when placing a
blasting cap in the side of a cartridge make the
hole pointing upward, then bend the fuse back
again upon itself to point toward the mouth of
the drill hole. Such a practice is bad and should
be discouraged, for the sharp bend might pull
the fuse free from the cap, or if it does not, the
sharp bend in the fuse might be sufficient to cause
a break in the train of powder or choke the fuse,
so the fuse will snuff out and a misfire result.

LIGHTING THE FUSE. — When all is ready for
firing the shots, the quarryman has but little time
at his disposal after he has lighted the first fuse,
and it is important that each fuse takes the flame
as he passes along. If an ordinary fuse be merely
cut off and a match or lighter applied, the powder
will not always ignite immediately and the lighter
might have to leave before all the fuses are light-
ed. In order to make sure that all the fuses take
fire, special flaming pieces are often provided.
In Fig. 60 is shown one method of priming fuses
for ignition. The end
of the fuse in this case
is split for a short dis-
tance and a wedge of G/'anf

, Fig. 60.

giant pOWder mtro- Fuse Primed for Lighting.

duced into the split. •

155

Rock Excavating and Blasting

When giant powder is ignited in the open it burns
with a bright, fierce flame, so that a small piece
lighted in the end of a fuse is almost sure to
ignite it.

Another method is shown in Fig. 61. A piece
of candle wick dipped in kerosense or alcohol is

twisted about the end
of the fuse, so that all
that is necessary is to
walk along the line of
drill holes applying
the flame of a torch to

Lampwick PrTmtr for Fuse. 6ach Candle wlck ln

turn. The kerosene

soaked wick will immediately burst into flame, and
the flame from the burning wick will ignite the
fuse.

As it is desirable to count the shots when blast-
ing by fuse to see that they have all gone off, the
fuses ought to be made of different lengths so
that one shot will follow another when they are
all lighted at the same time. Having the shots
follow one another instead of exploding simul-
taneously does not give as great disruptive force,
but it is safer for the workmen. Besides, it is
almost impossible to so time all the fuses in a
battery that the explosions will all take place
together. Electric blasting is the only method
which will accomplish this.

156

CHAPTER XIV

FIRING BLASTS BY ELECTRICITY.

DVANTAGES OF BLASTING BY ELEC-
TRICITY. — Blasting by electricity is
now conceded to be the safest, most
economical, most effective and by
far the most convenient way of fir-
ing explosives, surpassing any other for safety
and certainty of action. By electric firing the en-
tire strength of the explosive is developed at the
same instant, less explosive being thus required
where these are a number of drill holes than
when each hole is fired separately, as is more
than likely to be the case when fuses are used.

By electric blasting all holes are exploded simul-
taneously, and if all connections are properly
made there is no possibility of a second explosion.
If a misfire occurs by reason of improper connec-
tions, such missed hole will not hang fire and ex-
plode unexpectedly as sometimes occurs when
blasting with safety fuses. Electric blasting con-
sequently eliminates this dangerous feature in
connection with blasting operations.

ELECTRIC FUSES. — In electric blasting the elec-
157

Rock Excavating and Blasting

trie fuse takes the place of the blasting cap, and
is used in connection with a maganeto, or "blast-
ing machine," and copper wire instead of a safety
fuse. An electric fuse is shown in section in Fig.
62. The shell (a) is of copper and has a bead or

Fig. 62.
Section of Electric Fuse.

corrugation thrown out or pressed from the inside
to form a locking device to hold the sulphur
cement (b) more firmly in place than it would
be held in a smooth cylinder or cap. The explo-
sive, which consists mainly of fulminate of mer-
cury, is contained in the chamber (c), which is
sealed by the sulphur cement which likewise holds
the fuse wires firmly in place.

The copper fuse wires (d) are covered with
insulating material sufficient for all ordinary pur-
poses, and the bare ends of the copper wire pro-
ject through at (e) into the charge of fulminate of
mercury, where they are joined together by the
short platinum wire or bridge (f ) . It is the heat-
ing of this platinum wire to redness when an
electric current is passed through it that causes
the detonation to explode the dynamite cartridge.
Fuses are made with leading wires of from four
to thirty feet in length. If longer wires are
needed they may be spliced with the usual twisted
splice with which all electric wires are joined,
then insulated with insulating tape.

158

Rock Ea

Electric fuses are made of different strengths,
and for different purposes, such as for dry blast-
ing and for submarine work. Illustration of an
electric fuse is shown in Fig. 63. This fuse for

Fig. 63.
Waterproof Fuse for Submarine Work.

submarine work, it will be observed, is covered
with gutta percha to keep it from being affected
by the water, and the connecting wires leading
down to it must likewise be of waterproof quality.
For ordinary work the gutta percha covering is
not needed and is omitted. In rock excavating the
fuses should be ordered with wires long enough
to allow at least eight inches to project outside the
drill holes to be connected to the connecting wires.
The connecting wires should never be of smaller
size than the connecting wires to the electric fuses.

PLACING THE ELECTRIC FUSE. — The electric fuse
is best placed in the center of the charge, and in
placing the electric fuse a hole is usually made in
the side of the cartridge as explained for a cap
and fuse in Fig. 59, and the electric fuse inserted
in this cavity, pointing downward.

The wires from the electric fuse are then bound
to the cartridge with string to hold the fuse in
place, the free ends being kept above the mouth
of the drill hole for connecting to the leading
wires from a magneto. Instead of placing the
electric fuse in the center of the charge, some

159

Rock Excavating and Blasting

rock-men place it in the end of the cartridge as
explained for blasting with fuse, but they then
turn the cartridge upside down and bind the wires
to the cartridge, as shown in Fig. 64, so that the
fuse is at the bottom of the charge when loaded
in the bore hole.

Care should be taken when tamping a bore hole
that the electric wires are not broken or the in-
sulating materially injured, so the cur-
rent can short circuit, or there might ^
be a misfire. In the handling of the
electric fuse care is necessary, also,
not to break the sulphur cement, dis-
arrange the wires in the fuse, or break
the fine platinum wire or bridge.
Breaking the cement will leave a free
passage to any water which might be
in the hole, so that the fuse will become
spoiled and a misfire result.

The platinum bridge of an electric
fuse is of necessity very small and
delicate in order to keep down the cost,
and at the same time be capable of be-
ing heated red hot by the small current
of electricity generally used for this
purpose. If this bridge or wire be i
subjected to any great strain it is liable
to become broken, thereby destroying
the fuse.

Sharp bending of the electric wires might also
lead to a misfire. Damaging the insulation so
the current can short circuit will have this effect,

160

Dynan
Carfn

Rock Excavating and Blasting

and the wires need not touch to cause this dam-
age, for if they be bare there might be sufficient
moisture present to rob that particular cap of
part of its current, and the result will be the fuse
will miss fire.

Two ELECTRIC FUSES IN ONE DRILL HOLE. —
Two electric fuses are often used in deep drill
holes where there is a large charge of explosive,
so that the cartridge at the two ends can be
touched off simultaneously. When
such is the case the electric wires
to the fuses should be connected in
series, as shown in Fig. 65. One o'f
the wires from the lower fuse is
connected to one of the wires from
the upper fuse, and the two remain-
ing free wires are then brought to
the surface of the ground, and the
entire charge then treated as one
so far as subsequent wiring is con-
cerned. In considering the capac-
ity of a blasting machine, however,
each double-fused drill hole or
charge must be rated as two dis-
tinct charges, for it takes just as
much electric current to touch off
two fuses in a single bore hole as it
would to touch off two fuses in
separate drill holes.

Fig. 65

Two Electric Fuses
in One Drill Hole.

WIRING FOR MULTIPLE BLASTS.
— The manner of wiring for an
161

Rock Excavating and Blasting

electric blast when a number of charges are
to be exploded at once is shown diagrammatically
in Fig. 66. Starting at one end of the row of
drill holes, one pole of the blasting machine is
connected to one fuse wire of the nearest hole.
The other fuse wire is connected by means of
special connecting wire to one of the fuse wires
in the next nearest hole. The free wire in this
hole is in turn connected to one of the fuse wires

Fig. 66.
Two Wire Circuit for Multiple Blasts.

in the next succeeding drill hole, and so on until
the last hole is reached, when the remaining fuse
wire is connected by means of a leading wire to
the other pole of the blasting machine. It will be
seen that by this method of wiring, the electric
current must pass successively through every fuse
in the lot, thereby insuring them all being deton-
ated. In the illustration the blasting machine or

162

Rock Excavating and Blasting

magneto is shown in the background. This is
merely to show the entire apparatus complete,
however. In practice the blasting machine would
be located in some sheltered place out of range
of the rock broken out by the blast, and about 250
feet away.

The wiring shown in the illustration is for a
two-pole or two-wire blasting machine. Where

Fig. 67.
Three Wire Circuit for Multiple Blasting.

a great number of blasts are to be fired at the
same time, however, three-wire machines are fre-
quently used. The manner of wiring for a three-
wire machine is shown in Fig. 67. The series of
drill holes, 1, 1, 1 form one circuit and the series
2, 2, 2 another circuit, which could be fired separ-
ately by bringing separate return leaders to the

163

Rock Excavating and Blasting

middle binding post of the blasting machine or
may be connected up in one big circuit, as shown
in the illustration, by connecting the return wire,
a, to the connecting wires at the middle of the
battery of drill holes. The wires, a-b, form one
loop of the circuit, and the wires, a-c, the other
loop of the circuit, and if only the bore holes 1, 1
were to be fired the wires would be connected up
in the loop, a-c, without being joined to the other
half of the system, while if the bore holes 2, 2
were to be fired separately the wires, a-b, would
be used, but they would be disconnected from all
contact with wire c. When a three-post blasting
machine is used, the size of the leading wires
need not be so large as for two-wire work, and
almost 50 per cent, more fuses can be fired with

Fig. 68.
Joint for Electric Wires.

the machine than could be fired with a two-wire
blasting machine of equal size.

CONNECTIONS FOR ELECTRIC WIRES. — The
method of making a straight splice or joint in
copper electric wires is shown in Fig. 68. The
insulation is removed from the ends of the two

164

Rock Excavating and Blasting

pieces to be joined for a distance of about 21/2
inches back and the wires scraped with a knife
to brighten them if they have become dulled or
tarnished. The ends are next brought together
and twisted either with fingers or pliers into the
connections shown in the illustration. When a
branch joint is to be made, the insulation is scrap-
ed off the branch wire in the manner explained
and on the main wire the insulation is removed
for a distance of two inches where the connection
is to be made. The end of the branch wire is next
wound tightly around the main wire and the con-
nection is made. It is very important that the
wires when joined together be perfectly clean and
bright, and that they be twisted together tight
and firm. If the joints are not well made or if
any one of them is defective it will affect the
whole circuit, perhaps causing all the holes to
misfire.

The bare wire at joints should never be allowed
to touch the ground, particularly if it be wet, or
a ground current might result. This can be
avoided by putting dry stones under the wires at
the sides of the joints to keep them off the ground.
Insulating tape may likewise be used for this pur-
pose, but in ordinary rock blasting in fairly dry
places insulating the joint will hardly be neces-
sary.

TWO-POST BLASTING MACHINE. — Two-post
dynamo-electric, or magneto-electric, blasting ma-
chines of small size, occupying less than one-half

165

Rock Excavating and Blasting

a cubic foot of space and weighing less than twen-
ty-two pounds, are the kind most commonly used
for small work, such as ordinary rock blasting,
and on account of their reliability they are very
suitable for the purpose.

The interior and outside views of a two-post
blasting machine may be seen in Fig. 69. In this

Fig. 60.
Two-Post Blasting Machines.

apparatus there is a magnet, and an armature
which by revolving between the poles of the prin-
cipal magnet generates the electric current which
explodes the charges. Also there is a loose pinion
which has teeth to engage with the rack bar. By
clutching the spindle of the armature on the down
stroke it generates the current of electricity, and

166

Rock Excavating and Blasting

when it reaches the end of its stroke breaks the
contact between the small platinum bearings at
the bottom, thus causing the whole charge or cur-
rent of electricity to pass through the firing circuit
composed of the leading wire, connecting wire and
electric fuses.

THREE-POST BLASTING MACHINES. — The inter-
ior and exterior of a three-post blasting machine,

Fig. 70.
Three- Post Blasting Machines.

such as is used with three-wire circuits, is shown
in Fig. 70. The object attained by the use of
the third or middle post is that when a large
number of electric fuses are in circuit there will
be less liability of failure of some of those near
the middle of the circuit, if the big circuit is

167

@?VO Rock Excavating and Blasting C^tf®

really broken up into smaller loop or circuits, and
a common return brought back to the blasting
machine.

In firing in one circuit a moderate number of
electric fuses, only two leading wires need be
used, but one of these must be connected with the
middle post and the other may be connected with
either of the side posts.

The three-post machine requires more care in
the handling and connecting up than a two-post
machine, and for ordinary blasting operations the
two-post machine will generally be found satis-
factory.

THE CAPACITY OF A BLASTING MACHINE. —
Blasting machines are generally rated according
to the number of fuses or "holes" they will fire.
For instance, a machine rated at from one to ten
holes means that the machine has sufficient power
or will generate sufficient current to detonate the
electric fuses in from one to ten holes at once.
The difference between holes and charges must be
clearly understood, however. Sometimes it is
desirable, as when using deep holes with large
charges, to place more than one electric fuse in
each hole. When this is done it must be remem-
bered that each fuse is to be considered as a
charge or hole. It cannot be expected that a ten-
hole machine will explode two or more electric
fuses in each of the ten holes, for it will not do
so. The rating of the machines is on the assump-
tion that only one fuse will be in each hole. For

168

Rock Excavating and Blasting

each additional fuse put in a bore hole, one hole
must be omitted or deducted from the capacity
of the machine.

"PULL-UP" AND "PUSH-DOWN" BLASTING MA-
CHINES.— The blasting machines described in this
chapter are what are known as "push-down" ma-
chines. That is, the machines are operated by a
downward stroke of the handle bar. The only es-
sential difference between this and a "pull-up"
machine is that in the latter the upward stroke is
the effective motion.

FIRING WITH A BLASTING MACHINE. — After the
drill holes have been loaded all the fuse wires pro-
ject from eight inches to a couple of feet above
ground. These wires are connected up in series,
as previously explained, the joints supported on
stones so the bare wires will not be in contact with
the earth, and the free-end wires are then con-
nected to the blasting machine. The wires which
connect the fuse wires together are called the con-
necting wires, while the wires which connect the
free-end fuse wires to the blasting machine are
known as the leading wires. The leading wires
are first connected to the respective fuse wires
and the free ends are carried back to where the
blasting machine will be used, but the ends of
the leading wires are not attached to the binding
posts of the machine until everything is in readi-
ness for blasting. These connections are then
.made, the operator lifts the handle of the magneto

169

^Vf\ Rock Excavating and Blasting ^^®

to its full height, pushes it down slowly for the
first half inch or so, and then with all his force,
until the rack attached to the handle reaches the
bottom of the box and sends the current through
the outer circuit to the fuses.

When operating the blasting machine the han-
dle or rack bar should never be churned up and
down, but should simply be given the one vigorous
downward push for the "push-down" machine, or
a similar upward pull for the "pull-up" machine.

TESTING A BLASTING MACHINE. — A blasting
machine should always be kept in good condition,
clean, and never abused or played with. Its
strength should be tested from time to time to
see that sufficient power can be generated to fire
the fuses. A simple way to test a blasting ma-
chine is by means of an ordinary incandescent
electric lamp. A lamp and socket properly wired
must first be tested to see that they are in good
condition, the wires are then attached to the bind-
ing posts of the machine — to one side post and
the center post in the case of a three-post machine
— as when firing a blast, and, if the machine is
in good condition, the lamp will show when the
machine is operated a bright, incandescent light
or white flash if the current be strong. If the
light in the lamp cannot be made strong or bright
it is evident that the current generated is weak
and might not fire a fuse. If the lamp does not
show any light the machine is out of order, and a
blast cannot be fired with it until repaired. Most

170

Rock Excavating and Blasting

of the misfires blamed on poor fuses are as a mat-
ter of fact lack of current from the machine.

Another way to test a blasting machine is to
connect in series above ground the full number of
good electric fuses which the machine should be
able to explode if it were in good condition. Next
connect these electric fuses in a regular circuit to
the machine, placing the machine at a safe dis-
tance so as not to be damaged by tlie explosion of
the fuses. If the blasting machine, when properly
operated, then fails to explode all the electric
fuses in the series, it is because the current pro-
duced by the machine is weak and the machine
needs repairing.

The blasting machine when not in use should
not be left carelessly lying around the workings,
but should be kept in the office or some other dry
room until wanted. Never overload a blasting
machine. It is better to divide the holes up into
two blasts.

When all the electric fuses connected to a ma-
chine do not fire, in nine cases out of ten the fault
is with the blasting machine or its manipulation,
not with the fuses. Tests have repeatedly shown
that when some of the holes in a circuit explode
and some fail the cause is an insufficient amount
of electricity. Generally this is caused by the
blasting machine being in bad condition, or by the
operator giving only a comparatively light push
to the handle.

SOME PRECAUTIONS IN BLASTING. — In handling

171

Rock Excavating and

explosives and in preparing for a blast too great
care cannot be exercised to prevent accidents. It
is a poor policy to use a short fuse to hasten an
explosion or with the idea that it is economical to
do so, as the blast might be set off before the oper-
ator has time to seek cover. It is likewise danger-
ous to attempt to withdraw a wire from an electric
fuse. An explosion of the fuse might result.

Never fire a charge to chamber a hole, then im-
mediately reload it, as the hole will be hot and
might cause a premature explosion. When every-
thing is ready for the blast, do not fire the shot
before everybody is well beyond the danger zone
and protected from flying debris. Protect th^
supply of explosives also from danger from this
source.

In case of a misfire or an apparent misfire, do
not be in a hurry to seek an explanation of the
cause. Take plenty of time before approaching
the misfire. It might be only a delayed explosion.
In case the charge has missed fire, don't bore, drill
or pick out the misfire shot. Drill and charge
another hole at least two feet from the missed hole
and fire this charge.

172

CHAPTER XV.

HANDLING AND STORING EXPLOSIVES.

AWS REGULATING STORAGE AND HAN-
DLING OF EXPLOSIVES. — In most
States the handling and storage of
explosives is regulated by law, and
before commencing operations in
any locality the one responsible for the handling
and storage of the explosives should familiarize
himself with the requirements of the laws, and
then comply with them. Failure to do so will lead
to heavy damages in civil suits, and perhaps
prison sentence should an accidental explosion oc-
cur and cause loss of life, injury, or damage.

The Interstate Commerce Commission have
formulated regulations for the transportation of
explosives, as have likewise the American Railway
Association. These instructions are contained in
a little 140-page book which can be had for the
asking by applying to any freight agent. It is to
the interest of everybody handling and transport-
ing or shipping explosives, therefore, to secure a
copy and be guided by the rules and regulations
there laid down.

173

Rock Excavating and Blasting

HANDLING AND STORING OF BLASTING POWDER.
— Blasting powder can be handled with a high
degree of safety, still it is advisable to remember
at all times that it is an explosive, and that reck-
lessness in its handling should neither be practised
nor tolerated. When loading powders on cars,
wagons, or other vehicles for transportation they
should be so packed that they will remain firmly
in place and not slide or move about while in
transit. Kegs should likewise be protected from
snow, rain, direct rays of the sun, or extremes
of any kind.

The site for a magazine for the storage of blast-
ing powder should be such that the possibility of
damage due to an accidental explosion will be re-
duced to the minimum. The location should be as
dry as possible, and should consequently never be
constructed against rock or earthen banks where
moisture could trickle in or dampness penetrate.
The ground around and beneath the magazine
should be well drained and graded, and ample
space allowed underneath the floor to provide for
free circulation of air on all sides of the building.
The magazine itself should have provision made
for ventilating the interior, with means for clos-
ing the ventilators during stormy weather.

In storing the powder the kegs should be placed
on end, bungs down, to prevent the possible en-
trance of moisture to the powder. The floor of
the powder magazine should be kept scrupulously
clean, for loose powder on the floor is liable to

174

®\§ Rock Excavating and Blasting CJfl&

form a train to carry flame from a light to the
powder kegs.

Fuses or caps should never be stored in a pow-
der magazine or in a high-explosive magazine, as
they are more easily detonated than high explo-
sives, and if detonated close to dynamite might
cause it to explode. If lightning rods are placed
on the magazine the rods should have a ground
connection to water, otherwise they are worse
than useless.

No iron tools should be used in the magazine,
and the floor nails should be driven into the floor
so their heads will not project. In case a keg
becomes broken or powder is spilled on the floor,
a wooden scoop and broom brush should be used
to clean it up, never a steel shovel. It is danger-
ous to walk on loose powder in a magazine with
shoe nails projecting from the soles of shoes, as
they might fire the powder. For this reason the
floor of a powder magazine should be kept per-
fectly free from loose powder.

MAGAZINES FOR THE STORAGE OF DYNAMITE. —
Permanent magazines for the storage of high ex-
plosives are preferably made of bricks, stones,
concrete or some other equally fireproof and bul-
letproof materials. The magazines should be lo-
cated in isolated spots, and surrounded, if possi-
ble, with high banks. Brush, weeds and high
grass ought to be kept trimmed back a sufficient
distance to insure safety in case of fire in the un-
derbrush and dead grass near by. As in the case
of powder storage, the dynamite magazine must

175

Rock Excavating and Blasting

be well ventilated and at the same time so ventil-
ated that rain or snow cannot drift in during
stormy weather. The temperature m the maga-
zine should be regulated to about 80 degrees
Fahrenheit. The higher the temperature of the

Fig. 71.
Portable Dynamite Magazine.

explosive the more uncertain and unstable it be-
comes, so that temperatures above 100 degrees
Fahrenheit become correspondingly dangerous.
Besides, the nitrogen, although it has a high boil-

176

Rock Excavating and Bias ting

ing point, evaporates sensibly at a temperature a
little above 100 degrees, and thereby loses much
of its strength.

It is not necessary to build portable magazines
or magazines for temporary use out of bricks,
stone or concrete, but they ought to be made bul-
letproof and fireproof, or at least fire-retarding,
if not actually fireproof. A portable or temporary
dynamite magazine is shown in perspective in
Fig. 71. This building is mounted on a brick
foundation and is encased on the outside with
No. 24 or No. 26 sheet metal, which may be either
black or galvanized. When the cost of brick
foundations must be eliminated, the magazine
may be set on posts spaced from 4 to 6 feet
centers, sunk in the ground below frost level, and
capped with a 6x6 or larger sill. The outside of
the posts must then be boarded like the rest of
the building, clear to the ground, and covered with
sheet metal in the same way, so that fire cannot
creep under the building and set fire to the maga-
zine from beneath.

The details of construction of a portable maga-
zine can be seen in Fig. 72. The studding are
boarded on the outside with matched, or tongue
and groove, sheathing, and the outer surface, both
sides and roof, covered with a layer of No. 24 or
No. 26 sheet metal. This does not make a fire-
proof construction, but it is fire retardant, as the
sheet metal will not burn, although it will trans-
mit enough heat to the wood within to cause that
to take fire. The boards beneath the sheet metal

177

Rock Excavating and Blasting

will burn very slowly, however, owing to the fact
that but little air or oxygen can reach them, and
without air the boards will char, forming char-
coal.

To make the walls bulletproof, the inside of the
building is lined with boards, the same as the out-
side, and the space between the inner and the
outer boards is filled from sill to plate with good,
coarse, dry sand. Instead of using sand the maga-
zine can be bulletproofed by laying one course of
bricks in cement mortar in-
side the magazine, or filling
the spaces between the stud-
ding with bricks laid in ce-
ment mortar. As a rule, how-
ever, the sand will be found
preferable, although coarse
gravel is never to be used, on
account of the missiles that
would be thrown in case of an
explosion.

The thickness of the walls
of sand required to make a
^agazine bulletproof will de-
pend pretty much upon the
character of firearms used in
the locality. In places where
smokeless powder is used in
high-power rifles, such as the
Government Springfield, 11
inches of sand are absolutely
necessary to bulletproof the
magazine. When the 30-30
178

Fig. 72.

Detail of Portable
Magazine.

Rock Excavating and Blasting

Winchester, or equivalent, is the strongest rifle
in common local use, 8 inches of dry coarse sand
filling is sufficient. When shotguns and rifles not
heavier than 32 calibre are the firearms ordinarily
used, 6 inches of sand filling will bulletproof the
magazine. Nothing less than 6 inches of sand
filling, however, should be used.

179

INDEX

Page.

Active Base, Dynamite

with an 121

Air Reheaters 84

Air Required for Drilling

Machines 61

Air, Running with Com-
pressed 45

Amount of Explosive Re-
quired 101

Appearance of Dynamite. 122

Bags, Tamping 115

Base, Dynamite with an
Active 121

Base, Dynamite with an

Inactive 120

Bits or Steels, Rock Drill 51

Blacksmith Tools for

Forging Drill Steels.. Gl

Blasting Caps 147

Blasting, Explosives Used

in 91

Blasting, Free Faces in.. 4

Blasting Machine, Capac-
ity of a 168

Blasting Machine, Firing
with a 169

Blasting Gelatine 344

Blasting Machines, "Pull-
Up" and "Push-Down" 169

Blasting Machine, Test-
ing a 170

Blasting Machine, Three-
Post 167

Blasting Machine, Two-
Post . 165

Page.

Blasting Powder, Drying. 114
Blasting Powder, Tests of 113

Blasting Powders, Com-
position of 92

Blasting Powders, Prop-
erties of 96

Blasting Powder, Storing
and Handling 174

Blasting Powder, Under-
ground, Handling 114

Blasting, Some Precau-
tions in 171

Blasting, Terms Used in. 7

Blast, Force and Direction
of a 1

Blasts by Electricity,

Firing 157

Blasts, Effect of Multiple 13

Blasts, Wiring for Multi-
ple 161

Boxes, Thawing

130

Capacities of Channeling
Machines 86

Capacity of a Blasting
Machine 168

Caps, Blasting 147

Cartridges and Tamping
Materials 107

Cartridges, Size of Dyna-
mite 323

Channelers, Stone 75

Channeling Machines, Ca-
pacities of 86

Channeling Machines,

Drill Steels for 80

Channeling Machines, Du-
plex 80

Page.
Channeling Machines, Sim-

plex

Charging a Drill Hole,

Method of 109

Charging Drill Holes with

Powder

107

Charges, Detonators for
Exploding 147

Composition of Blasting
Powders 92

Compressed Air, Running

with 43

Connections for Electric
Wires . . 104

Depth and Diameter of
Drill Holes 10

Depth of Tamping 109

Detonators for Exploding
Charges 147

Diameter and Depth of
Drill Holes 10

Direction and Force of a
Blast 1

Drill Bits or Steels, Rock 51

Drill Hole, Method of

Charging a 109

Drill Hole. Two Electric

Fuses in One 161

Drill Holes . . 1

Drill Holes, Charging with

Powder 107

Drill Holes. Diameter and

Depth of 10

Drill Holes, Dry 46

Drill Holes for Tunnel

Driving 23

Drill Holes, Inclination of 2

Drill Holes in Shaft Sink-
ing 17

Drill on Mining Column,

Rock 41

Drill on Quarry Bar,

Rock 39

Drill on Tripod, Rock... 35

Drill Steels for Channel-
ing Machines SO

Drill Steels. Sizes and
Weights of 55

Page.

Drill Steels, Tools for
Forging 61

Drills, Hammer 69

Drilling Machines, Air
Required for 61

Drilling Machines, Oper-
ating 45

Drilling Near Fissures or

Faults 28

Driving Large Tunnels... 30
Driving Tunnel 23

Driving Tunnel, Drill

Holes for 23

Dry Drill Holes 46

Drying Blasting Powder. 114

Duplex Channeling Ma-
chines 80

Dynamite 117

Dynamite, Appearance of. 122

Dynamite Cartridges. Size
of 123

Dynamite. Magazines for
the Storage of 175

Dynamite. Methods of

Thawing 127

Dynamite. Properties of. . 124
Dynamite, Strength of... 122

Dvnamite with an Active
* Base 121

Dynamite with an Inactive

Base

120

Dynamites and Powders.

Tses for 112

Effect of Multiple Blasts.. 13
Electric Fuses 157

Electric Fuses in One
Drill Hole, Two 161

Electric Fuse, Placing the 158

Electric Wires, Connec-
tions for 164

Electricity, Firing Blasts
by 157

Exploding Charges, De-
tonators for 147

Explosion, Mechanical

Work of an 100

Page.

Explosions, Initial Force
of 98

Explosive Required,
Amount of 101

Explosives, Handling and

Storing 173

Explosives, High i?l

Explosives, High 117

Explosives, Low 91

Explosives, Means of Fir-
ing 150

Explosives Used in Blast-
ing 91

Faces in Blasting, Free... 4

Faults or Fissures, Drill-
ing Near 28

Firing Blasts by Electric-
ity 157

Firing Explosives, Means

of 150

Firing with a Blasting
Machine 169

Firing with Fuses 150

Fissures or Faults, Drill-
ing Near 28

Free Faces in Blasting... 4

Force and Direction of a
Blast 1

Force of Explosions, Ini-
tial 98

Forging Drill Steels, Tools
for 61

Fulminate of Mercury 157

Fuse, Description of a... 150

Fuse, Lighting the 155

Fuse, Placing the Electric 159

Fuses, Electric 157

Fuses, Firing with 150

Fuses in One Drill Hole,

Two Electric 161

Gelatine, Blasting 144

Guncotton 143

Page.
H

Hammer Drills 69

Handling and Storing
Blasting Powder 174

Handling and Storing
Explosives 173

Handling Blasting Pow-
der Underground 114

High Explosives 91

High Explosives 117

Hole, Method of Charging
a Drill 109

Holes, Diameter and

Depth of Drill 10

Holes, Drill 1

Holes, Dry Drill 46

Holes for Tunnel Driving,

Drill 23

Holes, Inclination of Drill 2

Holes in Shaft Sinking,

Drill 17

Houses, Steam Thawing.. 135

Inactive Base, Dynamite

with an 120

Inclination of Drill Holes 2
Explo-

Initial Force of
sions

1)8

Large Tunnels, Driving.

Laws Regulating Handling
and Storing of Explo-
sives ................. 173

Lighting the Fuse ........ 155

Low Explosives ......... 91

Mechanical Work of an

Explosion 100

Machine, Capacity of a

Blasting 168

Machine, Firing with a
Blasting 169

Page.

Machine, Testing a Blast-
ing 170

Machine, Three-Post Blast-
ing 167

Machine, Two-Post Blast-
ing 165

Machinery and Tools,

Rock Drilling 35

Machines. Air Required

for Drilling 61

Machines, Capacities of
Channeling 86

Machines, Drill Steels for
Channeling 80

Machines, Duplex Chan-
neling 80

Machines, Operating Drill-
ing 45

Machines, "Pull-Up" and

"Push-Down" Blasting 160

Machines, Simplex Chan-
neling 78

Magazines for the Storage

of Dynamite 175

Manure Filled Walls,

Thawing Houses with 132

Mercury, Fulminate of... 147

Method of Charging a

Drill Hole 109

Methods of Thawing Dy-
namite 127

Mining Column, Rock
Drill on 41

Multiple Blasts, Effect of 13
Multiple Blasts, Wiring

for

161

Nitroglycerine 117

Nitroglycerine, Proper-
ties of . . 118

Page.

Powder, Storing and Han-
dling Blasting 174

Powder, Tests of Blasting 113

Powder Underground.
Handling Blasting ... 114

Powders and Dynamites,
Uses for 112

Powders, Composition of
Blasting 02

Powders, Properties of

Blasting 96

Precautions in Blasting,
Some 171

Properties of Blasting
Powders 96

Properties of Dynamite.. 124
Properties of Nitroglycer-

ine .

118

"Pull-Up" and "Push-
Down" Blasting Ma-
chines 169

"Push-Down" and "Pull-
Up" Blasting Ma-
chines 169

Reheaters, Air 84

Rock Drill Bits or Steels 51

Rock Drill on Mining Col-
umn 41

Rock Drill on Quarry-
Bar 39

Rock Drill on Tripod 35

Rock-Drilling Tools and
Machinery 35

Rock. Sinking Shafts

Through 37

Running with Compressed
Air 45

Running with Steam 47

Placing the Electric Fuse 159
Powder 91

Powder, Charging Drill

Holes with 107

Powder, Drying Blasting. 114

Shaft Sinking, Drill Holes
in 17

Shafts Through Rock,

Sinking 17

Simplex ^Channeling Ma-
chines 78

Sinking Shafts Through

Rock 17

Size of Dynamite Cart-
ridges 123

Sizes and Weights of Drill

Steels 55

Squibbing . . Ill

Steam, Running with 47

Steam Thawing Houses.. 135

Steels for Channeling Ma-
chines, Drill SO

Steels or Bits, Rock Drill 51

Steels, Sizes and Weights

of Drill 55

Steels, Tools for Forging
Drill 61

Stone Channelers 75

Storage of Dynamite,

Magazines for the 175

Storing and Handling
Blasting Powder 174

Storing and Handling Ex-
plosives 1T3

Strength of Dynamite 122

Tests of Blasting Powder
Thawing Boxes

Thawing Dynamite, Meth-
ods of

Thawing Houses, Steam..

Thawing Houses with Ma-
nure Filled Walls....

Thawing Kettle

Three-Post Blasting Ma-
chine

Tools and Machinery,
Rock Drilling

Tools for Forging Drill
Steels

Tripod, Rock Drill on

Tunnel Driving

Tunnel Driving, Drill
Holes for

Tunnels, Driving Large..

Two Electric Fuses in One
Drill Hole

Two-Post Blasting Ma-
chine

113
130

127
135

I.'}-*

128

107

01
35
23

23
30

161
165

Tamping Bags 115

Tamping, Depth of 100

and

Tamping Materials
Cartridges .

.101

Terms Used in Blasting.. 7

Testing a Blasting Ma-
chine 170

Weights and Sizes of Drill

Steels 55

Wires, Connections
Electric

for

164
Wiring for Multiple Blasts 101

Work of an Explosion,

Mechanical 100

THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW

AN INITIAL FINE~OF 25 CENTS

OVERDUE.

LD 21-100m-7,'33

YC 13421

OF CALIFORNIA LIBRARY

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