The Bulletin of the Beach Erosion Board

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203

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VOL. 5

Vol.

DEPARTMENT OF THE ARMY
CORPS OF ENGINEERS

aT ETT ET MN a

Marine rine Bioloz sical Ls

[
| JAN 29 i951

WOODS HOLE, MAS

5) Apis

JAN 22 1957

AUIS
LIBRA HR RY

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THE oH oT
j DOCU : VENT )
BULLETIN : OOLeE : Sony

Rn AT ae

OF THE

BEACH EROSION BOARD

OFFICE, CHIEF OF ENGINEERS
WASHINGTON, D.C.

JANUARY 1, 1951 NO.1

go?

DEPARTMENT OF THE ARMY

CORPS OF ENGINEERS

THE BULLETIN
OF THE
BEACH EROSION BOARD

TABLE OF CONTENTS

Page
British Coast Protection act of 1949 .ccccccccccccee 1
Generalization of the Formula for Calculation of
Rock Fill Dikes and Verification of its
Coefficients e@eeeoeootcevoeaeevpeeeoesevsereoeve7ee eee eoeeeegeeeenes 4

Announcement of Publication .......- C0D006 d000000000 24

Application ef Asphalt in Hydraulic fngineering

Works PCSSTHSHCAOSHSHSOCHHSOHESHSSSSSSSSHETHHOESGHHHEHHHEHSHSHHEH BC 25

Beach Erosion Studies CR 65

Beach Erosion Literature eeoeeeetoeveoCeocseeoeoe ee eor77e 8% 69
VOL. 5

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BRITISH COAST PROTECTION ACT OF 1949

The purpose of the Coast Protection Act of 1949 is to amend the
law relating to the protection of the coast of Great Britain against
erosion and encroachment by the sea, to provide for the restriction
and removal of works detrimental to navigation, to transfer the
management of Crown foreshore from the Minister of Transport to the
Commissioners of Crown Lands, and for purposes connected with the
foregoing. The more important parts and sections of the act are
summarized in the following paragraphs.

Part I

Section 1. Coast protection authorities are established with
powers and duties in connection with protection of land in their
area as are conferred or imposed on such authorities by the act.
The council of each Maritime county area shall be the coast pro—
tection authority for that area.

Section 2. Coast protection boards may be established where
it appears expedient for the protection of land in any area. Such
boards shall be the coast protection authority for that area.
They shall consist of representatives of the council of every maritime
county area any part which is within the area for which the board
is constituted and may also include representatives of other af-
fected bodies or persons.

Section 3. Any coast protection authority may concur with
any one or more other coast protection authorities in appointing
a joint committee of those authorities either for the aggregate
of the areas of the authorities or for any part thereof.

Section 4. A coast protection authority is empowered to
carry out such coast protection work within or outside its area
as may appear to be necessary of expedient for the protection of
any land in its area. An authority may acquire any land required
for the purpose. —

Section 5. A coast protection authority proposing to carry
out any coast pretection work, other than maintenance or repair,
shall publish notice of that proposal. Any person objecting to
the proposal shall be granted a hearing, after which decision will
be made by the Minister of Health as to approval, rejection or
modification of the proposal. Urgently needed protective work
may be carried out without publication of notice.

Section 6. Where it appears to a coast protection authority
that persons interested in land to he protected should pay charges,
the authority may prepare a plan known as a “works scheme" which
shall indicate the nature and estimated cost of the proposed work.

Section 7. Coast protection charges shall be levied against
land benefiting by the work, as indicated by the works scheme.
The charges shall not exceed the amount by which the value immediately
after completion of the works is greater than the value would then
be if the works had not been undertaken; the works in the future
to be maintained without expense tc person interested in the land.

Section 8. <A coast protection authority shall publish notice
of the preparation of the scheme and serve copies of the scheme on
owners and occupiers of affected land and on persons on whom charges
will be levied. Objectors shall be granted a hearing after which
decision will be made by the Minister of Health as to approval,
rejection or modification of the scheme.

Section 9. After approval of a works scheme by the Minister
of Health, the authority is empowered to take all necessary steps
for carrying out the work. Land owners have the option of carrying
out the work themselves upon notice to the authority and subject
to certain time limitations.

Section 10. Coast protection charges levied upon a person
under a works scheme become due on completion of the work and
service upon him of a notice specifying the amount of the charge,
or in case of dispute, when the dispute is finally determined.
Coast protection authorities may declare charges payable in in-
stallments covering not more than 30 years with interest at such
rate as may be determined by regulations prescribed by the Minister
of Health.

Section 12. A coast protection authority may serve notice of
needed repairs to protective works on the owner or occupier of
land. If the repairs are not completed within the specified period
or if the repairs are urgently needed, the authority may take all
necessary steps for carrying out the work.

Section 13. The reasonable cost of maintenance accomplished
by an authority under section 12 may be recovered from the owner
of the land, except for works constructed, altered or improved
under a works scheme.

Section 14. A coast protection authority may be authorized
to acquire by compulsory purchase any land which it is authorized
to acquire under section 4 of the Act.

Section 16. Any person desiring to carry out coast protection
work, other than maintenance or repair, must secure the consent
of the coast protection authority in whose area the work is to be
carried out. Works constructed,altered or improved without such
consent, or in contravention of any conditions subject to which
the consent was granted, may be required to be removed or altered,

Section 18. The excavation or removal of any materials on or
forming part of the seashore is unlawful except under licens?
granted by the coast protection authority for the area, subject
to such conditions as it may determine.

Section 19. “here the performance of coast protection work
by a coast protection authority results in depreciation of land,
compensation therefor is authorized subject to certain conditions.

Section 21. The Munister of Health may make grants toward
any expenditure incurred under the Act by a coast protection
authority, subject to such conditions as may be determined by the
Treasury.

Fart VT

Part JI contains provisions for the safety of navigation.
Gonsent of the Minister of Transport must oe secured to construct,
alter or improve works, deposit or remove objects or materials
from the seashore so that obstruction or danger to navigation is
caused or is likely to result.

WwW

GENERALIZATION OF THE FORMULA FOR CALCULATION OF
ROCK FILL DIKES AND VERIFICATION OF ITS COEFFICIENTS

by
Ramon Jribarren Cavanilles
with the collaboration of
Casto Nogales y Olano
Highway Engineers

Published in the Review of Public Works, May 1950,
Madrid, Spain, as Generalizacion de la formula
para el calculo de los diques de escollera y
comprobacion de sus coeficientes, por Ramon
Iribarren Cavanilles con la colaboracion de Casto
Nogales y Olano, Ingenieros de Caminos; publicado
en la Revista de Obras Publicas de Mayo de 1950,
Madrid, Espana.

FOREWORD

The following translation is related to an article
by the same author which appeared in translation in the
Bulletin of the Beach Erosion Board, Vol. 3, No. l,
January 1949. It is published at this time for the
benefit of American engineers concerned with breakwater,

jetty, and groin design and as a means of acquainting
them with Mr. Iribarren's latest thinking on the subject.
Ths editors of the Bulletin wish to acknowledge the
kindness of Mr. Ro. O. Eaton, through whose efforts the
translation was made available.

The opinions expressed are those of the author and
not necessarily those of the Beach Erosion Board.

In the booklet Una formula para el calculo de los diques de
escollera (A Formula for the Calculation of Rock-fill Dikes),
published July 1938% there was determined the expression

Pe NA? a
(cosa — sinan)3 (d-1)3
whe re
P = weight of the individual stones or blocks in kilograms,
N = 15 for dikes of natural rock fill,
N = 19 for dikes of artificial block fill,
A = 2h = total height of the wave that breaks on the dike,

measured in meters
*Translated and published in the January 1949 Bulletin of the
Beach Erosion Board, Office, Chief of Engineers, Department of the
Army. The coefficient K of that booklet is denoted by N in this
one, to avoid confusion with K = cothw H, and similarly, the anglea
we here denote a. Translation was [ made by D. W. Hullinghorst.

4

d = specific weight of material of the stones in tons (metric)
per cubic meter
a= angle of the dike's side slope with the moraine;

Before the preliminary determination of those tentative values
of N, each based only on a single observed case - the natural rock
fill dike of Orio and the artificial rock fill dike of San Juan de
Luz —- the booklet also stated:

"It only remains now to determine the coefficient N and verify
if it is sensibly constant, as seems to follow from the material
presented, or varies with the other elements of the formula.

™In the worst case, a coefficient similar to the classic and
variable coefficient C of the formula of uniform flow, V = C YR i,
will be considered,"

In spite of the twelve years intervening, during which the
reasoning followed for the deduction of the formula has been re-
fined, in a manner that might have been advantageously taken into
account by the recent translators of the booklet, the coefficients
15 and 19 still stand, due to the satisfactory results always ob-
tained in numerous cases of practical application.

The formula is actually derived for the upper slope of the
dikes, and a generalization for-all the depths of the work was
indicated only tentatively at the end of the booklet. In this
connection substantially the following was said:

"This generalization of the formula assumes a certain margin
. Of security, but it is not logical to apply on the sea the
strict results obtained from theoretical formulas when on land it
is usual to multiply them by ample safety factors.

"I should be most grateful to my colleagues who, acquainted
in detail with concrete practical cases, would kindly furnish me
information for refining the coefficients."

Unfortunately those necessary details of each particular case,
and especially the damages experienced, are difficult to obtain.
Therefore, in this study, we are go ing to make special mention of
one of singular interest.

We refer to the interesting compilation on the port of Argel
concerning weights of stones or blocks and their corresponding
stable slopes at various depths, after repairs of numerous damages
to deficient slopes. This outstanding compilation was made by

#In this paper, the ton unit is the metric ton of 1000 kilograms =
2205 lbs. - Trans.

Messrs. J. Larras and H. Colin in their article of December 1947
published in the periodical Travaux.

The following data are obtained from page 609 of that
compilation showing the corresponding slopes, depths, and weights.

of blocks or stones.
Minimum weight,
metric tons slope

Minimum
Depth, meters

Materials

Artificial blocks —5

Natural stones ollal
same wld

Quarry waste By -18

There can also be adopted, as a stable upper surface slope,
that of 3/1 formed by 50-ton concrete blocks, adopted for strengthen-
ing the North dike which, according to the cited article, has

. withstood perfectly even the worst storm (3 February 1934) ever

suffered by the port of Argel and which destroyed a large part of
the Mustafa dike, Likewise, we can adopt the toe depth of 35
meters, which this North dike reaches,

The maximum characteristics of waves from that very violent
storm are known with an approximation acceptable for practical
purposes, and will be used in comparisons which follow, The wave
period reached 13 3/4 seconds. The maximum amplitude of a
beacon buoy** in the exterior of the port was 7 mters, and this
constitutes an approximate upper limit to the wave height.

To explain the 9-meter sheets observed passing over the
parapets of the dikes, it has been conjectured, simply by inertia,
and abstracting other forces such as those of buoyancy, that the
amplitude of the vertical movement of the buoy was less than the
wave height.

The buoy and whole float of constant horizontal section can be
likened to a vertical oscillator whose own natural period, was un-
doubtedly much less than the 13 3/4 seconds of the period of the
wave. Under these conditions, the maximum vertical amplitude of
the oscillator, or buoy, must be practically equal to or, better,
somewhat greater than that of the sea.

For hypothetical lesser periods of the sea, that might
approximate the buoy's own natural period the vertical oscillations
of the buoy, amplified by resonance, would be much greater than
*% See the view presented to the second question (subject) of the

second section of the XVI International Congress of Navigation by
Messrs. M. Benezit and M. Renaud,
*«i"boya de balizamiento"

periods even briefer than the buoy's own period, couldth2 buoy's
oscillations be less than those of the sea.

For this to have happened, during the observations of the
storm of Argel to which we refer, it should have been necessary
that the natural vertical period of the boy itself be significantly
greater than the 13 3/4 seconds, which we estimate to be impossible
in a buoy of that type.x

The maximum height of wave before reaching the dikes was, conse-
quently, approximately 7 meters or somewhat less, and only on break
ing over the dikes did this height, amplifieds* by the works
(structure) itself, reach the order of 9 meters, as is demonstrated
below.

Due to the steep side slopes of the rock fill dikes, or rather,
the short distance (relative to wave length) which the wave traverses
from the vertical line through the dike toe to the highest point
reached on the dike, the energy loss must be small, in spite of
the rock fill roughness, always small relative to the wave length.
Moreover, even were the energy loss to be appreciable, disregarding
it only augments correspondingly and conveniently the margin of
safety.

In a sense (limited, for a breakwater is not a beach although
the effects resemble one another for waves of the length under
consideration), the graphs of our article published in the Revista
de Obras Piblicas last November, in which the curves corresponding
to slopes exceeding 10 per cent are almost coincident with those
from conservation of energy, may serve to verify the smallness of
such energy loss.

More authentic verification, of this and other simplifying
assumptions that are necessitated in these complex subjects, is
the comparison with actual observations on the dikes of Argel,
themselves, which we make in the following,

* “Boya de balizamiento"

x* Inclosed in vertical dikes, a similar amplification is produced
by the structure itself--amplification which in this case makes
the amplitude of the vertical surface movement, on the wall,
generally exceed twice the wave height.

See the booklet Galculo de diques verticales (Calculation of
Vertical Dikes), also published in July 1938 and translated and
published in the Bulletin of the Inte-national Navigation Con-
gress, July 1939. Also see the experimental confirmation of said
amplification, constituted by Figure 13 and 18 of the article
of A. Stucky and 1). Bonnard, published in Travaux of January
1937. The results obtained in those publications are likewise
admissibly proportioned to the height of wave indicated and its
corresponding amplification,

If we designate by Hp the depth of the tce of the slope and by
Lp» hp, Kp the characteristics* of the wave over the depth Hp; by H
the depth of the point on the slope that we are considering, and by L,
h, K, etc., the corresponding characteristics of the wave, and if, for
the reasons presented, we admit the conservation of energy, one deduces
immediately: |

where

p=7K | = and Pp * {¥p 2 ’
p

deduced from the approximate curve

h a 28
ho a

of figure 22 of the cited report, or from its corresponding table,
pages 32 and 33.

The approximate curve can be utilized, neglecting the breaking
factor /b, because the action cf breaking is so very rapid that
there ie dnsuf ficient time for its effects to be really produced
before breaking, and even if this should not be entirely so, as the
said effects are very similar for all breakings, on being neglected
they would remain implicitly in the coefficients N, determined by
direct observation of the phenomena,

With respect to the generalization of the formula, mentioned at
the beginning of this study, it is proper to note that for some
years it has been refined on the basis of the following reasoning;
and that, although this reasoning also supposes some Simplifications,
the final result we get will confirm, on comparison with an actual
case (always the final test in technology), that the degree of ap-
proximation is also sufficient for practical applications.

The maximum horizontal particle velocity of the wave (on
breaking under its limiting conditions, y, = 4/gh,3*) being the
principal cause of the removal of the stones of the breakwaters, the
effects of the maximum orbital velocity, also horizontal, correspond-
ing to any depth

xBoth these notations and the others can be found in our report pre-
sented to the fourth communication of the Second Section of the
XVII International Congress of Navigation.

xxSee the cited booklet of July 1938, or its translation, and the
aforementioned report to the Lisbon Congress.

8

will be similar to those of a hypothetical, or virtual, wave of
equal velocity, That is, the equality “max = Yh would have to
hold, or in orther words,

Wr =z fen! =fe AM G
We 2

The semiperiod being

Ps) eae

g
immediately one obtains the height of the virtual wave:

Aly sh 2s 2.9rie re

Seen 3

LK
which, introduced in place of A in the formula, thus generalizing
it, permits us to calculate the slope or weight of the stones at
the depth under consideration,
Likewise, since

Ke Scaling! th LK ita,

and r in contact with the slope face

ASL TE Aga) h 9
Shia
one obtains
Moe) 12 Mike :
Loi Shfig E

The inclination of the slope, and other circumstances, could in-~
fluence all this somewhat, but not varying much from one dike

to another, its influence would also remain implicitly in the
coefficients which, as has been indicated, are determined by
direct observation.

As confirmation of all that has been presented, and has
been applied for several years on numerous works that have
resisted satisfactorily violent storms, we are going to apply
it to the authentic and interesting case of the dikes at Argel
on which for the reasons presented, we can soundly begin with:

Hy = 35 m.5 A, =2 hy = 7m,

2 Ly = 1056 (27) = 1.56 x 13.75% = 295 ms L, = 147.5 m.

fe)
For various values. of the depth H, measured from the mean level
of movement, we obtain the informtion shown in Table 1.

The curves of variation of A' and 2h as functions of the
depth H, referred to the mean level of movement, are shown in
Figure 1, in which also are drawn the curves of surface super-
elevations Sj and the line of theoretical breaking H = h,
corresponding to steep slopes of the rock-fill dikes.x

The point of intersection of this straight line with the
curve 2h determines for us the height of 9.70 meters of the
wave on breaking over the dike, approximating, though somewhat
‘greater than, the 9 meters adopted by the Argel engineers.

In Figure 2 are shown the wave heights 2h referred to the
level of the calm sea, H, = H = Sp, the superelevations S,
taken into account, and the corresponding curve that gives us
the virtual heights A', which we mst take into account for the
calcuation of the dike in its submerged zones,

The type section of the dikes of Argel, sanctioned by
very long experience and deduced from the interesting table
compiled by MM. LarrAds and Colin, is that indicated by the solid
line in Figure 3.

If, in a given zone, the slope of a dike is steeper than
that required for equilibrium or stability, settling will result
during storms, which, flattening the slope, will tend to adapt
it to said equilibrium. It is, therefore, logical to make
the corresponding confirmations, determining by means of
theoretical calculations and the coefficients which it is
desired to compare with actuality, the slopes corresponding to
the points or zones whose characteristics are known through pro-
longed direct observation,

For this, from the formla
P = N a3d
(cop & - sin a)? (d-1)?

x Note the section h, Rotura de las olas (Breaking of the Waves)
page 26 et seq., of the cited report presented to the XVII
International Congress of Navigation, convened in Lisbon.

10

0,2373

1,3231

222,96

0,9211

34,77 | 31,25

34,80

Table |

0,1898

1,4382

205,03

0,9372

27,72 | 24,18

Table

0,1424

1,6160

182,55

0,9690

0,93

0,38

20,62

0,32

20,68

2

11

0,1187

1,7460

168,92

0,9951

1,25

0,46

17,02

151,75

1,032

7,84

1,78

0,61

13,39

0,0712

2,1964

134,31

1,088

8,27

2,78

0,0237

3,7128

79,47

1,379

10,48

14,96

Depth H referred to the mean elevation in movement, in meters

Protundidad 4 referida al W.M. en movimento er m.

2h, A’ and Sp in meters
2h, ne os i Mm.
MTA i 2h le A 9 10 1 i213 th 6m

10

a Oahcabo ich MisIEe)
er ar, NG CE I”
ie BP el ed of on ig oli wt a

16 Terhade | ooh oe leclbey PORT OF ARGEL

Increment of fhe height
18 of wave over the batter

20 err tte aie t oes virtual wove

on submerged
parler e oo ec

A
30 | Aura de ola virtual er faluges

| sure, vdos HORE Attire seco rente ey cre nay
creed |

35
oe of wave approaching the dike.. .. 2hp = 7 meters
Altura oe ola gue aborda el adique 2hp=7 m.

Altura de ole 6/ romper sobre e/ dique— 2h = 9.70 m.

Height of wave on breaking ver the dike.......2h = 9.70 meters

Figure |

12

Depth H-, referred to the elevation of the calm sea, in meters

frofundidad Hr referida al N.M. en reposo, en mM.

2h, A’ and Spin meters
2h, A’ y Sh en mm.
Ci le Cie whe iG AGT. BY OO, TIE Bie 15 4 15

ine: 2h=9.7m]) ©

2 <7 = hotura: 2h=9.7 71.

,

6

8

10

see ee aa

Pay aes

De
ar i Weber lle |e
ae BG a a

6 a

20

a Ve
PRE E eo ME EE i ae
le |
FRE) Ua SAA
PUERTO DE ARGEL
28 |__ PORT OF ARGEL

Alturas de olg referidas al N.M.en repose

N
&

Height of wave approaching the dike uae 2hp = 7m
Altura de ola que aborda el dique- 2hp =7 MM.

Allura oe ola af romper sobre e/ ee =9.70 mM.
Height of wave on breaking. over the dike......2h=9.70m
Figura 2.

Figure 2

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we deduce

from which, the last member being known, immediately we deduce
the batter cta that enables us to draw the theoretical profile,
in order to compare it in Fieure 3 with that determined by
nature e

Thus, we obtain for the batter of the upper 50 tonx concrete
blocks:

cta-1 = 9.7 %igx2.36 = 0.688
ofl + cle 1.36 50,000

whence the batter ct aw = 3.51

For the rock fill of artificial blocks situated below the
dspth H, = -5 meters, referred to the calm level, we obtain

eta -l =5.6 3fi9 x 2.36 = 0.397

yl + Cte 1.36 50,000
whence the batter is cte = 1.83.

For the natural rock fill situated below H, = -ll m:

ete MEETS 12/5120 3/15 x 2.7 = 0.293 ,
Vl + ote a 1.7 4000

whence the batter is cba =1.53.

For that situated below H, = -l4m:

cts 2) 70 ea (sixes 0.343
Vl + ct-« 1.7 1000

or the batter is ct & = 1.67.
For the deep zone -H, 2 18 m, composed of the quarry waste
whose weight will vary from 1000 kilograms to a small minimum

weight, the weight of the stones obtained for the fixed batter,
ct &@ = 2, would be

P=15 x1.15?x 2.7. 2143 ke,
1\3
(73) «1.77
% Metric ton, 1000 kg = 2205 lbs.

SUB)

very acceptable for a weight of stones that, as has been indicated
can range downward from 1000 kg to a small weight, and whose in-
dividual stones of weight less than 143 kg placed near the upper
part would descend down the slope, so that by this process, and
surely without subsidence of importance, the surface would become
constituted of stones cof greater weight.

The necessary weight of stones at the foot of the dike, where
the height of virtual wave is 0.39 m, would be only

Pp =15 x 0.30°x 2.7 = 5.6 ke.
PE ae
(ye) 2-7
The theoretical profile is obtained in this way and is
indicated by the broken line in Figure 3, whose approximation to
the real profile is already very satisfactory. But, if instead
of adopting as height of incident wave its upper limit = 7 m;
deduced from oscillations of the buoy, we assume the maximum
height of wave of 9 m adopted by the engineers of Argel, we ob-
tain Table 2, similar to the preceding and corresponding to a

height 2 = 6.45 m, determined after several trials, so tha
the maximum height of wave on breaking should be the 9 m cited.

Figure 1' similar to Figure 1, confirms that, in effect,
the height of wave at breaking is 9.05 meters, that is, practically
the same as 9 m.

In Figure 2! similar to Figure 2, are determined the height
of virtual waves, A', corresponding to the various depths, in
which, again by analogous procedure, we obtain the following
batters; ;

For the surface slope of 50 ton concrets blocks:

ic ale1 2] Gh0s iGpamoT = O-Ga
nih emer les Vy 50000

whence, the batter should be ctb@ = 3.04

For the rock fill of artificial blocks situated below the
depth Hy = —5m:

cha-1 =5,0 %/19x 2.4 20.346

fi + ct2x 1.4 V 50,000
whence the batter should be ct@ =1.68

For the natural rock fill situated below H, = -1l m;

16

Depth H referred to the mean elevation in movement, in meters

Frofundidad H referida al N.M. en movimiento, en m.

2h, A' and §, in mters

ito Sh He
ON eA) WON A i O78. 10 tf 2 ss 6

2 ee eee
ee eee See
ges ete tre emf o| wir

rroredent of the O BE ARGEL over
the er o the dike
[TTT asi 2 ae
5OUL falud def argue aaa) ONSEN is
32 bee Altura de ola vitlual en t3ludes
| Hei f virtual ¥

Height of wave ae the dike Sdcc6 2 hp = 6.45 meters
Altura de ols que abarda e/ dique ely = 6.45 mM.

Mura de ola &# ronper sobre ef digue.,.2
Height of wave on breaking 6 Lag: ee = ILS Mo
Figura 1’.

9.05 meters

17

the elevation of the calm sea, in meters

Depth Mil referres i:

Frofundidad Hr referida al N.M. en reposo, en m

2h, A' and S) in meters

2h; A’ y Sp en m7.
) fo ND RNS 6 RB MS NOL NT) ONION, RAO Meh a inl Catt Ohne LoD

a are =

10
i fen
72 nian

th +4 Bid

30 TF Tabi to] 5 eee Alturasde ola referidas al N.M. en reposo
Le Sept has [asker | Wave Ca: referred to elevation of
S2\ul the calm e

Height of wave approaching the dike ... 2hp = 6.45 m

Altura de ols gue storda el aque. 2hp =6.45 17.

Altura de ols af romper sobre el oique_ 2h- 9.05 M.
Height of wave on breaking over the dike... 2h = 9.05 m.

Figura 2.

18

Giro el) = 195) Sexier = 0.248
Vl + ct-e 1.7 4000

whence the batter should b8 cta = 1.43

For that situated below H,, = —- 14 me

G2 Ge) a WS, Te) ee MP 4 Oe
dey 1.7 1000

whence the batter should be cta@ =1.51.

For the deep zone H, = - 18 m, one obtains a weight:
a ae P< 1,002 x.2.7 |= 94 kilograms
i, \e
[> x Lae

likewise quite acceptable, and the weight corresponding to the
toe of ths dike will be:

= 15 x 0.332 x 2.7 = 3.4 kilograms.
7 \ 3}
FF x 1.72

In this way we obtain a theoretical profile, shown in Figure 3!
Similar to 3, even more closely approximting the real profile; but
the really interesting fact is that both figures, whose calculated
wave heights differ by less than 8 per cent, a degree of approxima-
tion that we consider difficult for anything practical to really ex-
xeed, are now authentically confirmed by the very important direct
observation from this interesting compilation. It is also now con-
firmed undoubtedly, through authentic direct observation and despite
the simplifications one is forced to introduce into the complex
subjects of maritime engineering, that the degree of approximtion
really obtained is superior to that of many calculations of
engineering on terrestrial subjects, in which, even legally there
are imposed large safety factors, generally greater than two and
frequently approximating three.

In the rock fill dikes the proportional increase of cost
occasioned by these always convenient safety factors would not ‘be
greater than that for terrestrial works, and moreover, their cost
would be recovered in no long time, on the basis that, by placing
somewhat heavier stones or blocks the movements and consequent
expenditures diminish and thus very costly outlays for mintenance
are saved.

For these reasons it seems advisable, despite the very
satisfactory confirmation just made and which one must remember
refers to the strict equilibrium limit, to adopt at least a re-
duced factor of safety of 1.5 on the coefficients N, so that they

19

“£ emai

sl8qol 60°66 = US °° OXTp ouy JOAO JuTyeeiq uo SAeM JO TUsToR
W506 = 42 anbIp fa 21908 Jatluas /@ 80 ap Binyy
‘W 59'9= y2——enkip ja epsoge anb Yo 3p enyy Zz
oa
slejeu 67°9 = dyz** extp 6uy dutyoeoidde saem jo ys TeYy G24
a
ao
eqsem Lrzend Wee
CSWUEI FO sopsay + -jle
et
SE
ae
ao
ao
ee
= z a 7
HOR OF 7 BNET IIN as oa
: \
= ge sug SU = SOUOIS TEIN FEN - ae
WW #- SOJEINJEU SaJUeZ d oie
suo} Of4ZeU OG — SHOOTQ [LeLOLTyTqIaAV BA “-* -=+=+aTT youd [eot1 e10s8uy,
oO a,
wy og-sejernyyse sanboyg gh (ut[O9 pue seqizeT WA 04 dsutpz000e8) seTTjoud etqeqs
ZL = ODM [lsd
A uiyjog A sesse7 wy ungas) 298158 la
/2TIZ eu OS - SHOOT TeToOTsTIAV =
Bu04 L0G -SHYOWIYIE Sai oy, iis TI9aV FO OLYTNd
=) = ee UG 52! “908 [as1y jo 410g
(ore onal gnbiD * osodas Le o1pau arly ™

ees WTed |yy Jo uoTyeASTT

20

would be raised to 29 and 23, respectively, for the artificial
blocks and natural stones.

More, really, than the weight of these blocks or stones, this
increase would affect the batters of the projects, flattening them
a little, and it should be remembered that the said reduced safety
factor of 1.5 would only suppose a margin of </1.5 = 1.15 in the
wave height or in the size of stones.

In any event, and with respect for strict economy, one can
neglect said reduced safety factor, continuing to use the primitive
coefficients of 15 and 19 on large dikes where the stones are
carefully placed to a considerable depth, provided that the in-
crease of wave height produced by the work itself is always
calculated following the indicated procedure.

On the other hand, and to simplify the calculations on the
smaller dikes, said factor of 1.5 can be adopted, that is,
coefficients N equal to 23 and 29, on the dikes whose stones are
carefully placed to a lesser depth, and by virtue of this pre-
caution being able to take the incident wave height rather than
the height of wave that breaks over the dike, as already indicated
textually in 1938.

The theoretical relative breaking depths, deduced from the
cited table and the curve 1K of of Figure 22 of the report,
eing H = 0.03, to which a wave height amplification
Ty
factor of 1.3 applies, it will be possible to calculate a rock
fili dike on the basis ef the incident wave height and adopting
the cited coefficients 29 or 23 that include the safety factor
1.5, whenever the relative depth of its toe is less than H = 0.06,
Lo
corresponding to the amplification factor of the cited curve
ape = 1.13, or whenever the depth of careful placing of the stone
=
of the dike is tess than H xl = 0.06 x 250 = 15 meters on our

Cantabrian coasts, or x L, = 0.06 x 150 = 9 meters on the

H
ify

Mediterranean coasts.

As was made a matter of record in the XVII International
Congress of Navigation convened in Lisbon, it is also highly
satisfactory that the formula deduced in the American report of
Epstein and Tyrrel for reflecting rock fill dikes, starting
from our expression for pressures of refiection P,, = CV *, is

Fay

* Ses the cited report Calcuktion of Vertical Dikes (Caiculo de
diques verticales).

ao Soe SS ~~ g
a

21

similar to that which we obtained in 1938 for breakwater dikes.

In effect, the American formula is:

P. = Ry 5H-
5

and ours;

Naa
P = oe
(cosa - sinoc)? (d-1)?
in which
Py, = P = weight of the individual stones
H =A = 2h = wave height
Ss =4d = relative density of the material
M = natural batter of the rock fill=—1

tan @ = slope of the rock fill
Ry and N being the coefficients.

aR
i}

Expressing the American formula in our notation, it becomes:

1 Je costec aa
(cosa - sin a )? (d-1)3 ;
which is ours except only that it includes the factor cos“m in ths
coefficient.

It is a matter of record that on establishing our formula it
was already indicated, that the coefficient should be able to vary
with the data of the problem.

Practically the angle o , which varies most for the upper
part of the dike, will not vary much, for from cotana,=3, correspond—
ing to present rock fill dikes, it cannot get much steeper than cotan
@, = 2, even in the reflecting dikes, because of the enormous
weight of the stones this necessitates. Between those mximum
limits the relation is:

cos? ©1 ile

cos 3 & 2

which would represent only a small difference in the weight of
the stones and even less in their size, whose relation would be

1.2 =1.06. Only direct observation can determine properly N
or R.> including cases of very steep batters.

Concerning this last coefficient, it should be indicated
that the expression for it determined in the American report can
have reality only when the protecting blanket is made up of
parallelopiped blocks perfectly aligned, with their three
dimensions horizontal, normal to the slope, and following the line

22

of maximum slope, it being precisely under these theoretical con-
ditions, of reduced joints, when the calculating procedure follow-
ed, based on internal pressures which must be transmitted through
those joints, lacks applicability. If the blocks move through

any cause or settlement, the cited three theoretical dimensions

no longer really exist, the coefficient R, becoming the N determined
only on the basis of the overall dimension of the Stone.

Although only under the heading of curiosity, it is also inter-
esting to compare the results obtained for the theoretical value A!
= 27 xf with the practical results pertaining to the limiting

LK
velocities of erosion on the bottom of a canal, whose bed we
suppose horizontal, that is to say@® = 0, and the formla that
gives us the weight of the individual stones would be:

P= ma
(d - 1)3

as
RO 3 Bier
LK

we get

and since

pmax= Wr and T =/9 IK

one obtains

P= 8Nav ee

g? (d-1)3

Applying this formla for the velocity in the canal, y max =

1 meter/second, and with a mean specific weight of material that
constitutes the individual stones or grains of d = 2.6 metric tons/
m-, one obtains:

ped 8) 98 TLS) be nl) x 16 = 0.081 kilogram,
9.813 x 1.67

which represents a cube of side:

: = (oo = 0.081 = 0.03 meter,
1000 d 2600

23

- dimension of gravel whose order of magnitude is still in accord
with observed reality for said limiting velocity of erosion, on
“horizontal bottoms, of 1 m/sec, in spite of the enormous ex-
trapolation made, which it would not be permissible to carry on
indefinitely. The formla gives acceptable results, without
“modifying the constants from those applying to stones or blocks of
several .tons weight,to these gravels that don't weigh 100 grams.

As a consequence of the foregoing, we estimate that we have
confirmed authentically, through direct observations which always
constitute the definitive ratification of these matters of techno-
logy, the generalization of the formula and the valuss of its
coefficients, despite the simplifications whose introductions in
these complex subjects are unavoidable.

ANNOUNCEMENT OF PUBLICATION

The Beach Erosion Board announces the publication of its
Technical Memorandum No. 21, "The Interpretation of Crossed
Orthogonals in Wave Refraction Phenomena". Copies are being
miled to those individuals and institutions on the mailing list
for technical publications.

A limited number of copies are available for distribution

upon request to the President, Beach Erosion Board, Corps of
Engineers, 5201 Little Falls Road, N. W., Washington 16, D. C.

24

APPLICATION OF .ASPHALT IN HYDRAULIC
ENGINEERING WORKS
by

Jo He van der Burgt

FOREWORD

The following translation was furnished the Beach
Erosion Board by the author following a recent visit to
the Unitea States. It is published here to acquaint

American engineers with Dutch progress in the use of asphalt
mixtures for shore protection works. The paper has been
abridged to permit publication in the Bulletin. The
opinions and conclusions expressed are those of the author
and not necessarily those of the Beach Erosion Board.

Introduction

The extensive application of synthetic asphalt in road con-
struction work started around 1923, whereas it took another ten
years before this material was applied to any extent in hydraulic
engineering works. This is caused by the fact that the almost
horizontal road surface encased by the shoulders, was ideal for
testing the new and rather unstable material, whereas the sloping
surfaces of hydraulic works were highly unsuitable for this purpose.

The share of the Netherlands in the research work regarding
the application of asphalt in road construction and hydraulic works,
has been appreciable. Extensive research done by the Rijkswegen-
bouwlaboratorium at Scheveningen and the Research Laboratory of the
Royal Shell at Amsterdam, combined with thorough testing and ob-—
servation during the execution of ssphalt-works have led to such
control of the properties of asphaltic bitumen and bituminous
mixtures, that now it is possible to use this very durable product
appropriately on sloping surfaces, even on steep slopes.

Asphaltic Bitumen and Bituminous Mixtures

The asphaltic bitumen is derived to a small extent from
natural sources and synthetically made on a large scale.

The well known natural asphalt from Trinidad is a rather
impure product, which is unfit for use in hydraulic works, as the
enclosed clay-particles are affected by water.

The synthetic asphaltic bitumen is derived from petroleum.
The remaining product becomes harder as more oily components are
evaporated during the process of distillation.

xComposed after a lecture, given by the author on 10 Dec 1948 for
guests and members of the V.B.W. (Association of Bituminous Works)

25

The asphaltic bitumen consists of tiny carbon particles ap-
proximately of equal size called micelles, which might be imagined
as floating in an oily medium. The stability of the bitumen cepc nes
on the ratio of micelles and medium, Addition of a filler, i%e.,
a finely ground non-hygroscopic product increases the stability of
the bitumen because, according to Professor Nellensteyn, the finest
particles of the filler form new micelles, thus increasing the bind-
ing properties of the asphaltic bitumen.

Dependent on the kind of work, the asphaltic bitumen must meet
certain standards, which are specified in the instructions for test-
ing bituminous construction materials (K.V.B.B.). One of the most
important points in the testing of asphaltic bitumen and asphalt
mixtures for hydraulic works is the detemination of the softness of
the material, which is measured by the degree of softness or the
penetration index. ‘

Asphalt mastic or asphalt cement is the name of the mixture of
asphaltic bitumen and filler.

Asphalt mortar or sand asphalt is the name of the mixture of
asphalt mastic and sand.

Asphalt concrete is the name of the mixture of asphalt mortar
with gravel or broken stone.

In using asphalt mixtures which are to be transported over a
certain distance, one should take care to heat and preferably isolate
the containers, whereas for liquid mixtures the solid materials
should be kept in suspension by a special stirring device.

Standards for Asphaltic Ritumen and Asphalt Mixtures

For hydraulic works asphaltic bitumen and asphalt mixtures
should meet the following standards:

1. Remain plastic, even after cooling down slightly;

2. Be sufficiently elastic, even at low temperatures, so
that the material will follow if the underlying base
settles unevenly;

3. Remain stable upon a slope, even above the water sur-
face and at high temperatures;

4. Be proof against oxidation;

5. Stick to clean and dry surfaces;

6. Be proof against aggressive water (salt water, swamp
water, etc.);

7. Be proof against abrasion by sand;

8, Be proof against wave action.

The combination of elasticity and stability mentioned under 2
and 3 can hardly be expected in any material, but it has been
proven that a satisfactory compromise can be achieved.

Of course it depends entirely on the kind of work for which
the material is to be used, which of the above mentioned properties
should be predominant or whether any other standards should be met.

26

General Review on the Application of Asphalt Mixtures

For hydraulic works the asphaltic bitumen is mostly used ina
mixture, in which the percentage of the expensive asphaltic bitumen
is kept as low as possible. The other materials such as the filler
(partly), sand, gravel and broken stone are natural products, the
gradation of which greatly influences the quality of the mixture.
Therefore, to efficiently obtain reliable results, laboratory con-
trol and information are of great value.

In working with asphalt mixtures, one should keep the
temperature as high as possible until the job is reached. Care
should be taken that no superheating occurs, since then the
asphaltic bitumen will be cracked, which means that free carbon is
formed, changing the mechanical properties unfavorably.

In many instances wnere hydraulic works are constructed the
water can be retained temporarily so that the asphalt mixture can
be applied on a dry base. In other areas subject to tidal- and
wave-action it often occurs that the job must be completed within
a short period of time and the mixture has to be applied to a wet
base or even under water. In the latter case one cannot depend
on adhesion and special measures must be takem in order to carry
the asphalt mixture into place at the required temperature. The
recent experiments in the 1st kercsene-harbour at Rotterdam,
where a plastic mixture was carried to its destination through
isolated tubes, indicated that it is quite possible that this
material can even be applied under water. Certainly, the last
word regarding these problems has not been said yet, but by
proper cooperation between the research institutes and those who
design and execute hydraulic work bitumen is being used,
the solution of these problems can definitely be found.

Gola anc Hot Asphait

Asphaitic bitumen is used in hydraulic works as coid asphalt
and as hot asphait.
Hot asphalt may be used in;

1. Permeable works.

ic bitumen

1c

a. by penetration with pure asphai
b. by penetration with asphalt mas
Ge by sheeting with bituminous sand

u
+
iv)

2. Impermeable works.

a. by surface-treatment, with pure asphaltic bitumen
do. by sheeting with asphalt mortar (sand asphalt)

ce. by sheeting with asphalt concrete

d. by grouting with pouring asphalt.

27

Cold Asphalt

This material is liquid at normal temperatures as a result of
the addition of certain volatile components which evaporate and thus
cause the mixture to stiffen gradually. Therefore, as a rule this
material cannot be used under water or in thick layers as it remains
soft. It would be worth while to improve the quality of this pro-
duct, because it may prove of great value where hot asphalt cannot
be used or where repairs must be carried out. Cold asphalt was
used in 1936 at a trial section on the outer slope of the north
east polder dike near Urk.

Cold asphalt grouting containing 16% of asphalt emulsion, 25%
of cement, 53% of sand and 6% of water was applied at normal
Amsterdam level (N.A.P.). On eachsquare meter of the basalt stone
slope protection 19 kg of grouting material containing 3 kg of
asphalt emulsion were used. This grouting was often submerged and
almost constantly subject to wave action and has gradually vanished.

Hot Asphalt

This product has been used in various compositions both below
and above the water surface.

To apply thin layers (surface treatment with pure asphaltic
bitumen or asphalt mastic) above water, a dry and dust free base
is essential for good adhesion. For thick layers (sheeting with
bituminous sand, asphalt mortar or asphalt concrete) a stable
mixture is required, which often should be elastic as well.

On a wet base or under water there will never be any ad-—
hesion between the base and the bituminous material and therefore
the mixture should be carried to its destination in such a way
that the internal heat is preserved as long as possibie. This
can be achieved by applying the material in solid masses of sub-
stantial size, for instance by the aid of clamshells, shoots or
isolated tubes. Thus, even under water the masses will stick
together where they touch, because the surfaces which cooled
will be reheated by the radiation from the centre. Thanks to
this phenomenon asphalt grouting may penetrate deeply (1 to 1.5m

under water). This is necessary, not only to envelop the
stone in order to anchor it safely to its base, but also to fill
the cavities. In works along the seashore this is imperative
in order to insure that the wave and groundwater action does not
result in internal water and air pressures which may have a
disastrous effect. If the voids between the stones are too small,
the bitumen or the mixture cools off too rapidly and there will
be little penetration, resulting in unsound work. Therefore, the
kind of works and the forces to be resisted determine to what
extent the cavities should be filled. Hspecially in sea-work one
should be on the alert against being penny-wise and pound-foolish.

28

If the asphalt mixture travels freely through the water over
a certain distance or is exposed to wave action while it is being
poured, the mixture will change into a porous mass which hardly
penetrates at all, with unreliable work as a result. It has been
found that in poor mixture which are submerged permanently or
regularly, the film of asphaltic bitumen which covers the particles
is gradually replaced by water, causing the mixture to lose its co-
herence and fall apart. Since it is impossible to coat the wet layer
of porous material with an impermeable layer of asphaltic bitumen
or tar, it is recommended that a sufficiently rich mixture be
chosen initially for layers which are constantly or regularly sub-
merged by water.

In the following description of works executed with the use
of hot asphalt, the above-mentioned points will further be dis-
cussed where necessary.

Works Executed with the Use of Hot Asphait

Since hot asphalt has been used in a great many hydraulic works,
it is impossible to give a complete record in this short review.
Therefore only a description of a number of applications will be
given for the following constructions.

°

bank protection along canals

impermeable sheeting of the wetted profile of canals
impermeable sheeting of weirs

bank protection along rivers

slope protection along sea shores

mattresses

reinforcement of beach groins and harbour-—dams.

°

°

°

°

NOAWE Ww NE

°

The original translation contained discussions of the first
four types of works; these have been deleted in this presentation.

Slope Protection Along the Sea-shore

The following applications of asphaltic bitumen or asphalt
mixtures have been made.

Trial Section on the Outer Slope of the "Northeast Polder" Dike
Near Urk 1936

At this trial section (total area of 2000 m) tests were
made in cooperation with and under control of the Research Lab-—
oratory of the Royal Shell at Amsterdam. The slope of the dike
ranged from 124 at the bottom to 1:3 at the top, separated by a
5 m terrace at about 2.00 m + N.A.P. (Normal Amsterdam Level).

Test la. Penetration of macadam with pure asphaltic bitu-
mene The area extends from +2.00 to +3.50 m (Normal
Amsterdam Level) and is covered respectively by a layer
of set bricks, an 8 cm layer of dumped rubble stone
and an 8 cm layer of compacted broken stones of 3-5
cm. This last layer was penetrated with 9 kg/m@

29

asphaltic bitumen 60/70 covered with a 1, 5 cm layer
of broken stones of 1-2 cm which was treated in turn
with a surface treatment of 3 kg/m2 asphaltic bitumen
60/70 and finally protected by a 1.5 cm compacted cover
of broken stones of 1-2 cm. This protection has served
well although attack3d heavily during southwest gales.

Test lb. Penetration of macadam with asphalt mstic. The
area has approximately the same cover as described under
1. It reaches from N.A.P. to 3.50 m+N.A.P.. The
lower part is subject to wave action daily. Bulges
have formed in this lower part, the cause of which is
unknown. Possibly sand was deposited between the rubble
stones during the construction. Water may have accumu-
lated in this sand creating a2pressure behind the
impermeable cover. Since the voids in the rubble stone
are rather small anyway, it is imperative that care be
taken to prevent sand and fine material filling the
voids.

It seems undesirable to use the procedures des-
cribed under 1 and 2 under less favorable conditions
although they did prove satisfactory under the circum-
stances of the tests.

Test 2d. Grouting of set stone with pouring asphalt.
Three areas were covered, reaching from N.A.P. to
+0.90 and +2.00 m N.A.P. respectively. The stones were
set in the usual way, after which the spaces were filled
with rubble stone, gravel and sand to 8 cm from the
surface. Then the sides of the stones’were treated
with a cold bituminous priming coat, after which the
spaces were filled with pouring asphalt to 2 cm from
the surface. The pouring asphalt consisted of 43, 3%
DX 10, 4.7% asbestos fiber 2-4 mm and 52% sand 0-2 mn.
Twenty-two kg per square meter of pouring asphalt
wereused, containing 9.5 kg of asphaltic bitumen.
The lower parts of the spaces were kept open to let
the water pass freely and thus prevent the building up
of pressure under the layer.

This construction appears to be very solid, has
served well, and seems sound and economical at ex-
posed slopes.

Protection of the Dune Foot of the "Green Beach" at Terschelling
1937 (Figure 1)

In 1937 the beach near the dune foot at one end of the

"Green Beach" at Terschelling was repaired and protected after it
had been damaged by the sea during high tides. The beach was

30

SECTION OF REVETMENT

Lime grass

Clay layer
“20 thek

Clay shells

LOCATION MAP— WESTERSCHELLING

GREEN BEACH

WADDENZEE
Revetment

Constructed 1937

Figure 1. Protection of the "Green Beach" at Terschelling.

31

covered with a © cm layer of so-called shell-clay, which is a
natural deposit often found in the Wadden-sea, containing clay and
shells and being slightly permeable. Three layers of compacted
broken basalt stone (3-5 em) were placed upon this, each of which
was penetrated with pure asphaltic bitumen 60/70. Although the
cambered slope was rather flat, the construction proved unstable
and slides occurred. Saeieeely high ground water pressure under the
construction was the main reason for this failure since a high
range of dunes was near. The bituminous protection was removed
after some years and replaced by a brick pavement on shell-clay.

Repairs On the Outer Slope of the Westkapel Seadike 1946-47,
(Figure 2)

The Westkapel sea dike was badly damaged during the
struggle for Walcheren by bomb and shell explosions over a
section north of the gap which was made in 1944. This damage
was spreading gradually under the action of high tides.

Part of the slope protection was repaired with concrete; else-
where pouring asphalt was used extensively to form a protection in
a Quick and efficient maou of the loose stones which were pre-
sent on the slope.

Furthermore, part of the slope was protected at the top by
a layer of rubble stone penetrated with asphalt.

Test lb. Penetration of rubble stone with asphalt mastic.
Area IV, from +5.00 to +7.25 m N.A.P. was protected
by a 0.20 m layer of dumped rubble stone, penetrated
with asphalt mastic (15% bitumen, 7% filling and 78%
sand), in such a way that an impervious asphalt cover
was obtained at the surface.

The rubble stone layer was filled ge a depth of
10 em by 110 kg of asphalt mixture per m2 (Figures 3
and 4). In order to prevent the spaces in the rubble
stone being filled with water which might create a
dangerous pressure, the penetrated section was sealed
at the top by an asphalt coffer. This construction
has proved satisfactory, but it cannot resist water
pressure from beneath.

Test 2d. Grouting of set stone and dumped stone with
pouring asphalt.

In 1946 an area was repaired by simply arranging
the old and worn basalt stones in a more or less
orderly manner and filling the voids with pouring
asphalt. As the voids were large (50%) an average of

32

Cwest Kapelic
WALCHEREN

ASFALT BITUMEN 99/65
FILLER
SAND

“PEARL” GRAVEL

G.HW=160*

Se
GLW:I7
Slope protection | i Basalt stone set and | Bepteles |
Of basalt stone | grouted with asphalt. | gicuted
stone
i pele

sl

Figure 2. Reinforcement of the outer slope protection of the
Westkapel sea dike, partly with asphalt mixtures.

33

yt

p bes Tedeyysem oyy jo edojTs Jeqno ayy uo

*d¥N eAcge W OS*L 04 00°S Wours
uotzoaejord euoqys sTqqns ey jo uot ZeIyoUeg

°€ einatd

34

UV~ peqerqeued uofyoeqord euoys eTqqnaz syy Jo 4yno us04 qualseIy y

*oTaseu 4 [eudse
*exTp ees Tedeyxysom

*7 einaya

35

475 ke/m* of pouring asphalt, consisting of 13%
asphaltic bitumen 50/60, 7% filler, 35% dune sand and
45% "pearl" gravel was used. In 1947 other areas were
repaired by roughly setting the basalt stones on a thin
base of rubble stone and filling the spaces with pour-
ing asphalt, consisting of 17% asphaltic bitumen 50/60,
9% filler and 74% dune sand. 250 kg per square meter
of pouring asphalt were used, which filled the spaces
in the rubble stone base as well. About 12 ke/m? of
asphalt remained on the upper ends of the stones. This
was removed by wave action (Figures 5, 6, 7, and 8).

The protection built in this way proved satis-
factory; practically no damage was caused by gales.
The designers state that this construction method must
be considered as an experiment. Due to the urgency of
the work and the lack of time, there was no opportunity
to investigate the economy and efficiency of this con-
struction in comparison with others which might have been
preferable. In spite of this the work, which was ex-
ecuted within a short period of time, may be considered
as a success.

Sheeting of the New North Harbour Dam at Harlingen 1947-48,
(Figure 9)

Quite a different kind of experiment with the application of
asphaltic bitumen on a large scale is found in the protection of
the new North harbour dam at Harlingen, where a dam consisting
of sand was simply covered with a layer of so-called bituminous
sand, that is a warm mixture of 5% asphaltic bitumen and 95%
sea sand. This material was produced in the Netherlands for the
first time by the Research Laboratory of Royal Shell at Amsterdam
in the spring of 1947 at the road building section of the Dutch
Concrete Association Ltd. (Hollandsche Beton Maatschappy) at
Amsterdam. A small addition of asphaltic bitumen proved sufficient
to bind the sand-particles strongly. The 160 m test section of
the North harbour dam at Harlingen, which was built in the same
year, was protected to the low water level by a layer of bituminous
sand containing 5% asphaltic bitumen and 95% sea sand, 0.40 m
thick to +4.00 m N.A.P. and 0.25 m thick above that level.

The under water slope protection on the sea side, which was
constructed as a bituminous mattress, crumbled after it had
been undermined as it did not have the required flexibility.
Therefore during 1948 the existing work was re-covered over about
100 m length with a layer of a richer mixture containing 16%
asphaltic bitumen (40/50) and 84% sea sand.

In 1948 the 900 m harbour dam was completed (figures 10, 11
and 12). The 1947 method was used once more with the exception
that:

36

*4 ,eudse Zut.mod eyq Jo uofqgeozidde syq esozeq 4 [eseq utom Jo dead -cextp ees Tedexqsem °S SBT

°u0o
Ta e0TTdde reqzse aTeseq UsOm jo dead

"stp ees Tedeyqsey

*extp ees [Tedeyqysem

Q eunata

38

‘paaowed ueeq SBY SPTOA ayy OUT SxeLqoued 4oU PTpP YoTUM req ZOU a Teud
uopzeotidde ey, seqye syquow moj ‘yes ATYSNOI ‘seuo4s 4[BSeq UTS

*uot,zoe eaem AQ
se seul °yreudse jo
*exTp Bes Tedeyxqsom

39

-qTeudse Sutanod uytm peqynois suoqys 4[eseq jo uotyoeqo1d edoTg *extp ves [Tedeyqsom °g ound Ty

40

BITUMINEUS ZAND

8% ASF. BIT.40/50
10% stone filler
80/> % sand
1%, WETFIX

10% ASF. B1T.40/50

5% ASF. BIT.40/50
90% sand

BeSCINe 95% sand

WADDENZEE New Outport

; ... Bottom of new Fill.

As it on
mattress A-A
20% ASF. BIT. ALS /
60% §$ BOVEN
gnsend ( see NEW NORTH HARBOR NEW NORTH HARBOR DAM
above
WADDENZEE \C Asphalt mattress Asphalt mattress
vs
ge Be EE

a> Fascing mattress :
with stone

HARBOR ENTRANCE HARLINGEN

\\ \\WILLEMS
CONSTRUCTED : DOCK Bee

1947 = 1948 Se

Figure 9. Sheeting of the new north harbor dam at Harlingen with
bituminous sand and asphalt mattress.

41

Jeqjno ey uo puss

snouzuniyiq Sutpeeids pue Zutdung

*edots

*uesUTLIeY 92 Wep JoqIey YYtON

MeN

°OT sand ty

42

*sTleys pues ueum4tq ofq Teydse yoy
Ui peteaod pue peqyoeduoo ‘peeuds Suteq wep uesuT[zey jo edo[s seqno eyy jo zaAoo sul

*TT emats

43

°LY61 UT peqonazqysuoo uofZqoes 6uy Saver Sy

Ul ‘pues snouTuM4tq yytm peqyoeqyord st yoTym ‘wep meu ey JO 4OOs eUy 4B
ey, Jo uoTqoes @ ST pumalzgerloy euy UL “UusedUT [IBY ye Wep Joqaey eyy jo ded

wep [ety TuyT
SuUTSOLO yy

°ZL eaunaty

44

Le the under water slope protection at the side of the
vwadden sea was made of fascine mattresses, covered with
stone.

2. the terrace at +0.10 m N.A.P. and the lower part of
the outer slope were covered with a rich mixture, con-
taining 8% asphaltic bitumen (40/50), 10% filler, 80.5%
sea sand and 1.5% Wetfix.

36 the under water slope protection on the harbour side
below the terrace at +0.45 m N.A.P. was laid on a dry
base and consisted of bituminous sand containing 10%
asphaltic bitumen and 90% sea sand

4. the remaining surfaces were covered with bituminous
sand containing 5% asphaltic bitumen and 95% sea sand,
sheeted with an impermeable layer of pure asphaltic
bitumen or tar, and covered with shells.

Modification 1 was necessary because it had been proven that
the bituminous sand could not follow the local changes of the sea
bottom due to wave action andstrong currents. On a short section
of the under water slope prefabricated asphalt mattresses were
placed, containing about 20% asphaltic bitumen and 80% sea sand.
These will be discussed later in the section on mattresses.

Modification 2 proved necessary because in the original
mixture (5% asphaltic bitumen and 95% sea sand) the adhesion
diminished as a result of the replacement of the asphalt film
around the particles by water, It was impossible to provide this
area, which remained wet constantly, with an imvermeable sheeting.

For the same reason the under water slope on the harbour side
where no substantial changes of the bottom were to be expected, d
was provided with a rich cover of bituminous sand. :

The impermeable sheeting mentioned under 4 seemed desirable
to check the weathering of the porous layer which would be ex-
posed to waves running up the slope and to rain water, and
furthermore to form an acceptable construction i rom an aesthetic
point of view.

Post war conditions, which hampered the import of basalt
from Germany and the lack of foreign currency, were the main
reasons for this large scale experiment. The construction with-
stood the high tide of 1 March 1949 in an excellent manner and other-
wise lived up to expectations. The poor mixture however remiins
rather soft; and it remains to be sean whether the material will
last.

This experiment is very important to determine the solidity
of poor asphalt mixtures of various compositions as a temporary

45

or permanent slope protection along the sea shore.
Mattresses

Along the lower part of the Mississippi where the strong
current undermines the banks along the bends, mattresses of as-—
phalt mortar have been used extensively as a bank protection since
1932.

In April 1934 a great floating asphalt plant was put into .
use for this purpose, With this plant mattresses could be made
65 m in width and 190 m in length, reaching down to 50 m below
low water and covering slopes of 123 to 1:5. The maximum current
velocity was 2.4 m/sec.

In one season 7500 m@ of asphalt mattresses, 5 cm thick were
placed. The composition of the asphalt mortar was 12% asphaltic
bitumen 30/40, 22% filler (loess) and 66% river sand. The
mattresses were reinforced with steel wire netting (5 x 10 cm)
and provided with steel wire ropes, spaced at 0.9 m, for lower-
ing them into place.

In 1935 and 1936, reinforced asphalt slabls of 7 x 16.5 m
were used on the beach groins near Galveston and Florida City.
These slabs were placed under water with the aid of floating
crane Se

This method was also used on mattresses of asphalt mortar,
size 13 x 5 m and 0.15 m thick, weighing 20 tons, which were used
on the outer slope of the North harbour dam at Harlingen (Figures
13, 14, and 15). These asphalt slabs contained 20% asphaltic
bitumen and 80% sea sand, and were reinforced with four steel
wires of 1" diameter. Some slabs cracked while they were being
lifted, probably due to insufficient stretching of the wires
before and during the fabrication (Figure 16).

Other mattresses of asphalt mortar, 15 x 5 mand 0.05 m
thick were placed nearby. These were fabricated at Harlingen
and wrapped around a drum 2 m in diameter after which they were
transported and put into place (Figure 17). Both types of
mattresses, which emerge during low water, have fitted themselves
perfectly to the uneven base and show few if any defects.

Three slabs wrapped around drums were placed on the dumped
stone in front of the north east polder dike. The upper
part of these slabs has been destroyed completely; they contained
only 15% asphaltic bitumen and proved to be very porous, probably
as a result of insufficient stirring of the mixture during trans-
portation from the point to the construction site.

In preparation for the proposed drainage! of the Yssel lake
several asphalt mortar slabs 2 x 2 m, 0.06 m thick, and of varying
composition and reinforcement, were fabricated in 1948. The best
result was obtained with a mixture of 15% asphaltic bitumen, 15%

46

*ssouyotuy

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48

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49

PeqystT

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6

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dl

filler and 70% Yssel lake sand, and reinforcement of cocos
matting with 0.015 m gauge sprayed with a binder before use.

The methods described above for construction, at the site
or elsewhere, transportation and placing of asphalt mattresses
can only be used in quiet water, whereas the slabs must be of
restricted size when floating cranes or drums are being used.
For some time therefore attempts have been made to find a method
to transport and sink asphalt-mttresses, similar to the one
which can be used with fascine mttresses. Also, if an asphalt
mattress of any size could be kept afloat with inexpensive
means and could be towed through a medium swell, the skilled
fascine mattress workers could be used to assist in the difficult
naudling and placing of the mattresses, which would be of great
valuee in the system of W. J. van der Gord this can be achieved
by providing the asphalt mattress with a temporary flexible rim
of some impermeable mterial, thus forming a vessel of sufficient
buoyancy .

4 mattress of asphalt mortar was constructed for the piers
at Heok of Holland according to this system. The mixture con-
tained 20% asphaltic bitumen 60/70, 10% filler and 70% dune sand.
The slab, 7.5 x 3 x 0.07 m, was reinforced with cocos mtting
of O.C15 m gauge and three towing cables of wire rope. The
slab was constructed on a horizontal wooden floor which was built
at a small beach along the New Waterway near Hook of Holland,
at 0.80 m below the high water level (Figure 18). The slab
floated as soon as the water reached 0.20 m above the floor and
was towed out on the river. The asphalt slab and rim followed
the wave movement easily (Figure 19). Presently the slab was
towed back and anchored above the floor after which water was
admitted through the tube in the centre and the slab was sunk
for the time being to await transport to its final destination.

Although dependent on the most suitable construction method,
it is to be expected that the cost of such a mattress will be
considerably less than the cost of a fascine mttress with dumped
stone o

The advantage of an asphalt mattress over a fascine mattress
is that in sea water the former will not be attacked by the ship
worm (teredo navalis). Experience will show whether the asphalt
mattress will stand up under current and wave action and whether
it is suitable for the protection of steep and uneven submrine
slopes ©

Reinforcement of Beach Groins and Harbour Dams

One of the great difficulties met in the construction of
beach groins and harbour dams, is ths removal of damped stone
and set stone by wave action. This is true particularly near
deep water, where the effect of a avy ground swell may be

52

‘Teast Jeqem UST UeeWl MOTE W Og® = d¥N + UOT’ 42 peyenqgys sft 1ooTy sutyseo oul
*Sutaseo szeqge ATeqetpoumt w 40° x € xX S°L sserqqel qteqdsy °puelTOW JO HooH 4B Stetd “ST eins ty

s caien — "18 jem
Jo uotssTupe ey, Joy eqnq e& sft Jequed 9Yy4 UT *sqzoddns uepoom esoot Aq dn prey seaueo

peqeussoiduy jo espe st sseiqqe s7Tyy jo WTs Azeiodwey eu, °Aem1eqem MoU SY4 SSso1OB
pouoy Buteq (uz* qsesp ‘w LO* x € X S*L) ssetqquu qT EIdse UY “pULTTOH Fo Yooy ye Stet, 61 Sunsta

54

considerable, and rocks up to 3 tons and more have been moved.

In the United States an attempt was made to consolidate the
stones, for the first time in 1936 by filling the voids with
asphalt mortar. This method was used in the Netherlands for the
first time in 1938 by the Engineer in Chief of Delfland, A.C.
Kolff, on some beach groins near Scheveningen, Since 1945 it has
been increasingly used.

a. Groin at the mouth of Columbia river 1936. - The groin
is situated at the Pacific Ocean in an area of heavy wave-action
and reaches from 18 m below to 7.5 m above low water. It has a
top width of 12 m and is constructed of stones from 1 to 12 tons.
The asphalt grouting contained 15-18% asphalt mortar and was
applied only to the upper part.

b. Galveston Jetty 1936. - The asphalt—groubing of this
structurs proved satisfactory.

e. Delfland Groins. - The voids of the groins were filled
with an asphalt mortar containing 20% asphaltic bitumen [50/60
(6%), 60/80 (7%) and 80/100 (7%), LO% filler and 70% dune sand,
Three groins were treated from 1938 to 1940 and seventeen more from
1946 to 1948. On each zroin 30 tons of the mortar were used,
or an average of 0.5 tons per m-. This reinforcing method of
the beach groin proved entirely satisfactory. When a floating
mine exploded against one of these groins it was found that the
voids were filled to a depth of 1 m below the surface.

d. South Jetty of the outer saipping channel at Ymuiden,
1926. - This jetty which was often badly dameged during heavy
gales, was provided with asphalt mortar as described under c.
Between the dumped stones 0.8 tons of asphalt mortar per me
and between the set stones 0.5 tons per m* were used. Since
then no more damage has occurred.

@. WNorth- and South piers at Hook of Holland 1946-50,
(Figure 20). - The piers are 2 lm in length, with the top,
4m wide at mean sea level. The heavy stone protection (stones
of O.l to 3 tons) of the outer section could not resist the
heavy ground swell so that it was often damaged, and the normal
gauge railroad which was laid on oak girders on top of the
jetty required abnormally high expenditures for maintenance.
In view of this, it has been decided to convert the railroad
into a single lane road for trucks and to grout the set stone
and dumped stone with asphalt-mortar where the attack is
heaviest.

The outer 1 km section of the North pier and the so-called
connecting jetty, forming the connection between the South
jetty and the low jetty which was constructed at a later date,
were thus reconstructed (Figure 21-26) from 1946 to the middle

39

Trialsection bituminous sand eX,

MN O2OLe2 wo 2rE Je 4
aa eT AS I 5% ASFALT BITUMEN 60/70 i
(Sag F BP ° x

Fo nl 95% dune sand e
wD A ee

1 Poe
o> North pier

a pas =

ar La

: A O/
Ecaccting < wr Sy ew,
»)/
< A 2;
‘ (ei low dam
we | ou
Guiding SA a
. dam NC
South pier
Y \
LEGEND: \
Sections which have been ef will
HHH be treated with pouring asphalt.
PIERS AT HOOK OF HOLLAND ra

construction of

20% ASFALT BIT. 9%
asphalt mattress.

10% FILLER
70 % SAND

Pouring asphalt

Set and dumped stone

G H.W. = 066*

Concrete slabs

an @
7

OR ;
i asiages 2 ays
XC NEREVIE SIS SSA DOEES

AEN ata

Sy LAAAZKR RAZA ANAK ROARS s re oe SAIN NDONUS

Mattress

Figure 20. Reinforcement of the offshore sections of the piers at
Hook of Holland.

56

“L76T JO uunqne ut pet{dde 3utqnou3 uytm
uoyqoaz01d euogs payoegqe ATTAReY JO YIed *PUETIOH Jo Hooy 4e etd yqiou oyy Jo pug *Te eunsty

Figure 22. North pier, Hook of Holland. The conversion of the railroad
track,into track for trucks, consisting of concrete blocks and set stone
with asphalt grouting carried out in 1948. The gutler to carry the light-
house cable is in the center. In the foreground is the wide section near
the foot of the lighthouse.

58

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pe, eTduoo sem yoTuM yoeI4 BUY

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*pueltIOH JO Yooy 4e Jetd yynos aesu wep Zutqoeuu0g

W

@

eingty

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°Se eunaty

61

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°676T Yodel T Jo ates Aavsy ayQ 1eqye ATeqetpewwy Jeqem MOT Suftimp useyeq einyotgd ~*paet idde
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9

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62

of 1949. Itis osostese to finish this work in Tne The asphalt
mortar contained 20% asphaltic bitumen 60/70, 10% fille er and 70%
dune sand. “Sefore the pouring of the mortar, the nor : of
the stonss were wetted te prevent the 4 spha lb from st
surfaces irom which it would be removed by wave action after some
time in any event.°

The POU Ee quantities cf pouring asohalt were used
SUC ea Sean stween the peat s3s% stones and in the road on
the North pisr 250 ken; & stween the heavy set stones (100-500
) $00 Ke/m ; in the dumps ¢ stone (500-3000 kg} around the head
f the pier 1000-1500 ke jm. ‘Th 1 preatest care was taken to
Pall the voids completely in order to avoid cavities in which

Cc S$
air and water pressure Spee develop. The new construction with-
stood the gale of 1 March 1949 ex slave y

S sand against
tress which was

ie was re-
tic bitumen
325 m? of the mixture was

In order to test the spare of bin
wave action, part of the dumped s of
Situated in the breaker zone north
placed by bituminous sand consistin
60/70 and 95% dune sand. In tota
dumped on the mattress.

ca cee
Ky q

uring more than
dist nteerated by
of a

ay

It was learned from peri
year, that the bituminous sean

We ee action. Furthermore a Bee nae the fmerican
stone borer (Fetricola pholadiformis) was found in a sample.

In cooperation with the Rijkswesenbouwlaboratorium a con-
tainer with samples of bituminous sand of various compositi
has been placed in the breaker zone so that it may be det
which asphalt content is required to make the material pre
against the stone borer.

f. Miscellaneous asphalt works on beach eroins and harbour
jettiss. - In 1948 the Somes stone deposits around the outer
sections of the Scheveningen harbour jetties were filled with
pouring asphalt. In the same year a beach groin built as a
sand mound covered with bituminous sand, was constructed in the
1944 gap in the Westkapel sea dike (Fig In 1949 the

b

reinforcement of dumped stone deposits of ¢
of Delfland, and the province of North Holl
Kamperduin and along the North sea shore of
carried out.

mH Es ¢

Conclusion

In hydraulic works as in road construction, synt ae
asphalt has rapidly become a useful building materis
to the extensive research work of various laborato

i
Gales st is
now possible to produce asphalt mixtures with propert

63

suit the type of work.

In many instances, the use of asphalt mixtures in hydraulic
works has not led to favorable results, which seems only natural
in view of the fact that this material originally was unsuitable
for this purpose. However these failures should not make us look
for other methods instantly. The age old science of hydraulic
engineering has produced many an ingenious method to fight the
water which undoubtedly may be used once more in the application
of asphalt in hydraulic works. Only if this proves to be impossible
will new working methods have to be found to solve the problem.

Certainly the motto of J.i'.W. Conrad, which he used in 1864
for his prize-winning contribution to a contest regarding the
improvement of the Hondsbossche sea dike, still holds a truth:
"Don't condemn the old because it's old, nor the new because
it's new."

64

BEACH EROSION STUDIES

The principal types of beach erosion reports of studies at
specific localities are the following:

a. Cooperative studies (authorization by the Chief of
Engineers in accordance with Section 2, River and
Harbor Act approved on 3 July 1930).

b. Preliminary examinations and surveys (Congressional
authorization by reference to locality by name).

Ce Reports on shore line shanges which may result from
improvements of the entrances at the mouths of rivers
and inlets (Section 5, Public Law No. 409, 74th Congress).

d. Reports on shore protection of Federal property (author-
ization by the Chief of gngineers).

Of these types of studies, cooperative beach erosion studies are
the type most frequently made when a comminity desires investigation
of its particular problem. As tnese studies have greater general
interest, information concerning studies of specific localities con-
tained in these quarterly bulletins will be confined to cooperative
studies. Information about other types of studies can be obtained
upon inquiry to this office.

Cooperative studies of beach erosion are studies mad
Corps of Engineers in cooperation with appropriats age
various States by authority of Ssction 2, of the River
Act approved 3 July 1930. By executive ruling the cos
studies is divided equally between the United States and
operating agency. Information concerning the initiation of a co-
operative study may be obtained from any District Engineer of ths
Corps of Engineers. ‘fter a report on a cooperative study has been
transmitted to Consress, a summary thereof is included in the next
issue of this bulletin. A list of cooperative studies now in pro-
sress follows:

COOPERATIVE BEACH EHROSION STUDIES IN PROGRESS
Nev! HAMPSHIRE

HAMPTON BEACH. Cooperative Agency: New Hampshire Shore and Beach
Preservation and Development Commission.

Problem: To determine the best method of preventing further
erosion and of stabilizing and restoring the beaches,
also to determine the extent of deral aid in any
proposed plans of protection and improvement.

65

MASSACHUSETTS

PEMBERTON POINT TO GURNET POINT. Cooperating Agency: Department of
Public Works, Commonwealth of Massachusetts.

Problem: To determine the best methods of shore protection,
prevention of further erosion and improvement of beaches,
and specifically to develop plans for protection of
Crescent Beach, The Glades, North Scituate Beach and
Brant Rock.

CONNECTICUT

STATE OF CONNECTICUT. Cooperating Agency: State of Connecticut
(Acting through the Flood Control and Water Policy
Commission).

Problem; To determine the most suitable methods of stabilizing
and improving the shore line. Sections of the coast
will be studied in order of priority as requested by

‘ the cooperating agency until the entire coast.is in-
cluded,

NEW YORK
JONES BEACH. Cooperating Agency; Long Island State Parks Commission

Problem: To determine behavior of the shore during a 12-month
cycle, including study of littoral drift, wave re-
fraction and movement of artificial sand supply between
Fire Island and Jones Inlets.

NEW JERSEY
OCEAN CITY. Cooperating Agency: City of Ocean City.

Problem: To determine the causes of erosion or accretion and
the effect of previously constructed groins and
structures, and to recommend remedial measures to pre-
vent further erosion and to restore the beaches.

VIRGINIA
VIRGINIA BEACH. Cooperating Agency: Town of Virginia Beach.
Problem: To determine the methods for the improvement and

protection of the beach and existing concrete sea
wall. "

66

SOUTH CAROLINA

STATE OF SOUTH CAROLINA. Cooperating Agency: State Highway Depart-
ment.

Problem: To determine the best method of preventing erosion,
stabilizing and improving the beaches.

FLORT DA
PINELLAS COUNTY. Cooperating Agency: Board of County Commissioners.

Problem: To determine the best methods of preventing further
recession of the gulf shore line, stabilizing the
gulf shores of certain passes, and widening certain
beaches within the study area.

LOUISIANA

LAKE PONCHARTRAIN. Cooperating Agency: Board of Levee Commissioners,
Orleans Levee District.

Problem: To determine the best method of effecting necessary
repairs to the existing sea wall and the desirability
of building an artificial beach to provide protection
to the wall and also to provide additional recreational

beach area.
TEXAS

GALVESION COUNTY. Cooperating Agency: County Commissioners Court
of Galveston County.

Problem: To determine the best method of providing a permanent
beach and the necessity for further protection or ex-
tending the sea wall within the area bounded by the
Galveston South Jetty and Hight Mile Road.

To determine the most practicable and economical
method of preventing or retarding bank recession on
the shore of Galveston Bay between April Fool Point
and Kemah.

CALIFORNIA

STATE OF CALIFORNIA. Cooperating ‘genty. Division of Beaches and
Parks, State of California,

Problem: To conduct a study of the problems of beach erosion
and shore protection along the entire coast of Calif-
ernias The initial studies are to be madg in the
Ventura-Port Huneme area, the Santa Monica area and
the Santa Cruz area.

67

WISCONSIN
RACINE COUNTY. Cooperating Agency: Racine County.

Froblem: To prevent erosion by waves and currents, and to
determine the most suitable methods for protection,
restoration and development of beaches,

KENOSHA. Cooperating Agency, City of Kenosha.

Problem: To determine the best method of shore protection and
beach erosion control.

OHIO

STATE OF OHIO. Cooperating Agency: State of Ohio (Acting through
the Superintendent of Public Works).

Problem: To determine the best method of preventing further
erosion of and stabilizing existing beaches, of re-
storing and creating new beaches, and appropriate
locations for the development of recreational .
facilities by the State along the Lake Erie shore
line.

TERRITORY OF HAWAII

WAIKIKI BEACH:
WAIMBA & HANAPEPHE, KAUAI. Cooperating Agency: Board of Harbor
Commissioners, Territory of Hawaii.

Problem: To determine the most suitable method of preventing
erosion, and of increasing the usable recreational
beach area, and to determine the extent of Federal
aid in effecting the desired improvement.

a At x“
rN nw “

% %

BEACH EROSION LITERATURE

There are listed below some recent acquisitions to the Board's
library which are considered to be of general interest. Copies of
these publications can be obtained on 30-day loan by interested
official agencies.

"Refraction of Shallow Water Waves: The combined effect of currents
and underwater topography," Trans. American Geophysical Union,
Vol. 31, No. 4

This paper gives a solution for determining the re-
fraction effect according to Fermat's Principle for shallow
water waves moving in any given distribution of currents and
depth. Application is made to an analytic model of an intense
rip current and theresults are compared to actual rips.

"A Method of Measuring Electrically the Velocity of Fluids, B.
Thurlema nn

This paper discusses the theory on which an ocean current
velocity meter is developed and also discusses the construction
of a model instrument based on this theory.

"The Limitations of the Principle of Superposition," Paul R. Heyi,
Jour. Washineton Academy of Sciences, Vol. 40, No. 11, 1950.

This paper gives a brief discussion of the principle
of superposition as applied to harmonic analysis of wave
forms. Several allowable and several erroneous applications
of the principle are discussed which are of interest to
engineers studying wave forms such as wind waves and tides.

"Model and Prototype Stuides for the Design of Sand Traps," R. L.
Parshall, July 1950

The hydraulic laboratories at Fort Collins have made various
investigations to develop a means for ridding channels of bed
load deposits. Out of these investigations come two practical
means, namely the vortex tube and the ripple deflector-vortex
tube sand traps which are discussed in this paper.

"Turbidity Currents as a Cause of Graded Bedding, Jour. of Geology,
Vol. 58, No. 2, Narch 195C.

This paper discusses the causes and magnitude of
particle grading by the action of turbidity currents.
Naturally cbserved grading and artificially produced grading
are described.

69

"Talud limite entre la rotura y la reflexion de las olas: The
Critical Slope Between Incipient Breaking and Reflecting of
Waves! Ramon Iribarren Cavanilles, Casto Nogales y Olano, Feb.
1950.

Translation by Waterways Experiment Station and publish-
ed as Translation No. 50-2, 1950.

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