Proceedings of the Twelfth Canadian Soil Mechanics Conference

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P R O C E E D I N G S O F T H E

TGVELFTH C A N A D I A N S O I L M E C H A N I C S C O N F E H E N C E DECEMBER

8 AND

9, 1958

N A T I O N A L RESE.4RC3 C O U N C I L O F CANADA

A S S O C I A T E COMI4ITT-:8 ON SOIL AND SNOW M E C H A N I C S

These a r e t h e prboceedings of th2 %3lf t h Canadian S o i l Nechanics Conference h e l d i n Convoctitlon Y a l l , U n i v e r s i t y of Saskatchewan, Saskatoon on December 8 t h and qth,

1958.

The Conference w a s sponsored by t h e S o i l Mechanics Subconmittee of' t h e A s s c c i a t e Committee on S o i l and Snow Mechanics of t h e

N a t i o n a l Research Counc3l.

The theme of t h e f i r s t , day was damsitos and e a r t h embankments, Four p a p e r s were p r e s e n t e d on t h i s t o p i c , A

p a p e r on t h e performance e v a l u n t i on of highv~ays by t h e Benkelman Beam i n S a s k a t c h o n ~ n was a l s o p r e s e n t e d * A p a n e l d i s c u s s i o n on t h e problem of b u i l d i n g on s w e l l i n g and s h r j n k i n g c l a y s was h e l d on t h e second dayo The scope of t h e dj.scussions ranged from t h e

t h e o r e t i c a l behaviour of c l a y s w i t h r e g a r d t o volume change and

s w e l l i n g p r e s s u r e t o t h e b u i l d i n g of r o a d s and houses on c l a y d e p o s i t s o

On t h e e v e n l n g of December 8 t h , a d i n n e r meeting was h e l d j o i n t l y w i t h t h e E n g i n e e r i n g I n s t i t u t e of Canada and t h e A s s o c i a t i o n of P r o f e s s i o n a l E n g i n e e r s of Saskatchewano M r e ReFo Legget was

t h e g u e s t speaker and p r e s e n t e d a p a p e r " S o i l Engineering a t S t e e p Rock I r o n Mines, Ontario, Canadat', T h i s paper had been p r e s e n t e d t o t h e I n s t i t u t i o n of C i v i l E n g i n e e r s i n London, D i s c u s s i o n of

t h e paper a t Saskatoon was i n c l u d e d i n t h e d i s c u s s i o n which appeared i n t h e Proceedings of t h e I n s t i t u t i o n of C i v i l Engl.necrso

A t the c l o s e of t h e s e s s i o n s on December

qth,

t h o s e a t t e n d i n g had t h e o p p o r t u n i t y t o v i s i t s e v e r a l l a b o r a t o r i e s i n Saskatoon such a s t h e s o i l mechanics and t e s t d r i l l i n g f a c i l i t i e s of PeFeRaAe, t h e l a b o r a t o r y and d r i l l i n g equipment of

B O B o

Torchinsky and A s s o c i a t e s , t h e S o i l Mechanics and S o i l S c i e n c e l a b o r a t o r i e s of t h e U n i v e r s i t y of Saskatchewan and t h o P r a i r i e Regional l a b o r a t o r i e s of the N a t i o n a l Research C o u n c i l o

The A s s o c i a t e Committee on S o i l and Snow Fsechanics w i s h e s t o e x p r e s s i t s a p p r e c i a t i o n t o t h e U n i v e r s i t y of Saskatchewan

( D r . W,P, Thomson, P r e s i d e n t ) and t o a l l t h o s g who p a r t i c i p a t e d i n t h e d e l i b e r a t i o n s , The A s s o c i a t e C o r n i t t e e i s p a r t i c u l a r l y i n d e b t a d t o M r . R , P e t e r s o n , P.F.R.A., Saskatoon, and t h e members of h i s c o m i t t e e who a r r a n g e d t h i s nvelf t h Conferencee

PROGRAM

December

8,

hlornlng S e s s i o n

-

_--

-

R . P e t e r s o n , Chairlimn

1. I n t r o d u c t i o n

-

Dean A. P o r t s r , U n l v o r s i t y of Saskatchewan

-

R e ? , Legget, Cha3-rnan, Assoclete Commfttee on S o i l and Snow Mechanics

2. F i e l d bleasurement o f Pore I?t'ater P r e s s u r e s

D. J. Bazet-l;, Hydro E l e c t r i c Power Corn-r:~ission of Ontario, Toronto

3.

Damsites i n B r l t i s h Coluinbia

-

a Challenge t o the Encineor C.F. H i p l e y , R i p l e y and A s s o c i a t e s ,

Vancouver

December

8,

A f t e ~ n o o n S e s s i o n

-

Dean R.M. Hardy, Chairman

4.

T e s t Apparatus i n E a r t h Embankments

N. P e t e r s , P r a i r i e Farm R e h a b i l i t a t i o n A d m i n i s t r a t i o n , S R S ~ ~ ~ O O ~

5;.

The Proposed South Saskatchewan River Dam

A.S. Ringheim, P r a i r i e Farm R e h a b i l i t a t i o n A d m i n i s t r a t i o n , Sa aka t o o n

Dinner Meeting j o i n t l y w i t h E n e i n e o r l n g Institute of Canada and A s s o c i a t i o n of P r o f e s s i o n a l Engineers of Saskatchewan

6.

S o i l Engineering a t S t e e p Rock Lake, Ontario, Canada

R.F. Legget, D i v i s i o n of Burllding Research, N a t i o n a l Research Council, O t tswa December

gL

Morning S e s s i o n

-

C

.R.

Crawford, Chairman

7.

The General Problem of Buil-ding on S w e l l i n g and S h r i n k i n g Clays

C .B. Cranf ord, D i v i s i o n of B u i l d i n g R e s e a r c h ,

Nat .Lonal Research Council, O t tawa

0. Mechanism of Volume Change i n Clays

B.P. Warkentin, Macdonald College of McGill U n i v e r s i t y , Ste. Anne de B e l l e v u e

9.

Volume Changes measured i n Ledn Clay

M.

Bozozulc,, D l v i s i o n of B u i l d i n g Research, N a t i o n a l Research Council, Ottawa

10. S w e l l i n g and Shrinking Clays on 6 he Canadian P r a 2 r i e s A . B s r a c c s , U n i v e r s i t y of !Janitoba,

Wirlrlipe g

11.. Design, Perf ornlance and Economics of Basementless Houses on Clay S o i l s

L. P l o t k i n , Home Development Coo, Ltd., Winnipeg

12. P i l e F o u n d a t i a s i n S w e l l i n g C l a y s

BOB* Torchinsky, Torchinsky and

A s s o c i a t e s , Saskatoon Deconiber 9, Afternoon S e s s i o n

-

RoFo Lsgget, Chairman

13.

A p p l i c a t i o n s of t h e Eenkelman Beam on Saskatchewan Highways

B.C. Laws, Saskatchewan Depte of Highways, Regina

14.

Concluding Business 1 Laboratory V i s i t s

TARWE OF CONTENTS

SESSIONS

OF

DECEMBER 8 AND

9 ,

195Q a g e

S e o t i o n 1 Address of Welcome by Dean A. P o r t e r

S e c t i o n 2 I n t r o d u c t o r y Remarks by R e F e Legget

3.

S e o t i o n

3

F i e l d Mea surernent of P o r e Wator P r e s s u r e s by

D o J e Baze.bt 2

S e c t i o n

4

Summary of Damsites i n B e C e

-

a Challenge t o

the Engineer by C d F o Ripley

17

S e c t i o n

5

Summary of Tost A ~ p a r a t u s Sn

Earth

Embankments 20 by N B P o 5 s r a

S e c t i o n

6

Summary of Tho Pro9osed South Saskatchecran

R i v e r

Dam

Sy A.S, Ringheim 23

S e c t i o n

7

Applications o f t h e Bsnkolrnan

%am

on

Saskatchewan Hi gh~vays by B6C. Lava 2 9

S e c t i o n

8

Building F o u n d a t i o n s on C l a y s Su3ject t o Volume

43

C h a ~ g o

I.

PANEL D I S C U S S I O N S

( a ) The General P r o b l e m of B u i l d i n g on Swelling

;43

and Shrinkfng C l a y s by C o B e Crawford ( b ) The Mechanf vm of Voiune Ghango i n Clays

by B c P o VJ8r:centin

44

W r i t t e n Disoussion by GBY, Sebastyan

45

(a)

Designo P o r f o r m a n c o an6 Economics o f

Basementloss Houses on Clay Soils by

L,

P l o t k i n

50

( d ) P i l e Foundations i n Swelling Clays by

B ,Be T o r ~ h i n a k y 50

. W r i t t e n DfscussSon by G o Y e Sebastyan 52

f e ) Volume Changes Measured i n Leda Clay by

M e B O Z O Z U ~

53

.(2) Summary of Swelling and Shrinking Clays i n

₅₄

Western Canada by A. Baracos

11. OPEN DISCUSSION

56

APPENDIX A L i s t of those- Present a t t h e Twelfth S o i l Mechanics Conference

SESSIONS

-

OF

DECEMBER

8

AND

9,

_{1 9 2} S e c t i o n

-

l

Address of Welcome by Dean P o r t e r

Dean P o r t e r of t h e College of Engineering, U n i v e r s i t y of Saskatchewan weloomed the d e l e g a t e s :.o t h e u n i v e r s i t y campus on b e h a l f of t h e P r e s i d e n t of the U n i v e r s i t y . He c o m e n t e d on t h e c o - o p e r a t i o n between t h e U n i v e r s i t y and t h e N a t i o n a l Researoh Counoil and e x p r e s s e d h i s a p p r e c i a t i o n ol" the s p o n s o r s h i p of

u n i v e r s i t y d e l e g a t e s a t t e n d i n g t h e S o i l Mechanics Conferences. Dean P o r t e r p o i n t e d out t h a t S o i l Meohanics, l i k e many of t h e newer branches of s o i e n c e , had an i n t e r d i s c i p l i n a r y approaoh

-

t h a t i s , i t combined knowledge end d i s o i p l i n e s

developed by many of t h e o t h e r s c i e n c e s . He s a i d t h a t he b e l i e v e d t h i s approach t o be s u p e r i o r t o c o n c e n t r a + i o n i n narrow f i e l d s of s t u d y and t h a t t h e i n t e r d i s c i p l i n a r y s p p r o a c h should be encouraged. S e o t i o n 2 I n t r o d u c t o r y Remarks by R.F. Leg&

M r . Legget, Chairman of the A s s o c i a t e Cornlittee on S o i l and Snow Mechanios, welcomed t h e d e l e g a t e s t o t h e Conference on behalf of t h e A s s o o i a t e Committee. H 7 spoke of t h e c l o s e l i n k s between t h e U n i v e r s i t y of Saskatchewan where t h e Conference was b e i n g h e l d , and t h e N a t i o n a l Researoh Council.

Mr.

Legget p a i d t r i b u t e t o t h e l a t e P r o f e s s o r 1.F. Morrison whose i n s p i r a t i o n and f r i e n d s h i p had c o n t r i b u t e d s o much t o p a s t

conferences. He spoke of P r o f e s s o r Morrison's e a r l y work i n S o i l Mechanics; he d e l i v e r e d t h e f i r s t f o r m a l l e c t u r e s on s o i l mechanioa i n Canada, a t t e n d e d t h e f i r s t s m a l l S o i l Mechanics Conference i n 1947 and made many c o n t r i b u t i o n s t o t h e s c i e n c e * M r . Legget e x p r e s s e d h i s r e g r e t t h a t P r o f e s s o r Morrison had never w r i t t e n down i n permanent form some of h i s experience and knowledge i n s o i l mechanics. The d e l e g a t e s t h e n s t o o d i n s i l e n t memory of P r o f e s s o r Morrison.

M r . Legget t h e n reminded t h o s e p r e s e n t t h a t the A s s o o i a t e Committee on S o i l and Snow Mechanios was one of 2 1 committees sponsored by the N a t i o n a l Researoh Counoil t o u n d e r t a k e work i n

s p e c i a l f i e l d s . He e x p r e s s e d t h e hope t h a t I c e and Snow Mechanics would soon be p l a c e d on a s i m i l a r l e v e l t o t h e work i n S o i l

Mechanics. He mentioned b r i e f l y t h e work a l r e a d y u n d e r t a k e n t o s t u d y t h e a v a l a n c h e problem a l o n g t h e Trans-Canada Highway i n B r i t i s h Columbia.

M r . Legget a l s o spoke of' t h e r e s e a r c h g r a n t s a v a i l a b l e from t h e N a t i o n a l Researoh Council and was g r a t i f i e d t h a t i n t e r e s t had i n c r e a s e d t o t h e e x t e n t t h a t l a s t y e a r , f o r t h e f i r s t time, t h e sum of money g r a n t e d was n o t s u f f i c i e n t t o meet a l l r e q u e s t s and had t o be a l l o c a t e d t o t h e b e s t advantage.

M r . Legget mentioned t h a t t h e Foundations S e c t i o n of t h e N a t i o n a l B u i l d i n g Code was b e i n g r e v i s e d and t h a t a p r e l i m i n a r y d r a f t would soon be m a i l e d out. A l l t h o s e who wished t o comment on t h i s d r a f t would be encouraged t o do s o p r o v i d e d t h e i r s u b m i s s i o n s were i n w r i t i n g .

S e c t i o n

3

F i e l d Measurement of Pore Water P r e s s u r e s by

The p a p e r d e s c r i b e s i n moderate d e t a i l t h e h i s t o r y of

a

p i e z o m e t e r i n s t a l l . a t i o n t o measure p o r e w a t e r p r e s s u r e s w i t h i n a n e a r t h dam. The system chosen was one developed by t h e U.S. Bureau

of Reclamation. The r e a s o n s f o r t h i s c h o i c e and n e c e s s a r y m o d i f i - c a t i o n s a r e d e s c r i b e d , a s a r e l a b o r a t o r y t e s t s

run

p r i o r t o i n s t a l l a t i o n , A d i s c u s s i o n of t h e r e a d i n g s t o d a t e and d i s c r e - p a n c i e s from a c c e p t e d t h e o r y a r e included. I n t r o d u c t i o n The d i k e s c o n s t r u c t e d f o r t h e Pumping G e n e r a t i n g S t a t i o n a t Niagara a r e o f t h e r o c k f i l l

-

s l o p i n g c o r e t y p e . These d i k e s a r e u n u s u a l i n t h a t t h e y a r e s u b j e c t t o n e a r l y t o t a l drawdown e a c h day.

Because of t h i s , t h e i n c l u s i o n of some form of p i e z o m e t e r i n s t a l l a t i o n was t h o u g h t w a r r a n t e d , p a r t i c u l a r l y a s t h e p o r e w a t e r p r e s s u r e s might be t h e c o n t r o l l l . n g f a o t o r if i n o r e a s i n g t h e working head was c o n s i d e r e d .

The d e s i g n of the piezometer system was begun when c o n s t r u c t i o n was w e l l advanced and i n s u f f i c i e n t time was a v a i l a b l e t o c o n s i d e r t h e development of a p u r e l y o r i g i n a l

scheme. The d e s i g n , t h e r e f o r e , r e s o l v e d i t s e l f i n t o a s t u d y of e x i s t i n g systems and t h e m o d i f l . c a t i o n s which we would f i n d n e c e s s a r y .

Choice of Systerg

The two a l t e r n a t i v e s s e r i o u . s l y c o n s i d e r e d were a porous s t o n e system of t h e U.S. Bureau of Reclamation (1) and some form of e l e c t r i c a l s t r a i n gauge type. The USBR system c o n s i s t s

e s s e n t i a l l y of porous s t o n e s connected by w a t e r - f i l l e d t w i n p o l y t h e n e l i n e s t o Bourdon t u b e gauges a t a t e r m i n a l w e l l house, each t i p capable of b e i n g f l u s h e d o r d e - a i r e d by c i r c u l a t i n g

w a t e r * The e l e c t r i c a l t i p c o n s i s t s of a s e n s i t i v e diaphragm whose d e f l e c t i o n s under p r e s s u r e a r e measured w i t h e l e c t r i c a l r e s i s t a n c e s t r a i n gauges.

The d i f f i c u l t i e s of i n s t a l l i n g t h e two systems were e s s e n t i a l l y e q u a l and d i s c u s s i o n of t h e i r r e l a t i v e m e r i t s was r e s t r i c t e d t o t h e i r s e n s i t i v i t y and r o b u s t n e s s , S e n s i t i v i t y was a prime c o n s i d e r a t i o n beoause of the u n u s u a l l y r a p i d and c y c l i c n a t u r e of t h e drawdown. The USBR system would e n s u r e

adequate l o n g e v i t y but o n l y d o u b t f u l s e n s i t i v i t y . The e l e c t r i c a l system c o u l d be made s u f f i c i e n t l y s e n s i t i v e b u t t h e h i s t o r y of e x i s t i n g systems of t h i s t y p e was n o t encouraging i n r e s p e c t of l i f e o

The problem of s e n s i t i v i t y i n t h e USBR system i s twofold. F i r s t , t h e system r e a c t s t o changes i n t o t a l p r e s s u r e a s a

p r e s s u r e celX. That i s , a n i n c r e a s e i n t o t a l p r e s s u r e i n t h e c l a y c o r e of t h e dam w i l l t e n d t o oompress t h e p o l y t h e n e l i n e s and time w i l l be r e q u i r e d t o e x p e l t h i s w a t e r a t t h e t i p . There

w i l l , of c o u r s e , be a s i m i l a r e f f e c t upon a r e d u c t i o n i n s t r e s s * Second, if any a i r i s p r e s e n t i n t h e system, f l o w of w a t e r and time w i l l be r e q u i r e d f o r its compression b e f o r e o b t a i n i n g a t r u e r e a d i n g *

The p r e s s u r e c e l l e f f e c t was examined on a t h e o r e t i c a l b a s i s and it appeared t h a t t h e expansion i n tohe polythene cou1.d

indeed l e a d t o an e x c e s s i v e time l a g * However, t h i s could be reduced s u b s t a n t i a l l y by t h e use of copper l i n e s t o reduce t h e

s t r a i n i n t h e system. I t could be reduced s t i l l f u r t h e r by t h e u s e of u n u s u a l l y l a r g e porous s t o n e s t o i n c r e a s e t h e a r e a t h r o u g h which w a t e r would be gained o r l o s t . These m o d i f i c a t f o n s l e d

t o a t h e o r e t i c a l r e s p o n s e of n o t more t h a n 2 0 minutes i n s t e a d of t h e p r e v i o u s l y e s t i m a t e d 2,000 minutes o r more.

The problem of a i r i n the system could o n l y be c o n t r o l l e d by c a r e f u l d e - a i r i n g b o t h a t the t i m e of c o n s t r u c t i o n and a t

r e g u l a r i n t e r v a l s d u r i n g o p e r a t i o n .

On t h e b a s i s of t h e modified s t o n e s and copper l i n e s t h e USBR systeni was d e c i d e d upon w i t h only minor m o d i f i c a t i o n s t o t h e gauge house and i t s f a c i l i t i e s .

The l a y o u t of t h e system i s shown i n F i g , 1, The copper l i n e s were l a i d i n i t i a l l y b e n e a t h the r o c k f ill and t h e n , a f t e r t h e p l a c i n g of t h e r o c k and f i l t e r m a t e r i a l , were c a r r i e d up t h e f i l t e r s t o temporary s t o r a g e p o s i t i o n s , When t h e compacted c l a y c o r e r o s e t o t h e e l e v a t i o n of a s e t of t i p s , i t was t r e n c h e d and t h e t i p a were placed; t h e t r e n c h was t h e n b a c k f i l l e d and compacted by Barco rarnrner b e f o r e norma 1 c o n s t r u c t i o n proceeded.

L a b o r a t o r y T e s t s

Photographs of t h e p l a c i n g of t h e copper l i n e s i n t h e f oun- d a t i o n m a t e r i a l b e n e a t h t h e r o c k c o r e , of t h e p l a c i n g of a t i p and of t h e i n t e r i o r of t h e gauge house a r e i n c l u d e d a s F i g u r e s 2,

3

and

4.

During a w i n t e r h a l t i n c o n s t r u c t i o n a number of l a b o r a t o r y t e s t s were r u n u s i n g t h e f i e l d equipment, I n t h e s e t e s t s b o t h a

porous s t o n e and Plantema e l e c t r i c a l t i p were b u r i e d i n c l a y i n a l a r g e s t e e l box. This c l a y was loaded t o p r e s s u r e s s i m i l a r t o t h o s e e x p e c t e d i n the d i k e and t h e behaviour of tho g i e z o m e t e r s was noted.

To sumnarize the r e s u l t s of t h e s e t e s t s v e r y b r i e f l y , t h e Plantema t i p n o r m a l l y reaohed i t s f u l l r e a d i n g i n t h e o r d e r of

20

-

30

m i n u t e s , The porous s t o n e could r e a c h i t s f u l l r e a d i n g

i n

a b o u t t h e same time o r even l e s s i f r i g o r o u s l y d e - a i r e d b u t t o o k t i m e s i n t h e o r d e r of

4

h o u r s o r more i f p o o r l y d e - a i r e d . F l u s h i n g w i t h d e - a i r e d w a t e r was s a t i s f a c t o r y i f de-airine; of the s t o n e s was n o t r e q u i r e d , De-airing of the s t o n e s i n - p l a c e was found t o be

e s s e n t i a l l y i m p o s s i b l e ; t h e s t o n e s c o u l d only be d e - a i r e d by e v a c u a t i n g o r b o i l i n g under w a t e r

Although t h e b u l k of t h e l a b o r a t o r y t e s t i n g of t h e t i p s was c a r r i e d o u t i n c l a y c o n s i . d e r a b l y wet of optimum c o n d i t i o n s , one s e t of t e s t s used c l a y d r y of optimum a 3 p l a c e d i n t h e f i e l d . The

porous s t o n e piezometer r e a d i n g s were n e g a t i v e and a r e b e l i e v e d t o i n d i c a t e c a p i l l a r y t e n s i o n i n t h e water.

Piezometer Readings

The r e a d i n g of porous s t o n e s placed i n t h e embankment has now been c a r r i e d out f o r about 2 y e a r s . During c o n s t r u c t i o n t h e piezometers c o n s i s t e n t l y r e g i s t e r e d small n e g a t i v e p r e s s u r e s s i m i l a r t o t h o s e measured p r e v i o u s l y i n t h e l a b o r a t o r y .

During t h e f i l l i n g of t h e r e s e r v o i r and subsequent o p e r a t i o n i n d i v i d u a l piezometers have i n d i c a t e d g r a d u a l l y i n c r e a s i n g p r e s s u r e s

.

These p r e s s u r e changes have moved pro- g r e s s i v e l y downstream, i n d i c a t i n g t h e advance of seepage t h r o u g h t h e c l a y c o r e . By July,

1958,

a f t e r approximately one yoar of s e r v i c e , seepage was n e a r l y e s t a b l i s h e d .

No p a r t i c u l a r e f f o r t was made t o measure pore p r e s s u r e changes d u r i n g i n d i v i d u a l drawdowns d u r i n g t h e y e a r s t o p e r a t i o n s . However, i n J u l y

1958

t h e r e s e r v o i r was emptied and h e l d down f o r a c o n s i d e r a b l e time. Readings were t a k e n d u r i n g t h e complete drawdown and t h e piezometers had time t o s e t t l e because of t h e time involved.

D i s c u s s i o n

Skempton ( 2 ) and Bishop

( 3 )

d e s c r i b e pore p r e s s u r e

c o e f f i c i e n t s A and B and t h e u s e of t h e s e parameters i n p r a c t i c e . They a l s o d e s c r i b e a n o v e r - a l l c o e f f i c i e n t

B

which may be d e r i v e d from t h e o t h e r two. Since b o t h A and B w i l l vary w i t h degree of

s a t u r a t i o n i t i s e v i d e n t t h a t w i l l a l s o be dependent upon s a t u r a t i o n .

I n an a t t e m p t t o d e s c r i b e t h e s e c o e f f i c i e n t s b r i e f l y we w i l l c o n s i d e r a t r i a x i a l specimen s u b j e c t t o a v a r i a b l e c e l l p r e s s u r e : i f the sample i s s a t u r a t e d the change i n pore water p r e s s u r e w i l l e q u a l t h e change i n c e l l p r e s s u r e and B

=

1.

Should t h e sample be p a r t i a l l y s a t u r a t e d t h e water p r e s s u r e w i l l be some percentage of the c e l l p r e s s u r e , say

80

p e r c e n t , and B

=

0.8.

C o e f f i c i e n t A i n a s i m i l a r way t a k e s i n t o account t h e p o r t i o n of t h e

ore

p r e s s u r e r e s u l t i n g from changes i n d e v i a t o r s t r e s s . While B r e l a t e s pore p r e s s u r e t o change i n major p r i n c i p a l s t r e s s .

o r f o r s a t u r a t i o n ( B

=

1)

Where = change i n pore p r e s s u r e

o = change i n rn-lnor

3

p r i n c i p a l s t r e s s

A

u = _{p r i n c i p a l s t r e s s} change i n major Now i s p a r t i c u l a r l y u s e f u l i n s t a b i l i t y problems s i n c e most

e s t i m a t e s of pore p r e s s u r e a r e based upon t h e change i n v e r t i c a l s t r e s s above any p o i n t c o n s i d o r e d , That i s , the change i n major p r i n c i p a l s t r e s s ( ul) i s t a k e n t o be t h e change i n v e r t i c a l

s t r e s s o r t h e change i n u n i t l o a d above t h e p o i n t . I n i t s s i m p l e s t s e n s e , assuming t h a t the change i n pore p r e s s u r e w i l l e q u a l t h e change i n l o a d ,

3

r e p r e s e n t s t h e p e r c e n t a g e of t h i s changed l o a d r e f l e c t e d a s changed pore p r e s s u r e o Thus, i f t h e drawdown i s 1 0 f o o t above a p i e z o m e t e r and t h e p i e z o m e t e r -.... i n d i c a t e s a change of p r e s s u r e e q u a l t o

5

f e e t of head, B

=

0.5,

Bishop ( 3 ) s u g g e s t s t h a t a v a l u e of

3

= 1 be u s e d f o r draw- 2ovm d e s i g n , and s u p p o r t s t h i s by measurements a t t h e U . S . Bureau of Heclomations, Alcova Dam. T h i s c o r r e s p o n d s w i t h t h e t h e o r e t i c a l drawdown pore p r e s s u r e s d e s c r i b e d by T e r z a g h i and Peck

( 4 ) 4

I n our. measurements of drarrdown pore p r e s s u r e we found

B

t o v a r y from v a l u e s of a b o u t 0.5 a t t h e more a c t i v e u p s t r e a m t i p s t o a b o u t Oo05 a t t h e r o c k f l l l s i d e of t h e damo That i s , t h e changes of p o r e p r e s s u r e were v e r y much l e s s t h a n we e x p e c t e d and p o r e

Now we have a l r e a d y e s t a b l - i s h e d t h a t i s dependent upon t h e degree of s a t u r a t i o n . We know t h a t t h e c l a y was p l a c e d a t a low d e g r e e of sa t u r e t i o n c o r r e s n o n d i n g t o

3

e q u a l t o a p p r o x i - mately z e r o a s evidenced by t h e l a c k of c o n s t r u c t i o n pore

p r e s s u r e s . It i s r e a s o n a b l e t o suppose t h a t a s seepage becomss e s t a b l i s h e d t h e degree of s a t u r a t i o n w i l l r i s e and t h a t t h i s w f l l t a k e more e f f e c t a t t h e u p s t r e a m s i d e of t h e s e c t i o n where seepage h a s been c o n t i n u i n g f o r t h e l o n g e s t t i m , and t h e v a l u e s of

B

o b t a i n e d a p p e a r q u i t e l o g i c a l . I t i s b e l i e v e d , on t h e same b a s i s , t h a t t h e v a l u e s of

B

w i l l g r a d u a l l y i n c r e a s e t h r o u g h o u t t h e c l a y c o r e , t h e upstream v a l u e s r e m a i n i n g somewhat h i g h e r t h a n t h e downstresm. T h i s l e a v e s t h e i n f e r e n c e t h a t , i n c o n s i d e r i n g d e s i g n v a l u e s , B must be t a k e n a s v a r y i n g w i t h time ( o r , more s t r i c t l y , degree of s a t u r a t i o n ) and t h a t t h e worst c o n d i t i o n w i l l occur, a s it h a s i n o u r c a s e ,

s h o r t l y a f t e r t h e pore p r e s s u r e s have b u i l t up under seepage b u t b e f o r e t h e degree of s a t u r a t i o n h a s been much a l t e r e d .

T h i s i s n o t , of c o u r s e , t h e whole p i c t u r e a s f a r a s s t a b i l i t y i s concerned. I t can be shown t h a t t h e s h e a r para- m e t e r s c l and $ 1 a l s o v a r y w i t h s a t u r a t i o n , t h e e f f e c t on

s t a b i l i t y b e i n g o p p o s i t e t o t h e e f f e c t of the pore p r e s s u r e changes. That i s , w i t h i n c r e a s i n g s a t u r a t i o n , t h e s h e a r s t r e n g t h r e d u c e s b u t t h e r e d u c t i o n i n pore p r e s s u r e i n c r e a s e s and t e n d s t o compensate.

A s t u d y o f t h e s e e f f e c t s i s beyond t h e scope of t h i s papep a s a r e any firm recommendations f o r d e s i m e C e r t a i n l y , a n

a s s u m p t i o n of f u l l seepage p r e s s u r e f o r drawdown would be conser- v a t i v e b u t when drawdovrn o c c u r s w i t h i n the f i r s t months of t h e l i f e of a s t r u c t u r e t h i s assumpt3.on does n o t a p p e a r u n r e a s o n a b l e .

I t i s i n t e n d e d t o c o n t i n u e n1,easurement of our piezonieter system f o r some t i m e . We i n t e n d p a r t i c u l a r l y t o measure t h e changes i n t h e v a l u e s a s seepage c o n t i n u e s and we hope t o be a b l e t o re3.ate t h e s e t o l a b o r a t o r y measurements of t h e same p a r a - me t e r s e

R e f e r e n c e s

l o U n i t e d S t a t e s Bureau of Reclamation. E a r t h manual, Denver, J W ~

1951.

332 p.

2. Skempton, A e W o The p o r e - p r e s s u r e c o e f f i c i e n t s A and

B e

G6otechnigue, v o l e

4,

n o e

4,

1954-e

P *

1113.

3.

Bishop, AoW. The u s e of p o r e - p r e s s u r e c o e f f j . c i e n t s i n p r a c t i c e . G6otechnique, v o l . 4 , n o . 4 ,

1954.

p .

a 8 .

4.

Terzaghi, K e a n d R o B e .Peck. S o i l mechanics i n e n g i n e e r i n g

D i s c u s s i o n

M r . P e t e r s o n asked what t h e drawdown on t h j - s s t , r u c t u r e was, M r . B a z e t t r e p l i e d t h e normal drawdown was 2 5 f t which n o r m a l l y o c c u r r e d w i t h i n a p e r i o d of

8

h o u r s , The maximurn drawdown t h a t had o c c u r r e d was

60

f t . Cl~anges i n p o r e p r e s s u r e s t a r t e d t o show up a f t e r a p e r i o d of

4

h o u r s . S t e a d y c o n d i t i o n s o c c u r r e d a f t e r a p e r i o d of 2 4 h o u r s ,

Asked by M r Townsend whether i t was n e c e s s a r y t o conduct two s t a b i l i t y a n a l y s e s

-

one f o r r a p i d drawdown when t h e dam was i n

t h e u n s a t u r a t e d s t a t e , and a n o t h e r f o r t h e c a s e when t h e drawdown o c c u r r e d a f t e r t h e f i l l h a d become s a t u r a t e d

-

M r * B a z e t t r e p l i e d he d i d n o t know b u t t h a t t h e s h e a r s t r e n g t h f o r t h e u n s a t u r a t e d m a t e r i a l was p r o b a b l y h i g h e r t h a n t h e s t r e n g t h a f t e r t h e s o i l became s a t u r a t e d .

M r . R i p l e y s a i d t h e a u t h o r had i n d i c a t e d t h a t t h e f l o w p a t h s were e i t h e r t h r o u g h t h e c o r e o r t o t h e f o u n d a t i o n and wondered why d r a i n a g e d o e s n o t oci-:ur towards t h e u p s t r e a m f a c e of t h e c o r e . M r . B a z e t t r e p l i e d t h a t it, would seem t h a t t h i s s l ~ o u l d be t h e c a s e b u t

a p p a r e n t l y i t was n o t , S i n c e t h e y were u n s u r e of t h e shape of t h e f l o w n e t I n t h e u p s t r e a m s e c t i o n of t h e c o r e , t h e r e s u l t s were p r e s e n t e d i n t h e form o f low

B

v a l u e s .

M r . R i p l e y a s k e d whether t h e a u t h o r obta-lned low

B

v a l u e s from s h e a r s t r e n g t h s of t h i s m a t e r i a l . M r . B a z s t t r e p l i e d no s t r e n g t h t e s t s h s d been c a r r i e d o u t .

M r . S e b a s t y a n a s k e d what t h e p r o p e r t i e s of t h e c o r e m a t e r i a l were and what t h e e f f e c t of t h e d e g r e e of s a t u r a t i o n , d e n s i t y a n d w a t e r c o n t e n t was on p o r e p r e s s u r e . M r . B a z e t t r e p l i e d t h a t t h e optimum w a t e r c o n t e n t wss

18

p o r c e n t , t h e maximum d r y d e n s i t y was 1 0 5 Ib p e r cu f t and t h e d e g r e e of s a t u r a t i o n was

80

p e r c e n t . F o r t h e embankment w i t h a d e g r e e o f s a t u r a t i o n of 80 p e r c e n t c a p i l l a r y t e n s i o n of one-half a n atmosphere was measured, There was a p o s s i - b i l i t y t h a t t h e pore t e n s i o n might be a s h i g h a s two atmospheres. During c o n s t r u c t i o n t h e weight of m a t e r i a l above t h e t i p a p p e a r e d t o have no e f f e c t on t h e pore p r o s s u r e .

M r . C l a r k a s k e d i f any i n s t a l l a t i o n f o r measuring t h e w a t e r c o n t e n t and d e n s i t y a t t h e t i p had been madee M r . B a z e t t s a i d no t h a t t h e y had t r i e d t o keep t h e i n s t a l l a t i o n a s s i m p l e a s p o s s i b l e .

BASE LINE COMPACTED CLAY 7 E

0 10 20 30

i

SCALE IN FEET

ROCK FILL ROCK FILL TERMINAL

WELL HOUSE ILTER ZONE 2

SIR ADAM BECK-NIAGARA PUMPING GENERATING STATION DYKE PIEZOMETER INSTALLATION

( O n t a r i s Hydro photo

1

Figure 2

s e c

t ; ~ . o n A

---

Summary of

-

_e_

Damsites i n B r l t i s h Columbia

-

A Challenge t o t h e E n ~ f n e e r

--_CCI

-

The complexity of the geology of t h e u n c o n s o l i d a t e d

sediments i n t h e v a l l e y s of B r i t i s h Columbia p r e s e n t s a f o r m i d a b l e c h a l l e n g e t o t h e g e o l o g i s t end t h e e n g i n e e r w i t h r e s p e c t t o

i n v e s t i g a t i o n and a p p r a i s a l of damsites. Within t h e Province, s e d i m e n t - f i l l e d r i v e r v a l l e y s t o a d e p t h of 500 f t a r e common. Many of t h e v a l l e y s have been s u b j e c t e d t o r e p e a t e d advances of v a l l e y g l a c i e r e . G l a c i a l d e p o s i t s i n t h e form of t i l l s , modified t i l l s , g l a c i o f l u v i a l d e p o s i t s and g l a c i a l l a k e sediments form t h e major s o i l d e p o s i t s now occupyirig t h e v a l l e y s .

I n t e r p r e t a t i o n of t h e h i s t o r y and s t r a t i g r a p h i c r e l a t i o n - s h i p of t h e s o i l d e p o s i t s i s p r i m a r f l y t h e f u n c t i o n of t h e g e o l o g i s t . Normally, h i s i n t e r p r e t a t i o n i s based on exarrlination of l a n d f o m s and s u r f a c e exposures, t o g e t h e r w i t h t h e informa t i o n o b t a i n e d from e x p l o r a t o r y d r i l l i n g and sampling programs. Q u a n t i t a t i v e appraf s a l of t h e p h y s i c a l p r o p e r t i e s of t h e s u b s o i l and t h e g e n e r a l s u i t a - b i l i t y of t h e s i t e must be made by t h e e n g i n e e r . I n o r d e r t o do s o he a l s o must examine t h e s u r f a c e exposures t o g e t h e r w i t h t h e samples and r e l a t e d informa t i o n o b t a i n e d from t h e d r i l l i n g program i n o r d e r t o develop an a p p r e c i a t i o n f o r t h e g e n e r a l n a t u r e and degree of v a r i a t i o n i n p h y s i c a l c h a r a c t e r i s t i c s w i t h i n t h e v a r i o u s d e p o s i t s which hhe g e o l o g i s t i d e n t i f i e s . The n e c o s s i t y of d e t a i l e d examination and i n t e r p r e t ; a t i o n of exposures and samples by b o t h t h e g e o l o g i s t and t h e e n g i n e e r f o r t h e l r s e p a r a t e purposes i s

obvious e

I n many i n s t a n c e s , one of tho major problems of i n t e r - p r e t a t i o n i s t h a t of d i f f e r e n t i a t i n g be tween t h e more g r a n u l a r g l a c i a l t i l l s and sand and g r a v e l

i n

d r i l l h o l e s , T h i s problem i s a n y t h i n g b u t simple and y e t t h e q u e s t i o n of whether o r n o t

a p a r t i c u l a r l a y e r of s o i l i s g l a c i a l till. o r sand and g r a v e l can be of major s i g n i f i c a n c e w i t h r e s p e c t t o e v a l u a t i o n of t h e damsite. I t may be even more d i f f i c u l t t o i d e n t i f y gravel-sand l a y e r s l o c a t e d between o r w i t h i n t i l l s and t o determine t h e upper and lower b o u n d a r i e s of t h e l a y e r s *

Other d i f f r c u l - t - i e s of r e c o g n i t i o n may o c c u r -in d i f f e r e n - t i a t i n g t h e f i n e r g r a i n e d t i l l s f r o r 5-ncluslans w i t h i n t h e s e t i l l d e p o s i t s o r from h i g h l y p r e c o n s o l i d a t e d , f i n e - g r a i n e d , s o r t e d

m a t e r i a l s occurra5.ng above, below o r between t h e f l n a r - g r a i n e d . ti11 s h e e t s , Many exarrples of t h e s e v a r i a t i o n s b o t h between and w i t h i n i n d i v i d u a l f ino-gra i n e d t i l l s h e e t s c a n be observed from sxantina- t i o n s of exposuro s t h r o u g h o u t t h e P r o v i n c e o

I n t e r p r e t a t i o n of s t r a t i g r s p h i c r e l a t , i o n s h i p s of s o i l d e p o s i t s a t darnsites i n B r l t k s h Coluri~bia h a s been furbtkrer compli- c a t e d by t h e s t e e p r e l i e f of t h e i n t e r - m o u n t a i n v a l l e y s and t h e

s l o p i n g r a t h e r t h a n f l a t s u r f a c e s on which marly of t h e d o p o s i t s have b e e n l a i d . Some of the d e p o s i t s have been l a i d down on s u r f a c e s of v a r y i n g c u r v a t u r e r a n g i n g from n e a r v e r t i c a l t o h o r i z o n t a l o These

s u r f a c e s may r e p r e s e n t t h e r o c k w a l l s and f l o o r of the main v a l l e y o r t h e y rnay r e p m s e n t tkie w a l l s and f l o o r s of chanr1ol.s i n c i s e d i n t o o l d e r s o i l d e p o s i t s overly in^ t h e bedrock s u r f a c e * These i n c i s e d c h a n n e l s rnay be p a r a l l e l o r p e r p e n d i c u l a r t o t h e a x i s of t h e main v a l l e y depending on t h o i r o r i g i n .

As

a r e s u l t , t h e upper and l o w e r b o u n d a r i e s of i n d i v i d u a l d e p o s i t s a r e o f t e n n o t f l a t l y i n g b u t

s t e e p l y s l o p i n g , I n a d d i t i o n , the l a t e r a l bounciarie s of a d e p o s i t may v a r y c o n s i d e r a b l y w i t h i n any one s e c t i o n of t h e v a l l e y * The e x t e n t of s u c h v a r i a t i o a s and t h e p o s i t i o n of tha l a t e r a l boun- d a r i e s may be of c o n s i d e r a b l e s i g n i f i c a n c e t o t h e d a m s i t e problem.

I n

some i n s t a n c e s , we a r e a t t r a c t e d t o d a m s i t e s l o c a t e d a t t h e e n t r a n c e i n t o a main v a l l e y of a t r i b u t a r y s t r e a m because of t h e t o p o g r a p h i c f e a t u r e s , A t such l o c a t i o n s , the main v a l l e y may have been c o n s t r i c t e d by e x t e n s i v e d e p o s i t s l a i d down by t h e t r 3 b u t a r y s t r e a m , g i v i n g t h e s u r f a c e a p p e a r a n c e of a f a v o u r a b l e d a m s i t e o f smal.ler c r o s s e c t i o n t h a n l o c a t i o r l s e i t h e r upstream o r dowmstream. The i n t e r r e l a t i o n s h i p of d e p o s i t s 1al.d down by t r i b u t a r y s t r e a m s and

by t h e main s t r e a m i s o f t e n v e r y complex and d i f f i c u l t t o i n v e s t i g a t e and i n t e r p r e t .

I n view of t h e c o m p l e x i t y of s u b s o i l conclitions wbich w i l l be e n c o u n t e r e d a t many of the f u t u r e d a m s i t e s i n B r i t i s h Col-umbia, p a t i e n c e and p e r s e v e r a n c e t o make t h o r o u g h i n v e s t i g a t j - o n s , e x p e r i e n c e w i t h s i m i l a r complex s i t e c o n d i t i o n s and keen judgement a r e c a l l e d f o r i n b o t h t h e g e o l o g i s t a n d t h e e n g i n e e r * I t i s fundamental t h a t t h e p l a n n e r s and owners of p r o j e c t s be g i v e n a c l e a r u n d e r s t a n d i n g t h a t t h e s i t e c o n d i t i o n s a r e d i f f i c u l t s o t h a t t h e y w i l l d e v e l o p

a

s y m p a t h e t i c a p p r e c i a t i o n t h a t a g r e a t d e a l of b o t h time and money a r e r e q u i r e d f o r s u f f i c i e n t l y thorough i n v e s t i g a t i o n s t o d e t e r m i n e i f and how s a f e s t r u c t u r e s can be b u i l t o

A s e r i e s of s l i d e s showing examples of d i f f e r e n t t y p e s of s o i l d e p o s i t s and of complex s t r a t i g r a p h y were u s e d t o i l l u s t r a t e t h e problems a s s o c i a t e d w i t h i n v e s t i g a t i n g them. I t was n o t w i t h i n t h e

scope of the paper t o d i s c u s s methods of a n a l y z i n g t h e e n g i n e e r i n g p r o p e r t i e s of t h e in-place d e p o s i t s n o r t o p r e s e n t methods of

d e a l i n g w i t h the complex f o u n d a t i o n and abutment c o n d i t i o n s . I t

goes without s a y i n g t h a t e a c h s i t e must be t r e a t e d a s a n i n d i v i d u a l problem.

D i scusa i o n

P r o f e s s o r Baracos asked R i p l e y what d r i l l J . n g methods a r e used i n g l a c i a l t i l l s . M r . R i p l e y r e p l i e d t h a t s t a n d p i p i n g o r wash-boring i n

4-

o r 6-in. c a s i n g i s employed w i t h e x p l o s i v e i n c o a r s e t i l l s w i t h no binder. I n t i l l s w i t h b i n d e r , diamond b i t s a r e used and i n c o a r s e t i l l s and a l l u v i a l oones s t a n d p i p i n g

i s t h e method used. I n g e n e r a l the average r a t e of p u t t i n g a h o l e down i s 1 0 f e e t p e r s h i f t a t a c o s t of

$25.00

p e r f o o t .

M r . Graves asked t h e a u t h o r what t y p e of machinery i s

used. Mr. R i p l e y r e p l i e d t h a t most of t h e i r d r i l l i n g was done by c o n t r a c t o r s who use t e l e s c o p i n g c a s i n g s t a r t i n g w i t h 10-in. p i p e and

"H"

d r i l l i n g rods. M r . R i p l e y i n v i t e d M r . Thurber t o add t o t h e d i s c u s s i o n which he d i d by d e s c r i b i n g some of h i s B o C e d r i l l i n g e x p e r i e n c e and s a i d t h a t chopping and t r i c o n e b i t s had been used w i t h success. He a l s o s t r e s s e d t h e importance of keeping t h e c a s i n g f r e e i n the h o l e .

&.

F i s h e r asked t h e a u t h o r how t h e y could be s u r e when bedrook w a n encountered. hk. Ripley r e p l i e d t h a t they u s u a l l y d r i l l e d 30 t o 50 f t i n t o rock but a g e o l o g i s t should be c a l l e d upon t o make t h e fJ.nal d e c i s i o n whether o r n o t t h e y were a c t u a l l y

i n

bedrook.

Mr.

Maduke asked M r . R i p l e y i f BoC. g l a c i a l t i l l s l a c k c l a y s i z e s . The a u t h o r r e p l i e d t h a t i t depended on t h e d e f i n i t i o n of c l a y s i z e s but t h a t some t i l l s seem t'o be sand-bound and

o t h e r s silt-bound.

M r . P o l l o c k asked M r . R i p l e y i f he found any change i n p e r m e a b i l i t y w i t h depth. The a u t h o r r e p l i e d t h a t by simple pump- i n t e s t s i n t h e a l l u v i a l cone d e s c r i b e d i n t h e paper t h e permea-

b i l i t y v a r i e d from 10-I t o 10'3 f t p e r min. He s a i d f u r t h e ~ ~ t h a t P r o f e s s o r Terzaghi e s t i m a t e d t h e average p e r m e a b i l i t y a s 1 0 f t p e r min and t h a t the o v e r - a l l p e r m e a b i l i t y of a l l u v i a l cones was g e n e r a l l y lower t h a n the h i g h e s t v a l u e s determined from i n d i v i d u a l t e s t s . '

S e c t i o n 2

--

N a Peters

The perfornlance of t h e more i m p o r t a n t e a r t h dams b u i l t by t h e P r a i r i e Farm R e h a b i l i t a t i o n A d m i n i s t r a t i o n i s checlred by t h e i n s t a l l a t i o n of t e s t a p p a r a t u s t o deterniine t h e b e h a v i o u r of the e a r t h enibarikment and a p u r t e n a n t s t r u c t u r e s d u r i n g and a f t e r con- s t r u c t i o n . The a p p a r a t u s can be d i v i d e d i n t o two c a t e g o r i e s :

-

(1) p i e z o m e t e r s t o measure pore p r e s s u r e s i n t h e e ~ b a n k m e n t and t h e f o u n d a t i o n ; and ( 2 )

movement

a p p a r a t u s t o measure h o r i z o n t a l and v e r t i c a l movement of t h e embankment, f o u n d a t i o n and r e l a t e d

s t r u c t u r e s .

F i g u r e I i s a c r o s s - s e c t i o n of a dam w i . t h t h e v a r i o u s t e s t i n s t a l l a t i o n s . T h e open c i r c l e s i n the diagram denote embankment and f o u n d a t i o n p i e z o m e t e r s . This t y p e o f p i e z o m e t e r h a s been developed by t h e U.S, Bureau of Reclamation* I t c o n s i s t s of a

porous s t o n e s e t i n a p l a s t i c cup and connected t o a p a i r of p l a s t i c t u b e s which l e a d t o p r e s s u r e gauges i n t h e t e r m i n a l w e l l a t t h e

downstream t o e of t h e dam. Water i n t h e p l a s t i c t u b i n g t r a n s m i t s t h e pore p r e s s u r e s from t h e porous s t o n e t o t h e p r e s s u r e gauges.

Pore p r e s s u r e s a r e a l s o measured by means of a s t a n d p i p e p i e z o n ~ e t e r which i s spawn a t t h e dovmstream t o e of t h e dam

i n

F i g , I. Various t y p e s of s t a n d p i p e p i e z o m o t e r s a r o u s e d b u t t h e one most commonly i n s t a l l e d I n c l a y s i s t h e porous t u b e t y p e which was developed by A . Casagrande. T h e i n s t a l l a t i o n c o n s i s t s of a l e n g t h of porous t u b e s e t i n a d r i l l h o l o .

TI;

i s plugged a t one end, and surrounded by sand and h a s a s m a l l d i a m e t e r p l a s t i c s t a n d p i p e

e x t e n d e d t o t h e ground s u r f a c o e The p i e z o m e t r i c w a t e r l o v e 1 i s de t e r n i n e d by a n e l e c t r i c sounding d e v i c e o

Three t y p e s of movement i n s t a l l a t i o n s a r e d e p i c t e d

i n

Fig. I. The s e t t l e m e n t gauge vrhich h a s been developed by t h e UoS. Bureau o f Reclamation e n a b l e s measurements t o be made of t h e c o m p ~ e s s i o n of t h e enbankment and settl-err:ent of t h e f o u n d a t i o n , The gauge

c o n s i s t s of a c o l u n ~ n of t e l e s c o p i n g 1 l/2- and 2-in. p i p e s , t h e 1 1/2-in. p i p e s b e i n g anchored t o t h o embankment b y moans of c r o s s - arms. A s p e c j e l measuring t o r p e d o a t t a c h e d t o a t a p e -is u s e d f o r measuring; v e r t j c a l movemonts of' t h o 1 1 / 2 - i n n p i p e ,

'l?spor submitted t o t h o Eng%irooi:i.n(: I n t ! t i t ~ . l t e of Canada f o r p u b l i c a t i o n .

Alignment p i n s a r e used f o r d i r e c t measurements cf s e t t l e - ments and h o r i z o n t a l movements p a r a l l s L a s well. a s p e r p e n d i o u l a r t o t h e c e n t r e l i n e of t h e dam. The a l i g n ~ e n t p i n s a r e made up of a base p l a t e and a s h o r t l e n g t h of pipe. Since t h e s e p i n s a r e

t

e n e r a l l y i n s t a l l e d on t h e c r e s t of a dam t h e y have t o be b u r f a d t o

8

i n e below ground l e v e l t o p r o t e c t them from t r a f f i a . The s l o p e i n d i c a t o r fs a more r e c e n t developn~ent. I t

p r o v i d e s a means o f measuring h o r i z o n t a l movements i n t h e embankment and t h e f o u n d a t i o n . S p e o i a l grooved p l a a t i c c a s i n g

.is

i n s t a l l e d i n a d r i l l h o l e and an e l e o t r i . c a l instrument i a lowered i n . t o t h e casing

t o determine t h e i n c l i n a t i o n o f t h e p i p e a t predetermined l e v e l s . In a d d i t i o n t o the measuring a p p a r a t u s shown i n Fig. I very

e x t e n s i v e use h a s beon made of b r a s s r e f e r e n c e screws i n s t a l l e d i n c o n o r e t e s t r t t c t u r e o . D i r e o t o b s e ~ v a t i o n s a r e made on the screws by means of l e v e l s , t r a n s i t s and t a p e t o determine s e t t l e m e n t , heave, opening and c l o s i n g of o o n s t r u c t i o n j o i n t s and alignment.

The t e a t a p p a r a t u s ha,s proven t o be v e r y v a l u a b l e i n c o n s t r u c t i o n c o n t r o l of e a r t h embankments and i n the e v a l u a t i o n

of t h e performance of t h e s t r u o t u r e a f t e r oonstruo t i o n . The observa- t i o n s a l s o s e r v e ~ r r a guide f o r f u t u r e d e s i g n of e a r t h

damso

ALIGNMENT PIN

1

r

SETTLEMENT GAUGE

PIEZOMETER

IU

I

-SLOPE

INDICATOR HOLES

---

STANDPIPE

PIEZOMETER

FIGURE I

S e c t i o n

6

---

Sumr~~ary of

The S o u t h Saskatchewan R i v e r Dam by

AaSn Ringheim I n t r o d u c t i o n

In J u l y

195'8

a n agreement was s i g n e d by t h e Governments of Canada and Saslcatchevran which a u t h o r i z e d t h e s t a r t o f

c o n s t r u c t i o n of t h e S o u t h Saskatchewan R i v e r P r o j e c t , T h i s p r o j e c t i s a l a r g e m u l t i - p u r p o s e development l o c a t e d i n a semi- a r i d r e g i o n I n s o u t h c e n t , r a l Saska tck~ovian,

The p r i m a r y purpose of t h e South Saskatchewan R i v e r P r o j e c t

Is

t o s t a b i l i z e a g r i c u l t u r e i n c e n t r a l Saskatchewan b y i r r i g a t i o n and t h e p r o v i s i o n of more dependable w a t e r s u p p l i e s f o r a g r i c u l t u r n 1 purposes. Approximately one-half m i l l i o n a c r e s of farm l a n d c a n u l t i m a t e l y be developed f o r t h i s purpose. T h i s l a n d i s 1-ocated w i t h i n v a r i o u s b l o c k s w i t h i n a 70-mile r a d i u s of t h e main r e s e r v o i r and i s now b e i n g worked by d r y f a r m methods. A second purpose, and one which w i l l y i e l d t h e most immediate b e n e f i t s , i s t h e development ~f h y d r o - c l e c t r i c power a t t h e dam. The p r o d u c t i o n of power w i l l be t h e r e s p o n s i b i l i t y of t h e P r o v i n c e of Saskatchewan. I t i s c a l c u l a t e d t h a t a p p r o x i m a t e l y 475,000,000 kwh c a n be produced a n n u a l l y . Approximately 1 0 p e r c e n t o f t h i s p r o d u c t i o n w i l l be r e q u i r e d f o r p u ~ i p l n g when t h e irrigation

system i s f u l l y developed, and t h e r e m a i n d e r w i l l be a v a i l a b l e f o r dl s t r i b u t i o n t h r o u g h o u t t h o p r o v i n c e , Other b e n e f i t s t o be d e r i v e d from t h i s p r o j e c t a r e : r i v e r r e g u l a t i o n and f l o o d c o n t r o l , which w i l l i n c r e a s e t h e power p o t e n t i a l a t d o w n s t r e ~ m s i t e s ;

improvement of r u r a l and u r b a n w a t e r s u p p l i e s ; and a l s o a n improvernont i n g e n e r a l r e c r e a t i o n a l facilities i n t h e a r e a . D e s c r i p t i o n of S i t e

In t h e r e s o r v o l r a r e a , e x t e n d i n g some

l l C O

m:lles upstream from t h e dam, t h e Saska.tchev~an R i v e r f l o w s i n a v a l l e y a b o u t 200

f t d e e p , and a h a l f m i l e wide a t r i v e r l e v e l , and g e n o r a l l y a b o u t two m i l e s wide a t t h e t o p of t h o v a l l e y o A t t h e d a m s i t e , two

c o u l e e s e n t o r t h e r i v o r v a l l o y from t h e west, I n a n a r e a l o c a t s d betvieen the two c o u l e e s and t h e r i v e r a v a s t supply of sand and gi-avel o c c u r s , w h i c h I s s u i t a b l e f o r b o t h p e r v i o u s embaxllanent m a t e r i a l and, a f t e r p r o c e s s i n g , f o p c o n c r e t s a g g r e g a t e s , T h i s g r a n u l a r d e p o s i t o c c u p i e s a n a r e a of a l m o s t one s q u a r e m i l e and e x t e n d s t o a d e p t h of 100 f e e t . Thus t h e predominant overburden r n a t e r i a l on t h e west s l d e o f t h e r i v e r ir, t h e irmnedj-ate v i c i n i t y of t h e damsite i 3 g r a i ~ u l a r i n nature* On t h e e a s t s l d e of t h e r i v e r ,

t h e predominant r n a t e r i a l i s a l e a n t o medium p l a s t i c g l a c i a l c l a y o c c u r r i n g i n d e p t h s up t o 200 f e e t o Witllln t h e r i v e r channel i t s e l f , sand o c c u r s i n d a p t h s up t o 100 f e o t . The c o e f f i c i e n t of p e r m e a b i l i t y of t h e sand i s i n the o r d e r of 0 0 1 ft p e r minute.

Underlying t h e overburden m a t e r i a l i s t h e Bearpaw f'orrnation, consisting predominantly of s h a l e vrith some s a n d s t o n e , The Rearpalrv shale, which I s o f Upper C r e t a c e o u s age, i s a n o v e r c o n s o l i d a t e d c l a y - s h a l e of marine o r i g i n a n " u n d e r l i e s r ~ u c h of t h e p r a i r i e r e g i o n . I n t h e u n d i s t u r b e d s t a t e the s h a l e h a s a r e l a t i v a l y h a r d c o n s i s t e n c y e x c e p t i n :;he uppor zons where i t i s c o n s i d e r a b l y

s o f t e r due t o i n c r e a s e d rnolsture c o n t e n t a 3 a r e s u l t of w e a t h e r i n g and s w e l l i n g . T h i s s o f t e r zons i s g e n e r a l l y i n t h e range of 1 0 t o

30

f t

i n t h i c k n e s s , The l i q u i d l i m i t of t h e s h a l e i s commonly

i n

t h e 80 t o 100 r a n g e w i t h a p l a s t i c l i m i t of a b o u t 20 a l t h o u g h t h e r e

i s c o n s i d e r a b l e v a r i a t i o n from t h e s e v a l u e s duo t o sandy o r more h i g h l y p l a s t i c f r a c t i o n s b e i n g prnsen-t. Tha m o i s t u r e c o n t e n t v a r i e s f r o n 30 t o

35

p e r c e n t n e a r t h e s h a l e s u r f a c e t o s l i g h t l y below 2 0 p e r c e n t a t depth.

I n a r e a s whore t h e Bearpaw s h a l e o u t c r o p s o r i s c l o s e t o t h e s u r f a c e , e x t e n s i v e slutnping h a s o c c u r r e d i n t o t h o r i v o r v a l l e y . A s a r e s u l t of the movo~nonts whicl? have o c c u r r e d , t h e r i v e r banks

i n the u n s t a b l e a r e a s h a v e assumed s l o p e s i n t h e o r d e r of 8:1 t o 1 2 : l . I t i s b e l i e v e d t h a t t h i s mcvemerit has o c c u r r e d m o s t l y i n

tho s o f t e r s u r f a c e s h a l e zons which i s c o n s i d e r e d t o bc a r e l a t i v e l y u n s t a b l e m a t e r i a l , With r e g a r d s to e x c a v a t i o n s i n t h e s h a l a ,

s e r i o u s c o n s i d e r a t i o n must be g i v e n , n o t o n l y t o t h e s l o p e s a t

which t o c u t t h e s h a l e so t h a t s s t a b l e s l o p e w i l l remain, but a l s o t o t h e problem of rebound which o c c u r s when t h e s h a l e i s unloaded snd t h e e f f e c t of t h i s rebound on s t r u c t u r e s f o u i ~ d e d on t h e s h a l e . S t r u c t u r e Layouk

The major s t r u c t u r e s a t t h e s i t e of the S o u t h Saslratchewan R i v e r Dam a r e t h e main dam, t,he f i v e r i v e r d i v e r s i o n t u m s l s t h r o u g h

t h e west abutment, t h e reinf'orced c a l ~ c r o t e spi1lv:ay a n d t h e power- house. A l s o , a major dam w i l l be constructed i n t-hs Qu'Appelle V a l l e y i n o r d e r t o c o n t r o l the fl-ow from t h e n i u i i ? r e s e r v o i r i n t o t h a t v a l l e y .

F o u n d a t i o n c o n d i t i o n s a t t h e d a m s i t e have d i c t a t e d t h e u s e of an e a r t h f i l l t y p e dam- The s t r u c t ! ~ r a l s t r e n g t h and

s e t t l e m e n t c h a r a c t e r i s t i c s of t h e Bearpaw s h a l e f owndation p r e - c l u d e s the use of a c o n c r e t e g r a v i t y t y p e dam. One of t h e

f a v o u r a b l e f e a t u r e s o f t h e d a m s i t e i s t h e a v a i l a b i l i t y w i t h i n c l o s e h a u l d i s t a n c e s of m a t e r i a l c o n s i d e r e d t o be i d e a l f c r e a r t h dam c o n s t r u c t i o n , A s a r e s u l t of t h e s e two major f a c t o r s , a zoned t y p e o a r t h f i l l h a s been adopted, The dam w i l l have a h e i g h t of 210 f e e t i n t h e r i v e r c h a n n e l a n d a c r e s t l e n g t h of 8500 f e e t * The embanlrment s i d e s l o p e s w i l l v a r y frotn 2 : l n e a r t h e 6 0 - f t wide c r e s t t o

821

a t t h e bottom r e s u l t i n g i n a base w i d t h of 2600 f t i n t h e r i v e r c h a n n e l , e x c l u s i v e o f t h e u p s t r e a m b l a n k e t which e x t e n d s a n a d d i t i o n a l 1200 f t upstream, The t o t s 1 volume of t h e main dam i s 4 0 m i l l i o n c u b i c y a r d s ,

The ernbaldanent i s zoned s o t h a t a p p r o x i m a t e l y one-half t h e t o t a l volume i s comprised of p e r v i o u s g r a n u l a r m a t e r i a l and t h e r e m a i n i n g h a l f i s of a n impervious and seini-pervious n a t u r e . The c e n t r a l c o r e of t h e dain and t h e u p s t r e a m b l a n k e t c o n s i s t of

compacted impervious m a t e r i a l , On t h e downstream s i d e of t h e c o r e , a t r a n s i t i o n a l random m a t e r i a l of a l e s s p e r v i o u s n a t u r e i s

l o c a t e d , The u p s t r e a m and do~vnstream s e c t i o n s of t h e embankment a r e composed of compacted p e r v i o u s sand and g r a v e l * Beneath a p o r t i o n of t h e downstream p e r v i o u s s e c t i o n , a d r a i n a g e f i l t s r of c l e a n g r a d e d sand and g r a v e l i s l o c a t e d e The p o r t i o n oi' t h e up- s t r e a m s l o p s w i t h i n t h e drawdown r a n g e w i l l bo r i p r a p p e d w i t h a

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l a y e r of f i e l d s t o n e u n d e r l a i n by a 2 1 / 2 - f t l a y e r of viol1 graded g r a v e l and c o b b l e s .

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twenty-foot d i a m e t e r curved t u n n e l s w i l l be c o n s t r u c t e d t h r o u g h t h e w e s t bank of t h e r i v e r , The a v e r a g e 1er;;th of t h e

t u n n e l s i s 4,050 f t , Tho t u n n e l s w i l l be c o n s t r u c t c : i n t h e h a r d s h a l e a n d w i l l be l i n e d w i t h r e i n f o r c e d c o n c r e t e o T.le p r e s e n t p r o p o s a l i s t o l o c a t e t h e t u n n e l c o n t r o l s t r u c t u r e n ~ > a r the dam c e n t e r l i n o , Each t u n n e l w9,l have a s e p a r a t e c o i ~ t r o l s h a f t which w i l l house t h e g a t e s f o r r e g u l a t i n g t h e d i s c h a r g e . A t t h e d i s c h a r g e end of t h e t u n n e l s a s t i l l i n g b a s i n w i l l be c o n s t r u c t e d t o d i s s i p a t e t h e e n e r g y b e f o r e t h e w a t e r r e - e n t e r s t h e r i v e r a t t h e downstream s i d e of the damo A problem of major c o n c e r n i n t h e t u n n e l d e s l g n i s t h e s t a b i l i t y of t h e c u t s l o p e s i n Bearpaw s h a l e a t t h e p o r t a l s o I n t h i s r e g a r d , t h e r e i s t h e m a t t e r of s h o r t t e r m s t a b i l i t y d u a i n g t h e c o n s t r u c t i o n of t h e i n l e t and o u t l e t s t r u c t u r e s and a l s o t h e l o n g time s t a b i l i t y throughout t h e l i f e of t h e s t r u c t u r e , , I n c o n s i d e r i n g t h e s h o r t t e r m s t a b i l i t y i t i s assumed t h a t t h e f u l l q u i c k s h e a r s t r e n g k h o f t h e sl2a19 w i l l bo m o b i l i z e d v h o r e a s f o r t h e l o n g t i m e