The Foundation Failure of the Transcona Grain Elevator

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NATIONAL RESEl"iRCH COUNCT L

CANADA

THE FOTJNDATION FATLITJRE OF THE

TRANSCONA G R A I N ELRVATOR

by A , B a r a c o s

Department of C i v i l Engf n e e r i n g , U n i v e r s i t y o f Manitoba

For p r e s e n t a t i o n t o t h e Winnipeg Branch o f %he E n g i n e e r i n g I n s t i t u t e of Canada R e g o r t No,

45

o f t h e Divf s i o n of B u i l d f ng R e s e a r c h Ottawa September

1954

THE FOUNDATION FAILURE OF THE TRANSCONA G R A I N ELEVATOR

Duping t h e l a s t t w e n t y - f i v e y e a r s , a n d more r e c e n t l y w f t h con- s f d e r a b l e r e f i n e m e n t , me t h o d s have been a d v a n c e d permf t t f ng t h e e a l c u l a t f o n o f t h e u l t i m a t e b e a r i n g c a p a c f t y o f s o i l s , The s a f e t y faetolz n e c e s s a r y f o r sound engf n e e r f n g ~ r a c t i c e p r e c l u d e s

c o ~ r e l a t i o n o f t h e u l t i m a t e b e a r i n g c a p a c f t y w f t h t h e a n a l y t i c a l d e - c e r m i n a t f o n o f t h e b e a r i n g p r e s s u r e s f o r t h e i v p e n d f n g f a i l u r e , Thus on1.y on r a r e o c c a s i o n s when a c t u a l f a i l u r e o c c u r s i s a c b r r e l a - ticn p o s s i b l e , The f o u n d a t i o n f a f l u r e i n

1913

of a m f l l f o n -

b u s h e l g r a i n e l e v a t o r a t T r a n s c o n a , a few m i l e s from Viinnipeg, Manitoba, p r o v i d e s such an o p p o r t u n i t y . I t f s t h e p u r p o s e o f t h i s p a p e r t o c o r r e l a t e t h e d a t a on t h e f o u n d a t i o n f a i l u r e of the Transcona G r a f n E l e v a t o r w i t h a r e c e n t l y completed f f e l d a n d l a b o ~ a t o r y s o i l mechanic s i n v e s t i g a t i o n u s i n g t h e l a t e s t a n a l y t i c a l methods,

A t t h e Buf l d i n g R e s e a r c h C o n g r e s s h e l d i n London, England, f n

1951,

a n o t a b l e p a p r on "The B e a r i n g C a p a c i t y of C l a y s f g was p r e s e n t e d by D r . A , W, Skempton ( I ) , The Transcona E l e v a t o r f a i l u r e was u s e d by t h i s a u t h o r a s one o f h i s e x a m p l e s and is i n c l u d e d i n h i s t a b l e of " F i e l d Data can U l t i m e t e B e a r i n g C a p a c i t y o f C l a y s " , The t a b l e , however, was i n c o m p l e t e a s p r e s e n t e d , w i t h d a t e on a c t u a l s o i l p r o p e r t i e s m i s s i n g f o r two s t r u c t w e s , one o f them t h e Transcona E l e v a t o r .

Another s p e a k e r on t h e same program a s D r . Skempton was H.

>',

L e g ~ e t , W,E,I.C., D i r e c t o r o f t h e 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 o f t h e N a t i o n a l R e s e a r c h C o u n c i l , Ottawa, A s he was s p e a k i n g a b o u t " S p e c i a l F o u n d a t i o n Problems i n Canadatt, M r , L e g g e t a l s o u s e d t h e Transcona E l e v a t o r a s a n examplea I n d i s - c u s s i o n , t h e d e s i r a b i l i t y o f c o m p l e t i n g t h e t a b l e i n D r , Skemptonq s p a p e r waa s t r e s s e d , M r o Leg;et t h e r e u p o n promf s e d a t t h e m e e t i n g t o e x p e d i t e t h e s t u d y o f t h i s f o u n d a t i o n f a f l u r e which he had p r e - v i o u s l y p l a n n e d t o c a r r y o u t t h r o u g h h i s D e B o R o s t a f f when t i m e p e r m i t t e d . T h i s p a p e r r e p r e s e n t s t h e f u l f f l m e n t o f t h a t p r o m i s e , Owing t o t h e n e c e s s i t y o f c o m p l e t i n g o t h e r o u t s t a n d i n g s o i l end f o u n d a t i o n s t u d i e s , i t w a s n o t u n t i l l a t e i n t h e summer o f 1 9 5 2 t h a t t h e work h e r e i n d e s c r i b e d c o u l d be s t a r t e d , Only t h e n was i t found t h a t some tfme p r e v i o u y l y two s o f l b o r f n g s had been

p u t down a t t h e s i t e o f t h e E l e v a t o r u n d e r t h e d i r e c t i o n of

P r o f e s s o r

R,

8, Peck of' t h e U n i v e r s i t y o f I l l i n o i s o U n f o r t u n a t e l y , i t was t h e n t o o l a t e t o c o r r e l a t e t h e p r o p o s e d Canadian i n v e s t i - g a t i o n w i t h D r o P e c k l s work b u t i t was d e c i d e d t o p r o c e e d a s p l a n n e d ,

D r . Peck h a s now p u b l i s h e d h i s r e s u l t s (2), accompanied by a n e y e - w i t n e s s a c c o u n t of t h e f a i l u r e by

Mr,

L,

S c o t t White

( 3 ) 0

The i n v e s t i g a t i o n now t o be d e s c r i b e d was r a t h e r more e x t e n s i v e t h a n t h e American s t u d y , t h e two b e i n g g e n e r a l l y complementary, a g r e e - ment b e t w e e n t h e v a r i o u s t e s t r e s u l t s b e i n g r e a s o n a b l y c l o s e , e v e n t h o u g h c a r r i e d o u t q u i t e i n d e p e n d e n t l y e x c e p t f o r a c h e c k by t h e a u t h o ~ on a few o f t h e s o i l s a m p l e s o b t a i n e d by D r , P e c k o

2. G e n e r a l D e s c r i p t f o n o f t h e S t r u c t u r e Development o f C a n a d a ' s v a s t wheat l a n d s i n t h e e a r l y p a r t o f t h i s c e n t u r y r e s u l t e d i n s e r i o u s c o n g e s t i o n o f t h e Winnipeg r a i l r o a d y a r d s d u r i n g p e a k p e r i o d s o f g r a i n movemento C o n s t r u c - t . i o n was t h e r e f o r e s t a r t e d i n

1911

on t h e T r a n s c o n a E l e v a t o r i n c o n j u n c t f o n ' w i t h one o f t h e w o r l d t s l a r g s s t r a i l r o a d y a r d s t o f a c i l i t a t e r a p i d g r a i n rnovement a n d t o g i v e r e l i e f t o t h e Winnipeg r a i l r o a d y a r d s ,

The plan o f t h e E l e v a t o r i s shown i n F i g . 1, I t c o n s i s t s o f a d r y e r h o u s e

18

b y 3 0 by 6 0 f e e t h i g h , w o r k h c ~ i s e 70 by

96

by 1 8 0 f e e t h i g h , and t h e b i n h o u s e 77 b y

195

by 1 0 2 f e e t h i g h , a l l c o n s t r u c t e d m a i n l y o f r e i n f o r c e d c o n c r e t e , The f o u n d a t i o n f a i l u r e o c c u r r e d u n d e r t h e b i n h o u s e w h i c h was d e s i g n e d f o r s t o r i n g one m i l l i o n b u s h e l s of g r a i n o I t c o n s i s t s of

65

c i r c u l a r b f n s a r r a n g e d

1 3

i n e a c h of

5

rows r u n n i n g n o r t h a n d s o u t h , The

48

i n t e r s t i c e s between b i n s a r e a l s o u s e d f o r s t o r i n g g r a i n o A _{r a f t f o u n d q t i o n ,} o f r e i n f o r c e d c o n c r e t e 2 f e e t t h i c k , s u p p o r t s t h e b i n s a n d t h e c o n v e y o r t u n n e l s u n d e r t h e b i n s , The d e p t h t o t h e b o t t o m o f t h e f o o t i n g s was 1 2 f e e t below t h e g r o u n d s u r f a c e , The d e s i g n

b e a r i n g p r e s s u r e was

6,600

l b . p e r s q u a r e f o o t b a s e d on l o a d b e a r i n g t e s t s f o r which t h e d a t a a r e no l c n g e ~ a v a i l a b l e o Dead w e i g h t o f t h e b i n house was v e r y n e a r l y 20,000 t o n s ,

3,

G e n e r a l D e s c r i p t i o n of S o i l s G r e a t e r Winnipeg l i e s i n t h e b a s i n o f t h e g l a c i a l Lake A g a s s f z w h i c h e x i s t e d d u r i n g t h e r e c e s s i o n o f t h e W i s c o n s i n i c e s h e e t , G e n e r a l l y , i n t h i s a r e a , t h e s o i l s may be c o n v e n i e n t l y g r o u p e d a s

f o l l o w s . The t o p 1 0 f e e t o r l e s s c o n s i s t of p a s t Lake A g a s s f z d e p o s i t s o f o r g a n i c s o i l s , f l o o d - d e p o s i t e d s i l t s a n d s i l t y c l a y s a n d o u t w e s h from h i g h e r g r o u n d , a n d m o d i f i e d l a c u s t r i n e d e p o s i t s , Underp t h e s e a r e f o u n d

40

f e e t o r l e s s o f g l a c i a l l a k e d e p o s f t s formf ng two d i s t i n c t l a y e r s o f a p p r o x i m a t e l y e q u a l t h i c k m e s s , The t o p l a y e r is a byown c l a y and i s d i s t i n c t l y v a r v e d w i t h many

f ~ a c t i o n a l i n c h - t h f c k l a y e r s of s i l t s p a c e d be tween l a y e r s o f c l a y

1/4

i n c h o r mme t h i c k , The b o t t o m l a y e r f s a g r e y - a o l o u r e d c l a y , s o f t e ~ t h a r , t h e o v e r l y i n g rnaterf a 1 and h a v i n g numerous c a l e a ~ e o u s s i l t p o c k e t s and c o n t a i n i n g l i m e s t o n e g r a v e l and a t o n e s a t t h e

g r e a t e ~ d e p t h s o B e n e a t h t h e c l a y s a r e f o u n d g l a c i a l d e p o s i t s of r o c k f i o u r , s i l t s , sands, and g r a v e l , The u p p e r p o r t i o n s w e r e d e p o s i t e d a s 3he g l a c i e r r e c e d e d and a r e u n d e r l a i n by s u b g l a c i a l d r f f t which h a s beer, a c t e d on by t h e f u l l w e i g h t of t h e i c e s h e e t , The s u b g l a c i a l d r i f t i s h i g h l y c o n s o l i d a t e d and s u p p o r t s many of t h e h e a v i e r s t ~ u c t u r s s i n t h e Winnipeg a r e a o The t o t a l t h f c k n e s s o f t h e d r f f t f a a b o ~ t 10 f e e t b u t v a r i e s c o n s f d e r a b l y f r o m t h i s v a l u e , The e n t i r e a r e a f _{s u n d e r l a i n by O ~ d o v f e i a n l i m e s t o n e ,}

b0

D e s c r i p t i o n o f F a i l u r e The s t o r a g e o f g r a i n i n t h e b i n h o u s e w a s begun in S e p t e m b e r ,

1913D

wf t h c o n s i d e r a b l e c a r e t a k e n t o d i s t r i b u t e t h e g r a i n u n i - f o r m l y e O n O c t o b e r 18 when 875,000 b u s h e l s o f wheat were s t o r e d , a v e r t i c a l s e t t l e m e n t o f a f o o t was n o t e d w i t h i n an h o u r a f t e r movement h a d been d e t e c t e d , The s t r u c t u r e t h e n b e g a n t o t i l t t o

t h e w e s t a n d w i t h i n 24 h o u r s was r e s t i n g a t a n a n g l e of 260

530

f r o m t h e v e r t i c a l a n d t h e w e s t s i d e was 2 4 f e e t below i t s o r i g i n a l p o s i t i o n , The e a s t side h a d r i s e n

5

f e e t above o r i g i n a l e l e v a t i o n o

Eye w i t n e s s a c c o u n t s

( 3 , 4 )

s t a t e d t h a t t h e s t r u c t u r e a c t e d mono- l i t h i e a l l y w i t h o n l y a few s u p e r f i c i a l c r a c k s a p p e a r i n g * I t s coming t o r e s t , a p p r o x i m a t e l y 24 h o u r s a f t e r t h e movement began, c o r r e s p o n d e d w i t h t h e c u p o l a f a l l i n g o f f t h e t o p of t h e s t r u c t u r e ,

I t was r e p o r t e d t h a t d u r i n g t h e f a i l u r e , t h e s o i l a r o u n d t h e s t r u c t u r e r o s e t o a h e i g h t o f

5

f e e t above t h e ground s u r f a c e a r o u n d t h e e n t i r e b i n h o u s e . P h o t o g r a p h s t a k e n a f t e r t h e f a i l u r e show t h a t t h e g r e a t e s t u p h e a v a l o c c u r r e d on t h e w e s t s i d e and was c o n 3 i d e r a b l y more t h a n

5

f e e t ,

C a l c u l a t i o n s b a s e d on t h e dead w e i g h t of t h e b i n h o u s e , 20,000 t o n s , a n d 875,000 b u s h e l s of wheat a t

60

l b o p e r b u s h e l , g i v e a u n i t u n i f o r m l y d i s t r i b u t e d p r e s s u r e of 6,200 l b . p e r s q u a r e f o o t on t h e c l a y when f a i l u r e t o o k p l a c e ,

The o p e r a t i o n s t o r i g h t t h e s t r u c t u r e have been r e p o r t e d I n d e t a i l by A l l a i r e

( 5 )

,

The s t r u c t u r e h a s b e e n i n s u c c e s s f u l u s e s i n c e i t s p o s i t f o n was r e s t o r e d ,

5

N a t u r e o f F i e l d and L a b o r a t o r y I n v e s t i g a t i o n F i g u r e 1 shows t h e l o c a t i o n of 7 t e s t h o l e s u s e d t o o b t a i n s a m p l e s f o r t h e l a b o r a t o r y t e s t s , H o l e s

4

and 7 were s u f f i c i e n t l y removed from t h e s t r u c t u r e t o a v o i d d i s t u r b a n c e s c a u s e d by t h e f a f l i r e and t h e r i g h t i n g o p e r a t i o n s ,

The r e m a i n i n g h o l e s were l o c a t e d n e a r e r t h e s t r u c t u r e , some

60

f e e t from t h e b i n h o u s e , i n a n e f f o r t t o a s c e r t a i n t h e e f f e c t s of f a i l u r e , I t was r e a l i z e d , however, t h a t t h e s e h o l e s would show t h e e f f e c t s o f a l m o s t 4 0 y e a r s o f c o n t i n u e d pumping t h a t h a s

t a k e n p l a c e s i n c e t h e b i n h o u s e was r i g h t e d . Purnping h a s b e e n

n e c e s s a r y t o k e e p t h e b o t t o m o f t h e b i n house d r y , A f t e r r i g h t i n g , t h e b i n house was a p p r o x i m a t e l y

3 4

f e e t below t h e p r a i r i e g r a d e ,,

I t was n o t c o n s i d e r e d p r a c t i c a l t o p l a c e t h e t e s t h o l e s any c l o s e r t o t h e s t r u c t u r e a s t h e e n t i r e a r e a n e a r e r t h e b u i l d i n g was d i s t u r b e d by t - x ~ n e l i n g , e x c a v a t i o n , e t c , dur f n g t h e r i g h t i n g o p e r a t i o n s , To k e e p t h e b i n s d r y , a 1 2 - f o o t - d e e p t r e n c h had, i n z d d i t i o n , been e x c a v a t e d around t h e b i n house on a l l b u t t h e s o u t h s i d e , f u r t h e r d i s c o u r a g i n g t e s t h o l e s a n y c l o s e r t o t h e s t ~ u c t u r e t h a n t h o s e i n d i c a t e d ,

The h o l e s were b o r e d t o r e f u s a l a t a d e p t h between 40 and 50 f e e t where %he d e n s e and c o a r s e g l a c i a l d e p o s i t s w e r e e n c o u n t e r e d , A diamond d r i l l a d a p t e d f o r t a l r l n g t h i n w a l l S h e l b y t u b e s 2 i n c h e s

In

d f a m e t e r was u s e d f o r b o r i n g and s a m p l i n g . Samples a p p r o x i m a t e l y 2 1/2 f e e t l o n g were t a k e n a t 5-f o o t i n t e r v a l s c r l e s s where c h a n g e s

is a o f l were e v i d e n t e

A l l s a m p l e s wepe examined in t h e l a b o r a t o r y and n o t e s made on

c o l o u r , s t ~ a t i f i c a t i o n , e t c . On e a c h salt p l e , m o i s t u r e c o n t e n t s , densf t y , d e g r e e of s a t u r a t i o n , and ~ m c o n f i n e d c o m p r e s s i o n s t r e n g t h s were d e t e r m i n e d , On r e p r e s s n t a t i v e s a m p l e s , g r a f n s i z e , k t t e r b e r g

l i m i t s , u n d r a i n e d q u i c k t r i a x i a l s u n d c r c o n s t a n t l o a d i n c r e m e n t s , specilf f c g r a v i t y , a n d c o n s o l i d a t i o n t e s t s were performed,, The un- c o n f i n e d c o m p r e s s i o n and t h e u n d r a i n e d t r i a x f a 1 t e s t s were pepformed on u n d i s t u p b s d s a m p l e s trimmed t o

1,s

i n c h e s d i a m e t e r and alsproximntely 3.0 i n c h e s l o n g , B ~ t h t h e f i e l d and l a b o r a t o r y t e s t i n g were con- d u c t e d d w i n g t h e autuvnl o f 1952 and w i n t e r o f 1952-2?53,

6 .

T e s t R e s u l t s

R e s u l t s o f t h e t e s t s a r e shown i n t h e Log o f T e s t Holes,

F i g .

3,

No t e s t s were p e r f o r m e d on t h e m a t e r i a l above 1 0 f e e t i n H o l e s 1, 2,

3,

5, 6,

and 7 where f i l l p1 aced d u r i n g t h e r i g h t i n g of t h e e l e v a t o r was e n c o u n t e r e d , Hole

4

showed t h e s i l t s and s i l t y c l a y s a s t h e y p r o b a b l y w e r e o v e r t h e e n t i r e a r e a p r i o r t o t h e e x - c a v a t i o n f o r t h e f o u n d a t i o n s .

Below t h e 1 0 - f o o t l e v e l t o a d e p t h o f 2 0 , s f e e t i n Hole

4,

a n d f r o m 2 5 t o 26 f e e t i n t h e o t h e r h o l e s , a brown, h i g h l y s t r a t i f i e d o r v a r v e d s i l t y c l a y was f o u n d , The s t r a t i f i c a t i o n o r v a r v e s were more o r l e s s h o r i z o n t a l and c o n s i s t e d of l a y e r s of s i l t o f f r a c t i o n a l

i n c h i n thickness between c l o s e l y s p a c e d l a y e r s o f c l a y a p p r o x i m a t e l y

l/Il

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f e e t f r o m t h e s u r f a c e , a h i g h l y p l a s t i c g r e y s i l t y c l a y was f o u n d w i t h

numerous t a n - c o l o u r e d c a l c a r e o u s s i l t p o c k e t s and l i m e s t o n e

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

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showed no d i s t i n c t boundary between t h e g r e y ~ i l t a n d t h e u n d e r l y i n g g l a c i a l d r i f t o About

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f e e t o f a m i x t u r e o f b o t h m a t e r i a l s f o r d a t r a n s i t 1 on l a y e r , Average t e s t r e s u l t s f o r t h e g r e y s i l t y c l a y e x c l u d i n g t h e v e r y m o i s t m a t e r i a l e n c o u n t e r e d i n Holes 1,

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shows t h e r e s u l t s f o r e a c h t e s t h o l e , A l l t h e s a m p l e s below t h e 1 0 - f o o t d e p t h showed c o m p l e t e OF n e a r complete s a t u r a t i o n , Twelve u n d r a i n e d t r i a x i a l t e s t s on samples from Hole 2 c o n f i r m e d a n e g l i g i b l e a n g l e of i n t e r n a l f r i c t i o n f o r t h i s t y p e of l o a d i n g . The c o n s o l i d a t i o n t e s t r e - s u l t s ( f o r s a r p l e s from Hole

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P r e c o n s c l i - d a t i o n p r e s s u r g s a r e n o t a c c u r a t e l y d e t e r m i n e d on t h e s e c l a y s b u t i n d i c a t e t h a t t h e y a r e somewhat i n e x c e s s of o v e r b u r d e n p r e s s u r e s p ~ o b a b i y due t o d e s i c c a t i o n , The v o i d r a t i o p r e s s u r e c u r v e s a r e shown i n ? i g o

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4

f e e t o f t h e l e s s dense d r i f t were f o u n d , B o r i n g r e f u s a l was e n c o u n t e r e d ' i n t h e s u b g l a c i a l d r i f t c o r r e s p o n d 5 n g t o t h e d e p t h t o w h i c h t h e n o r t h end o f t h e b i n house s e t t l e d f o l l o w i n g t h e f a i l u r e Nurfierous s t o n e s p r e v e n t e d s t r e n g t h and c o n s o l i d a t i o n t e s t s f r o m b e i n g performed on t h e g l a c i a l d r i f t , The f o i l o w i n g d a t a , however, were o b t a i n e d : N a t u r a l m o i s t u r e c o n t e n t r a n g e ( $ )

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50 f e e t . 7 , T h e o r e t i c a l R e a r i n g C a p a c i t y The r e l a t l v e l y r a p i d l o a d i n g o f t h e e l e v s t o r o n s a t u r a t e d c l ~ y c o r r e s p o n d s t o t h e l a b o r a t o r y u n d r a i n e d q u i c k t r i n x i a l t e s t f o r w h i c h t h e u n c o n f i n e d c o m p r e s s i o n t e s t i s a s p e c i a l c a s e . F o r s u c h c o n d i t i o n s i t i s r e c o g n i z e d t h a t t h e a n g l e o f i n t e r n a l f r i c t i o n is n e g l i g i b l e a n d t h u s t h e c o h e s i o n i s e q u a l t o h a l f ' t h e u n c o n f i n e d c o m p r e s s i v e s t r e n g t h , I n g e n e r a l t h e u l t i m a t e u n i t b e a r i n g c a p a c f t y o f a s o i l may be e x p r e s s e d by : where qu = u l t i m a t e u n i t b e a r i n g c a p a c i t y c = c o h e s i o n y = u n i t w e i g h t of s o i l B

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a p p l i e s when t h e s t r e s s - s t r a i n c u r v e ( f r o m l a b o r a t o r y t e s t s ) i s o f t h e t y p e shown i n P i g . h a , o r i s a p p r o a c h e d when n e g l i g i b l e v a r i a t i o n e x i s t s i n b o t h l o a d i n g a n d s o i l c o n d i t i o n s . F o r r e c t a n g u l a r f o o t i n g s t h e v a l u e o f Nc h a s b e e n shown b y a n a l y t i c a l m e t h o d s , m o d e l s t u d i e s a n d a s t u d y o f a c t u a l f a i l u r e s t o L d be a f u n c t i o n o f

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The t h e o r y f o r d e r i v i n g e q u a t i o n (1) a s s u m a s t h a t t h e s o i l f a i l s on a l o g a r i t h m i c s p i r a l a s shown i n F i g . 4 b 0 The r a d i u s o f t h e l o g a r i t h m i c s p i r a l , pl = r o e 0 t a n 9 _{O O O . . . O . O . P O O O O . O D O O O ~ O O O O O O O ( ~} ) f s i n d e p e n d e n t o f t h e c o h e s i o n a n d a n y s u r c h a r g e a d j a c e n t t o t h e f o o t i n g s , A l t h o u g h t h e t h e o r y f o r e q u a t i o n (1) 1 s beyond t h e s c o p e o f t h i s r e p o r t , i t i s o f i n t e r e s t t h a t f o p t h e s n e c i . a l c a s e o f 9 = 0 , r

=

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of s o l 1 f a i l u r e a c t u a l l y d e v e l o n e d . 8 , S t a b i l i t y Analyrjis T h a t t h e b e a r i n g c a p a c i t y t h e o r y i s v a l i d t o a p p l y t o t h e f a i l u r e o f t h e T r a n s c o n a E l e v c t o r i s c o n f i r m e d by a g e n e p a l e x a m i n e - t i o n o f t h e t e s t h o l e a n d a c t u a l f a i l u r e d a t a , The d e p t h o f

37

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f e e t below t h a o r i g i n a l f o ~ m d a t f o n e l e v a t i o n ( 1 2 f e e t b e l o w

g r o u n d s u r f a c e ) t o t h e d e n s e g l a c i a l . d r i f t laces a l i m i t a t i o n on t h e r a d i u s o f a n y s i m p l e f a i l u r e p l a n e . A s shown by e q u a t f on

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38

1/2 f e e t p e r m i t t i n g a f a i l u r e a c c o r d i n g t o t h e o r y . The n e a ~ e s t t e s t h o l e s t o t h e s t r u c t u r e o n t h e s i d e o f t i l t i n g were

63

f e e t d i s t a n t and f r o m t h e e x a m i n a t i o n a n d t e s t i n g o f u n d i s t u r b e d s a m p l e s , t h e s o i l a p p e a r e d t o b e u n a f f e c t . e d by t h e f a i l u r e , w h i c h e s t a b l i s h e d a h o r i z o n t a l l f m i t on t h e e x t e n t o f t h e f a f l w e p l a n e . A l t h o u g h t h e f a i l u r e o c c u r r e d n e a r l y

40

y € s p S a g o , 5 5 is n o t b e l i e v e d t h a t t h e l o s s f n , ~ t r e n g t h o f t h e s o i l r e s u l t i n g from t h e f a i l u r e h a s b e e n r e g a i n e d . T e a t s o n s i r p f l a r Lake A g a a s i z d e p o s i t s ( 7 ) d o n o t i n d i c a t e a n y e x t e n s f v e t h f x o t r o p i c s t r e n g t h r e - g a i n f o r t h i s m a t e r i a l . A l t h o u g h n o r e m o u l d e d s t r e n g t h t e s t s w e r e p e r f o r m e d , i t h a s b e e n g e n e r a l l y f m n d t h a t r e m o u l d i n g r e s u l t s in a l o s s of o n e - h a l f o f t h e s t r e n g t h o f t h e Wfnnfpeg c l a y s o The g r e a t e s t u p h e a v a l on t h e s i d e o f t i l t i n g f u r t h e r c o n f i r m s the v a l i d i t y o f t h e a s s u m p t i o n s o n w h i c h t h e t h e o r y i s b a s e d , The a c t u : ~ l d i r e c t t o n o f t i l t i n g i s n o t i m p o r t a n t a s e v e n a v e r y m i n o r e c c e n - t r i c i t y i n l o a d i n g o r v a r i a t i o n s i n s o i l c o n d i t f o n s c o u l d c a u s e a f a i l u r e t o e i t h e r s i d e . It i s a l s o r e a s o n a b l e t o assume t h a t be- c a u s e o f t h e n a t u r e o f t h e l a b o r a t o r y s t r e s s - s t r a i n c w v e s a n d t h e p r e c a u t i o n s t a k e n t o a s s u r e u n f f o r m l o a d i n g o f t h e E 1 e v a t . o ~ ~ t h a t . t h e T e r z a g h i g e n e r a l s h e a r c o n d i t l o n s w e r e s n t i s f i e d , I t f s q u e s t f c l ; a b l e , how eve^, vrhvther t h e a s s u m p t i o n o f l o c a l s h e a r v a l u e

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c l a y o r t h e g r e y s i l t y c l a y a l o n e would be u n j u s t i f i a b l e h i g h and low r e s p e c t i v e l y s i n c e t h e f a i l u r e p l a n e p a s s e d t h r m g h b o t h

m a t e r i a l s , Use o f t h e a v e r a g e u n c o n f i n e d c o m p r e s s i v e s t r e n g t h

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1933

l b o p e r s q u a r e f o o t and p s o b a b l y ~ s f l e c t s t h e e f r e c t s o f c o n s c l f d a t i o n c a u s e d by t h e c o n t i n ~ ~ o u s p ~ m p ' i n g f r o m u n d e r t h e bfn Youse f o r a p e r i o d of a l m o s t 40 y e a y s , hlol.sture con- t e n t s and d e n s f t i e s f o r t h e g r e y s i l t y c l a y when compared f c r

h o l e s

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3,

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6

Average m o i s t u r e c o n t e n t ( % )

51.9

49.9

Average m o i s t d e n s i t y ( l b / ~ ~ o f t o ) The a v e r a g e u n c o n f i n e d c o m p r e s s i v e s t r e n g t h v a l u e s of

1933 Ib.

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3,

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t o 4 0 - f o o t d e p t h f r o m Hole s 1 and

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r e s p e c t i v e l y . The d i f f e r e n c e i n t h e v a l u e s of c o h e s i o n , d e n s i t y , and m o i s t u r e con-

t e n t m e n t i o n e d , however, a r e s m a l l and c o u l d s i m p l y r e f l e c t s t a t f s - t f e a P a c s u r a c y ,

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>O: lb, p e r cubPe f o o t and t h e c o h e s i o n a s h a l f t h e u n c o n f i n e d c c m p r e s s i v e s t r e n g c ' ~ , TABLE I Based on R e s u l t s f o r : Average uncon- f t ft Qu f i n e d c o m p r e s s i v e u l t i m a t e s t r e n g t h b e a r i n g c a p a - ( l b / s q . f t , ) c i t y (lb/sqof't.) Brown s i l t y c l a y

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6200 Ib/sr;, f t ,

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D i s c u s s i o n The u l t i m a t e t h e o r e t i c a l b e a r i n g c a p a c i t y o f l b , p e r s q u a r e f o o t u s i n g t h e most j u s t i f i a b l e v a l u e o f u n c o n f i n e d cornpressfva s t r e n g t h , 1 8 5 0 l b , p e r s q u a r e f o o t i s r e m a r k a b l y c l o s e t o t h e s e t u a l b e s r i n g c a p a c i t y a t f a i l u r e of 6 2 0 0 l b , p e r squaFe f o o t , The c o r r e l a t i o n i s e v e n b e t t e r t h a n s t a t i s t i c a l c o n s f d e r a t i o n s of t h e d a t a c a n s u b s t a n t i a t e . R e a s o n a b l e c o r r e l a t i o n , howe;ier, i s g a f n e d

u s f n g t h e o t h e r a v e r a g e c o h e s i o n v a l u e s a s shown i n T a b l e

I,,

T h i s i s i n s p i t e o f s u c h f a c t o r s a s pumping t h a t have c a u s e d s o l 1 c h a n g e s g i n c e t h e f a j l u r e . D I f f I c ~ l t t o e x n l a i n i s t h e l e n g t h o f t i m e , 2 L ~ O U P S ~ w h i c h e l a p s e d from t h e t i m e m o t i o n h e g m u n t i l t h e b u i l d i n g came t o r e s t , The p 3 a s t i c n a t u r e o f t h e s o i l s and t h e g r a d u a l t r a n s f e r o f l o a d from t h e u13per s t i f f e r c l a y s t o t h e 3 o f t e r u n d e r l y i n g m a t e r i a l may be r e s p o n s i b l e . The slow f a i l u r e and t h e v a r v e s i n t h e brown c l a y d o n o t apae:ir tlo have i n v a l i d a t e d t h e t h e o r e t i c a l f o r m u l a .

To the e n g i n e e r , i t i s most r e a s s u r i n g t h a t t h e ~ t i u d y of the Transcona E l e v a t o r f a i l u r e a n d s i m i l a r s t u d i e s (1) xleported f o r t h e f o u n d a t i o n f a i l u r e s on c l a y s i n w i d e l y s e p a r a t e d a r e a s , v e r i f y +,he ? r e s e n t t h e o r i e s , The a d v a n t e g e s of b e i n g a b l e t o p r e d i c t t h e u l t i - mate b e a r i n g c a p a c i t y from a s o i l s t u d y a r e o b v i o u s , With t h e f n f o r - m a t r o n now a v a i l a b l e and t h e a d d i t i o n a l ~ t u d i e s b e i n g made on

s e t t l e m e n t s , f o u n d a t i o n s on c l a y may b e d e s i g n e d w i t h r e a s o n a b l e knowledge o f t h e s a f e t y f a c t o r s i n v o l v e d and t h e f u t u r e b e h a v f o u r of t h e s t r u c t u r e , 1 0 , Acknowledgements The i n t e r e s t i n t h i s I n v e s t i g a t i o n of t h e Canadfan P a c i f i c R a i l w a y , t h r o u g h M r . R e A o Emerson, C h i e f E n g i n e e r , and t h e i r p e r - m i s s i o n f o r t h e s i n k i n g of t h e t e s t h o l e s on t h e i r p r o p e r t y i s

g r a t e f u l l y acknowledged. The t e s t b o r i n g s were p u t down by t h e

s p e c i a l s o i l b o r i n g crew u n d e r M r o Eo H a r g e s t o f t h e Manitoba D e p a r t - ment of P u b l i c 'darks. The a u t h o r i s I n d e b t e d t o 1uPo

W.

L o S c o t t

8 ~-,

Whf t e and t o t h e F o u n d a t i o n Company of Canada L i m i t e d f o r t h e e x c e l l e n t p h o t o g r a p h s which s e r v e a s i l l u s t r a t i o n s . The sof

P

t e s t i n g w a s c a r r i e d o u t by M r .

M.

Bozozuk i n t h e S o l 1 Mechenica L a b o r a t o r y o f t h e U n i v e r s i t y of Manitoba and t o him t h e a u t h o r

r e c o r d s h i s t h a n k s a s a l s o t o Dean A . Eo Macdonald, ~ ~ o E . ~ , ~ o and t o M r . R o F o L e g ~ e t , ~ ~ l o E o I o C . , D i r e c t o r o f t h e Divf s i o n o f BUtld9 ng R e s e a r c h , N q t i o n a l R e s e a r c h C o u n c i l , w i t h whose a p p r o v a l t h f s n a D e r i s z u b l i s h e d a s a j o i n t c o n t r i b u t i o n from t h e U n i v e r s i t y of Manitoba and t h e D i v i s i o n . REFERENCES Skernpton, A , W o The B e a r i n g C a p a c i t y of C l a y s , B u i l d i n g R e s e a r c h C o n g r e s s , London, I :l80-189.

1951

,

Peck, R.B. and F.G.Bryant. The B e a r i n g C a p a c i t y F a i l u r e o f

t h e Transcona E l e v a t o r . G 6 0 t e c h n i q u e ~ 111:201-208~

1953,

S c o t t White, Lo Transcona E l e v a t o r F a i l u r e : E y e - w i t n e s s Account. ~ 6 o t e c h n i q u e ~ 111 :209-214.

1953,

Winnipeg F r e e P r e s s , O c t o b e r 20,

1913

, A l l a i r e , A , The F a i l u r e and R i g h t i n g o f a M i l l i o n - b u s h e l G r a i n E l e v ~ t o r T r a n s . o f t h e Amer. Soc, o f C i v i l E n g i n e e r s , V o l e 80. December

1916.

T e r z a g h f ,

K O

T h e o r e t i c a l S o i l Mecharlics, A r t ,

11-7.

John

Wiley and Sons, I n c ,

19h3,

B e r g e r , Lo and J o G n a e d i n g e r . T h i x o t r o p i c S t r e n g t h o f C l a y s ,

Photograph 1 Weak a i d e of e l s w a t a r showing tilt and

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