frost thrust measurements on piles

8/16/2019 Frost Thrust Measurements on Piles

1/16

1 1 1 . 4 . FROST THRUST MEASUREMENTS O PILES

R . E . Reed

Upward t h r u s t on f o u n d a t i o n p i l i n g due t o f r o s t

a c t i o n h a s be en a pr ob le m i n t h e d e s i g n , c o n s t r u c t i o n , a nd

m ai nt en an ce of s t r u c t u r e s th ro u gh ou t a r c t i c , s u b a r c t i c ,

a nd t e m p e r a t e r e g i o n s . Se a so n a l f r e e z i n g and t h a wi ng o f

t h e u p p er l a y e r s o f g ro un d c a use d i f f e r e n t i a l movements

w hich c an be d e t r i m e n t a l t o a f o u n d at i o n . I n p i l e fo un da -

t i o n s , t h e h ea vi ng o f t h e g ro un d d u ri n g t h e f r e e z i n g s e a so n

i m p a r t s a n upward t h r u s t t o t h e p i l e by a d f r ee z e a nd t h e

s t a b i l i t y o f

a

p i l e f o u n d a t i o n i s dependen t upon t h e p r ope r

e v a l u a t i o n o f t h i s f o r c e w it h t h e o t h e r f o r c e s o n t h e

f o u n d a t i o n .

D ur in g t h e p a s t 1 5 y e a r s , c o n s i d e r a b l e r e s e a r c h

h as b een cond ucted t o e s t a b l i s h d e si gn c r i t e r i a f o r

e s t i m a t i n g t h e l o a d c ap a c i ty o f p i l e s i n p er ma fr os t

R e f e r e n c e s 1 2 , 3 , 4 , 5 and 6 . The pr ob le m o f f r o s t

t h r u s t o n p i l i n g h a s l o n g b ee n r e c o g ni z e d and s e v e r a l

methods have been used t o cope wi t h i t A ru le o f thumb

f o r embedment o f p i l e s t o

a

d e pt h i n p er ma fr os t e q u a l t o

t w i c e t h e e x pe c te d de p th o f t h e a c t i v e l a y e r h a s b ee n u se d

t o c o u n t e r a c t t h e h ea ve t h r u s t R ef er en ce

7 .

I n v e s t i g a -

t i o n s a t Fa i r ban ks , Alaska have in d i ca te d th a t a minimum

embedment of 10 f t i n p e rm a fr o st i s r e q u ir e d t o c o u n t e r a ct

heav e t h r u s t i n t h e a r e a R ef er en ce 5 . O i l - w a x f i l l e d

c a s in g s o r s l e e v e s , g r ea s e c o a t i n g s ,

t a r

paper wraps , and

t r e a t e d b a c k f i l l m a t e r i a l s h ave a l s o been u sed t o r ed uc e

o r e l i m i n a t e p i l e heave t h r u s t R ef er en ce 8 ) .

A lt ho ug h se v e r a l m ea sur es h av e be en i n v e s t i g a t e d

a nd u se d a s a nt i - h ea v e d e v i c e s o n f o u n d a t i o n p i l i n g , v e r y

l i t t l e i n f o rm a t i on h a s b een o b t a i n e d on t h e a c t u a l magni-

t u d e o f t h e f r o s t t h r u s t w hich c r e a t e s t h i s h ea ve pr ob lem .

T hi s p ap er p r e s en t s t h e r e s u l t s o f a f i e l d t e s t t o measure

t h e f r o s t t h r u s t on cr eo so te d t i mb er , and 8 i n . s t e e l p i p e ,

p i l e s . The t e s t i s one of a s e r i e s o f t e s t s c on du ct ed by

t h e U.S. Army Cold Regions Rese arc h and En gi ne er in g

La b or at or y USA CRREL).

A

c o m p r e h e n s i v e r e p o r t o n t h e

s e r i e s i s i n p r e p a r a t i o n R e fe re nc e 9 . The f i e l d d a t a

was o b t a in e d from a t e s t i n s t a l l a t i o n

a t

t h e A la sk a F i e l d

S t a t i o n AFS) o f CRREL a t Fa i r b a n k s , A l a sk a .


2/16

TEST INSTALLATION

S i t e C o n d i t i o n s

The A l ask a F i e l d S t a t i o n

i s

l o c a t e d a b ou t 2 . 5

m i l e s n o r t h e a s t o f t h e c i t y of F a i r ba n k s , A l as k a. F a i r ba n k s

h a s

a

c o n t i n e n t a l c l i m a t e , s h e l t e r e d from m ar it im e i n f l u e n c e s

by va ri o us Alaskan mountain ra ng es . The mean an nu al

t e m p e r a t u r e i s 25.E°Fwith ex tre me s of 93 t o -66OF. The

mean f r e e z i n g and thawing in di ce s a r e about 5300 and 3200

d e g r e e d a y s , r e s p e c t i v e l y . Average a n nu a l p r e c i p i t a t i o n

i s a b o u t 1 2 i n . o f w a t e r an d w a t e r e q u i v a l en t i n c l u d i n g a

mean annu al sno wf al l of about 40 in .

The heave fo r ce measurement s i n s t a l l a t i o n was

i n s t a l l e d i n P i l e S i t e a t AFS ( Fi gu re

1 .

This p i l e s i t e ,

approx ima te ly 100

x

200 f t i n s i z e , was o r i g i n a l l y c l e a r e d

o f a l l t r e e s , b ru sh , and s u r f a c e o rg an ic m a t e r i a l i n t h e

s pr in g o f 1950 . I n t h e summer o f 1952, 32 t e s t p i l e s were

i n s t a l l e d i n t h e a r e a and l a t e r t e s t e d i n e x t ra c t i o n and i n

l o a d - se t t l e m e n t ( R e f e r e n c e 1 .

S o i l co nd i t io ns a t t h e f i e l d s t a t i o n , i n g en e ra l ,

c o n s i s t o f o r g a n i c a nd i n o rg a n i c s i l t s w it h p e at l a y e r s t o

d e p t h s o f 75 t o 1 25

f t ,

wi t h s a n d s a n d g r a v e l s e n c o u n t e r e d

b e l o w t h e s i l t and e x t en d i n g t o s c h i s t b ed ro ck a t a bo ut

250

f t .

Fi g u r e 2 shows t h e b o r i n g l o g s , wa t e r c o n t e n t , and

d r y u n i t w e ig h t o f t h e m a t e r i a l i n t h e s e a s o n a l thaw zon e

a t

two l o c a t i o n s a t t h e t e s t s i t e of t h e t e s t i n s t a l l a t i o n .

S o i l d e s c r i p t i o n s a r e i n a c co rd an ce w it h t h e method o f

d e s c r i b i n g a nd c l a s s i f y i n g f r o z e n s o i l s d ev el op ed by

CRREL

and th e Na t io na l Resea rch Counc i l o f Canada (Refe renc es 10 ,

a n d 1 2 ) .

Heave Force Measurement Devices

I n t h e summer o f 1 9 62 , two he av e f o r c e t e s t p i l e s

were i n s t a l l e d i n P i l e S i t e

a t

AFS. The i n s t a l l a t i o n

i n c lu d e d r e s t r a i n e d h eave t e s t p i l e s o f c r eo s ot ed t i mb e r

and 8 i n . d i am e te r s t e e l p i pe and a l s o of i d e n t i c a l l y i n s t a l -

l e d b u t u n r e s t r a i n e d ( o r dummy) p i l e s , t h a t w ere a l lo w ed t o

move upward wi th t h e heaving ground ( Fig ur e 3 ) . The heave

f o r c e t e s t d e v ic e s c o ns i s te d of t h e t e s t p i l e s o f c r eo s ot e d

t i m b e r a n d s t e e l p i p e and 25 f t a n c h or p i l e s . The a n c h or

p i l e s were made f rom se c t io ns o f 6WF25 s t e e l se c t io ns and

8

i n . s t e e l p ip e f o r t h e t i mb er and p ip e t e s t p i l e s r e -

s p e c t i v e l y . The t e s t p i l e s e x te nd ed t o a d ep th of 6 . 5 f t ,

w hi ch a t t h e t i m e of i n s t a l l a t i o n was t h e a ssumed d e p t h o f


3/16

t h e s e a s o n a l thaw l a y e r , a nd t h e an ch or p i l e s e x te n de d

25 f t i n t o pe rm af ro st d i r e c t l y below t h e t e s t p i l e s

F i g u r e 3 ) .

F ou r i n . s t e e l r o ds e xt en de d t hr ou gh t h e f u l l

l e n g t h of t h e t e s t p i l e s t o t r a n s f e r t h e h ea ve t h r u s t t o

t h e an c h or p i l e s . I n t h e t i mb er p i l e i n s t a l l a t i o n , t h e

r o ds were welded t o t h e a n ch or p i l e . I n t h e p ip e p i l e

i n s t a l l a t i o n , t h e r o d s were h e l d by n u t s b e a r i n g on a

1 /2 i n . p l a t e w elded t o t h e i n s i d e o f t h e a nc ho r p i l e .

P r ov in g r i n g s were p l a c e d a t t h e t o p s o f t h e a s s e m b l i e s

b et we en two 1 /2 i n . t h i c k p l a t e s , a nd t h e t o p p l a t e s were

r e s t r a i n e d by n u t s on t h e i n . d i a m e te r r o d s . The j o i n t

be twe en t h e 8 i n . t e s t p i p e a nd an c ho r p i l e s was s e a l e d w i t h

a

r u b b e r g as k e t t o p r e ve n t t h e e n t r a n c e o f g ro und w a t e r o r

s l u r r y . Each a s se m bl y was p r e- a ss e mb l ed a nd i n s t a l l e d a s

a u n i t i n t o 1 8 i n . d i a me t er d ry a ug er ed h o l e s and b a c k f i l l e d

w i t h

s i l t

s l u r r y .

I n s t r u m e n t a t i o n

To r e c o r d g r o u n d t e m p e r a t u r e a n d t h e a d v a n c e o f

f r e e z e a n d t ha w t h r o u g h t h e s e a s o n a l th aw z o n e , t h e rm o -

c o u p l e a s s e m b l i e s we re a t t a c h e d t o e a c h t e s t a n d dummy p i l e ;

t h e t h e r m o c o u pl e s w er e s p a c e d

a t

6 i n . i n t e r v a l s f rom t h e

g ro un d s u r f a c e t o a d e p th o f 6 . 0 f t . A d d i t io n a l a s s e mb l i e s

were f a s t e ne d t o , and i n s t a l l e d w i t h , t h e an ch or p i l e s ,

w i t h t h er mo c ou p le s l o c a t e d a t 6 . 0 , 8 . 0 , 1 0 . 0 , 1 5 . 0 , 2 0 . 0,

25 .0 and 31.0

f t

d e p t h s .

V e r t i c a l movement s o f each t e s t and dummy p i l e

w e r e m o n i t o r e d by t h r e e e x t e n s o m e t e r - t y p e d i a l g a u g e s m ou nt ed

o n i n s t r u m e n t a t i o n beams F i g u r e 3 a nd p o s i t i o n e d 120

d e g r e e s a p a r t ar o un d t h e p i l e . The i n s t r u m e n t a t i o n beams

w er e s up p o r t e d by 4 . 5 i n . d i a m e te r p i p e p i l e s d r i v e n t o

a p p r o x i m a t e l y f t b el ow t h e g r o un d s u r f a c e w i t h

7

i n . ,

d i a m e te r p i p e u s ed a s c a s i n g t h r ou g h t h e a c t i v e l a y e r . The

a n n u l a r s p a ce be tw ee n t h e c a s i n g an d p i l e s was f i l l e d w i t h

o i l t o p re v e nt h e av in g o f t h e i n s t r um e n t a t i o n s u p p o r t s .

P ro vi ng r i n g s were i n s t a l l e d above e ac h t e s t p i l e

t o r e c o rd t h e hea ve t h r u s t d u r i n g t h e f r e e z i n g s ea so n .

6 0, 00 0 l b c a p a c i t y p r ov i n g r i n g

was

u s ed i n t h e p i p e p i l e

i n s t a l l a t i o n a nd

a

50,000 l b c a p a c i t y r i n g i n t h e t i m b e r

p i l e i n s t a l l a t i o n . Both p r ov i ng r i n g s were p r o t e c t e d by an

i n s u l a t e d e n c l o s u re , h e a t e d w i t h two t h e r m o s t a t i c a l l y

c o n t r o l l e d 100 watt e l e c t r i c l i g h t b ul bs t o m ai n t a i n t h e

t e m p e r a t u r e

a t

65OF Figure

4 .


4/16

s h e

The e n t i r e t e s t a r e a

was

l t e r t o f a c i l i t a t e maximum f r o s

by

a

wood frame

t

p e n e t r a t i o n by p r e v e nt -

i n g t h e a c c u m u l a t i on o f snow an d t o s h i e l d t h e i n s t r u me n t a -

t i o n f r om s u n l i g h t a nd s n o w f a l l whi ch c o u ld c a u s e d e f l e c t i o n s

o f t h e i n s t r u m e n t a t i o n b ea ms.

TEST PROCEDURE AND RESULTS

Ground and i r Tem pera tu res

l l t h e rm o c ou p l e a s s e m b l i e s we re o b s e r v e d t wo o r

t h r e e t i m e s w ee kl y f r om t h e

l a s t

week of October 1962

t h r o u g h J u n e 19 6 3 . T e m p e r a tu r e s w er e r e c o r d e d w i t h

a

p o r t -

a b l e p r e c i s i o n m i l l i v o l t p o te n t i o me t e r ha vi ng a n i c e b a t h

r e f e r e n c e j u n c t i o n . The g ro un d t e m p e ra t u r e i s o t h e r m s f o r

e a c h h ea ve t e s t p i l e , b as ed on t em p er a t ur e o b s e r v a t i on s

f ro m t h e t e s t p i l e a s s em b li e s , a r e p l o t t e d o n F i g ur e s 5 and

6 which a r e c om po si te p l o t s o f t h e r e s u l t s o f t h e two t e s t

i n s t a l l a t i o n s . The d ep t h t o p er ma fr os t

was

a ssu me d t o b e

a p p r o x i m a t e l y 6 . 5 f t . The 32OF i s o t h e r m d i d n o t p e n e t r a t e

t o t h a t d e p t h u n t i l mi d-F eb ru ar y

a t

t h e pi pe p i l e a nd l a t e

F eb ru ar y a t t h e t i mb e r p i l e . The s l i g h t d i f f e re n c e i n .

p e n e t r a t i o n c ou ld be be ca us e s t e e l

i s

a b e t t e r c o n du c to r o f

h e a t t h a n t i m b e r a nd c o l d

a i r

would n a t u r a l l y f lo w t o t h e

b ot to m o f t h e p i p e p i l e .

D a i l y a i r t e mp e r a t u re o b s e r v a t i o n s we re made a t

t h e t e s t s i t e a nd t h e mean

a i r

t e mp e ra t u re s a r e p l o t t e d on

F i @ r e s 5 a n d 6 . The mean

a i r

t em pera tu re d ropped be low

32 F i n m id O c tob er and r em ained below 32OF u n t i l mid A p r i l .

The t e m p e r a t u r e f l u c t u a t e d g r e a t l y d u r i n g t h e w i n t e r a nd

t h e l o w e s t t e m p e r a t u r e s we re o b s e r ve d i n e a r l y J a n u ar y .

The ave rage

a i r

t e m p e r a t u r e s i n J an u a r y we re t h e w ar mes t i n

2 6

y e a r s .

V e r t i c a l M o v e m e n t s

V e r t i c a l movement ob se rv a t io ns w ere made on bo th

t e s t p i l e s t w i ce d a i l y t h ro ug ho ut t h e f r e e z i n g se as on .

C on t in u ou s p l o t s o f t h e v e r t i c a l movement o f e a c h p i l e a r e

show n on F igures

5

and 6. V e r t i c a l movement of t h e dummy

p i l e s i n c r e a s e d d u r i n g t h e f r ee z eb a ck of t h e s e a s o n a l thaw

z on e an d t h e n c o n t i n u e d s l i g h t l y a f t e r co mp le te f r e e z eb a c k .

T o t a l he a v e a mou nte d t o 4.1 0 i n . a nd 4 .1 5 i n . f o r t h e

s t e e l a n d t i m b e r dummy p i l e s , r e s p e c t i v e l y . V e r t i c a l move-

ment o f t h e t e s t p i l e s , r e s t r a i n e d by t h e p ro v in g r i n g s and

r e a c t i o n d e v i c es ,

was

a maximum o f 0 . 7 i n c h e s f o r t h e s t e e l

p i l e a nd 0 . 3 i n c h es f o r t h e t i m be r p i l e .


5/16

Heave Force Measurements

P r o v in g r i n g r e a d i n g s w er e made t w i c e d a l l y a t

a p p r o x i m a t e l y t h e s ame t i m e e a c h m o rn i ng a nd a f t e r n o o n

f r o m t h e s t a r t o f t h e f r e e z i n g s e a so n u n t i l J u ne 19 63 . The

a v e r ge s o f t h e d a i l y he av e f o r c e m ea su re me nt s a r e p l o t t e d

o n F i g u r e s a nd 6 . The m e a s ur a b le h e av e f o r c e s t a r t e d

a f t e r t h e 32OF i s o t h e r m h ad p e n e t r a t e d a p p r ox i m a te l y 1 2 i n .

The maximum heave f o r c e oc cu rr ed when t h e 32OF is ot he rm had

p e n e t r a t e d be tw ee n 90 a nd 10 0 o f t h e s e a s o n a l t ha w z on e

a nd t h e n f l u c t u a t e d t h r o u gh o u t t h e r e ma i nd e r o f t h e w i n t e r

i n r es p on s e t o t h e f l u c t u a t i o n o f a i r ( gr ou nd ) t e mp e ra t ur e s .

DISCUSSION OF RESULTS

The r e s u l t s i n d i c a t e a s l i g h t l a g be tween t h e

p e n e t r a t i o n o f t h e 32OF i s o t h e r m an d t h e s t a r t o f m e a s u r a b l e

p i l e h ea ve f o r c e . F a c to r s ca u s in g t h i s s l i g h t l a g c ou ld

b e t h e weakness o f t h e a d f r e e z e bond d u r i n g t h e i n i t i a l

f r ee z eb a ck of t h e g round s u r f a c e , t h e f r i c t i o n a l r e s i s t a n c e

of t h e u nf r oz e n s o i l b e ne a th t h e f r o s t , a nd t h e f r e e z i n g

p o i n t d e p r e s s i o n . B ec au se o f t h i s f r e e z i n g p o i n t d ep r es -

s i o n an d t h e e r r o r f a c t o r i n th er mo co up le o b s e r v a t i o n s , t h e

a c t u a l f r o s t l i n e p e n e t r a t i o n p ro ba bl y l a g s be hi nd t h e

p e n e t r a t i o n o f t h e 32OF i s o t h e r m .

Hea ve o f t h e dummy p i l e s a n d t h e h ea v e f o r c e

i n c r e a s e d c o n s i de r a bl y d u r i n g t h e f r e e z e ba c k of t h e s e a s o n a l

t ha w l a y e r . G r a d u a l h e a v e o f t h e dummy p i l e s c o n t i n u e d

t hr ou gh ou t t h e w i n t e r u n t i l s u r f a c e t ha wi ng s t a r t e d i n t h e

s p r i n g . The a r e a s u r ro u n d in g t h e t e s t s i t e had a n u n d i st u r b ed

snow c ov e r i n c o n t r a s t t o t h e s h e l t e r e d a r e a a t t h e t e s t

p i l e s an d would h av e a sh a l l ow f r o s t p e n e t r a t i o n . T h i s

g r a d u a l h e a v i n g t h r ou g h o u t t h e w i n t e r s a t t r i b u t e d t o i c e

l e n s e s f or me d by t h e m i g r a t i o n o f w a t e r f r o m t h e s u r r ou n d -

i n g s o i l . He av in g t h ro u gh o ut t h e w i n t e r ,

a t

a d i m i n i s h i n g

r a t e , would a l s o o c c ur i n n on -p er ma fr os t a r e a s o r a r e a s

h a v i n g a d e ep a c t i v e l a y e r wh er e co m pl e te f r e e z e b a c k d o e s

n o t o c c u r e a ch y e a r .

Maximum h e av e f o r c e s o f 5 5, 80 0 l b f o r t h e s t e e l

p i p e a nd 3 5,6 00 l b f o r t h e c r e o s o t e d t i m b e r p i l e o c c u r r e d

when f r e e z e b a c k o f t h e a c t i v e l a y e r was b et we en 90 a n d 10 0

c o m p le t e . D u ri n g t h e re m a i nd e r o f t h e w i n t e r s e a s o n ,

d i s t i n c t f l u c t u a t i o n s i n h ea ve f o r c e were ob se rv ed . The

p e ak s o r maximum p o i n t s o f t h e s e f l u c t u a t T o n s o c c u r r e d

s h o r t l y a f t e r

a

d e cr e a s e i n a i r a n d g r o u n d t e m p e r a t u r e .


6/16

The low p o i n t s a p p ea r e d j u s t a f t e r warming t r e n d s i n t h e

a i r

t e m p e r a t u r e a nd ha d

a

d i s t i n c t t im e l a g w i t h de p t h , a s

o b se rv e d d u r i n g t h e c o o l i n g p e r i o ds . S i m i l a r f l u c t u a t i o n s

h a ve b e e n o b s er v ed by J a p a n e s e i n v e s t i g a t o r s R e fe r e nc e 1 3 )

a nd t h e d e c r e a s e i n he av e f o r c e was i n f e r r e d t o be

a

r e l a x a t i o n phenomenon. The r a t e o f a d va n ce o f t h e f r e e z i n g

f r o n t wo ul d b e l o w e r d u r i n g t h e wa rme r p e r i o d s a n d he a v e

f o r c e d e c r e a s e s when s o i l h ea ve d e c r e a s e s . D ur i ng p e r i o d s

o f h i g h e r s u r f a c e t e mp e ra t u re s , t h e r e l a x a t i o n r a t e o f t h e

s o i l i m me di a te ly s u r r o u n d i n g t h e p i l e m ight e xc ee d t h e

h ea ve r a t e a nd t h e f r o s t t h r u s t c o ul d b e r e d uc e d .

C re ep o f t h e a n ch or p i l e s i s a f a c t o r i n t h e

d e c r e a s e i n h ea v e f o r c e . P e r ma f ro s t t e m p e ra t u r e s a l o n g

t h e e n t i r e l e n g t h o f t h e a nc ho r p i l e s were r e l a t i v e l y h i g h

and m a rg in a l 31 . 0 31 . 5O F) .

t

t h e s e h i g h t e m p e r a t u r e s ,

t s

c o n s i d e r e d p o s s i b l e f o r p r o g r e s s i v e movement o f t h e

a n c ho r p i l e s t o o c c ur e s p e c i a l l y u n de r t h e h ig h l o a d s

i n d i c a t e d on t h e p r o v in g r i n g s .

l o a d o f 5 5 , 0 00 l b s on

t h e

8

i n . p i p e p i l e i n s t a l l a t i o n r e p r e s e n t s a n av er ag e u n i t

s t r e s s of a p p ro x i ma t el y

7

p s i on t h e 2 5 f t a n ch o r p i l e .

P i l e i n v e s t i g a t i o n s c on du ct ed i n p e rm a fr o s t i n d i c a t e move-

m en t s c o u l d o c c u r u n d e r su c h t e m p e r a t u r e a nd l o a d c o n d i t i o n s

R e f e r e n c e 5 . Movement o f t he ancho r p i l e s i s i n d i c a t e d

by t h e f a c t t h a t t h e r e

was

permanent movement of bo th t e s t

p i l e s

a t

t h e e nd o f t h e t e s t . Had no c r e e p o f t h e an c h or

p i l e s o c c u r r e d , a l l o f t h e v e r t i c a l movement s h ou l d h av e

b ee n p ro du ce d s o l e l y by t h e d e f l e c t i o n o f t h e p r o v i n g r i n g s

and t h e e l a s t i c e l on g a t i on o f t h e s t e e l r od s a nd p i l e s ,

i . e . , 0 . 0 4 i n . f o r

a

1 0, 00 0 l b l o a d . The f a c t t h a t a p p ro x i -

m a t e l y 0 . 5 i n . o f p er ma ne nt movement o f t h e s t e e l p i p e p i l e

a nd 0 . 2 i n . movement o f t h e t i m b e r p i l e r em ai ne d a t t h e e nd

of t h e t e s t i n d i c a t e d

t h a t

some movement of the anchor

p i l e s ha d oc cu r r ed d u r i n g t h e t e s t s .

CONCLUSIONS

Tne r e s u l t s o f t h i s f i e l d i n v e s t i g a t i o n i n d i c a t e

t h a t h e av i ng f o r c e s g e n e ra t ed on p i l i n g o f t h e s i z e s and

t y p e s t e s t e d d u r i n g t h e se a so n a l f r e e z i n g o f t h e f r o s t

s u s c e p t i b l e s o i l s may r e a ch o r e v en s u r p a s s 50,0 00 l b f o r

t h e s e m ov em en ts . U nd er n o rm al f i e l d c o n d i t i o n s , s u c h up-

l i f t f o r c e s c o u l d ex ce ed t h e sum o f t h e u l t i m a t e a n ch o r in g

c a p a c i t y o f t h e p e r m a f r o s t embedment a n d t h e i mp os ed p i l e

l o a d , r e s u l t i n g i n a n upward a n n u a l d i s p l a c e m e n t . Maximum

r a t e o f h ea ve o c c u r s d u r in g t h e e a r l y w i n t er months , a t

r e l a t i v e l y s h a l l o w d e p t h s , a nd t h e maximum h e av e f o r c e o n


7/16

p i l i n g o c c ur s d u r in g p e r i o ds o f a c t i v e f r o s t p e n e t r a t i on

wi th ve r y c o ld ne a r - s u r fa c e g round t e mp e r a t u r e s . Maximum

o r n e a r maximum h ea ve f o r c e s c a n b e pr o du ce d a t r e l a t i v e l y

s h a l l o w d e p t h s

3

f t ) o r

a t

g r e a t e r d e pt h s more t h a n f t )

u nd er t h e s e c o n d i t i o n s .

A lt ho ug h t h i s i n v e s t i g a t i o n was c on du ct ed i n

a

p e r m a fr o s t a r e a ,

t

may b e as su me d t h a t h e av e f o r c e s i n

t h e same o r d e r o f m a gn it u de c a n b e p r o du c ed i n t e m p e r a t e

r e g i o ns b ec au se o f f r o s t a c t i o n u nd er s i m i l a r s o i l and

m o i s t u r e c o n d i t i o n s n e a r t h e g ro un d s u r f a c e . Based on t h e

l a r g e r he av e f o r c e r e g i s t e r e d on t h e p ip e p i l e s ,

t i s

con-

c lu de d t h a t t h e e f f e c t i v e u n i t a d f r ee z e bond o f t h e a c t i v e

l a y e r i s d ep en de nt on s u r f a c e c o n d i t i o n s a s w e l l as on

s u r f a c e a r e a . Maximum a v e r a ge u n i t a d f r e e z e t a n g e n t i a l )

s t r e s s d ev el op ed on t h e s t e e l p i p e p i l e F i gu r e

7 )

was

a p p r o x i m a t e l y 4 1 p s i as o pp os ed t o 1 2 p s i o n t h e c r e o s o t e d

t i m b e r p i l e . S i m i l a r c o n cl u s i o ns h av e b ee n r e ac he d i n p i l e

l o a d s e t t l e m e n t

t e s t s

c o nd u ct e d i n p e r m a f ro s t R e f e r e n c e

5 ) .

Based on th e r e s u l t s o f t h i s f i e l d i n v e s t i g a t i o n

and p r e l i m i n a r y l a b o r a t o r y s t u d i e s c on du ct ed i n t h e c o l d

rooms, a n i n v e s t i g a t i o n s now be i n g made u s i n g s i m i l a r

f i e l d i n s t a l l a t i o n s t o i n v e s t i g a t e t h e e f f e c t i v e n e s s o f

v a r i o us p i l e s u r f a c e and b a c k f i l l t r e a t me n t s i n r ed u ci n g

t h e h ea ve t h r u s t on p i l e s a nd p ow er po l es . P r e l i m i na r y

r e s u l t s i n d i c a t e t h a t t may b e p o s s i b l e t o r e du c e t h e

h ea ve t h r u s t t o t o l e r a b l e m a gn it u de s w i t h o u t c om p l et e ly

i n s u l a t i n g t h e t o p t o

6

f t o f t h e p i l e w it h c a s i n g s o r

s l e e v e s , a p r oc ed ur e t h a t r e du ce s t h e l a t e r a l s t a b i l i t y o f

t h e p i l e .

ACKNOWLEDGMENTS

T hi s i n v e s t i g a t i o n

s

p a r t o f a s t u dy b ei n g

conduc ted a t USA CRREL f o r th e Of f i c e , Chie f o f En gi nee rs ,

D i r e c t o r a t e o f M i l i t a r y C o ns t ru c t i o n . S u b s t a n t i a l s u pp o r t

was f u r n i s h e d by p e r s o nn e l o f t h e A la sk a F i e l d S t a t i o n ,

USA CRREL, un de r t h e di r e c t i o n of

M r

F . F . K i t z e .


8/16

REFERENCES

1. U.S. Army Corps of Engineers, Pile Extraction Tests,

Fairbanks Research Area , ACFEL TR-59, Status Report

No. 1 and 2, June 1955.

2. Linell, K.A., Interim Report, on Load Tests of Piles

in Permafrost , ACFEL Technical Report 58, June 1955

3.

U.S. Army Corps of Engineers, Freezeback Control and

Pile Testing, Kotzebue Air Force Station, Alaska ,

Technical Report 66 (Draft) ACFEL, New England Division,

Corps of Engineers, May 1957.

4. Freezeback Control and Pile Testing, Bethel Air Force

Station, Alaska , USA CRREL Technical Report 143

(In preparation).

5. Crory, F.E., Installation and Testing of Piles in

Permafrost Pile Site C , USA CRREL Technical Report 140

(In preparation).

6.

U.S. Army Corps of Engineers, Arctic and Subarctic

Construction, Building Foundations , Engineering Manual

for Military Construction (Manual Corps of Engineers

EM 1110-395-374

.

7.

MJller, S.W., Permafrost or Permanently Frozen Ground

and Related Engineering Problems : 1st Ed., U.S. Geol.

Survey Spec. Report Strategic Eng. Study 62, 1943;

2nd Ed., U.S. Army Military Intelligence Div., Office

Chief Engineer,

1945.

8

Pewe, T.L. and R.A. Paige, Frost Heaving of Piles with

an Example from Fairbanks, Alaska , Geological Survey

Bulletin, 111-1, Washington, 1963.

9. Crory, F.E. and R.E. Reed, Measurement of Frost Heaving

Forces on Piles , USA CRREL Technical Report 145

(In preparation).

10

Linell, K.A. and C.W. Xaplar, Description and Classi-

fication of Frozen Soils , Proceedings of International

Conference on Permafrost, Purdue University, Nov. 1963.

11. U.S. Army Corps of Engineers, Engineering and Design,

Arctic and Subarctic Construction, Site

Selection and

Development (Manual Corps of Engineers EM 1110-345-371).


9/16

P i h l a i n e n ,

J . A .

and

G . H .

J o h n st o n , Guide t o a F i e l d

D e s c r i p t i o n o f P e r m af r o s t f o r E n g i n ee r i n g P u rp o se s ,

Tech. Mem. 79, N at io na l Rese arc h Cou nc i l ,

NRC

7576,

O c t . 1963 .

K i n o s h i t a , S. and T Ono, H eave Forc e o f F rozen So i l ,

Low Tem pera tu re Sc ie nc e , Se r . A Vol. 21, p. 117-139,

1 9 63 (T ex t i n J a p a n e s e ) .

D i s c u s s i o n

J . A .

Ellwo od a s ke d how t h e p i l e s a r e i s o l a t e d

f ro m t h e s o i l t o r e d u c e movements. The a u t h o r r e p l i e d

t h a t CRREL

i s

e x p e ri m e nt i n g wi t h s u r f a c e t r e a t m e n t s a nd

b a c k f i l l i n g w i t h t r e a t e d m a t e r i a l s . C o at i ng s , a p p l i e d by

b r u s h o r s p r a y i n g , w hi ch i n c l u d e e po xy a nd e na me l p a i n t ,

h a v e r e d u c e d t h e a d f r e e z i n g b on d by a s much a s 20 p e r c e n t .

C . A . No bl e a s k e d f o r i n f o r m a t i o n on t h e m a gn i tu d e

o f movement i n t h e a nc h o r p i l e s y st e m . Reed r e p l i e d t h a t

t h e t o t a l movement u n d e r 5 5 ,0 0 0 l b s . o f l o a d was a b o u t

2/10 i n c h . Be ca use o f c r e e p a c t i o n o f t h e a n ch o r p i l e

s y s t e m , t h i s m i gh t n o t b e t h e maximum mo veme nt. I n e a r l i e r

t e s t s t h e maximum f o r c e s w er e 2 5, 00 0 l b s h a l f o f t h e

p r e s e n t t e s t .


10/16


11/16

WATER CONTENT DRY UN IT WEIG HT

PERCENT OF

WV

WElOHT PCP

0

SOILS EXPLORATION MIDWAY BETWEEN 8 P IP E TEST AND DUMMY PI LE S

BORING LOG

23 MAy'61

EL.472.7

Thowd organic SlLT

Dark

W o r n SlLT

1.0 ThW.4

Oh.

brown, orgonle

SILT

k - ~ b l Fmmn

WATER CONTENT DRY UN IT WEIGH1

PERCENT OF ORY WEIQHT PCF

mWd

y driving

l Shllby Tub*

- /Jock

Hommw.

b.

SOILS EXPLORATION MIDWAY BETWEEN TIMBER TEST AND DUMMY PILES

F I G U R E B O R I N G L O G S N D S O I L D T

8a 9 4 J I / 6


12/16

F I G U R E

P L N N D E L E V T I O N V I E W O F T E S T I N S T L L T I O N


13/16

F I G U R E

V I E W O F I N S U L

P R O V I N G R I N G

T E D E N C L O S U R E R O U N D

a 459 2


14/16

F I G U R E 5

z

f

y

g

6

T E S T O B S E R V A T I O N S

8

S T E E L P I P E P I L E

OR

3 C f V Z l

2

4

ASSUMED

R

i

TABLE J U L Y

1962


15/16

F I G U R E 6

a

0

a

o=

6

S

k&

X V

T E S T O B S E R V T I O N S C R E O S O T E D T I M B E R P I

m

3 4 - 5 9 - 2 2

2

4

ASSUMED R E TABLE JULY

I9621


16/16

F I G U R E

A V E R A G E A D F R E E Z E B O N D S T R E S S V S

T IM

frost thrust measurements on piles

Documents