A Note on Planar Shear Vetween Geosynthetics and Construction Materials

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Geotextiles and G eomem branes

5 (1987) 63-67

T e c h n i c a l N o t e

N o t e o n P l an a r S h e a r B e t w e e n G e o sy n t h e ti c s a n d

C o n s t r u c t i o n M a t er ia l s

A B S T R A C T

The inf luence of di f ferent surface roughnesses on interracial shear between

geo synth etics an d variou s construction materials is discussed Interracial

shear s t rength data for d i f fe ren t combinat ions o f mater ia ls are g iven

De rivatio ns o f interfacial shea r strength fro m me re characteristic values o f

ma ter ia l are on ly poss ib le to a l imi ted exten t Larger pro jec ts dem an d

in si tu

tests to determine interfacial shear strengths at the expected operational

no rm al s t ress leve ls

1 I N T R O D U C T I O N

T h e i n c r e a s in g u s e o f g e o m e m b r a n e s a n d g e o te x t il e s in h y d r a u l ic s t r u c tu r e s ,

s u c h a s r e v e t m e n t s , i n t ro d u c e s t h e n e e d t o i n ve s ti g at e th e s h e a r b e h a v i o u r

a t t h e i n t e r f a c e o f g e o s y n t h e t i c s a n d o t h e r c o n s t r u c t i o n m a t e r i a ls . S h e a r

t es ts p e r f o r m e d o n b e h a l f o f t h e V E B S p e z i a l b a u k o m b i na t W a s s e r b a u h a v e

p r o d u c e d a s e ri e s o f in t e r e s t in g r es u lt s a n d l e d t o th e d e v e l o p m e n t o f a n e w

s h e a r a p p a r a t u s d e s c r i b e d e ls e w h e r e .~ I n t h e t es t p r o g r a m 1.5 m m t h i c k

P V C o r P E ( p o l y e t h y le n e ) f i lm w a s u se d to m o d e l g e o m e m b r a n e s a n d t h e i r

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

i n c l u d i n g g e o te x t il e s . A r a n g e o f n o n - w o v e n g e o te x t il e s w e r e e m p l o y e d

w i t h v a r i o u s t h i c k n e s se s a n d m a s s p e r u n it a r e a a n d a b r i e f s u m m a r y s

p r e s e n t e d f o r t h e r a n g e o f re s ul ts o b t a in e d .

2 T H E O R E T I C A L A S P E C T S

I n b r o a d t e r m s t h e c o n t a c t su r f a c e b e t w e e n t h e g e o s y n t h e t ic a n d t h e

c o n s t r u c t i o n m a t e r i a l c a n b e p l a n a r o r u n d u l a t in g , a s s h o w n i n Fi g. 1.2,3 F o r

63

Geotextiles and Geomem branes

0266-1144/87/ 03.50 © Elsev ier Ap plied Sc ience Pub lishers

Ltd , E ngland, 1987. Printed in Great Britain

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64 Werner Weiss Christoph Batereau

~ ~ ~ . -4-

F i g 1 I n t e r l o c k i n g a t t h e i n te r f a c e b e t w e e n g e o s y n t h e t i c s a n d o t h e r c o n s t r u c t i o n m a t e r i a ls

c o n s t r u c t i o n m a t e r i a l s s u c h a s p r e - c a s t c o n c r e t e b l o c k s s e r r a t i o n s o r

t o o t h i n g c a n b e i n t r o d u c e d t o p r o d u c e m e c h a n i c a l i n te r lo c k i n g . D e p e n d i n g

o n t h e n a t u r e o f th e c o n t a c t s u rf a ce t h e r e m a y b e

( i) f r ic t i o n w i t h o u t d e f o r m i n g o r d e s t ro y i n g th e s u r f a c e s o f t h e m a t e r i a ls ;

( i i ) f r i c t i o n w i t h p a r t i a l o r c o m p l e t e d e s t r u c t i o n o f t h e s u r f a c e o f t h e

m a t e r i a l s .

C l e a r l y , i n a g i v e n s i t u a ti o n , t h e s h e a r s t r e n g t h o f t h e i n t e r f a c e w il l i n c r e a s e

a s t h e d e g r e e o f t o o t h i n g o r i n t e r lo c k i n g i n cr e as e s. T h e n u m b e r o f v ar ia b l e s

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

s h e a r s t r e n g t h e s t a b l i s h e d b y t es t w i ll r e f e r t o t h e s p e c if ic m o d e l c a s e o n l y .

T h e e f f e c t s o f s tr e s s l e v e l, s u r fa c e r o u g h n e s s o f p r e f a b r i c a t e d c o n c r e t e s l a bs

a n d t h e g r a d i n g o f n o n - c o h e s i v e so il g r a in s r e sp e c t iv e l y h a v e b e e n c o n -

s i d e r e d e l s e w h e r e . 2 ~ T h e o re ti ca l c o n s i d e r a t i o n s c o n c e r n i n g c a s e l ( b ) , F i g. l ,

a r e r e p o r t e d i n R e f . ( 5) .

P o s s i b l e i n t e r l o c k i n g a t t h e i n t e r f a c e o f g e o s y n t h e t i c s a n d o t h e r c o n -

s t r u c t i o n m a t e r i a l s s te m s f r o m :

( i) u n d u l a t i o n s i n b e d d i n g m a t e r i a l ( F ig . l ( a ) ) ;

( ii ) t o o t h i n g b y c o a r s e c o n t a c t m a t e r i a l o n b o t h s id e s ( F ig . l ( b ) ) ;

( ii i) e m b o ss i n g d u e t o n o r m a l s t re s s ( F ig . l ( c ) ) ;

( i v ) i n t e r l o c k w i t h a n g u l a r f i l l , o r r o u g h c o n c r e t e su r f a c e s , o r s i n g l e

p a r t i c l e s .

3 T E S T I N G P R O C E D U R E A N D R E S U L T S

T e s t i n g t o d e t e r m i n e i n t e rf a c i al s h e a r b e h a v i o u r w a s c a r r i e d o u t u s i n g a

s p e c i a l l y c o n s t r u c t e d f ia t s h e a r d e v i c e 1 w h i c h w a s l o a d ( st re s s ) c o n t r o l l e d .

L o a d i n g w a s a p p l i e d i n tw e n t y in c r e m e n t s u n ti l f a il u re o c c u r r e d . N o r m a l

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T e c h n i c a l n o t e 65

s t r e ss e s i n th e r a n g e 5 k P a t o 50 k P a w e r e e m p l o y e d t o b o t h d r y a n d s a tu r a t e d

s a m p l e s . T h e i n t e r l o c k i n g e f fe c t s s h o w n i n F i g . l a ) a n d b ) w e r e n o t c o n -

s i d e r e d s i n c e t h e g e o s y n t h e t i c s w e r e m o u n t e d i n a p l a n ar s u r fa c e i n t h e s h e a r

a p p a r a t u s . I n p r a c ti c e t h e r e a r e u n d u l a t i o n s i n b e d d i n g a n d f il l m a t e r i a l

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

o b t a i n e d f r o m t h e a b o v e l a b o r a t o r y t e s t i n g . C o n s e q u e n t l y d e s i g n b a s e d o n

t h e s e c h a r a c t e r i s t i c v a l u e s m a y b e c o n s e r v a t i v e . A n o t h e r f a c t o r n o t

a c c o u n t e d f o r in t h e l a b or a to r y t e st s i s c r e e p in th e g e o s y n t h e t i c . H o w e v e r

c r e e p d e t e r m i n a t i o n s a r e l i k e ly t o b e s m a l l a n d ar e t h e r e f o r e n e g l e c t e d .

T a b l e s 1 t o 3 p r e s e n t t h e o b s e r v e d r a n g e o f i n te r r ac i al s h e a r st r e n g t h

v a l u e s o f f r e q u e n t l y u s e d m a t e r ia l c o m b i n a t i o n s . T a b l e 4 d e s c r ib e s t h e

p r o p e r t i e s o f g e o t e x t i l e s u s e d i n t h e t es ts .

F i e l d o b s e r v a t i o n s i n d i c a t e d t h a t s l o p e s w i t h a d e s i g n f a c t o r o f s a f e t y o f

u n i t y , b a s e d o n t h e a b o v e c h a r a c t e r i s t i c c o e f f i c i e n t s , w e r e s t a b l e . T h i s

c o n f i r m s t h e c a s e f o r

n s t u

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

p r e v a i l i n g s h e a r c h a r a c te r i st ic s .

T A B L E 1

C o e f f i c i e n t s o f l n t e r fa c i a l S h e a r Be t w e e n S m o o t h P o l y e t h y l e n e F il m a n d D i f fe r e n t

Cons truct ion Mater ia l s

a t e r i a l in contact w i t h

P I~lm

oefficients o f interracials h e a r

Dry Saturated

G e o t e x t i l es n o n w o v e n ) 0.20 0.25 0.16

Sil t

0.30 0 40

S a n d

0.25 0 45 0.2 0 0.4 0

P r e f a b r i c a t e d c o n c r e t e s la b

0 30 0.40 0.25 0.40

T A B L E 2

C o e f f i c i e n t s o f I n t er r a c ia l S h e a r Be t w e e n S m o o t h P V C F i l m a n d D i f f e r e n t C o n s t r u c t i o n

Mater ia l s

a t er i a l n c o n t a c t with

PV i lm

oefficients o f interfacial shear

Dry S a t u r a t e d

N o n w o v e n

0 30 0.45 0 25 0.45

Sil t 0.35 0.50

S a n d 0 50 0.60 0.40 0.50

P r e f a b r i c a t e d c o n c r e t e s l ab 0 . 5 0 - 1 . 0 0 0 - 5 0 - 1 . 0 0

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66 W erner Weiss , Chr i s toph Ba tereau

T A B L E 3

Coef f i c ien t s o f In t e r rac i a l Shear Be tween Non-w oven Geo tex t il e s and Di f f e ren t

Con st ruct ion Mater ia ls

M aterial in contac t wi th Coef f ic ients o f in terracial shea r

no n-w ove n geo tex t il e sa turated)

0.27--0-40

o n - w o v e n g e o t e x ti le

(dep ends on k ind of fi b res )

P re fab r i ca t ed concre t e s l ab

S m o o t h

R o u g h

No n-co hesiv e soi l (d~ = 63/~m)

d~o = 0 .2 -2 .0 mm

d~o = 2.0-5-0 mm

d~o = 5.0-10.0 mm

0.45-0.60

0-60--0.80

0.70

0.60

0-50

Th e non -coh esive soi l com prises sm ooth rou nded part ic les .

T A B L E

Prope r t ies of Geo text i les Used in the Tests

T h i c k n e s s a P o r e d i a m e t e r

D e s i g n a ti o n m m ) 0 9 0

turn)

P o l y m e r f i b r e

W T 5 2-7

W T 6 3 .4

P 10 5.2

Te s tm at 1 3 -1

Te s tm at 2 3 .2

Te s tm at 3 3 .2

0-07

0.06

0.25

50 po lyes t e r

50 polyvinyl chlor ide

50 po lyes t e r

50 polyvinyl chlor ide

100 po lyamide

100 po lyamide

100 polyes ter

100 polyvinyl chlor ide

a U nd er a ver t ica l s tress of 20 kN /m 2.

C O N C L U S I O N S

L a b o r a t o r y t e s t s u s i n g p l a n a r g e o s y n t h e t i c s s h e a r e d a g a i n s t v a r io u s

c o n s t r u c t i o n m a t e r i a l s a l l o w t h e f o l lo w i n g c o n c lu s i o n s t o b e d r a w n :

( i ) F r i c t i o n c o e f f i c i e n t s g i v e n i n t h e T a b l e s c a n b e u s e d f o r r o u g h

c a l c u l a t i o n s i n t h e n o r m a l s t r e ss r a n g e o f 5 t o 50 k P a .

( i i ) T h e c o m b i n a t i o n s o f m a t e r i a l s te s t e d in t h e l a b o r a t o r y w e r e o f

l i m i t e d e x t e n t o n l y a n d t h e r e f o r e i n s i t u t e s t s w o u l d b e n e c e s s a r y t o

c o n f i r m i n it ia l d e s i g n a s s u m p t i o n s .

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Technical note

67

ii i )

In s i tu

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

in t h e f i n is h e d w o r k s . E x t r a p o l a t i o n b e y o n d t h e r a n g e o f n o r m a l

s t r e s s e s s h o u l d o n l y b e t o a l i m i t e d e x t e n t . 2

R E F E R E N C E S

I . Ba t e re au , Ch . , Bes t imm ung de r Grenzf l~ i chenscherfest igke it zwi schen

K u n s t s to f f u n d L o c k e r g e s t e in . Bauinformation W issenschaft un d Technik, 25 3)

1982) 27-8.

2 . Ba t e rea u , Ch . , Z u r Norm al spannungsabh /ing igke i t de r Grenzf l / ichenscher -

fes t igkei t . Neue Bergbautechnik, 12 9) 1982) 506-8.

3 . R i c h t e r , H . - C h . , G l e it - u n d S c h e r v e r h a lt e n e b e n e r u n d u n e b e n e r m e c h a n i s c h

w i r k s a m e r T r e n n f l/ ic h e n . Zeitschrift far angewandte Geologie, 18 6) 1972)

258-62.

4 . F o rm az in , J . and B a t e reau , Ch . , Das S cher fes ti gke i t sve rha l t en un t e r sch i ed -

l icher M ater ia l ien a n d er Oberfl~iche von G eotex t i l ien . Pro c. Int . Conf. o f Soil

M echanics an d Foundation Eng ineering, San Francisco, 5 2) 1985) 1773-5.

5 . L y s e n k o , V . P . , Z u r F r a g e d es R e i b u n g sm e c h a n i s m u s n i c h tb i n d ig e r B 6 d e n a u f

p o l y m e r e n D i c h t u n g s b a h n e n v o n E r d b a u w e r k e n . Mittei lungen des VNIIG

Leningrad 1977)

119.

W erner W eiss and Chr i s toph a tereau

H o c h sc h u l e f i ir Arc h i t e k t u r u n d B a u w e se n W e i m a r ,

Kar l -Marz-Pla t z 2 ,

5 3 We i m a r ,

G e r m a n D e m o c r a t ic R e p u b l i c