Astm stp 1190 1993

STP 1190 Geosynthetic Soil Reinforcement Testing Procedures S... Foreword This publication, Geosynthetic SoilReinforcement Testing Procedures, contains papers pre- sented at the sympos

STP 1190

Geosynthetic Soil Reinforcement Testing Procedures

S C Jonathan Cheng, editor

ASTM Publication Code Number (PCN)

04-011900-38

1916 Race Street

Philadelphia, PA 19103

Geosynthetic soil reinforcement testing procedures / S.C Jonathan

Cheng, editor

(STP ; 1190)

Includes bibliographical references and index

ISBN 0-8031-1885-6

i Soil stabilization Testing 2 Geosynthetics Testing

I Cheng, S C Jonathan (Shi-Chieh Jonathan) If Series: ASTM special technical publication ; 1190

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Peer Review Policy Each paper published in this volume was evaluated by three peer reviewers The authors addressed

all of the reviewers' comments to the satisfaction of both the technical editor(s) and the ASTM

Prinled in Fredericklburg, VA August 1993

Foreword

This publication, Geosynthetic SoilReinforcement Testing Procedures, contains papers pre- sented at the symposium of the same name, held in San Antonio, TX on 19 Jan 1993 The symposium was sponsored by ASTM Committee D-35 on Geosynthetics S C Jonathan Cheng o f Drexel University in Philadelphia, PA, presided as symposium chairman and is the editor of the resulting publication

Contents

Overview s c JONATHAN CHENG

A New Device for Evaluating Load-Transfer in Geosynthetic Reinforced Soils

A J WHITTLE, D G L A R S O N , J T GERMAINE, AND M ABRAMENTO

Intrinsic Confined and Unconfined Load-Deformation Properties of Geotextiles

Pull-Oat Testing of Geogrids in Cohesive Soils K A FARRAG AND P GRIFFIN

The Influence of Test Parameters and Procedures on the Tensile Modulus of Still

Geogrids D N AUSTIN, K J WU, A N D D F W H I T E

High Strength Polyester Geotexile Testing and Material Property Evaluation

J N PAULSON

Laboratory Investigations on the Shear Strength of Geogrid Reinforced Soils

D C A Z Z U F F I , L PICARELLI, A RICCIUTI, A N D P RIMOLDI

Evaluation of Shear Strength and Dilatancy Behavior of Reinforced Soil from

Direct Shear Tests G E BAUER AND Y ZHAO

Material Parameters Used in Design of Geosynthetic Reinforced Soil Structures

R R BERG A N D J G COLLIN

Geosynthetic Installation Damage under Two Different Backfill Conditions

G R K O E R N E R , R M K O E R N E R , A N D V ELIAS

Comparison of Short-Term and Long-Term Pullout Testing of Geogrid

Reinforcements J G C O L L I N AND R R BERG

Pullout Resistance and Load-Slip Response of Mechanically Damaged Geogrids

Chemical Stability of Polyester Fibers and Geotextiles Without and Under

Testing for Biological Deterioration of Geosynthetics in Soil Reinforcement and

A Review of the Degradation of Geosynthetic Reinforcing Materials and Various

Polymer Stabilization Methods ',' G HSUAN, R M KOERNER, AND

Overview

This ASTM symposium provides a forum for presentation of state-of-the-art technologies and new developments in geosynthetic soil reinforcement testing The topics addressed include mechanical and durability properties with respect to the reinforcement function of geosynthetics, analysis of reinforcement testing results, and evaluation of testing results in rela- tion to design This symposium was also a result of an ASTM Committee D-35 seminar held

in June 1991, concerning the same topic of geosynthetic soil reinforcement testing

Since the use of geosynthetics in reinforcement applications is rapidly increasing, there is a need to institute a rational technical base for an understanding of the performance ofgeosyn- thetics in reinforcement applications The corner stone of this technical base is the timely development of standardizing test methods, that is the charter of Committee D-35 on Geo- synthetics Although much progress has been witnessed as more testing methods are made available through ASTM processes, there is a significant lag betwen the state-of-the-art and present standardized test methods This symposium attempts to provide a bridge between this time gap

The organization of this Special Technical Publication (STP) is as follows:

(1) Papers associated with either new testing equipment/procedures, or testing procedures for new reinforcement applications are included These papers provide direction in the development of standard testing methods (papers 1 through 5)

(2) Papers evaluating procedures of testing methods that are standardized or widely used are also included The discussions are focused on those factors that influence test results (papers 6 through 10)

(3) The next section of papers are concerned with the analysis of testing results in relation

to design In terms of standard practice, this is an area of need within ASTM (papers 11 through 14)

(4) Finally, papers associated with the durability issue of geosynthetic reinforcement appli- cations conclude this STP (papers 15 through 17)

All of the papers in this STP went through a rigorous review process I would like to extend

my most sincere appreciation to the authors for their enthusiastic participation and to the reviewers for their professional critiques My work as editor of this publication has been very rewarding, but the credit must go to the authors and reviewers In addition, I would like to thank the administrative support group from ASTM, especially Mrs Dorothy Savini, Ms Rita Hippensteel, and Mrs Therese Pravitz

This symposium is a step towards fully understanding the technical performance ofgeosyn- thetics It is my most sincere hope that it will catalyze further research work and technical advancement

Shi-Chieh Cheng

Drexel University, Philadelphia, PA; symposium chairman and editor

vii

2 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

s u r f a c e s , such as g r i d s a n d for g e o s y n t h e t i c m a t e r i a l s w h i c h exhibit

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

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

in a v a r i e t y of l a b o r a t o r y s h e a r t e s t s [~, ~] T h e s e d a t a s h o w t h a t the reinforcelnents p r o d u c e an a p p a r e n t c o h e s i v e s t r e n g t h c o m p o n e n t t h a t is

m a s s w i t h the i n c l u s i o n o r i e n t e d p a r a l l e l to the minor, e x t e r n a l

p r i n c i p a l stress T h e s e s t u d i e s p r o v i d e the b a s i s for the d e s i g n of a

WHITTLE ET AL ON EVALUATING LOAD-TRANSFER 3

plane strain compression mode by increasing the major principal stress,

~I, at the boundary of the element (with ~3 constant) For these loading conditions, the inclusion reduces the lateral tensile strains which would otherwise develop in the soil and hence, represents the optimal orientation for a planar tensile reinforcement Abramento and Whittle [~] have adapted technqiues of 'shear lag' analyses, widely used in the mechanics of composites [~, ~, ~], in order to derive approximate

analytical expressions for the tensile stresses in the reinforcement, G~x Initially these analyses have assumed the following:

i The soil matrix and reinforcement behave as linear, isotropic and elastic materials (with properties Gm, V m and El, vf, respectively, Fig i) It should be noted that deformation properties of the soil (and also some non-woven geosynthetic materials) are dependent on the confining stress level

2 The soil matrix and reinforcing inclusion are linked through a frictional interface, described by an angle of interface friction, 8

3 There is no axial stress acting at the ends of the reinforcement, (i.e ~ x = 0 at x=• as the inclusion is thin and is not physically bonded to the soil matrix

x

FIG 1 Geometry of the reinforced soil element

For the case where there is no slippage at the soil-reinforcement interface, the tensile stress in the reinforcement can be written as a linear function of the external principal stresses sl and ~3:

~ x = ~ I K I ~ i c~ K ~ i c o s h K ~ I ~ I (i) where,

4 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

WHITTLE ET AL ON EVALUATING LOAD-TRANSFER 5

a n d soil, Ef/Gm; a n d 3) the v o l u m e r a t i o of the r e i n f o r c e m e n t , a=f/m

F i g u r e 2 s u m m a r i z e s the ' m a x i m u m l o a d t r a n s f e r ratio', ~ a x / ~ f ~ as

a f u n c t i o n of the i n c l u s i o n h a l f - l e n g t h , L/2, a n d t h e s t i f f n e s s ratio,

Ef/Gm, for an i n c l u s i o n w i t h t y p i c a l t h i c k n e s s , f=imm, a n d spacing,

m = 0 5 m The r e s u l t s show that the ' p i c k - u p length' n e c e s s a r y to a c h i e v e

s t r e s s (i.e., ~fxx ~ ~f~) T h e s e t w o r e g i o n s are f u l l y d e v e l o p e d for

'long' i n c l u s i o n s (e.g., L / 2 = l 5 m ; F i g 3 a ) F o r 'short' i n c l u s i o n s

(L/2=0.25, 0.5m; Fig.3), the m a x i m u m l o a d t r a n s f e r is not a c h i e v e d , a n d

t h e s h e a r lag p a r a m e t e r , K 1 (Eqn 2a) c o n t r o l s t h e d i s t r i b u t i o n of

t e n s i l e s t r e s s e s in zone I

F i g u r e 3b s h o w s t h e l o a d t r a n s f e r for a s h o r t i n c l u s i o n w i t h h a l f -

length, L/2=0.5m, as a f u n c t i o n of t h e a p p l i e d s t r e s s ratio, ~i/~3 in

t h e soil matrix F o r a soil m a t r i x w i t h linear, i s o t r o p i c p r o p e r t i e s ,

t h e r a t i o ~i/~3 = (l-Vm)/Vm = I/K0 (i.e., for V m = 0 3 , I/K0= 2.3; Fig

C o p y r i g h t b y A S T M I n t ' l ( a l l r i g h t s r e s e r v e d ) ; T u e D e c 2 9 0 0 : 5 0 : 1 3 E S T 2 0 1 5

D o w n l o a d e d / p r i n t e d b y

U n i v e r s i t y o f W a s h i n g t o n ( U n i v e r s i t y o f W a s h i n g t o n ) p u r s u a n t t o L i c e n s e A g r e e m e n t N o f u r t h e r r e p r o d u c t i o n s a u t h o r i z e d

WHITTLE ET AL ON EVALUATING LOAD-TRANSFER 7

f a i l u r e w i l l i n i t i a t e in t h e m a t r i x (at l o c a t i o n s c l o s e to the t i p of the i n c l u s i o n ) w h e n the s t r e s s r a t i o m o b i l i z e s t h e f r i c t i o n a l

8 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

Y

, o ~ o , ,

r ' , , ' ' "

i<.i, w , , , , , , i./

, / / 9 - - ' '

9 - - " 9 9 , -

,

I T

~ y y

YmTx 5o m m

.'/.'/,,','.' ' '.,',.' '.,',c,.' ',j ,',/ ',/./,,', " 2 -', 2 ', ' I I ::::::::::::::i:i:::::: S,.a~d :::::::::::::::::::::::1 I, D e f o r m e d

" " ' ' " ' ' ' ' " " ' ' ' ' " ' ' ' " ' ' " " ] h

'-= ' *,',* :,' " ",'::,'::,'.'::-'.'.'.' '.'| t S ape Max, ~ L / 2 ~ : : : ] " i

contains a soil specimen of overall d i m e n s i o n s 570mm high by 450mm wide

by 150mm deep (plane strain direction), w h i c h is e n c l o s e d by a thin

rubber membrane The r e i n f o r c i n g inclusion, with h a l f - l e n g t h up to

L/2=450mm, passes t h r o u g h a slot in the rear wall of the cell a n d is

s u p p o r t e d by jacking against an external support arch T h e e n t r y slot

can be c u s t o m d e s i g n e d for inclusions up to 10mm thick The cell applies

air p r e s s u r e to the outside of the specimen to control the c o n f i n i n g

stress (03 ~ 50kPa), while the m a j o r p r i n c i p a l stress is i m p o s e d t h r o u g h

two l o a d i n g platforms via w a t e r b a g s w h i c h p r o v i d e u n i f o r m b o u n d a r y

tractions The device can impose relatively large axial strains (up to

10%)t which are n e c e s s a r y for i n v e s t i g a t i n g l o a d t r a n s f e r u s i n g

extensible r e i n f o r c e m e n t s [12], while the s p e c i m e n is free to d e f o r m

laterally into the air v o i d at the front of the cell The p l a n e strain

walls of the A P S R cell have an unique active control s y s t e m which

ensures that the lateral strains, s ~0.01% t h r o u g h o u t the test

The following paragraphs summarize the p r i n c i p a l d e s i g n features

of the A P S R cell [ii]:

i The length of the r e i n f o r c i n g inclusion is an i m p o r t a n t factor in

selecting the d i m e n s i o n s for the A P S R cell Shear lag a n a l y s e s show that

m a x i m u m load transfer, c o r r e s p o n d i n g to p r o t o t y p e field conditions can

be achieved for inclusions w i t h half-lengths, L/2=I.D to Z 0 m (cf Fig

2) These dimensions cannot readily be a c h i e v e d in a l a b o r a t o r y test

Instead, the dimensions of the A P S R cell have been s e l e c t e d to handle

c o m m e r c i a l l y available r e i n f o r c i n g m a t e r i a l s including t y p i c a l geogrids

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WHIT rLE ET AL ON EVALUATING LOAD-TRANSFER 9

~-Pistons / Support Arch ~ [ ~ i ~

1

Load Cell

~t@j~~iiiiiiiiiiiiiiiiiiii!iiii!!iliiiiiiiiiiiiiiiit,/ MembraneRUbber

Mechanism -./ ~.!i!i!i!.i.i !.i.!.!.!.!i!iiiiliiii!iii!iii!iii!i!i!.j,

Mailbox Slot - - - " llr"i:~ m -n ~ Key

i Water Bag FIG 5 Section through the A P S R cell

M e a s u r e m e n t s of load transfer o b t a i n e d for inclusions of d i f f e r e n t

lengths then p r o v i d e the basis for e v a l u a t i n g t e n s i l e stresses at

p r o t o t y p e scale

2 The m a g n i t u d e s of the a p p l i e d b o u n d a r y tractions d e t e r m i n e the

structural (strong box) d e s i g n of the A P S R cell The d e v i c e can apply

a m a j o r principal stress, ~I ~ 500kPa (Fig 4) through two w a t e r bags

m o u n t e d on m o v e a b l e rigid platforms U n i f o r m lateral confinement, ~3 ~

50kPa is p r o v i d e d by air p r e s s u r e acting on the rubber m e m b r a n e which

encloses the soil specimen All contact surfaces are l u b r i c a t e d with

a 50-50 m i x t u r e of high v a c u u m silicon g r e a s e and a release agent in

order to m i n i m i z e friction in the system

3 The cell can impose axial strains of up to 10% on the s p e c i m e n which

are sufficient to cause failure of u n r e i n f o r c e d sand specimens a n d

to d e v e l o p m a x i m u m load t r a n s f e r even for relatively e x t e n s i b l e

g e o s y n t h e t i c reinforcements Plane strain conditions are a c h i e v e d

t h r o u g h an active s y s t e m using a p r e s s u r i z e d w a t e r d i a p h r a g m within

the side walls This novel d e s i g n reduces s i g n i f i c a n t l y the size of

the walls that w o u l d o t h e r w i s e be required, a n d enables remote

m e a s u r e m e n t of the d i s p l a c e m e n t s w i t h i n the specimen u s i n g

radiography R a d i o g r a p h i c m e a s u r e m e n t s p r o v i d e a m e t h o d for

e s t a b l i s h i n g t h e u n i f o r m i t y of strains in t h e u n r e i n f o r c e d soil

s p e c i m e n and c a n also m o n i t o r the m e c h a n i s m s of s o i l - r e i n f o r c e m e n t

interaction

4 The A P S R cell is fully a u t o m a t e d a n d includes eight independent,

closed, f e e d b a c k control loops for the d i s p l a c e m e n t s of the drive

pistons, lateral d i a p h r a g m walls, arch support jack and confining air

pressure These are c o n t r o l l e d by a single m i c r o c o m p u t e r a n d three

custom-built, analog feedback circuits A u t o m a t i o n p r o v i d e s great

f l e x i b i l i t y in test procedures and enables soil specimens to be

s h e a r e d under conditions of stress or d i s p l a c e m e n t control These

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10 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

c a p a b i l i t i e s are p a r t i c u l a r l y useful in m e a s u r i n g load t r a n s f e r for

g e o s y n t h e t i c reinforcements w h i c h exhibit s i g n i f i c a n t t i m e d e p e n d e n t

properties Instrumentation for the control of b o u n d a r y t r a c t i o n s and

d i s p l a c e m e n t s includes: a) a p r o x i m i t y sensor t o m o n i t o r the

reference position, X (Fig 47; b) p r e s s u r e transducers, which

m e a s u r e the h y d r a u l i c p r e s s u r e in the w a t e r bags a n d the c o n f i n i n g

air pressure; c) displacement transducers, w h i c h m o n i t o r a n d c o n t r o l

the m o v e m e n t of the platforms a n d side walls; a n d d) a d d i t i o n a l

d i s p l a c e m e n t transducers which m e a s u r e d i r e c t l y the axial a n d lateral

d e f o r m a t i o n s of the specimen

5 S a n d specimens are p r e p a r e d by raining p a r t i c l e s t h r o u g h an a s s e m b l y

of sieves (dry pluviation) in order to a c h i e v e s p e c i m e n s of s p e c i f i e d

target d e n s i t i e s which are h o m o g e n e o u s a n d e x h i b i t r e p e a t a b l e

e n g i n e e r i n g properties The raining apparatus for the A P S R cell

c o m p r i s e s a s a n d hopper w i t h a p e r f o r a t e d b a s e m o u n t e d on a 1 4 m high

c h i m n e y w h i c h contains a series of wire m e s h screens The

d e p o s i t i o n a l p r o c e s s also introduces a s t r u c t u r e or fabric s u c h that

t h e m e c h a n i c a l properties of the sand are c r o s s - a n i s o t r o p i c The A P S R

cell is d e s i g n e d such that the specimen can be d e p o s i t e d a l o n g e i t h e r

the z or y axes (Fig 4) Sand specimens d e p o s i t e d in the z d i r e c t i o n

i n i t i a l l y e x h i b i t isotropic p r o p e r t i e s for p l a n e strain s h e a r i n g in

the x-y plane, while those f o r m e d in the y - d i r e c t i o n have c r o s s -

a n i s o t r o p i c properties This important d e s i g n feature d e c o u p l e s the

e f f e c t s of soil anisotropy in the m e a s u r e m e n t s of load t r a n s f e r using

the A P S R cell

6 The external load cell measures the m a x i m u m t e n s i l e force in the

r e i n f o r c e m e n t at the reference location X (Fig 4) A d d i t i o n a l

i n s t r u m e n t a t i o n can be d e s i g n e d to m e a s u r e local strains and/or

stresses at locations along the i n c l u s i o n for d i f f e r e n t types of

r e i n f o r c i n g material D e f o r m a t i o n s w i t h i n the soil s p e c i m e n are

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

t u n g s t e n - s t e e l m a r k e r s e m b e d d e d in the soil [13]

Larson [ii] describes the e x t e n s i v e p r o g r a m of p r o o f tests which

have b e e n p e r f o r m e d to evaluate the design a n d p e r f o r m a n c e of the A P S R

cell The tests are all p e r f o r m e d using dry Ticino sand as the reference

soil The p h y s i c a l and e n g i n e e r i n g properties of Ticino sand are typical

of m a n y natural sands and are well d o c u m e n t e d in the l i t e r a t u r e [!~]

The s a n d is d e p o s i t e d along the z-axis of t h e A P S R cell (Fig 4) w i t h

initial relative densities, Dr=30 and 75% (loose a n d d e n s e specimens,

respectively) The proof tests have: a) e s t a b l i s h e d that the s i l i c o n

g r e a s e l u b r i c a t i o n is successful in m i n i m i z i n g wall f r i c t i o n in t h e A P S R

cell; a n d b) r e f i n e d test p r o c e d u r e s such that m e a s u r e m e n t s of s t r e s s -

strain b e h a v i o r (for the u n r e i n f o r c e d sand) a n d l o a d t r a n s f e r for

e l a s t i c inclusions are repeatable a n d consistent The s t r e s s - s t r a i n -

s t r e n g t h p r o p e r t i e s of the u n r e i n f o r c e d Ticino sand, m e a s u r e d in the

A P S R cell, are in g o o d agreement with results f r o m other p l a n e strain

d e v i c e s r e p o r t e d in the literature [~]

M E A S U R E M E N T S O F L O A D T R A N S F E R F O R A S T E E L S H E E T I N C L U S I O N

A c o m p r e h e n s i v e reference p r o g r a m of l o a d t r a n s f e r m e a s u r e m e n t s

have b e e n o b t a i n e d in the A P S R cell using d e n s e a n d loose Ticino s a n d

r e i n f o r c e d with two-ply, elastic steel sheet i n c l u s i o n s [II] A l l of the

tests w e r e p e r f o r m e d at a c o n f i n i n g stress ~3=31kPa a n d i n c l u d e local

m e a s u r e m e n t s of the strain d i s t r i b u t i o n w i t h i n the r e i n f o r c e m e n t f r o m a

series of u n i f o r m l y spaced, b o n d e d resistance strain gauges w h i c h are

s a n d w i c h e d b e t w e e n the two thin steel sheets (each 0.13nun thick)

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WHITTLE ET AL ON EVALUATING LOAD-TRANSFER 1 1

35 3O

A P S R Test No 35

0.25 mm Steel Reinforcement, 36 cm Long

12 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

WHITTLE ET AL ON EVALUATING LOAD-TRANSFER 13

of h a l f - l e n g t h L / 2 = 3 6 c m in d e p o s i t s of b o t h d e n s e a n d l o o s e T i c i n o s a n d

at t w o s p e c i f i e d s t r e s s ratios F o r t h e d e n s e s a n d (yd=15.9kN/m3; Fig

8a), the p r e d i c t i o n s are in v e r y g o o d a g r e e m e n t w i t h t h e d a t a m e a s u r e d

,-, 25 ~ Shear Lag Prediction APSR Test 46 [

"~ 20 - E/GIn = 6"9x104 Vm = 0.31 R = ~1/o3 Symbol

14 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

an e l a s t i c steel sheet inclusion L o a d t r a n s f e r for long r e i n f o r c e m e n t s

can be e x t r a p o l a t e d using the shear lag framework in c o n j u n c t i o n with

A P S R m e a s u r e m e n t s for a number of short inclusions of d i f f e r e n t lengths

The A u t o m a t e d Plane Strain R e i n f o r c e m e n t cell is a new l a b o r a t o r y

device w h i c h p r o v i d e s a c c u r a t e m e a s u r e m e n t s of the l o a d - t r a n s f e r for a

p l a n a r r e i n f o r c i n g i n c l u s i o n as the s u r r o u n d i n g soil m a t r i x is d e f o r m e d

in a p l a n e strain c o m p r e s s i o n mode of shearing The A P S R cell applies

well c o n t r o l l e d u n i f o r m b o u n d a r y t r a c t i o n s a n d m e a s u r e s directly the

m a j o r t e n s i l e force at the center of the planar inclusion Simple

a n a l y t i c a l solutions, b a s e d on shear l a g analysis, p r o v i d e a framework

for p r e d i c t i n g and i n t e r p r e t i n g m e a s u r e m e n t s in the A P S R cell The p a p e r

summarizes the m e c h a n i c s of soil-reinforcement interaction, using shear

lag analyses, a n d d e m o n s t r a t e s how t h e s e studies have b e e n a p p l i e d in

the d e s i g n of the A P S R cell M e a s u r e m e n t s of t e n s i l e stress

d i s t r i b u t i o n s are r e p o r t e d for e l a s t i c steel sheet r e i n f o r c e m e n t s in d r y

Ticino sand These data illustrate the importance of t h e inclusion

length on the l o a d - t r a n s f e r and are in g o o d agreement w i t h shear l a g

predictions The A P S R cell offers a n e w e x p e r i m e n t a l c a p a b i l i t y for

WHITTLE ET AL ON EVALUATING LOAD-TRANSFER 15

R E F E R E N C E S

[1] De Buhan, P., Mangiavacchi, R., Nova, R., Pellegrini, G & SalenGon,

J " Y i e l d D e s i g n of R e i n f o r c e d Earth Walls by a H o m o g e n i z a t i o n

Method," G~otechnique, Vol 39, No 2, 1989, pp 189-203

[~] Schlosser, F and Long, N.T., proceedings of the 5th E u r o p e a n

C o n f e r e n c e on Soil Mechanics Ond F o u n d a t i o n Enqineerina, Madrid,

1972

[i] Fukushima, S., Mochizuki, Y., and Kagawa, K., P r o c e e d i n a s of the

International S y m p o s i u m on T h e o r y and P r a c t i c e of E a r t h

Reinforcement, Fukuoka, 1988

[~] Jewell, R.A Proceedinas of the I n t e r n a t i o n a l C o n f e r e n c e on

Geotextiles G e o m e m b r a n e s & R e l a t e d Products, The Hague, 1990

[~] Abramento, M and Whittle, A.J "Shear lag a n a l y s i s of a p l a n a r soil reinforcement in plane strain compression", t o a p p e a r ~ S C B Journol

of E n a i n e e r i n a Mechanic~, 1992

[~] Cox, H.A "The e l a s t i c i t y a n d strength of p a p e r a n d o t h e r fibrous

m a t e r i a l s , " B r i t i s h Journal of A p p l i e d Phvsics, Vol 3, 1952, pp

72-79

[~] Kuhn, P S t r e s s e s in aircraft and shell structures McGraw-Hill, New York, 1956

[~] Budiansky, B., Hutchinson, J.W., a n d Evans, A G " M a t r i x fracture in

f i b e r - r e i n f o r c e d ceramics," Journal of the M e c h a n i c s a n d Physics of

~ I / ~ , Vol 34, NO 2, 1986, pp 167-189

[~] Ladd, C.C., Foott, R~ Ishihara, K., Schlosser, F and Poulos, H.G

P r o c e e d i n a s 9th Internationa~ C o n f e r e n c e on soil M e c h a n i c s and

F o u n d a t i o n E n q i n e e r i D q , Tokyo, 1977

[I0] Bolton, M.D "The strength and d i l a t a n c y of sands," G~otechnique, Vol 36, No I, 1986, pp 65-79

[II] Larson, D G " A laboratory i n v e s t i g a t i o n of l o a d - t r a n s f e r in

reinforced soil," PhD Thesis, MIT, Cambridge, MA., 1992

[12] Palmeira, E.M., and Milligan, G W E " L a r g e scale direct shear tests

of r e i n f o r c e d soils," Soils and Foundations, Vol 9, NO l, 1989,

pp 18-30

[13] Arthur, J.R.F "Industrial radiography in soil m e c h a n i c s , " British Journal of N o n , D e s t r u c t i v e Testina~ Vol 29, No I, 1977, pp 9-13 [14] Baldi, G et al., Proceedings of the llth I n t e r n a t i o n a l C o n f e r e n c e

on Soil Mechanics and Foundation Engineering~ AGI Jubilee Volume,

1993

A B S T R A C T : T h i s p a p e r p r e s e n t s i n t r i n s i c l o a d - d e f o r m a t i o n p r o p e r t i e s o f

d i f f e r e n t g e o t e x t i l e s u n d e r c o n f i n e d a n d u n c o n f i n e d c o n d i t i o n s T h e

c o n f i n e d l o a d - d e f o r m a t i o n p r o p e r t i e s w e r e d e t e r m i n e d b y a t e s t m e t h o d (the i n t r i n s i c c o n f i n e d test) p r o p o s e d b y W u (1991) for d e s i g n a n d

s p e c i f i c a t i o n of g e o t e x t i l e - r e i n f o r c e d s o i l s t r u c t u r e s T h e i n t r i n s i c

c o n f i n e d t e s t h a s t h r e e d i s t i n c t c h a r a c t e r i s t i c s : (i) it is a n " e l e m e n t " test, t h u s the l o a d - d e f o r m a t i o n p r o p e r t i e s d e t e r m i n e d f r o m t h e t e s t a r e

a p p l i c a t i o n s i n v o l v e soil c o n f i n e m e n t p r e s s u r e s

It h a s b e e n d e m o n s t r a t e d that c o n f i n e m e n t p r e s s u r e s h a v e a

s i g n i f i c a n t i n f l u e n c e o n the l o a d - d e f o r m a t i o n c h a r a c t e r i s t i c s o f some IGEI C o n s u l t a n t s , Inc., E n g l e w o o d C O 80111;

2 D e p a r t m e n t o f C i v i l E n g i n e e r i n g , U n i v e r s i t y of C o l o r a d o at Denver, Denver, C O 8 0 2 1 7

16

Copyright 9 1993 by ASTM International www.astm.org

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BALLEGEER AND WU ON LOAD-DEFORMATION PROPERTIES 17

c o n s e r v a t i v e v a l u e s if s l i p p a g e at the i n t e r f a c e d o e s o c c u r

in a r e i n f o r c e d s t r u c t u r e (4) T h e m e a s u r e d p r o p e r t i e s a r e i n d e p e n d e n t of the c o n f i n i n g

18 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

20 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

with confining rubber membrane

FIG 3 Epoxy mold and reinforced specimens

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22 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

Test P r o c e d u r e - - T h e p r o c e d u r e for the intrinsic c o n f i n e d test

m e t h o d can be d e s c r i b e d by the following steps:

Step i: A rubber m e m b r a n e is s t r e t c h e d over the epoxy frame

e n c l o s i n g the entire u n r e i n f o r c e d area of the geotextile

The specimen is b o l t e d (through the holes in the epoxy) inside a p a i r of metal clamps creating a seal at the t o p

a n d b o t t o m of the g e o t e x t i l e along its entire width The rubber m e m b r a n e is e q u i p p e d w i t h a length of nylon tubing for a p p l i c a t i o n of v a c u u m pressures (see Figure 5) T h e tubing is g l u e d to the m e m b r a n e at a flange on the e n d of the tubing The flange is c r e a t e d by t o u c h i n g the e n d of the tubing to a h e a t e d hot plate and then q u i c k l y

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BALLEGEER AND WU ON LOAD-DEFORMATION PROPERTIES 23

24 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

BALLEGEER AND WU ON LOAD-DEFORMATION PROPERTIES 25

26 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

FIG 8 - - T y p i c a l l o a d - d e f o r m a t i o n p r o p e r t i e s for five

different g e o t e x t i l e s u n d e r confined conditions

28 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

BALLEGEER AND WU ON LOAD-DEFORMATION PROPERTIES 29

30 GEOSYNTHETIC SOIL REINFORCEMENT TESTING PROCEDURES

T A B L E 2 - - M e a n values of stiffness a n d s t r e n q t h for five

qeotextiles, intrinsic c o n f i n e d a n d u n c o n f i n e d tests

G e o t e x t i l e

Stiffness S t r e n g t h (Sec Mod @ 5%) (Load at failure)

N o n w o v e n

N e e d l e - p u n c h e d

G e o t e x t i l e A (Unconfined (Confined)

G e o t e x t i l e B (Unconfined (Confined)

N o n w o v e n

H e a t - b o n d e d

G e o t e x t i l e C (Unconfined (Confined)

G e o t e x t i l e D (Unconfined (Confined)

W o v e n

G e o t e x t i l e E (Unconfined (Confined)

r e i n f o r c e d soil structures T h e tests are h i g h l y r e p r o d u c i b l e a n d the

m e a s u r e d p r o p e r t i e s are s u p e r i o r to other c o n f i n e d tests for p u r p o s e s of

d e s i g n a n d specifications

Test r e s u l t s u s i n g the intrinsic c o n f i n e d test m e t h o d indicate

that p r e s s u r e c o n f i n e m e n t results in g e o t e x t i l e stiffness increases from

nil to 67 p e r c e n t a n d g e o t e x t i l e s t r e n g t h increases from 7 to about 30

percent The s t r e n g t h values for woven, p o l y p r o p e l e n e g e o t e x t i l e s u s i n g

the intrinsic c o n f i n e d test m e t h o d are l i m i t e d to the b o n d i n g s t r e n g t h

of the epoxy r e i n f o r c e m e n t a l o n g the edges of the geotextile Test

r e s u l t s o b t a i n e d by c o n f i n e d test m e t h o d s o t h e r than the intrinsic

c o n f i n e d test m e t h o d include a shear r e s i s t a n c e at the s o i l - g e o t e x t i l e

interface, thus g r e a t l y e x a g g e r a t i n g the s t i f f n e s s a n d s t r e n g t h of the

BALLEGEER AND WU ON LOAD-DEFORMATION PROPERTIES 31

D e t e r m i n i n g the In-Soil S t r e s s - S t r a i n Properties of G e o t e x t i l e s , "

P e r f o r m a n c e of G e o t e x t i l e s in Soils," Proceedings of the S e c o n d

I n t e r n a t i o n a l C o n f e r e n c e on Geotextiles, Las Vegas, U.S.A., 1982,

T e s t i n g Journal, GTJODJ, Vol 14, No 2, June 1991, pp 157-165

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R i c h a r d J B a t h u r s t I and Michael R Simac 2

ABSTRACT: This p a p e r describes a laboratory apparatus and test

p r o c e d u r e that was d e v e l o p e d by the authors to q u a n t i f y the

m e c h a n i c a l b e h a v i o r of the c o n n e c t i o n b e t w e e n mortarless modular

c o n c r e t e block units and g e o g r i d r e i n f o r c e m e n t materials The

paper illustrates that the tests should be c a r r i e d out with l-m

wide samples of g e o g r i d r e i n f o r c e m e n t in order to account for

the influence of block joints and surface g e o m e t r y irregulari-

ties that occur along the length of typical g e o g r i d - r e i n f o r c e d

concrete block walls This paper gives r e c o m m e n d a t i o n s for a 20

mm/min rate of loading The i n t e r p r e t a t i o n of c o n n e c t i o n

s t r e n g t h and e f f i c i e n c y for m o d u l a r b l o c k - g e o g r i d r e i n f o r c e m e n t

c o n n e c t i o n systems is related to c o n v e n t i o n a l index strengths

that are r o u t i n e l y r e p o r t e d in the literature based on the ASTM

D 4595 method of test

KEYWORDS: g e o s y n t h e t i c testing, m a s o n r y concrete, geogrid modula~

block, g e o s y n t h e t i c reinforcement, c o n n e c t i o n s

The use of m o d u l a r m a s o n r y c o n c r e t e b l o c k facing systems

in g e o s y n t h e t i c - r e i n f o r c e d soil retaining wall structures has

gained great p o p u l a r i t y in recent years The m a j o r i t y of these

structures have been built u s i n g p o l y m e r i c g e o g r i d materials as

the g e o s y n t h e t i c reinforcement The r e i n f o r c e m e n t layers are

placed between the m a s o n r y units to form an e s s e n t i a l l y

frictional c o n n e c t i o n (for example, [1-3])

C o n v e n t i o n a l design and analysis m e t h o d s such as those

r e c o m m e n d e d in g u i d e - l i n e s p u b l i s h e d by A A S H T O [4, 5],the Federal

H i g h w a y s A d m i n i s t r a t i o n [6] and the National Concrete M a s o n r y

iProfessor, Civil E n g i n e e r i n g Department, Royal M i l i t a r y

C o l l e g e of Canada, Kingston, O n t a r i o K7K 5LO

=Principal, Earth Improvement Technologies, i00 M a y f l o w e r

BATHURST AND SIMAC ON LABORATORY TESTING 33

A s s o c i a t i o n (NCMA) [ ~ ] , [~] r e c o g n i z e that the i n t e r n a l s t a b i l i t y

of the r e i n f o r c e d soil wall s t r u c t u r e m a y be c o n t r o l l e d by the

m e c h a n i c a l p e r f o r m a n c e of the m o d u l a r u n i t - g e o s y n t h e t i c rein-

f o r c e m e n t c o n n e c t i o n However, the l o a d - d e f o r m a t i o n p r o p e r t i e s of the c o n n e c t i o n can o n l y be q u a n t i f i e d by f u l l - s c a l e l a b o r a t o r y

c o n n e c t i o n testing The t e n s i l e l o a d - d e f o r m a t i o n p r o p e r t i e s are

i n f l u e n c e d by: a) g e o m e t r y and t y p e of g e o s y n t h e t i c - f a c i n g unit

i n t e r f a c e (i.e c o n t i n u o u s keys, lips, d o w e l s or pins), b) qual- ity of the concrete, c) w h e t h e r the f a c i n g u n i t s are h o l l o w or solid, d) w h e t h e r the h o l l o w core is left e m p t y or i n f i l l e d w i t h

m e n t m a t e r i a l s to be used However, this P a p e r is r e s t r i c t e d to the e x p e r i e n c e g a i n e d from the t e s t i n g of g e o g r i d r e i n f o r c e m e n t

p r o d u c t s since they are c u r r e n t l y the most c o m m o n g e o s y n t h e t i c

w i r e b a s k e t and p o l y m e r i c g e o c e l l facing c o n n e c t i o n s h a v e also

b e e n e v a l u a t e d for a c t u a l field structures

At the time of this i n v e s t i g a t i o n t h e r e was only one spec-

i f i c a t i o n for the t e s t i n g of m o d u l a r c o n c r e t e - g e o s y n t h e t i c con-

n e c t i o n s (Test M e t h o d GS-8) p u b l i s h e d by the G e o t e c h n i c a l Re-

s e a r c h I n s t i t u t e (GRI) [~] The test m e t h o d d e s c r i b e d in this

P a p e r t o g e t h e r w i t h t e s t r e s u l t s shows that t h e r e are some p o t e n - tial s h o r t c o m i n g s in the c u r r e n t GRI s t a n d a r d [~] w i t h r e s p e c t to: rate of loading; i n t e r p r e t a t i o n of test results; d e f i n i t i o n