undrained shear testing of jointed rock

7/29/2019 Undrained Shear Testing of Jointed Rock

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Rock M echan ics 5 , 129--14 9 (1973) by Spr inger-Ver lag 1973

Undrained Sh ear Test ing of Jointed Ro ckB y

R i c h a r d E . G o o d m a n a n d Y u z o O h n is h iWith 11 F igures

(Received December 20 , 1972)S u m m a r y - - Z u s a m m e n f a s s u n g - - R 6 s u m 6

U n d r a i n e d S h e a r T e s t i n g o f J o i n t e d R o c k . Water p ressu res mu s t ch an g e in s id ejo in t s u n d erg o in g sh ea r w i th o u t p e r fec t d ra in ag e . T h i s p ap er d esc r ib es a n ew d i r ec tsh ea r mach in e in w h ich j ack e ted samp les w i th o r i en ted jo in t s can b e t e s t ed u n d erc o n s o l i d a t e d u n d r a i n e d c o n d i t i o n s w i t h p o r e p r e s s u r e m e a s u r e m e n t . T r i a x i a l c o m -p ress io n t ech n iq u es fo r su ch t e s t s a re a l so d esc r ib ed an d ty p ica l r e su l t s w i th in t ac tan d jo in t ed san d s to n e samp les a re co mp ared w i th r e su l t s f ro m th e d i r ec t sh ea r t e s t s .Wh ereas in t ac t sp ec imen s d i sp lay ed in c reas in g p o re p ressu re fo l lo w ed b y d i l a t an cyan d p o re p ressu re d ec l in e b e fo re p eak lo ad in g , t h e p o re p ressu re in jo in t ed sp ec imen sco n t in u ed in c reas in g r ig h t u p to th e p eak lo ad .

Sche~'versuche an k l i i f t igen Geste inen ohne Drdnung. Wasserd ru ck in K l f i f t enmuff s ich ver~indern , w enn ohn e p erfek te D rf inage Sche rkraf t ausgei_ ib t wird . In derv o r l i eg en d en A rb e i t w i rd e in n eu er , d i r ek t w i rk en d e r S ch erap p ara t b esch r i eb en , inw e lch em u m ma n te l t e P r~ ifk/Srpe r m i t g e r i ch te t en K l i i f ten u n te r K o n so l id a t io n sb ed in -g u n g e n o h n e D r f i n a g e u n t e r s u c h t w e r d e n k 6 n n e n , w o b e i d e r P o r e n d r u c k g e m e s s e nw i rd . E s w i rd au f~ erdem d ie T ech n ik y o n T r i a x ia lv e r su ch en b esch r i eb en u n d ty p i sch eErgebn isse mi t ungest~Sr tem und gekRif te tem Sandste in werden mi t Ergebn issen ausd i r ek ten S ch erv e r su ch en v e rg l i ch en . W~ ih ren d u n g es t6 r t e P ro b en s t e ig en d en P o ren -d r u c k , g e f o lg t y o n D i l a ta n z , a u f w e i s e n u n d d e r P o r e n d r u c k v o r d e r H 6 c h s t b e l a s t u n gnach l~ if~t , n im mt derselbe in gek l /J fte ten Prob en b is zu r H6 chs tbela s tung s t~ ind ig zu .Essa is de c i sa i l I emen t non dra ind sur des dchan t i l Ions de roche con tenan t unediscont inui tY. Les p ress ions in ters t i t ie l les ~ l ' in t~ r ieur des d iscon t inu i t~s do iven tch an g e r lo r sq u 'e l l e s so n t so u mises au c i sa il l emen t e t q u e l e d ra in ag e n ' e s t p as p a r fa i t .C e t a r t i c l e d d c r i t u n e n o u v e l l e mach in e p o u r e s sa i s d e c i sa i l l emen t d i r ec t p e rmet t an td e t e s t e r , d an s d es co n d i t io n s d e co n so l id a t io n n o n d ra in d e , d es d ch an t i ll o n s d e ro ch eg a in 6 s co mp o r t an t u n e d i sco n t in u i td d ' o r i en ta t io n d &ermin 6 e . L a mach in e p e rmet l amesure de la p ress ion in ters t i t ie l le .L ' a r t i c l e d 6 c ri t 6 g a lemen t l es t ech n iq u es d e co m p ress io n t r i ax ia l e co r resp o n d an teset des r6su l ta ts typ iques ob tenus su r des 6chan t i l lons de g r~s in tact ou t ravers8 par unjo in t son t com pards ~i ceu x p rov en an t des essais d e c isa i l lement d i rect . Alors que les6 ch an t i l l o n s d e ro ch e in t ac t e mo n t ren t u n acc ro i s semen t d e l a p ress io n in t e r s t i t i e l l esu iv i d e d i l a t an ce e t d ' u n e r~ d u c t io n d e p ress io n av a n t q u e l a co n t ra in t e d e c i sa il l emen tm ax im u m n e so i t a t t e in t e , la p ress io n in t e r st i ti e l le d an s l es ~ ch an t i ll o n s co n te n an t u n ed i sco n t in u i td c ro l t j u sq u ' au d ro i t d e l a co n t ra in t e d e c i sa i l l emen t max imu m.

R o c k M e c h a n i c s , V o l . 5/3 9


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130 R . E . G o o d m a n and Y . O h n i s h i :I n j o i n t e d r o c k s , m e c h a n i s m s o f r o c k m a s s d e f o r m a t i o n i n c l u d e o p e n i n g

a n d c l o s i n g o f i n d i v i d u a l d i s c o n t i n u i t i e s . I f t h e ro c k m a s s i s s a t u r a t e d , a n d t h es h e a r i n g i s f a s t , o r d r a i n a g e i s i m p e d e d , w a t e r p r e s s u re s m u s t c h a n g e i n s i d et h e j o i n t s ; i n t u r n , t h i s m a y a c c e l e r a t e o r d e c e l e r a t e t h e d e f o r m a t i o n p r o c e s sa c c o r d i n g t o t h e s i gn o f th e i n d u c e d w a t e r p r e s s u r e . I f t h e j o i n t a p e r t u r e si n c r e a se d u e t o s h ea r i n g ( " d i l a t a n t" b e h a v i o r ) , o r d u e to e x t e n s i o n n o r m a l t ot h e j o i n t s ( j o i n t " o p e n i n g " ) , t h e j o i n t w a t e r p r e s s u r e w i l l d r o p . C o n v e r s e l e y ,a n a p e r t u r e d e c r e a s e d u e t o s h e a r d i sp l a c e m e n t ( " c o n t r a c t a n t " b e h a v i o r ) o rd u e t o c o m p r e s s i o n n o r m a l t o t h e j o i n t s ( j o i n t " c l o s i n g " ) w i l l i n c r e a s e p o r ew a t e r p r e s s u re . (A p o re w a t e r p r e s s u re i n c r e a s e is c o n s i d e re d p o s i t i v e ) .A s d i s c u s s e d b y L a n e *5, p o r e w a t e r p r e s s u r e c h a n g e s a r e s o m e t i m e sc r i t i c a l t o t h e s a f e t y o f e n g i n e e r i n g w o rk s o n ro c k s , e . g . a l l k i n d s o f d a m s ;n a v i g a t i o n l o c k s ; p o w e r h o u s e s ; s p i l l w a y e x c a v a t i o n s ; r e s e r v o i r s l o p e s ; a n du n d e r g r o u n d r e s e rv o i r s f o r f l u i d w i t h d r a w a l , o r r e c h a rg e . S e v e ra l i m p o r t a n tf a i lu r e s o f h y d r a u l i c s t r u c tu r e s a n d o f n a t u r a l s l o p e s h a v e b e e n a t t r i b u t e dm a i n l y t o t h e a c t i o n o f w a t e r p r e s s u r e i n s i d e t h e r o c k s . I t s t a n d s t o r e a s o nt h a t p r e s s u r e c h a n g e s w i t h i n t h e j o i n t w a t e r a r e i n v o l v e d i n a n i m p o r t a n tw a y ; y e t e x p e r i m e n t a l d a t a o n i n d u c e d p r e s s u r e s o n r o c k s a m p l e s w i t h j o in t sa r e v e r y s c a r c e . T h i s d o e s n o t o r i g i n a t e f r o m l a c k o f a p p r e c i a t i o n o f t h ep r o b l e m ' s i m p o r t a n c e b u t r a t h e r , w e s u s p e c t , f r o m t h e i n h e r e n t d i f f i c u l t i e s i ns u c h a n e x p e r i m e n t , i n v o l v i n g a s t h e y d o c h a n g e s o f s m a l l w a t e r v o l u m e s i nr e l at i v e ly in a c c e s s ib l e l o c a t i o n s w i t h i n l o w p e r m e a b i l i ty m a t e r ia l u n d e r c o m -p l e x s t re s s c o n d i t i o n s . D r . K e v i n R o s e n g r e n s t u d i e d j o i n t s l id i n g i n t r i a x i a lt e s t s w i t h c o n t ro l l e d j o i n t w a t e r p r e s s u re" '. L a n e 15 d i s c u s s e d r e s u l ts o f c o n -s o l i d a t e d u n d r a i n e d t e s t s o n a f r a c t u r e d c l a y s t o n e . T h e i n d u c e d p r e s s u r eb e c a m e n e g a t i v e a t p e a k l o a d w i t h l o w c o n f i n in g p r e s s u r es b u t r e m a i n e dp o s i t i v e a t h i g h e r c o n f i n i n g p r e ss u re s ," p r e s u m a b l y b e c a u s e d i l a t i o n c o u l d n o to c c u r o n t h e f r a c t u r e s a t t h e h i g h e r c o n f i n i n g p r e s s u r e .W e r e p o r t h e r e n e w l a b o r a t o r y e q u i p m e n t a n d p r o c e d u r e s f o r s t u d i e s o fj o i n t w a t e r p r e s s u r e d u r i n g r o c k d e f o r m a t i o n . I t i s r e a s o n a b l e i n r o c k j o i n tt e s t s t o u s e d i r e c t s h e a r a n d t h i s h a s b e e n o u r p r i m a r y m e t h o d . H o w e v e r a sw e k n o w o f n o p r e v i o u s w o r k o n u n d r a i n e d d i re c t sh e a r t es ts in r o ck " * , its e e m e d w i s e t o c o m p l e m e n t t h e s e w i t h c o n s o l i d a t e d u n d r a i n e d t r ia x i a l t e st sf o r w h i c h a s i g n i f i c a n t b o d y o f e x p e r i e n c e a l r e a d y e x i s t s . T h i s e x p e r i e n c er e c o r d w a s r e c e n tl y r e v i e w e d b y B r u h n a a n d b y M e s r i , e t a P 6. T h e e f fe c ti v es t r e ss p r i n c i p l e i s g e n e ra l l y a c c e p t e d a s a p p l i c a b l e t o ro c k s 22, 9 ,1 ~. H o w e v e r ,B r a c e a n d M a r t i n 2 s h o w e d t h a t e ff ec ti ve s tr es s b a se d u p o n g l ob a l w a t e rp r e s s u r e v a l u e s c a n o p e r a t e t o d e s c i r b e r e s p o n s e t o i n c r e m e n t s o f s t r e s s o n l yi f t h e s t r a i n r a t e s a r e b e l o w a c r i t ic a l v a l u e (o f t h e o rd e r o f 1 0 -7 / s e c fo rd i a b a s e , g r a n it e , g a b b r o , d u n i t e , a n d d o l o m i t e a n d 1 0 - 4 / s e c f o r a d e n s e s a n d -stone ':"=" :'). A t s t ra in ra te s fa s te r tha n the c r i t i ca l va lue , loca l w a te r p re s sure

::" Ph D Th esis, Australian N atio na l Univ., Can ber ra 1968.::'"~ J o u a n n a la,14 described an ap paratu s in w hich h e measu red permeability ofsamples of schist and of joints under varying combinations of principal s tress.: ' :


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Un drained Shear Testing of Jointed Rock 131t r a n si e n t s r a d i ca l l y a lt e r t h e r o c k b e h a v i o r p r o d u c i n g a s t r e n g t h e n i n g t e r m e d" d i l a t a n c y h a r d e n i n g " i f t h e i n d u c e d p r e s s u r e s a t p e a k l o a d a r e n e g a t i v e .R o b i n s o n a n d H o l l a n d 19 a r g u e d t h a t t h e e ff ec ti ve s tr es s p r in c ip l e is s tr ic tl yv a l i d o n l y f o r r o c k s w i t h b o u n d a r y p o r o s i t y o f u n i t y w h e r e a s s o m e d e n s er o c k s , s u c h a s a n I n d i a n a l i m e s t o n e t h e y s tu d i e d , c a n b e d e m o n s t r a t e d t o h a v el ow e r bounda r y po r os i t y , pa r t i c u l a r l y a t h i gh c on f i n i ng p r e s s u r e s ' : ' . I t i sr e a s o n a b l e t o e x p e c t t h a t j o i n t e d r o c k s d o p o s se s s b o u n d a r y p o r o s i t y o f u n i t y ,a t l e a s t a t l ow c on f i n i ng s t re s s le ve ls , a nd t he r e f o r e t ha t a g i ve n e f f e c ti ves tr e ss va l ue ( 8 = a - p ~ ) i s s u f f i c i e n t t o de t e r m i ne j o i n t s he a r s t r e ng t h un i qu e l y .O ur f i r s t i n t e r e s t he r e i s t o de s c r i be w a t e r p r e s s u r e bu i l dup i n j o i n t s a ndf r a c t u r e s u n d e r g o i n g u n d r a i n e d s h e a r . F o r s o i l s a n d i n t a c t r o c k s p e c i m e n su n d e r g o i n g " t r i a x i a l " c o m p r e s s i o n (i. e . a x y s y m m e t r i c w i t h a l = l o n g i t u d i n a ls tr es s) S k e m p t o n ' s e m p i r ic a l p o r e p r e s s u re p a r a m e t e r s 7i a n d B giv e t h ei ndu c e d po r e p r e s s u r e p i a s f o l l ow s 21 **

p t = B A a a + X ( A ~ 1 - A ~ a ) . ( 1 )U n d e r a n i n c r e m e n t o f a ll a r o u n d p r e s s u re , 3 a a , t h e r a t e o f in c r e a s e o f w a t e rp r e s s u r e w h e n t h e r e is n o d r a i n a g e w a s d e r i v e d b y B i s h o p ** *

1B = ( 2 )Cw - Cgl + n - -C b - C gw he r e Cg is t he c om pr e s s i b i l i ty o t t h e g r a i n s , C ,0 a nd C0 a r e t he c om pr e s s i b il -i ti es o f w a t e r a n d t h e b u l k r o c k r e sp e c t iv e l y a n d n is t h e p o r o s i t y e x p r e s s e da s a f r a c t i on . I n roc ks C w


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1 32 R . E . G o o d m a n a n d Y . O h n i s h i :s u r e s c a u s i n g B t o r e t u r n t o w a r d u n i t y . T h e s e c o n j e c t u r a l r e l a t i o n s h i p s a r ep o r t r a y e d i n F ig . 1 a lo n g w i t h t h e o b s e r v e d d a t a f o r i n t a c t sp e c i m e n s o f L y o n ss a n d s t o n e .

A s i m i l a r a n a ly s i s c a n b e m a d e f o r t h e p o r e p r e s s u r e c o e ff i c ie n t A . H o w -e v er , m o r e f u n d a m e n t a l t h a n t h e v a ry i n g v a l ue o f Cw/Cb as a non l inea r i z ingp a r a m e t e r i s n o w t h e v a r i a t i o n o f p o r e v o l u m e w i t h i n c r e a s i n g s h e a r i n gs tr ain *. A s s h o w n b y B i e n i a w s k i 1 a n d c o n fi rm e d b y H e c k u , B r u h n a a n do t h e r s , t h e v o l u m e c h a n g e o f r o c k s u n d e r g o i n g i n c r e a s in g d e v i a t o r i c st re ss i sm i r r o r e d i n t he i nduc e d po r e p r e s s u r e s . I n i t i a l l y , po r e p r e s s u r e r i s e s a s po r e sc o m p r e s s o r fi ss u re s cl os e. T h e n , a s n e w c r a c k s f o r m a n d e x t e n d f r o m p o i n t sB COEFFICIENTd P i / d o"3

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I [ I I I II O 0 0 2 0 0 0 :5 00 0 4 0 0 0 5 0 0 0 6 0 0 0ALL-AROU ND PRESSURE (o '3=o") psiF i g . 1 . V a r i a t i o n o f p o r e w a t e r p r e s s u r e p a r a m e t e r B w i t h i n c r e a s i n g a l l - a r o u n d p r e s s u r e( cr a= er l) . 1 p o r o u s r o c k - - a c t u a l d a t a f o r L y o n ' s s a n d s t o n e ( n i s a l m o s t c o n s t a n t ) ; 2 j o i n t e dp o r o u s r o c k - - h y p o t h e t i c a l c u r v e ( n is a l m o s t c o n s t a n t ) ; 3 f is s u re d r o c k ( n o n - p o r o u s ) - -

h y p o t h e t i c a l c u r v e ( n a p p r o a c h e s 0 w i t h c o n f i n e m e n t )~ n d e r u n g d e s P o r e n w a s s e r d r u c k - P a r a m e t e r s B m i t s t e i g e n d e m a l l s e i t i g e m D r u c k ( c r a = c q )1 P o r 6 s e r F e ls , ta ts ~ ic h li ch e s E r g e b n i s f i i r L y o n s - S a n d s t e i n ( n n a h e z u k o n s t a n t ) ; 2 g e k l i if t e te rp o r 6 s e r F e ls , h y p o t h e t i s c h e K u r v e ( n n a h e z u k o n s t a n t ) ; 3 g e k l ii f te t e r ( n i c h t p o r 6 s e r ) F e l s ,h y p o t h e t i s c h e K u r v e ( n n ~ ih e rt s i c h 0 m i t U m s c h l i n g u n g s d r u c k )V a r i a t i o n d u p a r a m & r e d e p r e s s io n i n te r s ti ti e ll e B e n f o n c t i o n d e l a p r es s i o n h y d r o s t a ti q u e(~ i =~3)of s tr e s s c on c e n t r a t i on , a nd d i l a t e a s t he y s he a r , t he i nd uc e d p r e s s u r e s de c l i ne .P o r ou s o r f i s s u r e d r oc ks a t l o w i n it ia l e f f e c ti ve c on f i n i ng p r e s s u r e t he r e f o r ee xh i b i t pos i t i ve A va l ue s i n i t i a l l y a nd ne ga t i ve t a nge n t A va l ue s e ve n t ua l l y .N o n po r ou s r oc ks , o r f i s s u r e d r oc ks a t h i ghe r i n i ti a l e f f ec t ive c on f i n i n g p r e s -

* S c o t t z i n t r o d u c e d a p a r a m e t e r X t o i d e n t i f y th i s c o n t r i b u t i o n t o p o r e p r e s s u r e s .


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Un drained Shear Testing of Jointed Rock 133s u r e s , s hou l d d i s p l a y ne g l i g i b l e i nduc e d po r e p r e s s u r e un t i l c r a c k i ng c om -m e n c e s a n d t h e n s h o u l d e x h i b i t n e g a ti v e i n d u c e d p r e s s u r e ( n e g a ti v e t a n g e n t A ) .( U n le ss t h e p o r e w a t e r is p r e - p f e s s u r e d h i g h e r t h a n t h e n e g a t i v e i n d u c e d p r e s -s u r e t ha t c a n de ve l op , c a v i t a t i on c a n r e s u lt ) . B r u h n a r e p o r t e d va l ue s o f in i ti a l

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_ 1 ~ h i " [ IDECREASE 4- -- 0 ~ INCREASE

I NDUCED PORE PRESSURE, p[Fig. 2. Ind uce d pore pressure variation d urin g shearing for intact (1) and join ted (2), (3)specimens in triaxial com pression (hypothetical)Induzierte Porendruck-KnderungwSihrend des Schervorganges iir un gest6rte (1) u nd geklii~-tete (2), (3) Pro ben bei triaxialem D ru ck (hypothetisch).el axiale VerformungVariation de ta pression interstitietle produ ite lo rs du cisaillem ent dch antillons intacts (1)ou traversds par un join t (2), (3), soumis ~ une com pression riaxialet a n A o f a p p r o x i m a t e l y 0.1 w h i c h th e n d e c r e a s e d t o - 0 . 5 o r le ss a t p e a k l o a df o r Be r e a s a nd s t on e i n t r i a x i a l c om pr e s s i on . Be l ow 5 ,000 p s i e ff e c t ive c on -f i n in g p r e s s u re , t h e f i n a l p o r e p r e s s u r e w a s n e g a t iv e . In o u r e x p e r i m e n t s w i t hL y o n s s a n d s t o n e , p o r e p r e s s u r e a t p e a k l o a d w a s n e g a t i v e b e l o w c~a = 3 5 0 0 p s i .T h e p r e s e n c e o f a r o u g h j o i n t in t h e t r i a x ia l c o m p r e s s i o n t e st m i g h t i n c r e a s et h e p o r e c l o s u r e e f f e c t a t t h e b e g i n n i n g o f d e v i a t o r i c l o a d i n g a s p r e v i o u s l yno t e d t he r e by i nc r e a s i ng t he i n i t ia l pos i ti ve A va l ue . S l id i ng o f t he j o i n t s hou l dp r o d u c e s u d d e n d i la t a n c y so t h e t a n g e n t A v a l u e w o u l d t h e n b e c o m e n e g a t iv ea f t e r p e a k l o a d ( b u t n o t b e f o re ) . T h e s e r e l a ti o n s h i p s a r e p o r t r a y e d i n F ig . 2 .I n t e s t i ng o r i e n t e d j o i n t s i n t r i a x i a l e x pe r i m e n t s i t is d i f f i c u lt t o i s o l a tet h e s e p a r a t e c o n t r i b u t i o n s o f j o i n t a n d r o c k d e f o r m a t i o n s . A p h y s i c al ly b a s e de m p i r i ca l p o r e p r e s s u r e f o r m u l a t i o n f o r j o i n t s l id i n g is m o r e n a t u r a l t o d i r e c ts h e a r c o n d i t i o n s w h e r e o n e c a n w r i t e :

pi=B1A~+A1 AT: (3)F o r a n u n f i l l e d r o u g h j o i n t o r i e n t e d p a r a l l e l t o t h e p l a n e o f t h e d i r e c t s h e a rt e st , B 1 w o u l d r e f l e c t m a i n l y t h e c l o s u r e o f t h e j o in t u n d e r i n c r e a s in g n o r m a ls tr es s a n d 2 il w o u l d r e f le c t m a i n l y j o i n t d i l a t a n c y (A 1 < 0 ) o r c o n t r a c t a n c y( A t > 0 ) du r i ng s he a r i ng a t c o ns t a n t or. F o r un j o i n t e d r o c k s pe c i m e ns o r c l a y -


6/21

13 4 R . E . G o o d m a n a n d Y . O h n i s h i :f i l le d jo i n t s i n d i r e c t s h e a r , t h e s i t u a t i o n is m o r e c o m p l i c a t e d a s t h e l o c a l st re ~ ss t a t e w i t h i n t h e s h e a r z o n e w o u l d i n d u c e p o r e p r e s s u r e i n t h e r o c k o r f i l li n gm a t e r i a l w h i c h h a v e t h e ir o w n v a lu e s o f -A a n d B . T h e d i r e c t s h ea r m o d e m a yb e a m o r e a c c u r a t e m o d e l o f c e r t a i n f i e ld s i t u a t i o n s , s u c h a s l a n d s l i d e s , d a mf o u n d a t i o n s o n b e d d e d r o c k , fa u l t m e c h a n i s m s , e tc . I t h a s b e e n p o s s ib l e t om e a s u r e B 1 a n d A 1 d i r e c t ly f o r j o i n ts i n r o c k , a n d f o r s o l i d r o c k s p e c i m e n s ,u s i n g a n e w s h e a r m a c h i n e e m p l o y i n g a w a t e r t i gh t c h a m b e r a r o u n d t h es h e a r b o x . T h e m a c h i n e a n d p r o c e d u r e s w i ll n o w b e d e s c r i b e d .

Direct Shear Machine and ProceduresT h e d i r e c t s h e a r m a c h i n e w a s b u i l t t o p e r m i t s h e a r i n g o f j o in t s a m p l e s

u p t o 2 0 s q u a r e i n c h e s ( 12 9 c m ~) i n u n d r a i n e d c o n d i t i o n s w i t h s i m u l t a n e o u sm e a s u r e m e n t o f j o i n t w a t e r p r e s su r e s . D e s i g n o f a n y d i r e c t s h e a r t es t re p r e s e n t sa se l e c t io n o f p r i o ri t i e s f r o m a m o n g c o m p e t i n g c o n s t r a i n ts i n c l u d i n g d e s ir e

Fig . 3 . Schemat ic drawings of d i rect shear machinea) schemat i c sec tion th roug h d i r ec t shea r m ach ine

1 test c ham ber ( se e Fig . 3b ) ; 2 norm al force load cel l ; 3 shear force load cell ; 4 shear fo rcepiston; 5 ro l ler bear ings; 6 f lexible react ion rod; 7 bal l and screw assembly; 8 dr ive gear ;9 bear ings; 10 base ( s ta t ionary) ; 11 chamber seal ing bol ts ; 12 sadd le ; 13 resis t ing abutment ;14 and 15 l i nea r po ten t iomete r s

b) Seal ing scheme for water - t ight test chamber (d iagrammat ic)1 w a t e r - t i g h t t e s t c h a m b e r - - f r e e t o m o v e u p a n d d o w n ; 2 s h e a r b o x w i t h p o t t e d r o c kspecimens (see Fig. 5); 3 seal pla te; 4 seal plate pressu re rod s, adjus table (actually c ente red onsea l p l a t e ) ; 5 "0" r ings fo r ho r i zon ta l mot ion ; 6 "0" r ings fo r ve r t i ca l mot ion ; 7 sadd le - -moves on ly ho r i zon ta l ly wi th p i s ton ; 8 p i s ton ; 9 r eac t ion rod ( see F ig . 3 a )Schematische Schnitte der Direkt-Schermaschine. a) L~ingsschnitt

1 Te stk am m er (s. A bb. 3b ); 2 Normalkraft-Mef~zeUe; 3 Scherkraft-Mei~zelle; 4 Sche rkraft-Druckzyl inder ; 5 Rol lenlager ; 6 f lexibel aufgeh~ingte Gegendruckstange; 7 kngelgelager teSchraubenmut t e r ; 8 An t r i ebsr ad ; 9 Druck lager ; 10 feste Basisplatte; 11 K a m m e r d i c h t u n g s -bo lzen ; 12 Schubk lo tz ; 13 Wider l ager ; 14 und 15 Linear -Po ten t iomete rb ) Abd ich tungsschema der wasse rd ich ten Ver suchskammer

1 Wasserdichte , ver t ikal f re i bewegl iche Testkammer ; 2 Scherbi ichse mi t befest ig ter Probe(siehe Abb. 5) ; 3 Dichtungsr ing; 4 Dichtungsr ing mi t nachste | Ibarem Spanngest f inge; 5 und 60-Ringe fi i r hor izo ntale un d ver t ikale Bewegl ichkeit ; 7 Schu bklotz , nur hor iz onta l bewegl ich ,zusammen mi t 8 ; 8 Schubvor r i ch tung ; 9 Gegendrucks t angea) Cou pe longi tudina le de la ma chine po ur essais de c isai llement d i rect

1 Cel lu le d 'essai - - voi r f ig . 3 b ; 2 , 3 Cel lu les des mesurer la charge ver t icale e t hor izontale ;4 Piston t ran sm et tan t l 'e f fo r t de c isai llement; 5 PallOr a rou leau x; 6 Barre de rdact ion f lexible;7 As sem blage art icul~; 8 R ou e du diffdrentiale; 9 Plier; 10 Base (fixe); 11 Boulon de f e rmetu rede la cellule; 12 Selle; 13 Butde; 14 et 15 Potentiometres l indairesb) Disposi t i f de fermeture de la chambre d 'essai &anche (schema)

1 Chambre d 'essai &anche; 2 Cel lu le dans laquel le est enchf isse l '&hant i l lon (voi r f ig . 5) ;3 P laque d 'ob tu r a t ion ; 4 Tr ing le assu ran t l e ma in t i en des p l aques d 'ob tu r a t ion ; 5 Jo in t an -nu la i r e pe rmet t an t des mouvement s ho r i zon taux ; 6 Jo in t annu la i r e pe rmet t an t des mouve-men t s ve r t i caux ; 7 Se l le - - ne pou van t se ddp lacer qu 'ho r i zon ta l em en t avec le p i s ton ; 8 P i ston ;9 Barre de rdact ion (vol t f ig . 3 a)


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Un drained Shear Testing of Jointed Rock 135f o r i n d e p e n d e n t c o n t r o l o f : t h e t h r e e tr a n s l a t io n a l a n d t h r e e r o t a t i o n a l m o d e so f r e l a t i v e d i s p l a c e m e n t , o r t h e i r r e a c t i o n f o r c e s ; e n v i r o n m e n t a l c o n d i t i o n s ;t h e p o s i t i o n a n d o r i e n t a t i o n o f t h e a p p l i e d l o a d v e c t o r w i t h r e s p e c t t o t h ej o i n t p l a n e t h r o u g h l a r g e d i s p l a c e m e n t s ; a n d l o a d o r d i s p l a c e m e n t r a t e s . T h es e le c t ed d e si g n p r o v id e s f o r c o n t r o l o f s h e a r i n g d i s p l a c e m e n t a n d n o r m a l f o r c e .L a t e r a l s he a r t r a ns l a t i on i s p r e ve n t e d a s a r e a l l r o t a t i ons . T he l i m i t a t i ons on

F i g . 3 aN

i a e -T5

i , , e I< T

Fig. 3 bd i s p l a c e m e n t a n d r o t a t i o n a r e n e e d e d t o p e r m i t se a li n g o f th e t e st c h a m b e rf o r i n t e r n a l w a t e r p r e s s u r e . T h e n o r m a l l o a d i s s t a t i o n a r y w h e r e a s t h e c e n t e ro f t he c on t a c t a r e a t r a ve l s ; t hus l a r ge d i s p l a c e m e n t s a r e no t f e a s i b l e .F ig . 3 a s h o w s a s c h e m a t i c s e c ti o n t h r o u g h t h e m a c h i n e . S h e a r in g is c o n -d u c t e d w i t h i n a w a t e r - t i g h t t e s t c h a m b e r w h i c h is o p e n e d f o r i n p u t t in g t h es a m p l e b y r e m o v i n g 8 m a c h i n e b o lt s ( 11 "). T h e s a m p l e w i t h a h o r i z o n t a l j o i n tp lane up to 4 .5 by 4 .5 inches (11 .4 by 11 .4 cm) in a rea , i s po t t ed wi th in a s t ee lb o x w h i c h is r ig i d ly c o n n e c t e d to t h e h o r i z o n t a l l y tr a v e ll in g p i s t o n (4) t h r o u g ha s a d d l e ( 2 ). T h e t h r u s t o f t h e f r o n t o f th e s a d d l e a g a i n s t t h e l o w e r h a l f o ft h e s a m p l e is r e s is te d b y t h e r e a r o f th e w a t e r c h a m b e r (3 ); t h e c h a m b e r a n dt h e r e f o r e t h e t o p o f t h e s a m p l e i s h e l d s t a t i o n a r y h o r i z o n t a l l y b y r e a c t i o nr ods ( 6). T he s e r od s c a n r o t a t e f r e e l y i n t he ve r t i c a l p l a ne t o a l l ow t he w a t e r

* Nu m ber references here refer to annota t ions o n the appropria te f igures .


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136 R.E. Go od ma n and Y. Oh ni sh i :cham ber to move ver tica lly th roug h a m axi m um a mpl i tude of 3/8 of an inch(0.95 cm) as the joint contracts, di lates, or closes. The maximum horizontalshear d isp lacement of th e bo t t om of the sample past the top is 0 .5 inch(1.27 cm). Th e ho rizon tal dis placem ent is created by a mo tor and v ariablespeed transmission, yielding a maximum shearing speed of 0 .275 inches permin ute (0.012 cm/sec) . Th e n orm al loa d is supplied by a hyd raulic pistonmain ta ined a t constan t p ressure by an accumula tor .The m ax im um no rma l and shear loads are bo th 40,000 pounds (0 .178 MN )This provides a maximum normal or shear s t ress on the la rgest specimen of2000 psi (13.8 M N/m ~). Load s a re mea sure d by strain gauge load cells (2) and(3) and displaye d on a digital voltm eter , a pr inter , an d an XYY plo t te r . Manualfeedback of the norm al pressure permits fine contro l on the norm al force . There la t ive normal d isp lacement be tween the top and bot tom of the specimen isref lec ted in the re lat ive mo vem ent be tween the wate r cham ber and a po in t onthe s ta t ionary base (10). A l inear po ten t iometer (14) between these po in tsthus measures the normal deformat ion of the specimen*. Shear deformat ionis measured by a l inear potentiometer (5) between a point on the base (10)

* At first the chamber bottom itself was used as a reference; but expansion ofthe chambe r whe n pressuring it with water added to the actual joint closure or opening.To offset this, a bar connected to the lower corners of the water chamber, which donot balloon during pressuring, now serves as the upper abutment for the linearpotentiometer.

Fig. 4. Direct shear machinea) top view, with cover removed; b) side view; c) during a testi Normal load cell and cover plate; 2 Test chamber - - can move only vertically; 3 Seal plate;4 Seal plate compression rod (to put vertical mot ion"0" rings in commpression) ; 5 Roller bearingsfor horizontal motion of pistons inside chamber; 6 Shear force reaction rods, f lexible in verticalplane; 7 Normal load system; 8 Specimen saddle; moves horizontal ly inside chamber; 9 Outlets,intra-specimen pore pressure lines; 10 Pore pressure transducers; i 1 Roller bearings to mainta inhorizontal motion direction; 12 Piston

Direkt-Schermaschinea) Draufsicht ohne Abdeckung; b) Seitenansicht; c) w~ihrend des Versuches

1 Normalbelastungszelle und Deckplatte; 2 Versuchskammer -- nut vertikal beweglich;3 Dichtungsring; 4 Dichtungsring mit Spanngest~inge; 5 Rollenlager zur horizontalen Be-wegung der Gest~inge in der Kammer; 6 Scherkraft-Gegendruckstange; 7 Normalbelastungs-system; 8 Probenschubklotz (bewegt sich hor izontal in der Kammer); 9 Fltissigkeitsausl~isse;i0 Porendruckanzeiger; /1 Rollenlager zur Einhaltung der horizontalen Richtung der Be-wegung; 12 SchubvorrichtungPhotos de la machine pour essais de cisaillement directa) vue d'en - - haut; b) vue latdrale; c) pendan t l'essai1 Cellule de mesurer la charge verticale et couvercle; 2 Chambre d'essai - - ne peut se d6placerque verticalement; 3 Plaque d'obturation; 4 Tringle de maintien de la plaque d'obturation(met sous pression le joint annulaire permettant les mouvements verticaux) ; 5 Pallets ~t rouleauxpour le mouvement horizontal des pistons fi l'int6rieur de la chambre; 6 Barre de r4action,

flexible dans le plan vertical; 7 V6rin de mise en charge verticale; 8 Selle de l'6chantillon; seddplace horizontalement ~t l'int~r ieur de la chambre; 9 Tuyau d'~vacuation du liquide de miseen pression; 10 Appareil indicateur de la pression interstitielle; 11 Paliers ~t rouleaux maintenantla direction du mouvement horizontal; 12 Piston


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Undrained Shear Testing of Jointed Rock 137

Fig. 4


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138 R . E. G o o d m a n a nd Y. O h n i s h i :and the piston. (Jewelled dial gauges also give direct readings of these dis-p lacements). D ur ing a tes t the ou tputs o f po ten t iome ters (14) and (15) areconnected to Y1 and Y2 of the plotter while X receives ei ther the output ofload cell (2) or (3) according to the stage of the test.

The un ique fea ture of the machin e is the sea ling mec hanism for the w atercham ber , which susta ins w ater p ressure ins ide the cha mbe r of up to 700 psi(4.83 M N /m 2) thr ou gh ou t the test , despite differential displacem ent acrossthe sam ple o f 0.5 inches (1.28 cm) h oriz ont ally a nd 0.375 inches (0.95 cm)vert ically'*. Fig. 3 b show s ho w the seals wo rk. T he sides of the box have anopening la rger than the ac tua l p is ton (8) by the amount of the a l lowablevert ical motion (3/8 inch) (0.95 cm). Close fitting seal plates (3) are pressedagainst the sides of the chamber by adjustable tension rods (4) . The vert icalmot ion of the chamber i s accommodated by s l id ing be tween the sea l p la tesand the s ides of the chamber whi le hor izonta l mot ion of the p is ton is accom-mo date d by s lid ing be tw een the seal p la tes and the p is ton . The f r ic tion in tro-duced by "0" r ings (6) is signif icant at higher pressures, even though tef lon"0" r ings are used, so for tests at lower chamber pressure, the seal plate pres-sure rods (4) are loosened by adjust ing the nuts with a torque wrench.

Th e d i rec t shear cham ber is show n wi th the cover and load cel l remov edin Fig. 4a. Fig. 4b shows a side view. During a test , the cover is bolted onand the mac hine i s l i f ted by hydrau l ic jacks pushed a long i ts t racks un t i l thechamber i s cen tered under the normal load press (7) and lowered onto thetable of that press. Fig. 4c shows the machine during a test .For und rain ed tests, ja cketing of th e specimens is neccessary**. Fig. 5depic ts the jacket ing ar rangement developed af ter numerous t r ia ls and modi-f icat ions . C ircu lar samples four inches in d iameter , a re sa tura ted un der va cuumand enveloped in a mo torcycle inn ter tube and resa tura ted . A lum inum discs(6) with circumferential "0" r ings (7) are f i t ted under the inner tube againstbo th ends of the specimen and hose c lamps (8) a re t igh tened over them. Af tera f ina l resa tura t ion to remove a i r bubbles th rough the measur ing ho les in thebot tom d isc , the specimen is po t ted in su l fur ins ide the shear box . Two porepressu re piezom eter holes 3/32 inch (0.238 cm) diam eter are cored to interceptthe cen ter o f the jo in t p lane . The shear box is then bo l ted in p lace on the

sadd le (2). (The piez om ete r holes an d filters (Fig. 5, (11)) can be seen clear lyin Fig . 4a (9) ). Fig . 6a show s the com ponen ts of the shear box . T he assembledspecimen before po t t ing in the shear box is shown in Fig . 6b ; the two halvesseparated af ter a test are shown in Fig. 6c.

The wate r p ressure supply and contro l c i rcu i ts a re represen ted schemat i -cally in Fig. 7 . Ch am be r w ate r pressure pc, supplied by an air pum p, is requir ed* The actual ma xim um internal pressure is limited by leakage, not b y structuralintegrity. T o appro ach the safe upper limit of 2000 psi internal w ater pressure requiresso much force on the seal plates as to introduce unacceptable friction in the test

apparatus. Accordingly 700 psi has been ado pte d as the practical uppe r limit.** Originally it was considered possible that low joint permeability would permitjoint water pressure to be measured in quick shearing of unjacketed specimens. Thisdid no t pro ve to be true. (A ma xim um Pf of 25 psi (172.5 KN /m 2) was measured).


11/21

U n d r a i n e d S h e a r T e s t in g o f J o i n t e d R o c k 1 39t o p r e v e n t b l o w o u t o f t h e ja c k e t d u r i n g a p p l i c a t io n o f i n i ti a l p o r e p r e s s u re( b a c k p r e s s u r e ) p ~. T h e b a c k p r e s s u r e s u p p l i e d f r o m a w a t e r r e s e r v o i r p r e s -s u r e d b y a n i t r o g e n c y l i n d e r is i n t e n d e d t o i n c r e a s e t h e d e g r e e o f s a t u r a t i o n

[7//////////////////////////////|

W/////////////////I/J13VTL'/Z

////J j 7

1 F - -F i g . 5 . Ar r angem en t o f sample in s ide shear box

1 rock sample - - upper po r t ion (4 inch d i amete r cy l inder ); 2 j o in t su r f ace ; 3 rock sam ple - -lowe r po r t ion (4 inch d i amete r cy l inder) ; 4 3 /32" d i amete r w a te r p r essu re measurem en t bo reho le (2 ho les ) ; 5 i nner j acke t - - b i cyc le inner t ube ; 6 a lumin ium d isc - - 4 i nches d i amete r by1 /2" th i ck ; 7 "0" r ings ; 8 hose c l amps ; 9 su l fu r po t t i ng m ate r i a l; 10 s h e a r b o x ; 1i p o r o u s b r as sfilter; 12 sadd le conn ec ted to t e s t ing mach ine p i s ton ( see F ig . 3b ) ; 13 p iezomete r ho les i nshear boxAnordnung des Pr i i fk6rpers in der Scherbi ichse

1 Gesteinsprobe, oberer Tei l (4" Zyl inderdurchmesser ) ; 2 Kluf t f lSche; 3 Probenunter te i l ;4 2 Bohrungen (3 /32" ) zu r Wasse rd ruckmessung ; 5 inhere Umscha lung ; 5 Alumin iumsche ibe ,4" Durchmesser , 1 /2" d ick; 7 0-Ring; 8 R6hrenklemme; 9 Schwefel -Vergufgmasse; 10 Scher-biichse; 11 por6ser Messingfil ter ; 12 Schubk lo tz , ve rbunden mi t de r Schubvor r i ch tung ( s i eheAbb . 3 b ) ; 13 Piezometerbohrungen in der Scherbi ichseDisposi t ion de lchant i l lon a l ' in t&ieur de la cel lu le

1 Echant i l lon de roche - par t ie super ieure (cylindre de 4" de diametre) ; 2 Surface du jo int ;3 Echan t i l l on de roche - p a r t i e i nfdr ieu re ( cy lind re de 4" de d i amht r e ; 4 Tro u d 'un d i am& rede 3 /32" pour l a mesure de la p ress ion d ' eau (2 t r ous) ; 5 Env e loppe in te r i eu re - cham breai r de b icyclet te ; 6 Disque en a luminium - 4" de diametre e t 1/2" d 'epaiss eur ; 7 Join t annulai re ;8 Collier de serrage ~ vis; 9 Lit de soufre dans lequel l 'dchantil lon est enchfisse; 10 Cellule;11 Fi lt re en la i ton poreu x; 12 Selle relied a u pisto n (voir f ig. 3 b); 13 Ouver tu r e pour p idzomet r ea n d t o i n s u r e p o s i t i v e p o r e p r e s s u r e p ~ t h r o u g h o u t t h e t e s t d e s p i te n e g a t i v ei n d u c e d p r e s s u r e .

pp = pb + p~ (4)w h e r e p ~ is t h e i n i ti a l b a c k p r e s s u r e

p,,: i s t h e i n d u c e d p o r e p r e s s u r e a t a n y t i m ep p is t h e p o r e p r e s s u r e a t a n y t im e

D u r i n g t h e s h e a r t e s t , t h e d if f e r e n c e b e t w e e n p o r e a n d c h a m b e r p r e s s u r e( p ~ - p c ) is m e a s u r e d b y d i f fe r e n t ia l p r e s s u r e g a g e s l o c a t e d c l o s e t o t h e te s tc h a m b e r . R u p t u r e o f t h e ja c k e t i s s i g n a l le d b y a z e r o r e a d i n g o f t h e s e g a u g e s .


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140 R . E . G o o d m a n a nd Y. O h n i s h i :T h e c o m p l e t e r e c o r d o f a s h ea r t e s t i n c lu d e s a d e s c r i p t i o n o f t h e r o u g h n e s s

a n d w a v i n e s s o f th e jo i n t s u r fa c e , c o m p u t e d f r o m d i g it a l h e i g h t m e a s u r e m e n t su s i n g a m il l b e d . ( T h e p e r m e a b i l i t y o f t h e j o i n t c a n b e m e a s u r e d a t i n t e r v a ls

Fig. 6. Test sample and preparation s: a) compo nents fo r preparing a jacketed specimen1 bottom disc with "0" ring edge grooves and pore pressure holes, protected by "0" rings (7)(top disc 8 lacks measuring h oles); 2 hose clamp s; 3 side for lowe r half of shear bo x with sidegrooves for bolting to testing m achine; 4 bo ttom plate; 5 upper sides; 6 top plate.b) Assembled jacketed saturated specimen ready for potting in shear box

c) Jacketed specimen halves after shear test; note water pressure measuring holes connectingshear surface with base of sample box

Priifk6rper-Vorbereitungen: a) Bestandteile des ProbengeMuses1 Bodenscheibe mit Ran dnu t fiir den 0-Ring und 0-Ring-gedichteten Porend ruck-B ohrung en(7), 8 Deckscheibe; 2 R6hrenklem men; 3 Um rand ung der unteren ScherbiichsenMlfte mitNuten zum Verbolzen mit der Testmaschine; 4 Bodenplatte; 5 oberer Scherbiichsenrahmen;6 Deckplatte

b) vollst~indiger, ummantelter, testbereiter Prtifk~Srperc) um man telter Priifk6 rper, Obe r- und Unterseite, nac h dem Scherversuch. Beachte die Wasser-druck -Metgb ohrun gen, welche die Scherfl~iche mit der Basis der Scherbiichse verbin den

Photos illustrant la pr4paration de l '&hantillona) E16ments n&essaires ~ la pr6paration de l'6chantillon

1 Disque infdrieur don t la tranche en forme de g orge sert de si6ge au joint annulaire; (7) Trou sde prise de pression interstitielle mun is de leur joint ann ulaire; (8) Disque sup& ieur sans trous ;2 Collier de serrage a v is ; 3 Paroi laterale de la moiti6 infdrieure de la cellule, rainurde p ou rperm ettre le bou lon nag e fi la mach ine de cisaillement; 4 Plaque inf6rieure; 5 Paroi lat&ale dela moitid sup&ieure; 6 Plaque supdrieureb) Ech anti llon satur 6 rev &u, pr~t ~t &re enchfiss6 darts la cellule

c) Deux moiti4s de l'4chantilonl sdpar4es apr~s ]'essai rioter les trous reliant la surface decisaillement fi la base de la cellule et pe rm ett an t la me sure de la pressio n interstitielle

d u r i n g t h e te s t b y f l o w i n g w a t e r f r o m o n e p i e z o m e t e r h o l e t o t h e o t h e r a n dt h e n t h r o u g h a f l o w m e t e r o r i n t o a b u r e tt e . I n t e r p r e t a t i o n o f t h e s e d a t a t oy i e ld p e r m e a b i l i t y c o e f fi c i en t s r e q u i r es c o m p u t a t i o n t a k i n g i n t o a c c o u n t t h ep o s i t i o n o f t h e p i e z o m e t e r h o l e s i n t h e j o i n t p la n e ) .


13/21

Un dra ined Shear Tes t i ng o f Jo in t ed Rock 141Triaxial Compression Machine and Procedures

T h e t r i a x i a l te s t c h a m b e r u s e d is t h e U . S . B u r e a u o f R e c l a m a t i o n c el l( d e s ig n e d b y O . O l s e n ) * . F ig . 8 s h o w s a t w o i n c h ( 5.0 8 cm ) d i a m e t e r j a c k e t e ds p e c i m e n a t t a c h e d t o t h e h e a d o f t h e t r i a x i a l c e l l ( i t i s i n v e r t e d i n t h i s v i e w ) .B i c y c l e i n n e r t u b e is s l i p p e d o v e r t h e r o c k a n d o v e r " 0 " r i n g s o n s t e e l e n dp ie c e s, a n d a n o i l r e s i s ta n t r u b b e r o u t e r j a c k e t is f a s t e n e d d o w n w i t h h o s ec l a m p s . P o r o u s s t a i n l e s s s t e e l e n d d i s c s a r e u s e d t o c o l l e c t w a t e r i n p r e s s u r e

A I R

-@S G

~m

AIR (FO R DRAINING CH~,NBER)- 7, - . . . . . _ L . . . ._ _ ~ JA C K E T ( P c ) l) ' , I [ R O C K I I ,

' I F T I 'i) i

[ ~ , , , " . , ll . ll k , k' ~ C O N N E G T I O N

Fig. 7. Simplified scheme of water pressure measuring an d control circuitsC water chamber; @ valve; DPT differential pressure transducer, 0--500 psi; APT absolutepressure transducer, 0--2000 psi; SG sight glass ; N2 nitrogen bo ttle; M mano meter(Bourdon type)

Vereinfachtes Schema fiir Wasserdruck-Mef~- un d SteuerschaltungenC Wasserkammer; @ Ventil ; DPT Differentialdruckgeber; APT Geber fiir den Absolutdruck;

SG Sichtglas; N2 Stickstoffflasche; M Mano meterPlan sim plifi6 des circuits de contrgle et de me sure de la pression interstitieileC Cham bre d'essai; @ So upape; DPT Ap pareil indicateur de pression diffdrentielle,0--500 psi;APT Appareil indicateur de pression absolue, 0--2000 psi; SG Regard; N2 Bouteille d'azote;M Manom ~tre ( type Bourdon)l in e s a t b o t h e n d s o f t h e s p e c im e n . T h e u p p e r l in e p a ss e s d i r e c tl y t h r o u g h t h eh e a d w h i l e th e l o w e r l i n e r u n s t h r o u g h t h e c o n f i n i n g f l u i d i n s id e a s p i ra l li n ea n d t h e n t h r o u g h t h e h e ad . T h e o il a n d w a t e r p r e s su r e s u p p l y a n d r e g u l a ti n gs y s te m w a s b u i lt , w i t h f e w m o d i f ic a t i o n s , f r o m d r a w i n g s o f t h e M i s s o u r iR i v e r D i v i s i o n L a b o r a t o r y o f t h e C o r p s o f E n g i n e e rs a n d is as d e s c r i b e d b yN e f f ]7, D e k l o t z e t a P a n d H e c k 11. P r o c e d u r es u s e d a r e s im i la r t o t h o s e

* De.scr ibed in the U. S . Bureau of Reclamat ion Repor t No. SP-39.


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142 R . E . G o o d m a n a n d Y . O h n i s h i :d e s c r i b e d b y B r u h n a . F o r t e st s w i t h j o i n t s , p i e z o m e t e r h o l e s w e r e d r i l l e df r o m b o t h e n d s t o i n t e r c e p t t h e j o i n t p l a n e a s s h o w n i n F ig . 8.

5

1 i

Fig. 8 aFig. 8. Jacketed rock specimen triaxial test apparatus1 Head of tr iaxial cell ; 2 joint in rock sample; 3 3/32" dril l hole for water pressure measure-ments; 4 stainless steel high pressu re tubin g; 5 s train gaug e leads; 6 por ous stainless steel disc;7 inner jacket , bicycle inner tube; 8 o uter jacket , oi l res is tant rubber ; 9 hose c lamp

Triaxia lversuchs-A nordnu ng f/ .ir umm ante l te Geste insprobe1 Kopfte i l der Tr iaxia lze l le ; 2 Kluf t in d er Geste insprobe; 3 3/32"-Bohrloch zur Wasserdruck-messung; 4 korros ionsfes te Hoch druckv errohrun g; 5 Verformungs-Met~vorrichtung; 6 por6se ,korro sionsfes te Stahlscheibe; 7 innere Um schalung; 8 Auf~enmantel aus 61festem Gu mm i;9 R6hrenklemme

Echant i l lon de roche rev&u po ur l 'essa i t r iaxia l1 T&e de la ce l lule t r iaxia le ; 2 Surface du jo int ; 3 Tr ou de 3/32" de diamhtre pour la mesurede la press ion d 'eau; 4 T ube & haute press ion en ac ier inoxy dable ; 5 Cfible de la jauge demesure des d6format ions; 6 Disque en ac ier inoxyd able poreux; 7 Chemise int6r ieure , chambreair de bicyclette; 8 Ch emise ext6rieure, caoutch ouc resistant ~ l 'huile; 9 Co llier de serragefi vis


15/21

U n d r a i n e d S h e a r T e s t i n g o f J o i n t e d R o c k 1 4 3

Fig. 8 b

T a b l e 1. P r o p e r t i e s o f L y o n s S a n d s t o n e

O v e n d r i e d Sa t u r a t e d i n w a t e r *

U n i t w e i g h t . . . . . . . . . . . . 2 .2 0 g m / c m aP o r o s i t y . . . . . . . . . . . . . . . 19.6%A i r p e r m e a b i l i ty . . . . . . . .W a t e r p e r m e a b i li t y . . . . . .Modulus o f e l as t i c i ty**"~. .Po i s s o n ' s r a t io * * ** . . . . . .B r a z i l i a n te n s i le s t r e n g t h .M o d u l u s o4 r u p t u r e . . . . .

106 mil l idarc ies* ' :0 . 6x 106 psi (4 .1 x 10 a M N /m =)0.30260 ps i (1 .79 MN/m 2)520 psi (3.58 M N / m ~ )

Cohesion ........" : . . . . . . . . . . 4 5 0 p s i ( 3. 10 MN / m ~)Fr ic t ion ang le***** . . . . . . 560Fr i c t i o n a n g l e o f s a w e d

j o in t s . . . . . . . . . . . . . . . . . 3 40

2 .3 7 g m / c m a17%

49 mi l t idarc ies**0.36 x 10 ~ psi (2.5 x 103 MN /m 2)0.26135 psi (0 .93 MN/m 2)230 ps i (1 .58 MN/m 2)250 ps i (1 .72 MN/m 2)49 034 0

* v a c u u m s a t u r a t e d a t r o o m t e m p e r a t u r e ;** 1 mil l id arc y equ als 9 .87 x 10 -12 cm~-;

*** t a n g e n t t o s t r es s s t r a i n c u r v e a t 5 0 % o f p e a k l o a d ;**** a t 50% of pea k load ;

***** the cohes ion and f r i c t ion ang le g iven descr ibe the average l ine fo r the in i t i a l par t o f theMo h r e n v e l o p e , w h i c h a c t u a l l y i s c u r v e d . T h e e q u a t i o n s o f t h e Mo h r e n v e l o p e , f o rd ry spec im ens ( in ps i un i t s ) a re 3= 21 .6 cr2/a ( ;> 500 ps i3= 5 .46 ~0 .sa +4 50 o r< 500 ps iSa t u r a t e d s p e c i me n s t e s t e d a t a s t r a i n r a t e o f 1 0 - 2 p e r s e c o n d i n u n d r a i n e d c o n d i t i o n ss h o w s s o m e w h a t s m a l le r s t r e ng t h .


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144 R.E. G oo dm a n and Y. Oh ni sh i:Ty pica l Tes t Resu lt s

Results of testing with various rock types will be presented in a laterpaper. Here we present some illustrative results of triaxial and direct sheartests using specimens of quartzose sands tone of the Lyons format ion (Permianof Colorado). Samples were sawed from a homogeneous large block. Thesandstone is a fine-grained, well-sorted, orthoquartzite, weakly cemented withiron oxide. The properties are influenced by saturation as shown in Table 1.

Fig. 1 showed changes of the B coefficient of intact Lyons sandstonemeasured in the triaxial test. The hypothetical curves for jointed samples alsoshown in Fig. 1 proved accurate in detail as shown in Fig. 9. The B coefficient,

I 0

0. 8

0. 6

0. 4

0. 2

B C O E F F I C I E N T_ d P [ / d o ' -

0 I I ; I I I0 [ 0 0 0 2 0 0 0 3 0 0 0 4 0 0 0 5 0 0 0 6 0 0 0A L L - A R O U N D P R E S S U R E ( o -3 = G I ) ps i

Fig. 9. Variation of B coefficientmeasured for intact and jointed samples of Lyons sandstonein undrained triaxial compressioni Porous rock; 2 jointed porous rock

_Knderung des KoeffizientenB, gemessen an ungest6rten und gekliKteten Proben yon Lyons-Sandstein im Triaxialdruck ohne Dr~inung1 Por6ses Gestein; 2 gekliKtetes,por6ses GesteinVariation du coefficient B mesur4 pour des 6chantillons de gr& de Lyon intacts (1) outravers4s par un joint (2) et soumis 5 un essai triaxial non drain4

for a triaxial specimen with an inclined saw cut and sandblasted joint, wasinitially 1.0; the jointed specimen behavior became identical to that of theintact specimen above ~ =2800 psi.

The measured changes of induced pore pressure with deviator stress aregiven in Fig. 10, and should be compared with Fig. 2. As premised earlier, thedata show a positive pore pressure at the moment of joint slip, whereas theintact sample dilated long before peak loading. Tangent A values initiallywere 0.11 for both intact and jointed samples. The A value determined by asecant to the peak positive pore pressure was 0.7 for both samples.


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Und rained Shear Test ing of Jointed Roc k 145T h e d i r e c t s h e a r r e s u l t s a r e s h o w n i n F i g . 1 1 . F i g . 1 1 a g i v e s t h e c o m p re s -

s i o n o f t h e i n ta c t r o c k a n d o f t h e s a m p l e w i t h a s a w e d j o i n t d u r i n g n o r m a ll o a d i n g . F ig s. 1 1 b , c , a n d d g iv e t h e n o r m a l d i s p l a c e m e n t , s h e a r d i s p l a c e m e n ta n d i n d u c e d w a t e r p r e s s u r e d u r i n g t h e s h e a r in g p h a s e o f t h e t e st . S in c e t h ed i r e c t s h e a r m a c h i n e i s n o r m a l s t r e s s c o n t r o l l e d , r a t h e r t h a n n o r m a l d i s p l a c e -m e n t c o n t r o l l e d , t h e s a m p l e is f r e e t o d i l a t e o r c o n t r a c t d u r i n g s h e a r in g , e x c e p t

P [6 0 0 4 0 0 2 0 0 0 - 2 0 0 - 4 0 0 - 6 0 0 - 8 0 0 - I0 0 0/(c5 l I i ~ 7I I I - 0"3) P S I

[ ~ ~ 6 0 ~ -1 5 ,0 0 0

!J

~ - / I I I I0 0 0 0 5 0 0 1 0 0 0 1 5 0 . 02 0L O N G I T U D IN A L S H O R T E N I N G ( I N / I N )Fig. 10. U ndrained triaxial test results w ith intac t and jointed samples of Ly on s sandstoneunder deviatoric loadingErgebnisse yon Triaxialversuche n ohn e Dr~inung mit u ngest6rten und gekRifteten Probe n vonLyons-Sandstein unte r Belastung mit ungleichen L~ings- und SeitendriickenRdsultats d'essais triaxiaux non drainds sur des dchantillons de grhs de Lyon intacts outravers6s par un jointo f c o u r s e fo r t h e i n e r ti a o f th e w a t e r . I n it ia l ly , t h e n o n - j o i n t e d r o c k c o n t r a c t e dv e r y s li g h tl y ; t h e n i t b e g a n t o d i l a te . U n t i l o n e t h i r d o f th e p e a k s h e a r d e f o r m a -t i o n , t h e p o r e p r e s s u r e i n c r e a s e d u n i f o r m l y a t a r a t e g i v e n b y A 1 e q u a l t oa p p r o x i m a t e l y 0 . 1 3 ( se e E q . (3 )). A f t e r a p p r o x i m a t e l y t w o t h i r d s o f p e a kd i s p l a c e m e n t t h e ta n g e n t A 1 v a l u e b e c a u s e n e g a t iv e a s t h e i n d u c e d w a t e rp r e s s u r e d e c r e a s e d f r o m t h e m a x i m u m o f 6 0 p s i (4 14 K N / m 2 ) . A t p e a k l o a dt h e in d u c e d p r e s s u r e w a s - 6 0 p s i. A s i n t h e t r i a x ia l t e s t, th e p e a k l o a d i n t h ej o i n t e d s p e c i m e n w a s n o t p r e c e d e d b y a r e d u c t i o n i n i n d u c e d p r e s s u r e . T h ew a t e r p r e s s u r e i n d u c e d i n t h e j o i n t w a s a t it s m a x i m u m v a l u e o f 5 1 p s i(3 5 1. 9 K N / m 2) a t t h e p e a k s h e a r l o a d o f 4 8 0 p s i ( 3.3 1 M N / m ~) ( t a n g e n t A 1a t p e a k e q u a l t o 0 . 1 2 ) .

D is c u s s io n a n d C o n c lu s io nT h e p u r p o s e o f t h is p a p e r b e i n g t o p r e s e n t a n e w e x p e r i m e n t a l te c h n i q u ef o r s t u d y o f j o in t s i n t h e l a b o r a t o r y , o n l y a b r i ef d i s c u s si o n o f t h e r e s u lt sp r e s e n t e d i s a p p r o p r i a t e . T h e s e d a t a a r e t y p i c a l o f t h e t e s t r e s u lt s o b t a i n e d .

J o i n t w a t e r p r e s s u r e i s g e n e r a t e d i n t h e c o m p r e s s i n g p o r e s p a c e o f t h e r o c k ;a t h i g h n o l m a l p r e s s u r e s t h e j o i n t i t s e l f a p p a r e n t l y c o n t r i b u t e s a d d i t i o n a l l y a sa p r e s s u r e s o u r c e . A t l o w c o n f i n i n g p r e s s u r e s, t h e d i l a ti n g j o i n t w i ll d r a i n t h ep o r e w a t e r a n d t h e i n d u c e d p r e s s u r e c a n b e n e g at iv e . T h e j o i n t s t r en g t h i s

R o c k M e c h a n i c s , V o L 5/3 1 0


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1 4 6 R . E . G o o d m a n a n d Y . O h n i s h i :

r e d u c e d b y a p o s i t i v e p o r e p r e s s u r e i n a c c o r d a n c e w i t h t h e e f f e c t i v e s t r e s sp r i n c i p a l . A f t e r j o i n t s l i p i n i t i a t i o n , t h e j o i n t a p e r t u r e i n c r e a s e s a n d t h e w a t e rp r e s s u r e d r o p s . P r e s u m a b l y , t h i s a u t o m a t i c j o i n t w a t e r p r e s s u r e d e c l i n e c o u l dr e l o c k t h e j o i n t w a l l s g e n e r a t i n g a st i c k s l ip b e h a v i o r ; t h is h a s n o t b e e n s t u d i e d .E x p e r i m e n t a l r e s u l t s w i t h j o i n t s i n n o n - p o r o u s r o c k c o u l d p r o d u c e d i f f e r e n tre su l t s .

T h e d i r e c t s h e a r m a c h i n e a l l o w s i m p o r t a n t e x p e r i m e n t s w i t h j a c k e t e d o ru n j a c k e t e d j o i n t s p e c i m e n s ; i t c o u l d b e c a l le d a u n i v er s a l t est i n g m a c h i n e f o r

0

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N O R M A L S T R E S S , G - ( PS I)I 0 0 2 0 0 5 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0

G 7 5o_ IC~z L.

~ 2 5m~ 3og 3 5z

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S H E A R D I S P L A C E M E N T , u ( IN C H E S )0 . 0 5 0 1 0 0 2 5 0 . 2 0 0 . 2 5 0 . 3 0

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J .

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0 0 5 0 . 10 0 . 15 O . 0 O . 5 0 . 3 0 0 3 5S H E A R D I S P L A C E M E N T , u (I N C H E S )

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' ' ' 0~0 0'~5 00 05SHEAR u

F i g . 1 1 . U n d r a i n e d d i r e c t s h e a r t e s t r e s u l t s w i t h i n t a c t ( 1 ) a n d j o i n t e d ( 2 ) s a m p l e s o f L y o n ss a n d s t o n ea ) N o r m a l d i s p l a c e m e n t d u r i n g n o r m a l l o a d i n g ; b) n o r m a l d i s p l a c e m e n t d u r i n g s h e ar l o a d i n g(orn c o n s t ) ; c ) s h e a r d i s p l a c e m e n t d u r i n g s h e a r l o a d i n g (~rn c o n s t ) ; d ) i n d u c e d w a t e r p r e s s u r ed u r i n g s h e a r l o a d i n g (~ rn c o n s t )E r g e b n i s s e e i n e s D i r e k t - S c h e r v e r s u c h e s o h n e D r ~ i n u n g a n u n g e s t 6 r t e n ( 1 ) u n d g e k l i i f t e t e n ( 2 )P r o b e n y o n L y o n s - S a n d s t e i na ) N o r m a l v e r s c h i e b u n g b e i N o r m a l b e l a s t u n g ; b ) N o r m a l v e r s c h i e b u n g b e i S c h e r b e l a s t u n g ,c ru k o n s t a n t ; c ) T a n g e n t i a l v e r s c h i e b u n g b e i S c h e r b e l a s t u n g , % ~ k o n s t a n t ; d ) i n d u z i e r t e r W a s -s e r d r u c k b e i S c h e r b e l a s t u n g , c rn k o n s t a n tR d s u l t a t s d ' u n e s s a i t r i a x i a I d i r e c t n o n d r a i n d s u r d e s & h a n t i l l o n s d e g r ~ s d e L y o n i n t a c t s ( 1 )

o u t r a v e r s & p a r u n j o i n t ( 2 )a ) D @ l a c e m e n t n o r m a l s o u s c h a r g e n o r m a l e ; b ) D d p l a c e m e n t n o r m a l s o u s e f f o r t d e c i s a i l l e -m erit (orn c o n s t a n t e ) ; c ) D d p l a c e m e n t a u c i s a i l l e m e n t s o u s e f f o r t d e c i s a i l le m e n t (c% c o n s t a n t e ) ;d ) P r e s s i o n i n t e r s t i t i e l l e p r o d u i t e s o u s l ' e f f o r t d e c i s a i l l e m e n t (~rn c o n s t a n t e )


19/21

Undrained Sh ear Testing of Jointed Rock 147jo in ts . Dr a ine d a nd un d r a i ne d she a r t es t , j o in t pe r me a b i l i t y t e s ts und e r c on -t r o l l e d no r m a l a nd she a r s tr e ss , a nd n o r m a l c onso l ida t ion te s t s on f il le d j o in t sc a n b e a c c o m m o d a t e d . T h e t r i a x i a l t e s t w i t h j o i n t s a m p l e s b e t w e e n p o r o u se nd d i sc s a l so ha s un ta ppe d c a pa b i l i t i e s . F o r e xa mple i n t r oduc ing a l ong i tu -d ina l j o in t , i t s pe r me a b i l i t y unde r c on t r o l l e d no r ma l s t r e s s c a n be me a su r e d .I n t r o d u c i n g a n u n j a c k e t e d h o l l o w c y l i n d e r s a m p l e , H a b i b - B e r n a i x r a d i a lp e r m e a b i l i t y t e st s c a n b e p e r f o r m e d 22. The t r iax ia l te s t can sa fe ly employh ighe r no r ma l s t r e s se s whe r e a s t he d i r e c t she a r t e s t c a n pe r mi t l a r ge r she a rd i sp l a c e me n t s . I n bo th t e s ts , me a su r e m e n t o f j o in t wa te r p r e s su r e s nec e s s it a te sd r il li n g s m a l l h o l e s i n t h e s p e c im e n , i n t r o d u c i n g i n c o m p l e t e l y d e t e r m i n a t ein te r fe rences .W e f e e l t ha t t he c a pa b i l i t i e s f o r c on t r o l l i ng e nv i r onme n ta l c ond i t i ons i nl a b o r a t o r y j o i n t t e st s, a s s h o w n h e r e, m a k e l a b o r a t o r y t e s t in g o f j o in t s a m p l e sa t t r a c tive f o r p r a c t i c a l e ng ine e r ing wo r k .

AcknowledgementsT h e d e v e l o p m e n t o f t h e d i r ec t s h e a r m a c h i n e d e s c r ib e d h e r e r e fl ec tsn u m e r o u s c o n t r i b u t i o n s f r o m c o l le a g u es . D r . K a r el D r o z d c o n c e i v ed o f t h es e al in g m e c h a n i s m ; P r o f es s o r E v e r t H o e k a n d D r . D a v i d P e n t z f re e ly d is -c u s s e d d e s i g n o f t h e i r s h e a r m a c h i n e a n d f u r n i s h e d s h o p d r a w i n g s ( w h i c hw e re n o t u se d). D r . H u g h H e a r d a n d M r . D u a n e N e w h a r t h e lp e d t oe v a lu a t e d if fe r in g d es i g n c o n c e p t s. T h e b i g g es t s t ep w a s m a d e b y M r . K e n n e y

o f K e n n e y E n g i n e e ri n g C o . ( 1 3 0 1 S o u t h S h a m r o c k A v e n u e , M o n r o v i a , C a li -f o rn i a ), w h o d r e w u p o r i g in a l d e s ig n s b a se d u p o n n u m e r o u s c o n fe r en c e s a n dt h e n b u i l t t h e p r o t o t y p e . P r o f e s s o r T . L . B r e k k e c o n t r i b u t e d i n d i s c u s s i o n sw i t h K e n n ey E n g in e er in g . M a j o r m o d i f ic a ti o n s w e r e m a d e b y M r . Q u e n t i nG o r t o n , i n c l u d i n g r e d e si g n o f th e i n n e r s h e a r b o x , p la c i n g t h e f r a m e o nt r a c ks , i n s t a l l a t i on o f c on t r o l s on the no r ma l l oa d p r e s s , a nd de s ign o f ah y d r a u l i c c o m p e n s a t i n g s y s te m to c o u n t e r t h e w e i g h t o f t h e w a t e r c h a m b e ra n d u p p e r s h e a r b o x . M o s t o f th e i n s t r u m e n t a t i o n , i n c l u d i n g t h e h y d r a u l i cc on t r o l c i r c u i t , wa s i n s t a l l e d by Ke nne y Eng ine e r ing a nd l a t e r mod i f i e d byt h e a u t h o r s a s n o t e d in t h e t e x t. D r . F r a n co i s H e u z d c o n t r i b u t e d to d e v e l o p -m e n t o f p r o c e d u r e s f o r s a m p l e p r e p a r a t i o n a n d t e st in g . T w o b l o c k s o f L y o n ss a n d s t o n e o b t a i n e d a n d s h i p p e d b y P ro f e s so r D a v i d S n o w s u p p l i e d t h esa mple s f o r t e s ti ng .T h e m a c h i n e d es i g n a n d t h e p r o g r a m o f s a m p l i n g a n d t e s ti n g w e r e f u n d e du n d e r a g r a n t fr o m t h e N a t i o n a l S c i en c e F o u n d a t i o n ( G r a n t G K -2 97 9). M o d -i f ic a t ions t o t he m a c h ine a f t e r de s ign we r e m a de a s pa r t o f C on t r a c t H0210020f r o m t h e A d v a n c e d R e s e a rc h P r o je c ts A g e n c y (A R PA ) o f t h e U .S . D e p a r t m e n to f De f e nse , mon i to r e d by the U . S . B ur e a u o f Mine s . ( The v i e ws a nd c onc lu -s ions a r e t he a u tho r s ' a nd do no t r e p r e se n t po l i c y o f e i t he r AR P A o r NS F . )T h e t r i a x ia l c o m p r e s s i o n w a t e r c o n t r o l a n d o i l p r e s s u re s u p p l y a n d r eg -u l a t i ng c ir c u i t wa s f a b r i c a t e d by M r . B . R i l e y o f t he Un ive r s i ty o f C a l i fo r n i a ,C i v i l E n g i n e e r i n g D e p a r t m e n t s h o p f r o m p l a n s o f t h e C o r p s o f E n g i n e e r sp u b l i s h e d i n [ 6 ] . T h e t r i ax i a l c h a m b e r w a s f a b r i c a te d b y R i e h l e T e s t i n gM a c h i n e C o m p a n y u s i n g p l a n s p r o v i d e d b y t h e U . S . B u r e a u o f R e c l a m a t i o n

10"


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148 R . E . G o o d m a n a nd Y . O h n i s h i :a n d d e s c r i b e d in U . S. B u r e a u o f R e c l a m a t i o n R e p o r t N o . S P3 9. T h e f r e ea c c e s s t o t h e s e s h o p d r a w i n g s a n d c o o p e r a t i v e s pi r it o f p e r s o n n e l o f t h e s ea g e n c i e s a r e g r e a t l y a p p r e c i a t e d . M r . A n d r e K o 11 b r u n n e r a n d L o u T r e s c o n ye s t a b l i s h e d p r o c e d u r e s f o r t h e t r i a x i a l c o m p r e s s i o n t e s t s .

R e f e r e n c e s1 B i e n i a w s k i , Z . T . : " M e c h a n i s m o f b r i t t l e f r a c t u r e o f r o c k " , R e p o r t M E G580 CSIR, Preto r ia , Sou th Afr ica , 1967 .2 B r a c e , W . F . , a n d R . S. M a r t i n : " A t e s t o f t h e l a w o f e f fe c ti ve s tr es s f o rc ry s t a l li n e ro ck s o f l o w p o ro s i ty " , In tl . Jo u rn a l o f R o ck M ech . a n d Min . S cien ces,vol. 5 , no. 5 , p . 415 (1968).8 B r u h n , R . W . : " A s t u d y o f t h e e f fe c ts o f p o r e p re s s u re o n t h e s t r e n g th a n d

d efo rmab i l i t y o f B erea san d s to n e in t r i ax ia l co mp ress io n " , C o rp s o f E n g in ee r s ,M i s s o u r i R i ve r D i v. L a b . , T e c h . R e p o r t M R D L 1 - - 7 2 ( 19 72 ).4 B y e r l e e , J . D . , a n d W . F . B r a c e : " R e c e n t e x p e ri m e n t a l s tu d ie s o f b r it t lef r ac tu re o f ro ck s" , P ro c . 8 th S y mp o s iu m R o ck Me ch . (A IME ) , p . 5 8 (19 67 ).5 C o r n e t , F ., a n d V. F a i r h u r s t : " V a r ia t io n o f p o r e v o l um e in di si nt eg r at in gr o c k " , P r o c . S y m p o s i u m o n P e r c o l a t i o n T h r o u g h F i s s u r e d R o c k , I S R M , S t u t t g a r t ,S ep tem b er 1 97 2.6 D e k l o t z , E . J ., W . J. H e c k , a n d M . J. A l d r i c h : " D e v e l o p m e n t o f e q u ip m e n tfo r s tu d y in g p o r e p ressu re e f f ec ts i n ro ck " , M isso u r i R iv e r D iv . L ab . , C o rp s o f E n g i -n ee r s , T ech . R ep o r t N o . 3 - -6 8 (1 9 6 8 ) .7 G o o d m a n , R . E ., a n d J. L . D u b o i s : " T h e d u p li c a ti o n o f d i la t an c y i n t h ean a ly si s o f jo in t ed ro ck s" , Jo u rn a l S o il Me ch . an d F o u n d . D iv . , P ro c . A S C E , v o l . 98 ,no. SM4, p . 399 (1972).8 H a b i b , P ., a n d B e r n a i x J . : " L a f i s s u ra t i o n d e s r o c h e s " , P r o c. 1 st C o n gr e ssISRM, Lisbon, vol . I , p . 185 (1966).9 H a n d i n , J ., R . V . H a g e r , J r., M . F r i e d m a n , a n d J . N . F e a t h e r : " E xp e ri -men ta l d e fo rmat io n o f sed imen ta ry ro ck s u n d er co n f in in g p ressu re : P o re p ressu retests" , Bull . AAPG, vol. 47 (1963).

10 H e a r d , H . C . : " T r a n s i t i o n f r o m b r i t tl e f r a c t u r e to d u c ti le f lo w i n S o l e n ho f e nl imes to n e as a fu n c t io n o f t em p era tu re , co n f in in g p ressu re ; an d in t e r st i ti a l f lu id p res-su re" , i n R o ck D efo rmat io n , Memo i r 7 9 , G S A , p . 1 9 3 (1 9 6 0 ) .11 H e c k , W . J .: " D e v e l o p m e n t o f e q u i p m e n t f o r s t u d y in g p o r e p r e s su r e e f fe c tsin ro ck " , P ro c . 1 0 th S y mp o s iu m o n R o ck Mech an ics , (A IME ) , p p . 2 4 3 - -2 6 6 (1 9 7 2 ) .1~ J a e g e r , J . , a n d N . C o o k : F u n d a m e n t a l s o f R o c k M e c h a n i c s , C h a p . 8 : " F l ui dp ressu re an d f lo w in ro ck s" , p . 1 9 5 - -2 1 4 (19 69 ).13 J o u a n n a , P . : " E f fe t des so l li c i ta t io n s md can iq u es su r l es d co u lemen t s d an sce r t a in s m i l ieu x f i s su res" , T h es i s fo r D o c to r o f P h y s ica l S cien ce , T o u lo u se U n iv e r s i ty(1972).1 4 J o u a n n a , P . : " E s s a i s d e p e r c o l a t i o n a u l a b o r a t o i r e s u r d e s e c h a n t i l l o n s d emicasch i s t e so u mis a d es co n t ra in t es" , P ro c . S y mp o s iu m o n P erco la t io n T h ro u g hF i s su red R o ck , IS R M , S tu t tg a r t 1 97 2.15 L an e , K . S .: " E n g in ee r in g p ro b d u e to f lu id p ressu re in ro ck " , P ro c . 1 1 thS y m p o s iu m o n R o ck Mec h an ics , (A IM E ) , p. 5 01 (19 69 ).


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21v. 4, p.

22f e r e n c e

16 M e s r i , G . , R . A . J o n e s , a n d K . A d a c h i : " I n fl u e n ce o f p o r e w a t e r p r e s su r eo n th e en g in ee r in g p ro p er t i e s o f ro ck " , R ep o r t t o A R P A f ro m U n iv er s i ty o f I l l i n o i s ,Dept. of Civil Engineering (1972).17 N e f f , T . L . : " E q u ip me n t fo r m easu r in g p o re p ressu re in ro c k sp ec imen s u n d ert r iax ia l load" , ASTM Spec. Tech . Pub l . 402 , p . 3 (1965) .18 R o b i n s o n , L . H . : " T h e e f f e ct o f p o r e a n d c o n f in i n g p r e s s ur e o n t h e fa i lu r ep ro cess in sed imen ta ry ro ck " , P ro c . 3 rd S y mp o s iu m o n R o ck Mech an ics , (Q t ly .Colorado School o f Mines , v . 54 , p . 178 (1960) .19 R o b i n s o n , L . H . , a n d W . E . H o l l a n d : " S o m e i n te r p re t a ti o n s o f p o r e f lu ide f fec t s in ro ck fa i lu re" , P ro c . 1 1 th S y mp o s iu m o n R o ck Mech an ics , (A IME ) , p . 585(1969).20 Sco t t , R . : P r incip les o f So i l Mechan ics , Addison Wesley , Chap ter 6 (1963) .

S k e m p t o n , A . W . : " T h e p o r e p r e ss u r e c o e ff ic i en t s A a n d B " , G e o t e c h n iq u e ,143 (1954).S k e m p t o n , A . W . : " E f f e c t i v e s tr es s in s oils c o n c r e t e a n d r o c k " , P r oc . C o n -o n P o re P ressu re an d S u c t io n in S oi ls , B u t t e rw o r th , L o n d o n , p .4 (19 60 ).

2a T e r z a g h i , K . : " S tr e ss c o n d i t i o n f o r th e f a i lu r e o f sa t u r a te d c o n c r e t e a n drock" , P roc. ASTM, vo l . 45 , p . 777 (1948) .

A d d ress o f th e au th o rs : R ich ard E . G o o d m a n , A sso c ia t e P ro fesso r o f G e o lo g ica lE n g in ee r in g ; Y u zo O h n i s h i , U n iv e r s i ty o f C a l i fo rn ia , B erk e ley , C A 9 4 72 0, U . S . A .

undrained shear testing of jointed rock

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