Anisotropic hardening of an initially isotropic porous limestone

87A

A mathamatical model is u~ed to analyse the stress distribution of anlsotropic rock disks subject to diametrical lime load~mg. Ex~mlmes the validity of t~:e split cyli~ier test (Brazilian test) of transversely Isotropic rocks. 81~0~6 G E N ~ FAYLURE C~ITERXON FOR ROCKS Price, A M; Farmer, I W Proc 21st US Symposium on Rock Mechanics, Ro!la, Missouri, 28-30 May 1980, P256-263 Reports triaxia! c o ~ e s s l o n tests using a servo c o n t r o l l e d testing machine on 7 m~iium to low strength sedlmemt~rT rocks with a rar~e of confimlng pressures up to 42 MN/sq m and axial strains up to i0 per cent. Test results illustrate both strain hardening and strain softening post peak stress behaviour and related dilation. The plotted results suggest a critical state model for predicting failure mechanisms. 815057 ~'~'~6'TOF STRES~ PATH G E O ~ ON SOIL BRInnV.EZ'E,S$ Law, K T Geotechnlque, V31, N2, June 1961, P279-287 Shows am explicit relationship exi~cs bet~-een brittleness ani stress path gecme~-y for soils of given peak a~d post-peak strength envelopes. Results from tri~xial tests on clays ~mdlcate that drained teats yield the hi~hest brittleness either when the stress paths a r e re~himg failure at the same colliding ~tress cr when they start at the same consolidation pres~ure prior to shesrimg. 8150~8 RESIDUAL STRENGTH OF L~DF~CLAY Burlington, D; SteDhenson, R W; Rockaway, J D Proc 21st US Symposium on Rock Mechanics, R ~olla, Missouri, 28-30 May 1980, P~35-~5 Describes direct shear tests on s~bcoal samples to determine residual strem@~ah. The results are compared with results of earlier plate load tests to e~tablish a relationa~p between residual s~remgth arzl in situ strength based on lowest b~arirg capacity and lowest shear strer4~th. 81~0~9 C ~ s s I r V E ~gI'HEhDTH OF A B ~ I ~ J S COKING COAL Udd, J F; Eudson, K; Templeton, D Prcc 2!st US Symposium on Rock Mechanics, Rolla, M~s~ouri, 28-30 May 1980, P~68-~75 U~axlal compression tests on coal demonstrate a clear relationa~p between cc=~essive strength and dimensio,m ~ the samples. Disl gauges o~i electrical resistance strain g~uges were used to determine the defcrmatlo~al properties plotted as stress-strain curves. Results indicate deflr.ite non elastic behavlour umd~" stress. 815060 ULTT~i~.TE LOAD BEHAVIOUR OF LATERALLY CONSTRAIneD ROCK BEAMS Sterling, R L Proc 21st US Symposium om Rock Mechanics, Rolla, Missouri, 28-30 ~£'~y1980, P533-5~2 Describes tests on laterally constrained beams with various s ~ d e F t h ratios, materials, loadi~ conditions, ani supl~rt co~iltlons. The testing a ~ r a t u s was servo controlled. Load/ deflection, isteral thrus~vertical load, eccentriclty/vertical load curves determine

failure l,x~i. It was found thst shear or slip failures ~re critical at low s p ~ d e I ~ h ratios, lateral comlressive stresses control at mid spar/delfch ratios and buckllrg failure occurs at h~gh spa~depth ratios. 815061 APPLICATION OF THE P O I ~ LOAD INDI~( TEST TO STREEE/I~. DETERMINATION OF ROCK AND FROFOSAL~ A NEW SIZE-CC~RECTION CEART Hassani, F P; Scoble, M J; Whittaker, B N Proc 21st US Symposium on Rock Mechanics, Rolla, Missouri, 28-30 May 1980, P543-553 This paper re.~orts on t h e findings of an investigation into the effect of core diameter on point load i~iex value. A diameter-correction chart and s ~ t i n g equations f~r diameters up to !00me is p r ~ . s e n t e d as an aid to sta~dardlsed index reporting. Detsiled studies are reported on the deprivation of uniaxlal and triaxial rc~k strengths fTom point iced testing data. The paper is based upon data from extensive testiDg undertaken by the authors together with data ex*~ac*~d from lr~viously published work in the field. Auth. 21 refs. 8150E2 PROGRESSI~E FAILURE S D ~ A T Y O N M.ODEL~OR BRITTLE ROCK Lundquist, R G; Helns, R W Froc 21st US Symposi~ on Rock Mechanics, Rolla, Misso~-i, ~8-3o May 1980, P591-595 Uses a two dimensions/ finite element model tO investigate the IX,ssible relationship bei~,~een rock irAhomogeneity and progressive failure. The behaviour and validity of th~ model were exami~d by modelling the Brazilian test.

Deformation characteristics 815063 MEASURING SOIL PROPERTIES WITHOUT S~4PLES Dalton, J C P Int ',tater Power Dam Cozmtr, V32, N9 Se.wt 1980, P3z-34 Discusses the problem of meas~u'ing s o i l strer~th and stlffr~ss and in situ stress in. a bcrshole and describes the Cambridge self-borir~ eXl~Lnsion and load cell pressure~ters. 815064 HVORSI~V SUHFACE IN ROCK DEFORMATION Price, A M; Farmer, I W Int J Rock Mech Min Sci, VI8, N3, June 1981, P22~234 Triaxial compression tests were carried out on rock s~It and marl spec4mens at conflni~g pressures up to 42 MN/sq m. Volumetric strains were measured using a specially adapted triaxial cell. The results showed the brittle/ductile transition to be separate from the critical state add indicated the ey.lstence of a Hvaralev surface, relating shear strength to normal stress and specific volume, bet~'een these two points. These results are fur+her validated by comparison with those reported by other .~ork~'s. Auth. 815065 ANI~0TROPIC EABDENTNG OF AN Ir~ITAALLY ISOTROPIC POROUS L.~.{E,~PONE Celle, C C; Cheatham, J B Rock Mech, %~-3, -~, March 1981, P221-233

~A

Experimental results :~re reported for true triaxlal t e s t s on a porous limestone to determine the yield surface in stress Sl>~ce, +/%..-flow rule, a~i i~iuced amisotropy. The ir4tial yield sm-face is obtained by compression te~ts, extension tests ~md a hydrostatic ~+n~ess test. Permanent deformation occur~ under a hydrostatic stres~ for t~he dry, IX~OUS !~mestone used in the~e teats, thus the initial yield surface forms :~ closed surface in stress space. Ncrmslity of the str~in increment vector with respect to the yield surface is investigated by using d~fferent loadlm~ psth~ in stress space. Frc~ these different paths of lo~iing the morms~Ity l~rinciple can ~e v~rified. Work hardening along one axis ~roduces changes of the yield stress along the other axes so a sample that was initially isotropic becomes a~isotropic as a resttlt of the work hardening.

81~o66 LIQUEFACTION OF DIFWFRENT MINE TAILINGS UNDER STRESS CONTROLLED LOADIIW} Highter, W H; V~1_lee, R P Engmg Geol, V!6, NI-2, 1980, PLY7-150 Describes consolidated-undrained stress controlled triaxial tests on garnet ani zinc tailir4~s. The results are m ~ r i s e d by i~e critical void ratio or steady s-~ate ctu-ves. Despite similsr index l~operties the ~teady state curves for g~rnet and zimc differ. 815067 VT~SATILE HOLLOW CY~IND~.~ ."~IAYIAL DEVICE Dusseault, M B Can Geotech J, VI8, I~-, Feb 1981, PI-7 Describes a high-~ass~re, thick-walled hollow cylimder tri~xial device designed to ~rovide data from tests with caref111 stress path control radial strain tests, axial atrain-contrc~led and stress-co~trolled tests ani ccc~resslbility ~ests. Presents results of cyclic plane axial s~r~in c ~ e s s i b i l i t y tests on dense Ottawa sands.

81~o68 STRESS-STFJ~IN RELATIONSHIP FOR GRA~V~LR MA_e~IALS DERIVF~ FROM M~CROSCOPIC SHF;~ M ~ C E A I ~ Matsuoka, H; Takeda, K Soils Foumd, V20, N3, Sept 1980, P~-~8 Simple shear tests were carried out usimg a pile of alu~inium rods to simulate ~rcmmlar materials in a two ~mensionsl state. Granular materials are cor~idered to be a unit elmment composed of two particles, termed 'two particle models'. Slidi~g displacements between two particles across the ~teztial s l i d i n g p l a n e were f~cmulated by considering the mechanism of ~isalm~earar~e a~i generation ~f angles of i ~ t e r ~ I c l e contacts. A stress-st~aln relationship was derived from the a!idlmg displacements ami compared with the results of cyclic simple shear tests on alumlni~m rod mass. Strems-straln characteristics of a sa~i u ~ i ~ cyclic loadimg were explained ~y the proposed e~uation.

815o69 BEKAVIOR OF G ~

MATERIALS IN SIMPLE SHE~/R

Nemat-Nasaer, S Soils Found, V20, HS, Sept 1960, P59-73 Presents a simple model for two dime~.slomal deformation a~i flow of granular material accounting for initial denslflcation~ subsequent dila~rncy ax~ t h e n e t smount of der~ificatlon which accompanies cyclic shesrir~.

815070 STrESS-STRAIN BF}La.VIOUR OF AN IDEA!IZED P~qSOTROPIC GPA~SAR MATFLRIAL Tat suoka, F Soils Found, V20, N3, Sevt 19~0, P75-90 Presents a simple elasto-plastic theory for anisotro~c gre-.mllsr materials incorporat~ ng aniso+~opic yielding, plastic Ix~,ential furntious and en~iricBl, hardening which involve perimeters ex~m'e~s~ng inherent anis~cropy. Inhere~ anisO+~rOpy ar~ arlsotropic yielding in three dimensior~l stress conditions can be modelled by this theory. 81~)71 WHAT CONSTI~JTES A ~ R N ~ TECH}~CAL NGPE ~.ov~cs, ~.~D Ceotee_h Test Y, V3, N3, Sept 1980, P127-130 Proposes a definition of a turn of rope arovmd the cathead used to perfca~, the. sta~iard penetration test. The d~f~erence betweez clockwise sni counterclockwise rotation results in substantial wariation in the ez;ergy delivered to the s~mple and in the blow ccu~t for the same soll coz~itiom~. 815672 DEVF~RWENT OF HOLOGR~PHIC TECHEqQ~ES TO ~glX~DY THeY INDUCED D F ~ C A T ! O N Gilbert J A; Vedder, D T Exp Mech, V21, N~, A~ril 1980, P].~8-1~4 The effect of urifcrm tamperature rise on limestone specimen is ~nalysel. Displacement ~:tterns are o~talmed using ~ holographicMoire technique. These patterns ~re smalyse~ for strain due to teml:~'a~Te ir~rease. Transformation equations are applied to ~redict l~rlr~ipal streir~ and their correspondi~ directions. V~lues obtained for thermal coefficients of exI~nsion aEree with the more co~ventionsl ~(~erlmental .methods.

8~o~3 M E A S U P ~

OF ~.~ ELASTIC TENSOR IN ROCK-LIEE ANT OOTROPIC MATERIALS Cotza, R; Mar~a, P P; Vivanet, C Proc 21st US Symposimm on Rock Mechanics, Rolls, Mi.-souri, 28-30 ~ay 1980, 92~9"~5~

Demonstrates mathematically that for linearly elastic ~terial~ it is po~slble to determine experimer~tslly all the 21 independent components of the elastic tensor by carrying out :~ni.qxlsl comlm'ession tests on prismatic sample~ c~t from 6 directions in t h e material. It is not neces38ry to make amJ assumptions about the anisotro~t ~ the msteri~!, Results of tests on a mlcrocryst~llin~ limestone are ~esented.

815o74 PERFORATED

PHOT~.ASTIC CO~LNGS .TO X~2ASURE LOW GRADIim/~f STRAIN IN ROCKS Sknxtrzyk, F J; Aughenbau~h, N B Proc 21st US Symposi~ on Rock Mechanics, Rolla, Missouri, 28-30 May 1980, ~06-516

Proposes a method that employs a _.~erfcr~ted i~otuelastic coating to measure principal stral~s a~d their directions. The photoelsstlc c~,ting is perforated with city,Afar holes. Around each hole the coating is protect~i against cementir~ to the rock surface. The theoretical background fc~ the method, i~ presented ~md the response of the perforated l~hotoelastic coating to s ~ b~axial strain field is discussed. As an ex~,~le cf how thls technique can he ~pplied, this paper briefly describes its use to measure the timedependent recovery of well cores to establish ~n situ stress conditions.