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Effect of the intermediate principal stress on the failure of a foliated anisotropic rock
150A
description of the jointed rock mass as a quasi-continuum. Influences of confining stress, stress anisotropy, and joint persistence on behaviour as predicted by model and analytical methods are in good agreement. 923086 Effect of the intermediate principal stress on the failure of a foliated aulsotropie rock Kwasniewski, M; Mogi, K Proc lnternatimml Conference on Mec&mics of Jointed and F~ited Rock, Vienna, 18-20 April 1990 P407-416. Pubi Rotterdam: A A Balkema, 1990
Cube specimens of foliated Chichubu schist were tested in a true triaxial apparatus. Specimens were cut such that their vertical axes (coincident with the maximum principal stress) were perpendicular to or at 30 deg to the plane of foliation. Influence of magnitude of intermediate principal stress on stress strain behaviour was examined. Its effects are strongly dependent on its orientation with respect to planes of weakness. 923087 Mechanical properties of joints in coal bearing strata Rakowski, Z; Fialova, V; Polacek, J, Zamarski, B Proc lntermatomd Cmuference on Mechanics of Joined and Faulted Rock, g i c u , 18-20 Api11990 P463-468. Publ Rotterdam: A A Balkema, 1990
Coal measures strata contain many lithologic, genetic, and tectonic discontinuities. Type and origin of weakness planes are examined. A large shear box apparatus developed for testing joint properties is illustrated. Results are presented for tectonic, genetic, and artificial joints in siltstones and sandstones of the Ostrava-Karvina coalfield in Czechoslovakia. The geomechanical problems of this basin and the application of the joint property data to their solution are discussed. 923088 Physical assessment of test specimens in the post-peak regime Felice, C W; Norman, D; Senseny, P E Rock Mechmu'cs as a Msdtidisciplinory Science: Proc 32rid US Symposimn, Norman, 10-12 July 1991 P283-292. Publ Rotterdam: A A Balkema, 1991
X ray computerised tomography is a nondestructive technique which shows promise for examination of damage and its development during deformation of geological materials. Preliminary results indicate the ability of CT to detect small and subtle variations in density through specimens in triaxial compression tests. Changes induced by the deformation may possibly be quantified and applied to improve understanding of constitutive behaviour. 923O89 Determination of the elastic properties of anisotropic rock mass from in-situ expansion tests Amadei, B; Savage, W Z Rock Mac&roles as a Mdtidisciplimwy Science: Proc 32nd US Sympmiam, Norman, 10-12 July 1991 P303-312. Publ Rotterdam: A A Balkema, 1991
A method is presented for the determination of the elastic constants of transversely isotropic rock masses from the results of dilatometer and NX-jack tests in boreholes and gallery tests in tunnels. The results show that the variation of the modulus of deformation observed along the circumference of a borehole or tunnel during expansion tests not only provides a qualitative assessment of anisotropic character of the rockmass of interest but can also be used to determine its anisotropie properties.
923090 Eff~Vls of teml~mtwe and Wmmre on the Woperti~ of IAc dn ilon~t grey granite Lau, J S O; Jackson, R; Gorski, B Rock Mechanics as a MMtdiscipli~ry Sgience: Proc 32nd US Symposium, Norman, 10-12 Jnly 1991 P313-323. Publ Rotterdam: A A Balkema, 1991
As part of the Canadian radioactive waste disposal program, effects of pressure and temperature on mechanical properties of Lac du Bonnet granite have been examined at the URL. Compressive strength, axial failure strain, and Poisson's ratio increase with confining pressure but decrease with temperature. Deformability increases with confining pressure up to values about 17MPa, and is only slightly affected by temperature up to about 125 deg C. A slight reduction in predicted peak strength of the Hock Brown failure envelope in seen with increasing temperature. The degree of stress induced microcracking does not appear to influence thermal response.
Fracture processes See also: 923233, 923250, 923259, 923509 923091 Simultaneous inversion for Q and source parameters of microearthquakesaccompanyinghydraulic fracturing in granitic rock Fehler, M; Phillips, W S Bull Seismol Soc Am V81, N2, April 1991, P553-575 A modification of the method of De Natale et al (1987) has been used to simultaneously fit spectra and determine source parameters for 223 microearthquakes induced by hydraulic fracturing in granodiorite. Q values, seismic moments, and stress drop are evaluated. Applying the constraint that stress drops be similar, but not equal, for all events did not significantly degrade the fit of the spectra, but gave a surprisingly low value of average stress drop, 3.7 bars. Reasons for this are examined. 923O92 Review of the Brazilian test for rock tensile strength determination. Part h calculation formula Andreev, G E Min Sci Teclmol 1/13, N3, Dec 1991, P445-456 Although there is an opinion that the Brazilian test in not valid where the ratio of compressive to tensile strength is low, it is proposed herein that this test is valid even for brittle materials. Two models of the Brazilian test developed by the author are presented: the Delta model and the Beta model created on the basis of effective tensile stress. Experimental evidence from materials with a wide range of ductility is presented to support the theories. 923O93 Review of the Brazilian test for rock tensile strength determination. Part II: contact conditions Andreev, G E Min S¢i Tecln~i 1/13, N3, Dec 1991, P457-465 The contact conditions of the Brazilian test can determine whether failure initiates in the centre of the specimen (valid test) or under the loading device (invalid test). It is generally held that the loading device should be stiffer than the test material such that tensile stresses are not caused under the specimen contact area. Theoretical and experimental examination of load transmission by both soft and stiff testing devices
© 1992 Pergamon Press Ltd. Reproduction not permitted
description of the jointed rock mass as a quasi-continuum. Influences of confining stress, stress anisotropy, and joint persistence on behaviour as predicted by model and analytical methods are in good agreement. 923086 Effect of the intermediate principal stress on the failure of a foliated aulsotropie rock Kwasniewski, M; Mogi, K Proc lnternatimml Conference on Mec&mics of Jointed and F~ited Rock, Vienna, 18-20 April 1990 P407-416. Pubi Rotterdam: A A Balkema, 1990
Cube specimens of foliated Chichubu schist were tested in a true triaxial apparatus. Specimens were cut such that their vertical axes (coincident with the maximum principal stress) were perpendicular to or at 30 deg to the plane of foliation. Influence of magnitude of intermediate principal stress on stress strain behaviour was examined. Its effects are strongly dependent on its orientation with respect to planes of weakness. 923087 Mechanical properties of joints in coal bearing strata Rakowski, Z; Fialova, V; Polacek, J, Zamarski, B Proc lntermatomd Cmuference on Mechanics of Joined and Faulted Rock, g i c u , 18-20 Api11990 P463-468. Publ Rotterdam: A A Balkema, 1990
Coal measures strata contain many lithologic, genetic, and tectonic discontinuities. Type and origin of weakness planes are examined. A large shear box apparatus developed for testing joint properties is illustrated. Results are presented for tectonic, genetic, and artificial joints in siltstones and sandstones of the Ostrava-Karvina coalfield in Czechoslovakia. The geomechanical problems of this basin and the application of the joint property data to their solution are discussed. 923088 Physical assessment of test specimens in the post-peak regime Felice, C W; Norman, D; Senseny, P E Rock Mechmu'cs as a Msdtidisciplinory Science: Proc 32rid US Symposimn, Norman, 10-12 July 1991 P283-292. Publ Rotterdam: A A Balkema, 1991
X ray computerised tomography is a nondestructive technique which shows promise for examination of damage and its development during deformation of geological materials. Preliminary results indicate the ability of CT to detect small and subtle variations in density through specimens in triaxial compression tests. Changes induced by the deformation may possibly be quantified and applied to improve understanding of constitutive behaviour. 923O89 Determination of the elastic properties of anisotropic rock mass from in-situ expansion tests Amadei, B; Savage, W Z Rock Mac&roles as a Mdtidisciplimwy Science: Proc 32nd US Sympmiam, Norman, 10-12 July 1991 P303-312. Publ Rotterdam: A A Balkema, 1991
A method is presented for the determination of the elastic constants of transversely isotropic rock masses from the results of dilatometer and NX-jack tests in boreholes and gallery tests in tunnels. The results show that the variation of the modulus of deformation observed along the circumference of a borehole or tunnel during expansion tests not only provides a qualitative assessment of anisotropic character of the rockmass of interest but can also be used to determine its anisotropie properties.
923090 Eff~Vls of teml~mtwe and Wmmre on the Woperti~ of IAc dn ilon~t grey granite Lau, J S O; Jackson, R; Gorski, B Rock Mechanics as a MMtdiscipli~ry Sgience: Proc 32nd US Symposium, Norman, 10-12 Jnly 1991 P313-323. Publ Rotterdam: A A Balkema, 1991
As part of the Canadian radioactive waste disposal program, effects of pressure and temperature on mechanical properties of Lac du Bonnet granite have been examined at the URL. Compressive strength, axial failure strain, and Poisson's ratio increase with confining pressure but decrease with temperature. Deformability increases with confining pressure up to values about 17MPa, and is only slightly affected by temperature up to about 125 deg C. A slight reduction in predicted peak strength of the Hock Brown failure envelope in seen with increasing temperature. The degree of stress induced microcracking does not appear to influence thermal response.
Fracture processes See also: 923233, 923250, 923259, 923509 923091 Simultaneous inversion for Q and source parameters of microearthquakesaccompanyinghydraulic fracturing in granitic rock Fehler, M; Phillips, W S Bull Seismol Soc Am V81, N2, April 1991, P553-575 A modification of the method of De Natale et al (1987) has been used to simultaneously fit spectra and determine source parameters for 223 microearthquakes induced by hydraulic fracturing in granodiorite. Q values, seismic moments, and stress drop are evaluated. Applying the constraint that stress drops be similar, but not equal, for all events did not significantly degrade the fit of the spectra, but gave a surprisingly low value of average stress drop, 3.7 bars. Reasons for this are examined. 923O92 Review of the Brazilian test for rock tensile strength determination. Part h calculation formula Andreev, G E Min Sci Teclmol 1/13, N3, Dec 1991, P445-456 Although there is an opinion that the Brazilian test in not valid where the ratio of compressive to tensile strength is low, it is proposed herein that this test is valid even for brittle materials. Two models of the Brazilian test developed by the author are presented: the Delta model and the Beta model created on the basis of effective tensile stress. Experimental evidence from materials with a wide range of ductility is presented to support the theories. 923O93 Review of the Brazilian test for rock tensile strength determination. Part II: contact conditions Andreev, G E Min S¢i Tecln~i 1/13, N3, Dec 1991, P457-465 The contact conditions of the Brazilian test can determine whether failure initiates in the centre of the specimen (valid test) or under the loading device (invalid test). It is generally held that the loading device should be stiffer than the test material such that tensile stresses are not caused under the specimen contact area. Theoretical and experimental examination of load transmission by both soft and stiff testing devices
© 1992 Pergamon Press Ltd. Reproduction not permitted