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Minimum undrained strength of two sands
9A from results of tests at constant normal stress, removing the need for complicated servo-controlled test equipment, It is shown that under constant or variable normal stiffness two peak strengths can occur. This suggests that more than one set of strength parameters is needed to describe the shear strength of dilatant rock joints under such conditions.
911063 Estimating Mohr-Coulomb friction and cohesion values from the Hock-Brown failure criterion. Technical note Hock, E lnt d Rock Meek Min Sci V27, N3, June 1990, P227-229 The Hoek-Brown criterion has constants which may be evaluated from geological data using Bieniawski's RMR. Many stability analyses are, however, formulated in terms of the MohrCoulomb criterion. Equations are presented to enable MohrCoulomb friction and cohesion values to be estimated from the Hoek-Brown failure criterion for cases of specified normal effective stress, specified minor principal effective stress, and where uniaxial compressive strength of the rock is the same for both criteria.
911064 Minimum undrained strength of two sands Konrad, J M J Geotech Engng Div ASCE V116, N6, June 1990, P932-947 Results of isotropically consolidated undrained triaxial tests on a rounded and a subangular sand are presented. The tests were carried out to establish conditions for induction of strain softening during monotonic loading. Upper and lower limits of the mean steady state strength were found. This line is not uniquely related to void ratio for a given sand. The influence of confining pressure, void ratio, stress history, and mode of loading on undrained steady state strength is examined. A modified definition of state parameter is necessary to clearly identify conditions for minimum undrained shear strength.
911065 Minimum undrained strength versus stendy-state strength of sands Konrad, J M J Geoteck Engng Div ASCE V116, N6, June 1990, P948-963 Previous consolidated undrained triaxial tests on sands (ibid, June 1990, P932-947) demonstrate the presence of upper (UF) and lower (LF) limits of the steady state shear strength. This work is supported by other published data. The LF line is dependent on initial state of the sand. Unlimited and limited flow are seen for samples consolidated within three regions, which are defined in a state diagram. The limits between these regions appear to be related to the slope of the UF line, as is the ratio of minimum strength from the LF line and steady state strength from the UF line.
911066 Finite strain analysis of pressuremeter test. T~hnical note Voyiadjis, G Z; Tumay, M T; Kiousis, P D J Geoteck Engng Div ASCE V116, N6, June 1990, PiO02. 1007 Prediction of soil parameters from in situ tests is often made on a semi-empirical basis as analysis is complicated due to difficult boundary conditions. The plane strain (cylindrical cavity expansion) analysis of the pressuremeter test using finite strain elastoplastic analysis is presented. The aim is to evaluate the importance of some commonly made assumptions in analysis of this test.
911067 Stiffm~m and penetration resistance of sands versus state parameter. Technical note Carriglio, F; Ghionna, V N; Jamiolkowski, M; Lancellotta, R d Geoteck Engng Div ASCE VII6, N6, June 1990, P!0151020 Results of calibration chamber and conventional laboratory penetration tests on pluviaily deposited Ticino and Hokksund sands suggest that normalised penetration resistance and stiffness measured inside the primary yield surface are functions of the state parameter of Been and Jefferies 0985). It is thus proposed that correlations between results of drained penetration tests and stiffness of granular materials be limited to values assessed within the primary yield locus, corresponding to the overconsolidated state.
911068 Size effects, stress and couple stress gradients in jointed rock Chappell, B A Min Sci Teclmol VII, NI, July 1990, PI-18 When jointed rocks are considered at a large scale, deformation and relative displacements lead to establishment of couple stress gradients from couple moments, in addition to stress concentrations, forming stress gradients. Joints reduce the shear modulus and introduce anisotropy into the stress distribution and deforrnational process. A characteristic length, defined in terms of couple moments and shear modulus, is compared with interacting contact areas in order to characterise couple moments. The effect of moments on stress distribution is examined by comparing characteristic length with contact area. Rock mass classes with specific joint spacings are compared with characteristic length, and the mode of behaviour of the rock mass, continuum, psuedo-continuum, or structural frame, is indicated.
911069 Comparison of two Drueker-Prnger-type constitutive models for granular material behaviour in uniaxial compression Brekelmans, W A M Powder Tecimol V62, NI, July 1990, P21-26 Two relatively simple constitutive models, one with an elliptical yield surface, the other with a linear yield surface closed by a cap, are compared when modelling uniaxial compression of granular materials. Predictions disagree when model parameters are related by assuming the same global dimensions of the instantaneous yield surface. Parameters can,however, be selected to obtain quantitatively similar stress development. The yield criterion for a particular material must be formulated using sufficient parameters to assure satisfactory reliability and be evaluated against sufficient data to allow its application in other circumstances. 911070 Structural strength of frozen soil during thawing Vodolazkin, V M; Sorokin, V A; Fedoseev, Y G Soil Meek Found Engng 1/26, 315, Sept-Oct 1989, P207-209 The strength of frozen soils can be characterised by a value Pst, corresponding to the pressure during thawing for which no deformation develops. It is difficult to measure as most tests consider only the top 10-15cm of soil, which is ice rich, and ice lenses interfere. It is thus difficult to isolate Psi for the mineral portion of the soil. Careful tests were carried out at depths to 41m on a thawing soil. Results indicate Pst for the mineral portion is close to the effective pressure at that depth. Implications of this for current design procedures are considered.
© 1991 Pergamon Press plc. Reproduction not permitted
911063 Estimating Mohr-Coulomb friction and cohesion values from the Hock-Brown failure criterion. Technical note Hock, E lnt d Rock Meek Min Sci V27, N3, June 1990, P227-229 The Hoek-Brown criterion has constants which may be evaluated from geological data using Bieniawski's RMR. Many stability analyses are, however, formulated in terms of the MohrCoulomb criterion. Equations are presented to enable MohrCoulomb friction and cohesion values to be estimated from the Hoek-Brown failure criterion for cases of specified normal effective stress, specified minor principal effective stress, and where uniaxial compressive strength of the rock is the same for both criteria.
911064 Minimum undrained strength of two sands Konrad, J M J Geotech Engng Div ASCE V116, N6, June 1990, P932-947 Results of isotropically consolidated undrained triaxial tests on a rounded and a subangular sand are presented. The tests were carried out to establish conditions for induction of strain softening during monotonic loading. Upper and lower limits of the mean steady state strength were found. This line is not uniquely related to void ratio for a given sand. The influence of confining pressure, void ratio, stress history, and mode of loading on undrained steady state strength is examined. A modified definition of state parameter is necessary to clearly identify conditions for minimum undrained shear strength.
911065 Minimum undrained strength versus stendy-state strength of sands Konrad, J M J Geoteck Engng Div ASCE V116, N6, June 1990, P948-963 Previous consolidated undrained triaxial tests on sands (ibid, June 1990, P932-947) demonstrate the presence of upper (UF) and lower (LF) limits of the steady state shear strength. This work is supported by other published data. The LF line is dependent on initial state of the sand. Unlimited and limited flow are seen for samples consolidated within three regions, which are defined in a state diagram. The limits between these regions appear to be related to the slope of the UF line, as is the ratio of minimum strength from the LF line and steady state strength from the UF line.
911066 Finite strain analysis of pressuremeter test. T~hnical note Voyiadjis, G Z; Tumay, M T; Kiousis, P D J Geoteck Engng Div ASCE V116, N6, June 1990, PiO02. 1007 Prediction of soil parameters from in situ tests is often made on a semi-empirical basis as analysis is complicated due to difficult boundary conditions. The plane strain (cylindrical cavity expansion) analysis of the pressuremeter test using finite strain elastoplastic analysis is presented. The aim is to evaluate the importance of some commonly made assumptions in analysis of this test.
911067 Stiffm~m and penetration resistance of sands versus state parameter. Technical note Carriglio, F; Ghionna, V N; Jamiolkowski, M; Lancellotta, R d Geoteck Engng Div ASCE VII6, N6, June 1990, P!0151020 Results of calibration chamber and conventional laboratory penetration tests on pluviaily deposited Ticino and Hokksund sands suggest that normalised penetration resistance and stiffness measured inside the primary yield surface are functions of the state parameter of Been and Jefferies 0985). It is thus proposed that correlations between results of drained penetration tests and stiffness of granular materials be limited to values assessed within the primary yield locus, corresponding to the overconsolidated state.
911068 Size effects, stress and couple stress gradients in jointed rock Chappell, B A Min Sci Teclmol VII, NI, July 1990, PI-18 When jointed rocks are considered at a large scale, deformation and relative displacements lead to establishment of couple stress gradients from couple moments, in addition to stress concentrations, forming stress gradients. Joints reduce the shear modulus and introduce anisotropy into the stress distribution and deforrnational process. A characteristic length, defined in terms of couple moments and shear modulus, is compared with interacting contact areas in order to characterise couple moments. The effect of moments on stress distribution is examined by comparing characteristic length with contact area. Rock mass classes with specific joint spacings are compared with characteristic length, and the mode of behaviour of the rock mass, continuum, psuedo-continuum, or structural frame, is indicated.
911069 Comparison of two Drueker-Prnger-type constitutive models for granular material behaviour in uniaxial compression Brekelmans, W A M Powder Tecimol V62, NI, July 1990, P21-26 Two relatively simple constitutive models, one with an elliptical yield surface, the other with a linear yield surface closed by a cap, are compared when modelling uniaxial compression of granular materials. Predictions disagree when model parameters are related by assuming the same global dimensions of the instantaneous yield surface. Parameters can,however, be selected to obtain quantitatively similar stress development. The yield criterion for a particular material must be formulated using sufficient parameters to assure satisfactory reliability and be evaluated against sufficient data to allow its application in other circumstances. 911070 Structural strength of frozen soil during thawing Vodolazkin, V M; Sorokin, V A; Fedoseev, Y G Soil Meek Found Engng 1/26, 315, Sept-Oct 1989, P207-209 The strength of frozen soils can be characterised by a value Pst, corresponding to the pressure during thawing for which no deformation develops. It is difficult to measure as most tests consider only the top 10-15cm of soil, which is ice rich, and ice lenses interfere. It is thus difficult to isolate Psi for the mineral portion of the soil. Careful tests were carried out at depths to 41m on a thawing soil. Results indicate Pst for the mineral portion is close to the effective pressure at that depth. Implications of this for current design procedures are considered.
© 1991 Pergamon Press plc. Reproduction not permitted