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Estimation of pile friction degradation from shearbox tests. Technical note
213A 934O46 Estimation of pile friction degradation from shearbox tests. Technical note Airey, D W; AI-Douri, R H; Poulos, H G Geotech Test J V15, N4, Dec 1992, P388-392 Cyclic loading tests in a modified shearbox apparatus have been carried out on uncemented carbonate sand under conditions of constant normal load and constant normal stiffness. Similarities between variation of skin friction of cyclically loaded piles and test behaviour under constant normal stiffness conditions are discussed. It is demonstrated that response in shearbox tests under constant normal stiffness can be predicted from response in conventional shearbox tests, which can thus be used to predict cyclic degradation of pile skin friction. 934O47 Experimental method of determining membrane penetration. Technical note Choi, J W; Ishibashi, I Geoteeh Test J V15, N4, Dec 1992, P413-417 A new and simple procedure is presented for measurement of the membrane penetration during triaxial or hollow cylinder tests. It requires neither special devices nor questionable assumptions about particle packing, being based on results of a series o f isotropic compression tests in a conventional triaxial cell with plastic liners. Results from this method are compared to those from several current experimental and analytical methods. 934048 Sample disturbance in London Clay Chandler, R J; Harwood, A H; Skinner, P J Geoteclmique V42, N4, Dec 1992, P577-585 Soil suctions were measured using the filter paper method on London Clay specimens taken from two sites using open tube driven (U 100) sampling and block sampling. Difference in suctions is taken to be a consequence of the mechanical disturbance during tube sampling. Driven sampling increases suction values, the increase being larger for the stiffer soil. Disturbed samples will give optimistic values of undrained strength and excessive values of Ko. 934049 Measurement of the properties of sand in a calibration chamber by the cone pressuremeter test Schnaid, F; Houlsby, G T Geoteehnique V42, N4, Dec 1992, P587-601 The cone pressuremeter, a recently developed instrument with a pressuremeter behind a standard cone penetrometer tip, requires more complex interpretation than the self-boring pressuremeter, as the pressuremeter test is carried out in conedisturbed soil. A series of calibration chamber tests using 3 prototype instruments is described. Effects of relative density, stress level, and stress ratio on values of limit pressure and cone resistance have been examined. A method to evaluate in situ stress, density, and friction angle is presented and used to back analyse test data. 934050 Observations on the resilient shear stiffness of granular materials. Technical note O'Reilly, M P; Brown, S F Geotechnique V42, N4, Dec 1992, P631-633 When granular materials are repeatedly loaded between two stress states far below failure level, strains become predominantly recoverable (resilient) after a certain number of cycles.
The resilient shear modulus is not a constant, but increases with increasing average normal stress. A definition of resilient modulus within a frictional concept is proposed to explain this observed behaviour. Change in shear stress ratio (change in tangent of mobilised angle of shearing resistance) principally controls resilient shear strains. Data from tests on crushed rock support the hypothesis. 934051 Finite element analysis of direct shear tests on stiff clays Cividini, A; Gioda, G Int J Num Anal Meth Geomech V16, N12, Dec 1992, P869896 Finite element analysis is presented of tests on stiff, heavily overconsolidated clay. A simple strain softening elastoplastic material model is used. The finite element code SOSIA2 and its main characteristics are illustrated and its use in interpretation of the shear tests discussed. Mesh dependence of the numerical results is considered. The solution procedures are finally applied to model compression tests and investigate the possibility of detection of spontaneous formation of shear zones. 934052 Rheology and deformation mechanisms of an isotropic mica schist Shea, W T; Kronenberg, A K J Geophys Res V97, NBll, Oct 1992, P15201-15237 The translational semi-brittle deformation of a mica-rich schist has been examined. Triaxial compression tests were cartied out to varying strains on samples cored at 0, 45, and 90 deg to the foliation, over a range of constant strain rates and temperatures 25-400 deg C. Deformation is concentrated i r l one or more millimetre-wide throughgoing shear zones, which localise at low strains by nucleation and coalescence of intragranular kink bands. An unexpected absence of measurable orientation dependence of strength is revealed. 934053 Fine Ottawa sand: experimental behavior and theoretical predictions Dakoulas, P; Sun, Y J Geotech Engng Div ASCE Vl18, NI2, Dec 1992. P19061923 A comprehensive experimental program has been carried out on loose and dense fine Ottawa sand specimens in a hollow cylinder apparatus. Isotropic, triaxial compression and extension, simple shear, torsional, and other combined stress paths have been followed. Results are discussed with emphasis on generalised failure and yield criteria. Laboratory data closely match predictions of Lade's single hardening constitutive model for cohesionless soils. 934054 Density changes during undrained loading - membrane compliance Evans, M D J Geotech Engng Div ASCE V118, NI2, Dec 1992, P19241936 Changes in specimen density of gravels during laboratory testing may be masked by membrane penetration effects. Cyclic undrained triaxial tests have been carried out on sets of gravel specimens using a conventional compliant system and one in which peripheral voids were sluiced with sand to reduce membrane penetration. Specimen preparation, measured volume changes, permanent membrane deformation, and density changes due to membrane compliance are discussed. The effects of using multiple membranes are also examined.
© 1993 Pergamon Press Ltd. Reproduction not permitted
The resilient shear modulus is not a constant, but increases with increasing average normal stress. A definition of resilient modulus within a frictional concept is proposed to explain this observed behaviour. Change in shear stress ratio (change in tangent of mobilised angle of shearing resistance) principally controls resilient shear strains. Data from tests on crushed rock support the hypothesis. 934051 Finite element analysis of direct shear tests on stiff clays Cividini, A; Gioda, G Int J Num Anal Meth Geomech V16, N12, Dec 1992, P869896 Finite element analysis is presented of tests on stiff, heavily overconsolidated clay. A simple strain softening elastoplastic material model is used. The finite element code SOSIA2 and its main characteristics are illustrated and its use in interpretation of the shear tests discussed. Mesh dependence of the numerical results is considered. The solution procedures are finally applied to model compression tests and investigate the possibility of detection of spontaneous formation of shear zones. 934052 Rheology and deformation mechanisms of an isotropic mica schist Shea, W T; Kronenberg, A K J Geophys Res V97, NBll, Oct 1992, P15201-15237 The translational semi-brittle deformation of a mica-rich schist has been examined. Triaxial compression tests were cartied out to varying strains on samples cored at 0, 45, and 90 deg to the foliation, over a range of constant strain rates and temperatures 25-400 deg C. Deformation is concentrated i r l one or more millimetre-wide throughgoing shear zones, which localise at low strains by nucleation and coalescence of intragranular kink bands. An unexpected absence of measurable orientation dependence of strength is revealed. 934053 Fine Ottawa sand: experimental behavior and theoretical predictions Dakoulas, P; Sun, Y J Geotech Engng Div ASCE Vl18, NI2, Dec 1992. P19061923 A comprehensive experimental program has been carried out on loose and dense fine Ottawa sand specimens in a hollow cylinder apparatus. Isotropic, triaxial compression and extension, simple shear, torsional, and other combined stress paths have been followed. Results are discussed with emphasis on generalised failure and yield criteria. Laboratory data closely match predictions of Lade's single hardening constitutive model for cohesionless soils. 934054 Density changes during undrained loading - membrane compliance Evans, M D J Geotech Engng Div ASCE V118, NI2, Dec 1992, P19241936 Changes in specimen density of gravels during laboratory testing may be masked by membrane penetration effects. Cyclic undrained triaxial tests have been carried out on sets of gravel specimens using a conventional compliant system and one in which peripheral voids were sluiced with sand to reduce membrane penetration. Specimen preparation, measured volume changes, permanent membrane deformation, and density changes due to membrane compliance are discussed. The effects of using multiple membranes are also examined.
© 1993 Pergamon Press Ltd. Reproduction not permitted