Rate effects and cyclic loading of sensitive clays

223A 876048 Directional shear cell experiments on a dry cohesionless soil Sture, S; Budiman, J S; Ontuna, A K; Ko, H Y Geotech Test J VIO. N2, June 1987, P71-79 A directional shear cell has been developed which accepts 178mm cubical specimens and can simulate changes in magnitude and direction of principal stress such as may occur under field conditions. Results show that stiffness moduli are significantly reduced when principal stresses rotate with respect to soil fabric, and that relatively large shear strains arise when principal stress directions are rotated while stress magnitudes remain constant. 876049 Investigation of boundary friction effects in polyaxial tests. Technical note Demiris, C A Geotech Test J VIO. N2, June 1987, P86-90 Experiments have been carried out to investigate ways of reducing boundary friction forces in polyaxial testing. Side friction may be minimised by the use of special PTFE-grease pads. Ineffective lubrication can cause apparent increase in strength and Young's modulus. Effects of boundary friction on volume changes under polyaxial stress states are also examined. 8"76O5O Rate effects and cyclic loading of sensitive clays Lefebvre, G; LeBouef, D J Geotech Engng Div ASCE VlI3, N5, May 1987, P476-489 Monotonic and cyclic triaxial tests were carried out on samples of three undisturbed sensitive clays to study the influence of strain rate and cycle rate on shear strength. Pore pressure and peak strength envelope behaviour were different for naturally overconsolidated and normally consolidated clays. The increase in shear strength with strain rate is, however, similar for both structured and destructured materials, and is linear for at least 5 log cycles of strain rate. 876051 True triaxial yielding and hardening of rock Michelis, P J Geotech Engng Div ASCE Vl13, N6 June 1987, P616-635 Analysis of monotonic, cyclic, and true triaxial tests on intact and jointed marble has been undertaken to explore the physical basis of proposed constitutive relations and to extend these relations, particularly for hardening under equal and unequal minor and intermediate principal stresses. Yielding and hardening under standard and true triaxial conditions were studied. A polyaxial yield equation and hardening rule are proposed and experimentally verified. 876052 Shear modulus and internal ft:iction of calcite rocks at seismic frequencies: pressure, frequency, and grain size dependence Jackson, I; Paterson, M S Phys Earth Planet Inter V45, N4, May 1987, P349-367 Shear modulus and internal friction have been measured for four calcite rocks, grain size 4-1000 microns, using forced torsional oscillations at high pressure and room temperature. Up. to 100 MPa, increased pressure results in a marked increase in G and decrease in internal friction, attributable to crack closure, except for the sample of negligible crack porosity. At higher pressure, G is less pressure sensitive and internal friction essentially pressure independent. Within the pressure

regime, internal friction was essentially indewndent of frequency for periods 3-100s, and varied by only 30% across the grain size range, 876053 Axios river sand under multiaxial stresses (In French) Demiris, C A; Bakassis, I A: Schinas. C A Rev Fr Geotech N39, 1987, P17-31 Samples of Axios river sand were subjected to four stress paths under multiaxial and triaxial loading. Interrelations between axial stress, axial strain, and lateral strains were derived. Variations of the deviatoric ratio (deviatoric stress average stress) as a function of deviatoric strain, and volume strain versus deviatoric strain and deviatoric ratio versus volume strain were also investigated. 876054 Deformability study of Gezhouba Dam foundation rocks Dong Xuecheng Rock Mech Rock Engng V20. N2, April-June 1987. P95-109 Plate bearing tests, flat jack tests and large scale triaxial compression tests were used to study the in situ deformability of sandstones, clayey siltstones, and conglomerates at the Gezhouba damsite. Results are analysed to indentify factors influencing the modulus of deformation. The dependence of axial strain or displacement on the stress state is investigated, and methods of assigning deformability parameters for calculations discussed. Finally, some improvements for deformability studies for future major projects are made. 876055 Effect of density on the drained deformation beha~iour of Shirasu (volcanic sandy soil) under three dimensional stresses Haruyama, M Soils Found V27, N1, March 1987, Pl-13 Hydrostatic compression tests and radial shear tests maintaining a constant principal stress were carried out on Shirasu specimens prepared by pluviation through water. Results indicate reconstituted Shirasu specimens are characterised by an inherent cross-anisotropy and density dependence of deformation characteristics. 876056 Deformation of granular material in simple shear Moroto, N Soils Found V27, N1, March 1987, P77-85 Deformation of sand under simple shear has been analysed, paying particular attention to friction and dilatancy effects. Using the simple sliding block theoD ~, two state functions are analytically derived and a basic deformation model formulated. This simple model is a good approximation in the intermediate range of stress ratios, and a further model is developed which can be extended to a wider range of stress ratios. 876057 Physical properties of southeastern Washington loess related to cut slope design Beard, L D; I-Iiggins, J D; Fragaszy, R J; Kilian. A P; Peters, A J Trans Res Rec N1089, 1986, P29-38 Physical, chemical, and index properties of loess soils in southeastern Washington have been determined and compared with those from other sites in the USA. Based on cut slope design experience at these locations, preliminary slope design and maintenance guides have been produced. Near vertical slopes

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