YIELDING OF OVERCONSOLIDATED SAND AND LIQUEFACTION MODEL UNDER CYCLIC STRESSES

Abstract

Static undrained triaxial shear tests were performed on the sand specimens overconsolidated to OCR-values of 1.0 to 5.0 under cyclic as well as monotonous loading conditions. It was discovered that pore water pressures and shear strains which developed during undrained shear tests were lower for overconsolidated sand than for normally consolidated sand even when the density of the sand was kept virtually unchanged. To advance a reasonal interpretation for the hardening effect brought about by overconsolidation, the concept of yield loci was introduced, establishing a family of curves in the stress space (effective mean principal stress versus deviator stress plot) which governs the onset of yielding in overconsolidated sand. On the basis of the yield loci thus established the deformation model previously established for normally consolidated sand was modified and generalized so that the pore water pressures and shear strains under irregular loading condition could be predicted for both normally and overconsolidated states.