A double hardening constitutive model for fine sands based on both the dilatancy feature and strain softening

Aiming at the characteristic of Shanghai fine sands for which a unique critical state line does not exist,the traditional models for sands were modified and a constitutive model for fine sands was developed which can describe both dilatancy feature and strain softening reasonably.The two yielding surfaces can individually reflect shear deformation and compression deformation.The traditional dilatancy equation of Cam-clay model was modified and the relativity between the phase transformation stress ratio and initial effective pressure was considered.In order to describe the characteristic of strain softening,a strain softening equation using the stress ratio at steady state and peak state was formulated,which can preferably reflect strain softening of fine sands.The model was verified by several test results of Shanghai fine sands.The good predictions show the rationality and validity of the proposed model.