Drained Cyclic Behavior of Sand with Fabric Dependence

The behavior of sand is characterized by dilatancy, an increase in overall volume as particles move over each other when the sand assembly is subjected to shear stresses. A stress-dilatancy model for sand in the cyclic loading regime, taking into account microstructural changes, is presented. The model is subsequently integrated into a constitutive model based on hypoplasticity so as to accurately calculate volume changes induced by fabric and dilatancy changes during cyclic loading. Furthermore, it is assumed that fabric evolution is a function of the ratio of deviatoric to mean principal stress. Some numerical examples that capture the effect of fabric changes on the drained cyclic behavior of sand are presented. Among others, it is found that initial fabric can drastically alter both the dilatancy response and net volume change at shakedown conditions even though the initial void ratio and confining pressure are kept unchanged. The void ratio here is defined as the volume of voids to that of solids.