Abstract:

Based on the framework of critical state soil mechanics，a new bounding surface constitutive model for sand, being applicable to cyclic loading, is proposed. No pure elastic region hypothesis is given in this model. Elastic region of sand reduces to a point. Reverse bullet-shaped yielding surface is adopted. No unique relationship between void ratio and the mean normal stress for sand prevents the direct coupling of yield surface size to void ratio. Incremental deviatoric strain is used as a hardening parameter, instead of adopted plastic volumetric strain as hardening parameter in Original Cam-clay model. The model combines the concept of state-dependent dilatancy by incorporating state parameter concept in Rowe’s stress dilatancy equation. Bounding surface magnitude ratio ? to loading surface gives plastic modulus evolvement. Formulation of d? is deducted. A single set of model constants, once calibrated, can simulate cyclic stress-strain response under different initial void ratios and different confining pressures.

Key words: shear hardening, critical state, bounding surface model, state parameter, dilatancy