Generalized Plasticity Model for Sand with Enhanced State Parameters

This paper presents a constitutive model for sand based on the framework of generalized plasticity and the concept of critical state soil mechanics. In order to model the nonlinear relationship between the critical void ratio and the pressure level more precisely, an enhanced version of the critical void ratio curve is proposed and included in a pressure and density dependent state parameter. In contrast to previous versions, the constitutive relation for the critical void ratio can be adjusted more accurately to a wider range of pressures. The new state parameter is embedded in the plastic modulus, loading vectors, and plastic flow direction vectors of a generalized plasticity model originally developed by Pastor, Zienkiewicz, and Chan. The simulation of a series of drained and undrained triaxial compression tests were used to validate the performance of the modified model under monotonic loading. The comparison between the results of numerical calculations with experimental data shows that the modified model can simulate the stress-strain characteristics of cohesionless sand in a wide range of initial densities and confining pressures with a single set of constitutive parameters. (C) 2018 American Society of Civil Engineers.