On the numerical implementation of hyperplasticity non-linear kinematic hardening modified cam clay model

Abstract

A continuous hyperplasticity model named kinematic hardening modified cam clay (KHMCC) is a constitutive soil model based on thermodynamic principles. This model has addressed some shortcomings of the modified cam clay (MCC), specifically on small strain stiffness. Because of employing multiple surfaces plasticity, it can simulate a smooth transition from elastic to plastic behaviour as well as the effect of immediate past stress. This article aims to present some important issues on the numerical implementation of the continuous hyperplasticity non-linear KHMCC model. The incremental stress–strain response is calculated based on a rate-dependent algorithm. A significant advantage of the rate-dependent calculation is that it is not necessary to attach with the consistency condition during calculation of plastic strains. Effect of time step and number of yield surfaces in rate-dependent algorithm will be also presented. A discussion on using of numerical integration rules of hardening functions is addressed. Furthermore, model verification is performed against analytical solution of ideal undrained response which has been obtained from theoretical integration of the MCC function over the imposed stress or strain path. Finally, some numerical demonstrations are also carried out to illustrate several key features of the model.

Keywords:

• hyperplasticity
• small strain
• rate-dependent
• hardening function