Elastoplastic modelling the creep behaviour of cataclastic rock under multi-stage deviatoric stress

Abstract

The objective of this paper is to realise the elastoplastic modelling of the creep behaviour of cataclastic rock under multi-stage deviatoric stress. The multi-stage triaxial creep tests show that the cataclastic rock exhibits pronounced irreversible time-dependent deformations which enlarge with the increase in deviatoric stress. The plastic shearing mechanism of the rock can be identified based on the observation that the rock shows typical plastic strain and large strain rate during the creep tests. Towards this, a unified creep model is developed to describe both the instantaneous and the time-dependent elastoplastic behaviour of the cataclastic rock. The elastoplastic model for describing the instantaneous behaviour is developed based on classic plasticity using a revised Drucker–Prager criterion and a non-associated flow rule, and the time-dependent deformation is described in terms of evolution of microstructure in the context of irreversible thermodynamics. The time-dependent deformation is considered as a macroscopic consequence of progressive degradation of material structure in microscopic scale. Finally, the proposed model is applied to predict the material responses in short-term triaxial compression tests and multi-stage creep tests. Comparisons between experimental and simulated results show that the proposed model is able to describe the main features of the creep behaviours observed in this material.