This tutorial example aims to provide an overview of two models available to model creep in conjunction with critical state plasticity, a behaviour commonly observed in shales and chalks. The model must be used in conjunction with the SR3 plasticity model (SR4 is not available at the moment) and usage of either constant elasticity or poroelasticity is enabled.

 

In this tutorial first an overview of the model equations will be provided. Then two cases demonstrating the effect of model parameters in experimental test simulations using the two models available will be discussed. The simulated experimental tests consists of a series of hydraulic compression tests (hct) and triaxial tests (ctc) performed at different rates (some cases including holding periods at constant load to allow creep to develop) and exploring the effect of the different parameters. It should be noted that in this tutorial we do not back analyse a given experiment although published experimental data is used to provide a reference.

 

 

Schematic of boundary conditions for the simulated experimental tests

 

Simulation Cases

 

Overview of the creep models

 

Case01 Power law creep model

 

Case02 Power law creep model with accelerated creep at high deviatoric stress