Constitutive equations and numerical modelling of time effects in soft porous rocks
by
Maria Datcheva
Institute of Mechanisc,Bulgarian Academy of Sciences
Coauthors: Robert Charlier (University of Liege), Frederic Collin (Univercity of Liege)

A constitutive model is developed within the framework of Perzyna's viscoplasticity for predicting the stress-strain-time behaviour of soft porous rocks. The model is based on the hiperelasticity and multisurface viscoplasticity with hardening. A time-stepping algorithm is presented for integrating the creep sensitive law. An example of application to one-dimensional consolidation is presented. The objectives are to: 1. present a soft rock model which is capable of taking into account the rate sensitivity, time effects and creep rupture; 2. to discuss the use of an incremental procedure for time stepping using large time increments and 3. to extend the FEM code Lagamine(MTM-ULg) for viscoplastic problems in geomechanics.

Date received: February 2, 2000