THE BIOT-COSSERAT CONTINUUM MODEL FOR COUPLED HYDRO-DYNAMIC ANALYSIS IN SATURATED POROUS MEDIA AND FINITE ELEMENT SIMULATION OF STRAIN LOCALIZATION

The Biot-Cosserat continuum model for coupled hydro-dynamic processes in saturated porous media is proposed by means of the combination of both Biot theory and Cosserat continuum theory to simulate the strain localization phenomena due to the strain softening. In the present contribution, the Biot formulation of the skeleton material is extended with the rotational degree of freedom and associated coupled stresses defined in the Cosserat continuum. The finite element formulations governing the coupled hydro-dynamic behavior with the primary variables of the displacements and the microrotation for the solid phase and pressure for the fluid phase are derived on the basis of the Galerkin-weighted residual method. The strain localization phenomena in saturated porous media due to the strain softening are numerically simulated by using the developed model with corresponding finite element method and the non-associated Drucker-Prager yield criterion particularly considered for the pressure-dependent elasto-plastic Cosserat skeleton. Numerical results of the plane strain slope illustrate the capability of the developed model in keeping the well-posedness of the boundary value problems with strain softening behavior incorporated, and the availability of modeling the strain localization phenomena in saturated media.