Anisotropic Bounding Surface Plasticity Model for Porous Media

An anisotropic plasticity model for the description of nonisotropic mechanical behaviors of porous media is presented. This model is developed using bounding surface plasticity theory within the critical state framework. The inherent and stress-induced anisotropy has been accounted for by an anisotropic variable, which is employed with the consideration of both irrecoverable deformation and stress state. The evolution of anisotropy has been described by both rotational and distortional hardening rules. The rotational hardening rule is proposed for the consideration of bounding surface inclination induced by inherent or induced anisotropy. The distortional hardening rule is developed to capture the varying shape of bounding surface associated with the accumulation of irrecoverable deformation and anisotropy. This model has been validated through modeling the stress-strain responses of porous media under various loading conditions, including triaxial drained/undrained compression/extension tests on both isotropically and anisotropically consolidated samples. Good agreement between model simulation and experimental results has been achieved for all cases taken into consideration, demonstrating the capability of the proposed model.