Unified Modeling of the Influence of Consolidation Conditions on Monotonic Soil Response Considering Fabric Evolution

This paper proposes an anisotropic plasticity model to address the effect of consolidation conditions on the responses of soils within the framework of the anisotropic critical state theory (ACST). Double-yield surfaces are employed to describe the plastic deformation caused by both deviatoric shear and compression. A fabric tensor is defined to quantify the internal structure of soils and its evolution during the plastic deformation under both loading mechanisms is explicitly proposed. The novel expression of the fabric evolution rules allows for both hardening and softening types of variation in the fabric norm that are manifested by discrete element method simulations. A modified anisotropic variable is proposed, engaging with the effect of the anisotropic consolidation and the subsequent loading path and rendering the combined dilation-contraction deformation patterns being simulated, which are exclusively pertinent to the anisotropic consolidation conditions. The complex sand and clay responses caused by the varying consolidation conditions in terms of the anisotropic consolidation ratio and the over-consolidation ratio (OCR) can be simulated in a unified manner. The predictive capacity of the model is demonstrated by triaxial tests on both sand and clay. A satisfactory comparison is found between the model response and test results.