Practical constitutive model for soil liquefaction

A practical constitutive model is presented that incorporates shear-induced effects in both loading and unloading as well as rotation effects. It is developed within a classical plasticity approach combined with a multi-laminate model. A multi-laminate model uses many mobilized planes, but the proposed model has only two mobilized planes; a maximum shear stress plane, and a horizontal plane. The application of more than one mobilized plane can intrinsically handle anisotropy as well as rotation of principal planes. The procedure focuses on simple shear conditions because they simulate field conditions under earthquake loading. The rotation effect associated with simple shear loading from a K0 consolidated state and its effect is incorporated with the Two Plane model. This constitutive model is incorporated into the dynamic coupled stress-flow finite difference program FLAC (Fast Lagrangian Analysis of Continua). It is verified by capturing the cyclic undrained behaviour of Fraser River sand. The numerical simulations under two different K0 conditions, 0.5 and 1.0 are compared with measurements.