Multi-Plane Model for Soil Liquefaction

A simplified constitutive model based on a multi-plane concept is presented for monotonic and cyclic soil response including liquefaction. The proposed model uses 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 without additional parameters. The soil skeleton behaviour observed in cyclic drained simple shear tests, including compaction during unloading and dilation at large strain is considered in the model. Undrained and partially drained monotonic and cyclic response can be predicted by considering the volumetric constraint of the water on the drained or skeleton behaviour. The rotation effect associated with simple shear loading from a K₀ consolidated state is incorporated in the proposed model. This constitutive model is incorporated into the dynamic coupled stress-flow finite difference program FLAC (Fast Lagrangian Analysis of Continua). The model is calibrated by capturing the undrained cyclic behaviour of Fraser River sand, and can be used in the design of liquefaction remediation measures involving densification and drainage.