Coupled peridynamics modelling of liquefaction-induced shear strain localisation and delayed failure

Liquefaction-induced shear strain localisation and delayed failure occur when a low-permeability overlying soil layer impedes the dissipation of excess pore water pressure generated by the underlying sand. When this phenomenon is simulated by the classical finite-element method (FEM), the predicted strain localisation and lateral deformation are mesh-size dependent. In this study, the non-local peridynamics theory is introduced as a novel regularisation technique for modelling such a phenomenon. The computational model is based on coupling the non-ordinary state-based peridynamics (NOSBPD) and FEM for the solid and pore fluid phases, respectively. The liquefiable sand is modelled using a plastic model for large post-liquefaction shear deformation of sand (CycLiq) in the NOSBPD layer and the fluid flow is solved in the FEM layer. After validation of the proposed method using a VELACS centrifuge model test, the seismic response of an idealised one-dimensional sloping site with a low-permeability interlayer is analysed using various discretisation resolutions. The results show that the proposed method for liquefaction-induced strain localisation analysis is insensitive to spatial discretisation density. Finally, the Lower San Fernando dam failure case is revisited. The localised sliding and delayed failure of the dam observed in the field is achieved in the simulation. The results demonstrate the potential of the proposed method in assessing realistic cases associated with liquefaction-induced shear strain localisation.