Development and validation of a modified moving boundary model to simulate liquefaction-solidification behaviors of seabed under wave loading

An analysis method is proposed based on an existing moving boundary model to assess the response of seabed under wave loading, accounting for the effects of fluid viscosity and the boundary of the seabed. The potential flow equations in the original model are replaced by the laminar Navier-Stokes equations so that the viscous two-layer fluid system consisting of the liquefied/fluidized seabed and the water above it can be described reasonably. Meanwhile, the source term in the governing equations for the wave-induced shear stress calculation model is updated to consider the effects of the seabed boundary. The centrifugal model tests are carried out to validate and calibrate this model, as well as to demonstrate its capability of modelling the liquefaction/solidification of the seabed, in terms of the development of excess pore pressure and void ratio. The results show that the liquefied seabed has a high viscosity, which may lead to overestimation of the seabed movement amplitude, especially for sandy soils. Comparisons between the calculations based on seabed with infinite and finite depths show discernible discrepancies, thus it is suggested the effects of the seabed boundary should be considered in modelling. This model is also found to be capable of capturing the increase in soil strength within a certain depth after wave loading and the amplification of the pore pressure amplitude.