A Coupling Model For Interaction Between Wave And Sandy Seabed

The process and mechanism of interaction between wave and seabed have important theoretical significance and broad application value for offshore,coastal and geotechnical engineering research.Establishment of a coupling model for wave,seabed and its surrounding structure provides a more comprehensive understanding about wave loading on seabed,attenuation effect of seabed on waves and structure foundation instability.This paper analyses and improves the elastoplastic model of sandy seabed under wave loading.Combined with the wave motion equations,a 2-D coupling model is eastablished to simulate the wave propagation over a sandy seabd.Based on the present 2D coupling model,a series numerical study is conducted to investigate the soil response under wave loading.Compared to the previous theoretical approach,the present model has a more broad application both on scientific research and engineering practice.In order to take full account of the elastic response of sandy seabed,this study uses the “u-w” Biot dynamic form to control the soil model,which contains acceleration of both soil skeleton and pore fluid.On the basis of previous studies,the analytical solution of “u-w” equations is derived.The present analytical solution agrees well with field observations and flume experimental tests.On the basis of analytical solution,the impact of a uniform flow on wave-induced soil response,including soil displacements,pore pressures and stresses,are investigaredThe elasto-plastic response of sandy seabed is based on the Biot's consolidation equations.The residual component of pore pressure is considered through a simple but workable plastic constitutive relationship with cumulative contraction of soil under cyclic loading,which leads to the pore pressure accumulation process.Based on the elasto-plastic model,the concept of boundary layer is introduced to realize the disspation process of residual pore pressure.The good agreement between present model and the centrifugal test proves the ability of present model to simulate both the accumulation and dissipation processes of pore pressure.A parametric study is conducted to analyse the distribution of pore pressure along the horizontal direction and the development of liquefaction zone under various wave loadings.This study describes the basic equation of wave motion including wave maker,wave propagation and wave absorber.In order to simulate the wave breaking process,a turbulent model is added to Reynolds averaged equations.Comparison with the analytical solution and flume tests show that the proposed mathematical model and finite element solution method can accuratly simulate wave generation,propagation and dissipation.The elasto-plastic soil model and wave motion equations are coupled with COMSOL,a finite element method software,to slove the whole domain simultaneously.The comparision results between coupling model and experimental test indicate that the coupling process between different types of wave,seabed and structure are valid.The numerical anslysis confirms the attenuation effect of seabed on wave motion.The influence of coupling process on wave induced soil response is also investigated.