波浪作用下粘弹性海床动力响应的数值分析

NUMERICAL ANALYSES OF DYNAMIC RESPONSE OF VISCO-ELASTIC SEABED UNDER WAVE LOADING

基于广义Biot理论,采用Kelvin-Voigt模型描述海床土骨架的应力应变时间的本构关系,从Galerkin加权余量法出发建立以土骨架位移u和孔隙流体全位移U表达的u^U形式的有限元边值方程,采用Newmark逐步积分法求解时域内动力方程。数值计算表明土骨架和孔隙流体的加速度对粘弹性海床动力响应的影响极小。当土的粘滞系数的数值小于其弹性剪切模量的大小时,体粘滞系数和偏粘滞系数的变化对超静孔压幅值的影响较小,但对有效应力幅值的影响相对显著。对于粘滞系数较大的海床,波浪荷载可能导致其变形在很短的时间内单调迅速增长至破坏。

Based on generalized Biot抯 theory, the u^U finite element formulations for dynamics of seabed under wave loading are derived by applying Galerkin抯 weighted-residual procedure, where u and U are the displacements of soil matrix and porous fluid respectively. The Kelvin-Voigt visco-elastic model is used to reproduce the constitutive relationship of seabed soils. The governing equations are numerically solved by Newmark抯 time integration scheme. Numerical results show that the accelerations of soil matrix and porous fluid have little effect on the dynamic response of visco-elastic seabed. When the value of viscosity coefficients is less than that of elastic shear modulus, the amplitudes of pore pressure change slightly with the variation of the viscosity coefficients and the viscosity coefficients affect the amplitudes of effective stresses considerably. For the seabed with large viscosity coefficients, wave loading induces monotonically increasing shear strains and the soil may reach failure state in short time.