不同边界条件下非饱和土地基中的Rayleigh波传播

Propagation of Rayleigh wave in unsaturated soil at different boundary conditions

地球表面绝大部分土层并非处于完全饱和状态,故采用传统的饱和土两相介质理论进行动力学分析时,计算结果往往与实际情况不符。针对这一客观问题,以非饱和土为研究对象,在三相孔隙介质波动理论的基础上开展了非饱和土体半空间中Rayleigh波的弥散特性研究。分别考虑了两种不同的边界条件:(a)不透水不透气地基边界;(b)透水透气地基边界。根据边界条件及相关的本构关系式,推导出相应Rayleigh波的弥散方程,再通过Newton-Raphson法进行数值求解。最后讨论了在不同边界条件下,非饱和土地基表面附近Rayleigh波的弥散特性受到地基土饱和度、频率以及土体固有渗透系数的影响。计算结果表明:在两种边界条件下Rayleigh波的传播均受到地基土饱和度变化的影响。并且,频率及渗透系数在不同边界条件下对Rayleigh波特性的影响明显不同。

Most of the soil of the earth＇s surface is not completely saturated,so when the traditional twophase media theory is used for dynamic analysis,the results are often inconsistent with the actual situation. In view of this objective problem,the unsaturated soil is chosen to be our research object. Based on the wave theory of three- phase porous media, the research on the dispersion characteristics of Rayleigh wave in unsaturated soil half-space is carried out. Two different boundary conditions are considered：（a）water/air impermeable boundary,and（b） water/air permeable boundary. According to the boundary conditions and constitutive relations,the corresponding dispersion equations of Rayleigh wave are derived. Then,through the Newton-Raphson method,the equations could be solved numerically. Lastly,the influences of soil saturation degree,frequency and intrinsic permeability of the soil on the dispersion characteristics of the Rayleigh wave at different boundary conditions are discussed,respectively. The results show that,at both these two kinds of boundary conditions,the propagation of the Rayleigh waves with various frequencies is affected by the saturation change. Moreover,the influences of frequency and permeability coefficient on the propayation characteristics of Rayleigh waves at different boundary conditions are quite different.