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针对饱和半空间中任意形状不均质体对地震波的散射问题,采用一种新型基本解方法(MFS)进行求解分析。该方法结合饱和半空间中膨胀波源和剪切波源的格林函数,首先由分布在不均质体和半空间交界面附近两虚拟波源面上的PI、PII、SV波源分别构造了不均质体内外的散射波场,然后由交界面连续性条件建立方程并求解确定了虚拟波源密度,总波场反应由自由波场和散射波场叠加而得,最后在精度检验的基础上,通过一组典型算例研究了平面P波在饱和半空间中不均质体周围散射的基本规律。研究结果表明:两相介质波动的MFS模拟具有极高的数值精度和高频稳定性;波在饱和不均质体中的散射特征取决于入射波的频率和方向、边界渗透条件、介质孔隙率等参数,与在单相介质中的情况具有很大差别;地表位移特征反映了波的散射和饱和不均质体的自振特性,随着介质孔隙率增大,位移幅值谱振荡更为剧烈,且不均质体刚度越小,地表位移放大效应越显著,但最大不超过自由场反应的2倍。
Aiming at scattering of seismic waves by arbitrary shape heterogeneous bodies in saturated half-space, a new basic solution method (MFS) is used to solve the problem. This method combines the Green’s function of the swell wave source and the shear wave source in a saturated half-space. Firstly, the PI, PII and SV wave sources distributed on the two virtual wave sources near the interface between the inhomogeneous body and the half-space are used to construct the inhomogeneous body And the scattering wave field inside and outside, and then establish the equation by the interface continuity conditions and solved the virtual wave source density, the total wave field reaction by the free wave field and the scattered wave field superimposed on the basis of the accuracy of the test, through a group A typical example studies the fundamental law of plane-P wave scattering around an inhomogeneous body in a saturated half-space. The results show that the MFS simulation of two-phase medium fluctuation has very high numerical accuracy and high frequency stability. The scattering characteristics of the wave in a saturated heterogeneous body depend on the frequency and direction of the incident wave, the boundary infiltration conditions, the medium porosity And other parameters are quite different from those in a single phase medium. The surface displacement characteristics reflect the scattering of the wave and the natural vibration of the saturated heterogeneous body. As the porosity of the medium increases, the amplitude of the displacement amplitude spectrum becomes more Violent, and the smaller the heterogeneous body stiffness, the more significant the effect of surface displacement magnification, but not more than 2 times the free field reaction.