Scattering Of Elastic Waves By An Arbitrary Shape Underground Cavity

Site response problems are a kind of important problems in earthquakeengineering. A lot of investigations of earthquake damage show that the existenceof local sites affects the scattering and diffraction of seismic wave greatly.Accordingly, there are sensitive change of earthquake response of ground surface,underground structure and buildings in narrow spatial dimension. The local sitesinfluence distribution of earthquake damage therefore. Generally site has irregularshapes, but analytical method only is used to regular shapes. Hence, theinvestigation of numerical solution of scattering by irregular sites has importantmeaning on both theory and engineering application. Cavity is a common site in engineering. During dig the cavity, the sections ofthe cavity are always irregular shape instead of a circle. Based on this asengineering background, numerical solution of incident SH waves and P waves byan underground cavity of arbitrary shape in a half-space are presented. In principle, the numerical method can resolve dynamic response problems ofearthquake waves in various kinds of complex sites. Among various numericalmethods in the analysis of wave scattering and diffraction are the finite differencemethod (FDM), the finite element method (FEM), and the boundary elementmethod (BEM). The weighted residual method introduced in this paper provides anew method for numerical solution of the scattering and diffraction of plane SHwaves and P waves by a cavity of arbitrary shape. This paper presents the weighted residual method in solving numerically thetwo-dimensional scattering and diffraction of plane elastic SH waves and P wavesby arbitrary shape underground cavity. Numerical solutions on scattering of twentyrandom arbitrary shape cavities subjected to incident plane SH waves is given inthis thesis; mean value and standard deviation of surface displacement of thetwenty cavities are also given. The effects of the frequency of the incident waves,the shape of the cavity, the incident angle and position of cavity on displacementamplitude of ground surface are analyzed. Some beneficial conclusions are givenin the end of the thesis.