Scattering Of Plane P & SV Waves By An Underground Circular Lined Tunnel In Saturated Site

It has been shown that local site conditions have important effect on seismic wave propagation. Theoretical analysis of this problem mainly relies on analytical method and numerical method. In principle, the numerical method can resolve dynamic response problems in various kinds of complex sites. But, analytical method plays an unique role that can not be replaced in analyzing the essentials of the problems, and it can be used to verify the precision of the numerical method. To analytical method, there are already many analytical solutions. But, due to many restrictions, most of these results are based on one-phased media assumption. And the results in saturated site are very few because of complexity. Then how to get the analytical solutions in saturated site (two-phased saturated porous media) referred to the results in the elastic-half space and analyzing the response will be a very significant research topic.Scattering and diffraction of earthquake waves by the large, underground tunnel structures can affect the ground motion near the tunnels, still, it can also affect the buildings on the ground nearby. Therefore, to solve this kind of problem has important significance on both theory and engineering application. For this local site, the research to SH wave is very perfect. To P and SV wave, although there is the problem of changes of wave types at boundaries, there also have many results by now. But all these results are based on the assumption of one-phased media. In a fluid-saturated porous media half space, there are two longitudinal waves(PIand Pâ…¡)by incident P or SV wave and there will be two critical angles by incident SV wave. This makes the problem very complex. On the basis of the Biot dynamic theory, the saturated site is simplified to two-phased saturated porous media, and the surface is approximated by a cylindrical surface with large semi-diameter. And the incident wave, reflect waves and scattered waves are represented by the series of Bessel function expansion. Finally, an analytic solution of this problem is solved through drained and un-drained boundaries respectively. Furthermore, the effect of factors such as tunnels'diameter, incident wavelength, incident angle and lining's rigidity on the surface displacement is also analyzed. Some beneficial conclusions are given at the end of the thesis.