| Along with the severity of the problem of excess traffic jam, environment deterioration increasingly, it is an inevitable trend for modern city development to exploit and utilize the underground space cosmically. In construction, Scattering and diffraction of cylindrical SH waves by the underground tunnel can affect the ground motion near the tunnel and the dynamic stress concentration of the tunnel. So, the cylindrical waves generated by the explosion may affect the safety of the original underground tunnel and it is necessary to compute the impact quantitatively. Up to now, the analysis of the scattering of cylindrical waves by tunnel is still limited to the full space and the analytic solution of the semi-infinite space. Hence, this thesis researched on the scattering of cylindrical SH waves by canyon firstly, and then by an underground circular cavity, verified and provided new results for achievements which have already obtained, and also explored a new method for the further research.In this paper, the method of solution applied by Ohsaki (1973) will be adapted for two kinds of topographies. Basing on the characteristic of SH waves, the wave functions with unknown variables is first chosen to satisfy the wave equation, and all the wave functions should be transferred to the same coordinate. Then the boundary conditions are satisfied in a least-square sense by a generalized inverse method. The solution is controlled by the residual errors.The accuracy of the numerical result is checked up by the analytic solution and residual errors of boundary conditions with the increase of the truncation order. At the same time, the effects of some factors such as the frequency of the incident waves, the distance between the place where the cylindrical waves are excited and the tunnel and the depth of the tunnel on the dynamic stress concentration factor on the wall of the tunnel and also the ground motion are illustrated. And some useful conclusions are derived in this thesis. |
PDF Full Text Request