間接邊界元素法在平面P、SV、Rayleigh入射波對多層沉積地形之繞射研究

Abstract

本論文採用間接邊界元素法研究平面P、SV、Rayleigh 入射波對多層沉積 地形之繞射問題，採用單層勢邊界源之積分式表示繞射波場。假設每材料 為均質、彈性、等向性，層之接觸為 well bonded，因此接觸面上的位移 及牽引力必須滿足連續條件，各層邊界條件導出一積分方程式系統，經由 全空間格林函數數值及解析積分之離散化過程，方程式變成一矩陣式。本 文數值結果顯示地表運動放大形式受入射波種類、頻率、角度等參影響， 另外本文二、三層的例子顯示各層之阻抗、數目、形狀會影響放大 形式 ，結果展示了P、SV、Rayleigh 波入射軟弱沈積層可能造成局部地表運動 非常之放大。 The indirect boundary method is applied to study the diffrac- tion of plane harmonic P, SV, Rayleigh waves by dipping allu- vial layers. The integral representation of the diffracted wave field is in terms of single-layer boundary sources. The boundary conditions of layers lead to a system of integral equ- ations. The equations become a matrix form after a discretiza- tion process based on the numerical and analytical integration of full-space Green functions. The numerical results show that surface ground motion ampli- fication patterns depend on some parameters, such as, type, fre- quency, and angle of incident wave. The cases of two and three layers even show the impedance, number, and shap of layers can influence the amplification pattern. The results demonstrate the presence of soft alluvial layers may cause locally very lar- ge surface ground motion amplification under incident P, SV, and Rayleigh waves.