薄層地盤モデルにおける境界積分方程式法の利用

抄録

The boundary integral equation method involving the Green's function of the multi-layered medium by the thin layer method is very useful to evaluate the foundamental physical quantities in the dynamic soil-foundation interaction problem. However, there exist two complexities in evaluating these quantities by this method ; 1) the calculation of the stress components of the Green's functions introduces substantial errors near the applied point, 2) the solution of the dynamic stiffness analysis is disturbed in wide range near the natural frequency of the fundation (the internal resonance). In spite of the complexity 1), both of the imaginary part of the impedance and static impedance are rather exactly calculated by the indirect integral formulation. So, the real part can be indirectly obtained from them by the Hilbert transform, and also it can be directly calculated by modifying the solutions of the stress from the condition that the internal stress might be real value. The complexity 2) is resolved by putting the internal constraint surface in the foundation to take away the internal resonance point from the frequency range of interest. In order to verify the accuracy of the proposed method, this paper presents the torsional impedance analysis of axi-symmetric foundation by use of the ring-line-load solutions in a thin layered soil.