傾斜地層場址的地盤反應之數值模擬

Abstract

在大地工程中，地震所造成由下往上的波傳往往對地面上造成嚴重的災害，振動波傳經過不同地地層條件，例如: 土層密度、土壤剪力波速、不同土層間的傾斜角度…等等，都會造成放大或是縮小的效果，對原本預期的結果產生了更為嚴重災害危害我們的安全，此種效應被稱之為場址效應，本研究主要是探討不同的地形幾何條件、傾斜角度，邊界條件下所造成的場址效應以探討土壤的線性以及非線性行為。 在真實地盤中，土壤的性質極為複雜，為了簡化模擬時獲取土層參數的困難性，我們將土層視為好幾區均質土壤的結合，當土壤材料在小應變的情形下，我們將土壤的行為視為線彈性體，土體仍然保持著線彈性行為，當我們進行動態分析的模擬時，雷利阻尼通常被設置在土體材料模擬土壤的消能反應，然而，當土體的剪力變變形過大的時候，土體由線彈性轉換為塑性，除了雷利阻尼以外也需要利用遲滯阻尼來模擬非線性的土壤消能行為，以便數值模擬的分析，本研究透過上述的不同土層材料條件，經由FLAC 2D 7.0軟體配合DEEPSOIL軟體驗證，歸納出場址效應所造成對地表面的影響以及在地震時後，所可能發生災害的危險區域。

In geotechnical engineering practice, the seismic wave propagation from bottom to the ground surface often cause damaging disasters on the ground. Vibration waves pass through different stratigraphic conditions, such as soil layer densities, soil shear wave velocities, and tilt angle between different soil layers etc., would cause amplification or declination of site response. The effect is so-called site effect. This study mainly discusses different geological conditions to explore the tendency of ground motion. In the real site, the nature of the soil is extremely complicated. In order to simplify the difficulty of obtaining soil parameters during the simulation, we regard the soil layer as a combination of several homogeneous soils. With small shear strain of soil material, the behavior is regarded as a linear elastic body, and the soil performs elastic linearity. In dynamic analysis, Rayleigh damping is usually assigned in the soil material to simulate the energy dissipation of soil. However, with larger deformation, the behavior of soil convert linear elasticity into plasticity. It is also necessary to use hysteretic damping to simulate nonlinear soil energy dissipation in numerical simulation. The study summarizes the results of different soil conditions, developing the trend affected by the influence of site effect. Also, evaluating the most dangerous region of the basin while earthquake occurred.