本文研究目的為探討埋地管線受斷層作用下之大變形行為,利用有限元素模擬埋地連續鋼管在不同斷層運動形式以及不同埋設條件下的反應。其中管線使用四節點殼元素模擬,考慮彈塑性材料組成律;而土壤與管線間的相互作用則根據ALA-ASCE(2001)所定義的非線性土壤彈簧模擬,並且提出兩種等效土壓力分佈形式進行參數分析。數值模擬結果顯示在相同斷層位移量之下,由於逆斷層運動可能會造成管線的局部挫屈,故對管線的影響最為顯著。此外,若欲提高管線抵抗地表大變形能力,可在合理安全的範圍內減少管線的埋設深度;而回填材料的摩擦角越小以及比重越小,管線在斷層作用下所產生的變形越小。管材的使用應具備一定的延展性,俾利抵抗正斷層和平移斷層所可能引致的拉伸破壞;而管線軸向與斷層線在埋深方向的傾角越小,對管線的承載能力越不利。此外,本研究亦以新城斷層地下埋設的大口徑鋼管進行案例分析,定義不同的破壞準則來推估臨界地震規模。上述的結果可供在管線設計時參考。
The purpose of this research is to study the responses of buried pipelines subjected to large reverse faults by the nonlinear finite element analysis. The pipeline is modeled by 4-node shell elements with elasto-plastic material properties. In addition, the interaction of soil and pipelines is modeled by nonlinear springs in accordance with the ALA-ASCE guidelines for soil springs. Two distribution forms of the equivalent soil pressure are proposed in this study. Parametric studies are carried out to investigate the responses of pipelines subjected to different fault motions, buried conditions and material properties of pipelines. Numerical results indicate that the reverse fault motion, particularly with small dip angle, could results in the occurrence of local buckling of pipelines, which has remarkable influences on the safety of the water supply system. The decrease in buried depth and small friction angle of backfill sand with less unit weight are suggested to improve the bearing capacity of buried pipelines. Pipelines composed of ductile materials are also suggested to resist the normal fault and strike fault movements. Finally, a real case of buried pipelines subjected to the Shin-Cheng reverse fault is investigated in this paper. Two different failure criteria are proposed to estimate critical earthquake magnitude.