隧道受地震和移動列車載重之動力反應

Abstract

隨著都市人口增加，地面交通日趨擁塞，而捷運系統所能提供快速且便捷之特性，儼然成為各大城市主要交通運輸工具之一，而由於都市土地價值高，大部分之捷運路線皆採地下隧道方式興建。為了運輸每日大量的旅客，捷運列車數量多，往返行駛頻繁，列車載重對地下隧道造成之影響成為一重要課題，此外，台灣又位於活耀的環太平洋地震帶上，地震活動頻繁，對地下隧道而言也是另一個沉重之負擔。而捷運系統所載運之人數眾多，如果發生任何意外，將會造成嚴重的人員傷亡。有鑑於此，本文之目的即希望能藉由有效之數值分析方法，探討地下隧道受移動列車和地震力作用下之影響。 本研究根據Yang et al.(1996)提出的有限和無限元素混合模式分析法，與Zhao 和 Valliappan (1993)提出之地震力輸入方式，分析地震力作用下，隧道與土壤互制之行為，並與前人之研究作比較。此外，針對移動列車對隧道之影響，則依據Yang 和 Hung (2001)發展出的2.5維有限/無限分析方法，以無限元素模擬無限域土壤輻射阻尼之作用，考慮列車和軌道粗糙度之特性，模擬隧道受一完整列車載重下產生之反應。除此之外，並進一步探討土壤、隧道之幾何和材料參數，對隧道反應產生之影響。

For their instant and convenient characteristics, mass rapid transit (MRT) systems have become one of the major transportation tools in metropolitan areas to resolve the traffic congestion caused by increasingly large population. Most MRT lines have been built as underground tunnels as the acquisition of urban lands has become too expensive. A typical MRT train is composed of a large number of carriages, which can move back and forth along the same lines for tens of times in one day to transport tens of thousands of passengers. Therefore, what the vast amount of trainloads will do to the underground tunnels is an issue of concern from the engineers’ point of view. Another concern is that Taiwan is an island located on the circum-Pacific seismic belt, which is exposed to frequent earthquakes each year. Due to the large volume of passengers carried by the MRT lines daily, if a major earthquake causes any damages on the underground tunnels and railways, the casualties incurred could be tremendous. Accordingly, the purpose of the thesis is to investigate the impact of both the moving train loads and earthquake effects on the underground tunnel structures using effective numerical simulation methods. The soil-tunnel interaction system subjected to earthquakes will be analyzed using the coupled finite/infinite element approach proposed by Yang et al. (1996), with the earthquake excitations simulated by the technique proposed by Zhao and Valliappan (1993). The results obtained will be compared with those available in the literature. To simulate how the moving train actions affect the underground tunnel structure, considering particularly the rail surface irregularity, the 2.5D finite/infinite element method proposed by Yang and Hung (2001) is adopted, with the infinite elements used to model the radiation effect of infinite soil domains. Besides, parametric studies are conducted to examine the effect of various geometric and material parameters on the tunnel response.