列車行駛於地下隧道時引致之土壤振動

Ground-Borne Vibrations Induced by Trains Moving in Underground Tunnels

許琳青(Lin-Ching Hsu)

指導教授 ： 楊永斌

國立臺灣大學/工學院/土木工程學研究所/博士(2006年)

https://doi.org/10.6342/NTU.2006.10293

摘要

在人口密集的區域，地下化的軌道運輸系統可有效紓解繁忙的地面交通，已經成為都會地區不可或缺的大眾運輸工具，但是隨著都市建築密度的提高以及人們對於生活環境品質的要求，軌道車輛行駛於地下隧道時所產生之振動往往經由周遭的土壤傳遞到鄰近的建築物，嚴重者則對附近居民的生活造成干擾，引起民怨，因此列車行駛於地下隧道時所引致之土壤振動問題，已經成為一個引起高度重視的環保議題，世界各先進國家均定有明確的規範以限制振動公害的大小，而相關研究也不斷的在進行中。
本論文將針對起因於列車行駛於地下隧道時所引致之土壤振動問題作一綜合性探討，首先就此種振動問題的特性、對環境的影響與相關振動評估規範以及近三十年來部分學者專家所得到的研究成果加以介紹，其中有關古典波傳理論在此種振動問題的應用亦有詳盡的討論；此外，本研究更以有限和無限元素混合法作為數值分析工具，對於各項影響土壤振動的參數作一系統性的分析，整個土壤與隧道結構系統將被分為近域與遠域兩部分，近域部分以傳統有限元素模擬，而遠域部分則以無限元素模擬邊界無限遠之特性。此數值模擬方法因可建立在傳統有限元素的架構中，在實際應用上容易被一般工程師所接受，更可有效模擬土壤的輻射阻尼效應。研究中曾針對列車行駛於明挖覆蓋的隧道系統所引致的地表振動加以分析，經由與其他數值分析方法所得到的結果之比較，此有限和無限元素混合法的正確性亦可得到證實。
研究中先以2維的有限與無限平面元素來模擬土壤-隧道互制作用系統，並將列車模擬為簡諧震盪的無限長線載重，進行各項土壤參數的分析，而另一方面，為了更深入探討列車的動力特性對於土壤振動的影響，本研究更將原本的2維元素擴展至2.5D的有限與無限元素，在此2.5D的模式下，列車可以移動點載重的方式來模擬；經由各項參數分析結果顯示，即使在一般地下化軌道運輸系統的營運速度下，當外力的振動頻率與土層的自然振動頻率接近時，土壤的動力反應即會產生明顯的共振現象，因此解決此種振動問題的根本方法，就是要避免車輛的振動頻率與土層的自然振動頻率過於接近，以減少共振反應發生的機會。

關鍵字

列車 ； 地下隧道 ； 土壤振動 ； 無限元素

並列摘要

Ground-borne vibrations resulting from the underground railway traffic have become an important environmental issue, which has received increasing attention from both engineers and researchers. In this dissertation, an integrated investigation is conducted of the ground-borne vibration problem induced by trains moving in underground tunnels. Starting from an extensive literature review, practical parameter analyses were carried out for a two-dimensional simulation of the soil-tunnel interaction system, which were then extended to a 2.5D simulation with account taken of the moving effect of the train loads. The numerical procedure adopted here is called the coupled finite/infinite element method. With this approach, a soil-tunnel system is divided into two regions, i.e., the near and far fields. The near field, including the loads and other geometric/material irregularities, is simulated by the finite elements as conventional, and the far field covering the soils with infinite boundary by the infinite elements. This hybrid approach can overcome the inherent drawback of the finite element method in simulating the radiation damping for waves traveling to infinity. On the other hand, it can be established within the framework of the finite element method, which is commonly used by most structure analysis programs and is likely to be favored by most practicing engineers.
From the results of this research, it can be concluded that even in most underground railways systems with the normal operating velocities, the coincidence of the loading frequencies with the fundamental frequency of the soil layer can still result in an apparent increase of the vibration level. Accordingly, to relieve the vibration of this kind, a fundamental solution should be resorted to avoid the coincidence of the loading frequencies of train with the fundamental frequency of soil layer.

並列關鍵字

train ； underground tunnel ； ground-borne vibration ； infinite element

參考文獻

Achenback, J. D. (1973). Wave Propagation in Elastic Solids, North-Holland Publishing Company, New York.

Achenback, J. D. and Sun, C. T. (1965). “Moving load on a flexibly supported Timoshenko beam”, International Journal of Solids and Structures, Vol. 1, pp. 353-370.

Andersen, L. and Jones, C. J. C. (2002). “Vibration from a railway tunnel predicted by coupled finite element and boundary element analysis in two and three dimensions”, Proc. 5th European Conf Struct Dyn, Eurodyn’02, Munich, Germany, pp. 1131-1136. A.A. Balkema.

Balendra, T., Chua, K.H., Lo, K.W. and Lee, S.L. (1989). “Steady-state vibration of subway-soil-building system”, Journal of Engineering Mechanics, Vol. 115, No. 1, pp. 145-162.

Balendra, T., Koh, C. G. and Ho, Y. C. (1991). “Dynamic response of buildings due to trains in underground tunnels”, Earthquake Engineering and Structural Dynamics, Vol. 20, pp. 275-291.