Mountain tunnels are generally constructed in the stratified rock mass. For the satisfactory seismic performance of mountain tunnels, adequate evaluation of the effect of stratification is absolutely necessary. This study reports the influence of stratification on the seismic behaviour of mountain tunnels through numerical investigation using discrete-element software UDEC (universal distinct element code). Tunnel liner forces are compared for a single-layer and a two-layer geological set-up considering both harmonic excitation and earthquake time histories. It is observed that tunnel supports are more vulnerable to damage when the tunnel passes through a stratified medium. For assessment of the vulnerability of tunnels in the stratified deposits of rock mass under earthquake motions, seismic fragility curves have been derived for different damage states with varying grades of concrete. It is observed from the fragility curves that the probability of damage may significantly be reduced by using higher-grade shotcrete for the tunnel liner, especially in stratified rock deposits.

中文翻译：

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山地隧道分层的影响及脆弱性曲线评估

山地隧道一般建在层状岩体中。山地隧道要获得满意的抗震性能，充分评价分层效应是绝对必要的。本研究通过使用离散元素软件 UDEC（通用不同元素代码）进行数值调查，报告了分层对山地隧道地震行为的影响。考虑到谐波激励和地震时程，比较了单层和两层地质设置的隧道衬砌力。据观察，当隧道穿过分层介质时，隧道支护更容易受到损坏。用于评估地震作用下岩体层状沉积物中隧道的脆弱性，对于不同等级混凝土的不同损伤状态，已经推导出地震脆性曲线。从脆性曲线可以看出，隧道衬砌使用更高等级的喷射混凝土可以显着降低损坏的概率，特别是在分层岩层中。