为研究马蹄形隧道的抗震性能并预测隧道地震后的灾害情况，以滇中引水工程磨盘山隧道为例，建立围岩-隧道相互作用的有限元模型，并采用非线性动力时程法开展结构动力分析。考虑到不同场地条件对结构性能的影响及地震的不确定性，针对2种不同场地条件，选取合适的地震动强度指标； 同时，考虑损伤参数对结构易损性分析的影响，分别以截面相对变形率和弯矩承载能力比为损伤指标。分析结果表明： 1）在隧道结构的易损性分析中，PGA(peak ground acceleration) 离散程度较低，是较为有效的地震强度指标； 2）不同损伤指标下隧道易损性趋势基本一致，而采用相同损伤指标时，较软场地的隧道易损性更高，抗震性能偏差，应着重关注复杂场地结构的安全性； 3）抗震设防条件下隧道各性能水准破坏概率较低，满足设计要求，在罕遇地震下，各等级破坏概率较高，隧道损伤较为严重。

To explore the seismic performance of horseshoeshaped tunnel and predict the postearthquake disaster situation of the tunnel, a case study is conducted on the Mopanshan tunnel, a water diversion project in central Yunnan, a finite element model of rocktunnel interaction is established, and structural dynamic analysis is conducted using nonlinear dynamic timehistory method. Considering the uncertainty of site conditions and earthquakes, suitable seismic intensity indices are selected for two different site conditions. Meanwhile, considering the impact of damage parameters on the fragility analysis of the structure, the relative deformation rate of the section and the bending moment bearing capacity ratio are used as damage indices respectively. The results show the following: (1) In the fragility analysis of tunnel structures, peak ground acceleration has a low degree of dispersion and is a more effective seismic intensity index. (2) The trend of tunnel fragility under different damage indices is basically consistent, but when the same damage index is used, the fragility of tunnels in softer sites is higher, and the seismic performance deviates. Therefore, the safety of structures in complex site should be guaranteed. (3) Under fortification conditions, the probability of failure at each performance level of the tunnel is relatively low, meeting the design requirements. In rare earthquakes, the probability of failure at each level is relatively high, and the tunnel damage is relatively severe.