Research on the Target Reliability Index of Railway Tunnel for Seismic Resistance

China preliminarily completes the transition of limit state design method for railway tunnel currently and establishes the limit state design method for railway tunnel structure under self weight and surrounding rock load. However, detailed research are not conducted on the limit state method for railway tunnel under seismic load. In order to improve the limit state design system of railway tunnel, clarify the target reliability index of railway tunnel structure for seismic resistance and establish the limit state method for railway tunnel for seismic resistance, the paper calibrated the reliability of railway tunnel lining and open cut tunnel in current general reference maps for seismic resistance by calibration method, and put forward the target reliability index of railway tunnel for seismic resistance based on calibration results. The results show that: The reliability index of railway tunnel structure for seismic resistance is mainly related to the surrounding rock level and structure type, specifically, the reliability index of the lining is significantly lower than that of the open cut tunnel, and the reliability index of the structure under Grade Ⅴ surrounding rock is significantly lower than that under Grade Ⅳ; After considering the weight coefficients of various structures under different surrounding rock levels, the average reliability index of railway tunnel for seismic resistance is 6.81, which is greater than target reliability index of 4.2 for railway tunnel structure under self weight and surrounding rock pressure, the reliability level of the current structure for seismic resistance is relatively high; Based on the calibration results of the current general reference maps of railway tunnel for seismic resistance and the target reliability index in current code, the target reliability index of railway tunnel for seismic resistance is determined to be 4.7 for Level 1, 4.2 for Level 2, and 3.7 for Level 3.