研究目的:现行铁路隧道设计规范中概率极限状态法的适用范围局限于单线铁路隧道的整体式衬砌，而我国铁路隧道的现状是双线及大跨隧道越来越多，复合式衬砌已经广泛使用，因此现行规范中的概率极限状态法无法满足隧道工程设计需要。为拓展概率极限状态法在铁路隧道设计中的适用范围，便于开展国际交流，有必要开展铁路隧道概率极限状态设计方法研究，而结构目标可靠指标是应用概率极限状态的前提和基础。
研究结论:研究表明:(1)现行铁路隧道复合式衬砌通用参考图可靠性水平较高，对于钢筋混凝土衬砌、素混凝土衬砌抗压及素混凝土衬砌抗裂三种极限状态下，其对应的可靠指标均值分别为4. 27 、13. 71和7.48;(2)国内相近规范中在结构安全等级为二级的情况下，对于延性破坏状态其日标可靠指标变化范围为3. 2-4. 2，对于脆性破坏状态其目标可靠指标变化范围为3.7-4.7;(3)北欧国家的日标可靠指标不区分混凝土的延性破坏或脆性破坏，在结构安全等级为二级时，北欧国家规定设计日标可靠指标取4.26，而英国的CIRIA标准规定设计目标可靠指标取值3.71;(4)综合考虑参考图校准及国内外调研结果，提出我国铁路隧道衬砌承载能力极限状态目标可靠指标，对于延性破坏和脆性破坏两种情况:当安全等级为二级时，其对应的目标可靠指标分别为4. 2和4. 7，当安全等级为一级或三级时，对应的目标可靠指标分别提高或降低0.5;(5)本研究成果已经成功应用于《铁路隧道极限状态法暂行规范》。
Research purposes:In the current design code of railway tunnel，the application scope of the probability
limit state design method is confined to the single line railway tunnelintegral lining，however, the present situation of
railway tunnels in China is the lane and large span tunnel are more and more，the composite lining has been widely used
in tunnel. Therefore the probability limit state method in the current design codecan not meet the need for tunnel
engineering design，the application scope of the probability limit state method in railway tunnel design need to be
extended. At the same time，for thefacilitate international communication，it is necessary to study railway tunnel
probability limit state design method，and the structure design target reliability index is the basisfor application of
probability limit state.
Research conclusions:Research shows that:(1)On three kinds of limit state of reinforced concrete limit state，concrete
compressive and tensilelimit state，the corresponding mean value of reliable index are respectively 4. 27，13.71 and7.48. These calculation results show that the reliability level of existing railway tunnelliningreferenee maps is higher.
(2)In the related codes of China，under the second safety level condition of the structure，for the ductility failure type，
their reliability indexes are between 3 .2 and 4. 2，for the brittleness failure type，their reliability indexes are between
3 .7 and 4. 7.(3)The target reliability index of European countries has no relationship with failure mode，for the
structure of the second level of safety grade，European countries regulations design target reliability index is 4. 26，and
however it is 3. 71 in Britain.(4)Considering the calibration calculation results andtarget reliability indexes from the
domestic and foreign codes，the target reliability index of railway tunnel lining on bearing capacity limit state was given，
which will establish a basis for China railway tunnel structure reliability design. When the safety grade is the second
level，for two state of ductile failure and brittle failure，the corresponding target reliability index were 4. 2 and 4. 7，if
the safety grade is first or third level，the eorrespondingtarget reliability indexes are increased or decreased by 0. 5.
(5)The research results had been successfully applied to the Provisional Code for Railway Tunnel Limit State Method.
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