铁路隧道洞门目标可靠度及分项系数确定方法

Method for Determining Target Reliability and Partial Coefficient of Railway Tunnel Portal

研究目的:铁路隧道洞门受力复杂、断面变化大,洞门可靠度研究少。研究隧道洞门目标可靠度及分项系数计算方法可为铁路隧道洞门的可靠度设计提供参考。研究结论:(1)目标可靠指标由各极限状态中最小的可靠指标决定,目标可靠度分项系数基于目标可靠指标求得;(2)目标可靠指标计算中,不同计算方法计算结果有差异,通过对三种适用于铁路隧道洞门目标可靠指标计算方法进行分析比较和结合实例计算,认为分位值法相对比较简便实用,可用于隧道洞门目标可靠指标的计算;(3)明确了分位值法计算铁路隧道洞门目标可靠指标分项系数的详细计算过程,并通过实例计算验证了分位值法计算分项系数的可行性;(4)土压力分项系数对铁路隧道洞门各极限状态均有影响且最大,因此应加强隧道洞门土压力统计特征研究;(5)本文提出的铁路隧道洞门目标可靠度及分项系数确定方法,可直接用于铁道隧道洞门结构设计。

Research purposes： There is a little research on the reliability of railway tunnel portal structure because of large section and complicated mechanical behaviors. The analysis process and calculation method can provide some references for the reliability design of railway tunnel portal. Research conclusions： （ 1 ） The objective reliability index is dominated by the smallest one of the whole possible failure modes. Partial coefficient can be calculated based on a given target reliability index. （2） Reliability index values are different when computed by different methods. Based on calculation methods and calculation example, contribution value method is considered more accurate, handy and practical when compared with the result from the other computational methods. Contribution value method is recommended as the best calculation way for the target reliability index for tunnel portal structure. （3） The processes of contribution value method for partial coefficient are described, and the mathematical description of the method is given clearly. Contribution value method is proved to be feasible through the calculation example. （4） Among five partial coefficients, the greatest impact to the limit state of tunnel portal structure is the partial coefficients of coefficient of earth pressure. So the study of statistical character for soil pressure should be enhanced. （5） The method for determining target reliability and partial coefficient of railway tunnel portal can directly be applied to the design of railway tunnel portal structure.