基于可靠度理论的铁路隧道洞门极限状态设计方法

针对铁路隧道洞门结构稳定性极限状态功能函数具有非线性及其参数具有随机性的特点,提出了基于可靠度理论的铁路隧道洞门结构设计方法.通过分析铁路隧道洞门的极限状态,建立了其极限状态方程.基于可靠度理论,以时速140 km/h的单线电气化铁路隧道端墙式洞门可靠指标计算为例,根据采用同样方法对3种设计时速共16种形式、22种类别隧道洞门的可靠指标计算结果,确定各极限状态下的目标可靠指标,建立极限状态设计式,求解并优化抗力分项系数.研究结果表明:铁路隧道洞门主要有抗裂、抗压、倾覆、滑动和地基承载力不足5种极限状态;极限状态方程中基本随机变量的统计特征是铁路隧道洞门可靠度设计是否准确的关键,可靠指标的确定是洞门结构极限状态设计的核心;建立的极限状态设计方法可直接用于铁路隧道洞门结构设计. 

Limit State Design Method of Railway Tunnel Portal Based on Reliability Theory

From the characteristics that limit state functions for the stability of a railway tunnel portal structure are nonlinear and the parameters are random, a new design method for railway tunnel portal structures was put forward based on the reliability theory. Limit state equations for railway tunnel portal structures were founded by analyzing the limit states of railway tunnel portal. Based on the reliability theory, reliability indices of a single-track railway tunnel portal with a design speed of 140 km/h were calculated as an example, target reliability indices for different limit states were determined from the calculated reliability indices of railway tunnel portal under three design speeds, including 16 kinds of portal forms and 22 kinds of portal categories, and partial resistance coefficients were calculated and optimized based on establishing the design expressions for different limit states. The research results show that major limit states of railway tunnel portal are cracking, crushing, overturning stability, sliding stability and insufficient foundation bearing capacity; the statistical characteristics of basic random variables in the limit state equations are the key whether reliability design of railway tunnel portal is accurate or not, and the determination of the reliability indices is the core issue in the limit state design of railway tunnel portal. The established method can be directly used to the limit state design of railway tunnel portal.