基于稳定系数法的盾构隧道开挖面失稳概率分析

基于B. B. Broms等提出的开挖面稳定系数的概念,结合概率分析方法,考虑了土性参数的空间变异性,将黏土参数不排水抗剪强度看作服从对数正态分布的随机变量,形成了盾构隧道开挖面稳定性概率分析法;并讨论了不排水抗剪强度的变异系数和其均值随深度线性增加的特征对开挖面失稳概率的影响规律。研究结果表明:黏土参数不排水抗剪强度的空间变异性对盾构隧道开挖面稳定性有着重要的影响,参数变异程度越高,开挖面发生失稳破坏的概率也就越大;开挖面失稳概率会随着线性系数的增大而逐渐降低。单一的开挖面稳定系数很难恰当地反映盾构隧道开挖面的稳定性状态,而采用失稳概率的表示方法更为合适。

Probability Analysis of Face Stability in Shield Tunnelling Based on Stability Ratio

A probabilistic method for the stability of shield tunnelling face is proposed based on the concept of stability ratio defined by B.B.Broms and H.Bennermark in consideration of the spatial variability of soil parameters.The undrained shear strength of clay is regarded as a stochastic variable following lognormal distribution,and the failure probability of excavation face affected by the linear increases of variation coefficient and mean value of undrained shear strength against depth is analyzed.Results indicate that the spatial variability of undrained shear strength has a significant effect on face stability.The probability of failure increases correspondingly as coefficient of variation increases,but decreases with the growing of linear coefficient of the mean undrained shear strength.Probabilistic method is more suitable in evaluating the face stability of shield tunnelling than single face stability ratio.