考虑黏土土性参数与支护压力变异性的盾构掌子面稳定性分析

盾构掌子面稳定性的不确定性分析多侧重于土性参数的变异性，较少考虑支护压力的变异性。基于K-L级数分解法建立描述土性参数空间变异性的三维随机场，研究土性参数变异性对掌子面失稳模式、极限支护应力的影响规律，讨论支护压力的均值与变异系数对失效概率的影响，并据此确定支护压力均值特征值。结果表明：黏性土黏聚力与内摩擦角的空间变异性对掌子面稳定性有重要影响，其中内摩擦角的影响更甚；掌子面失稳模式与随机场局部分布密切相关，当掌子面前方随机场较分散时，可能发生局部破坏；掌子面的失效概率与支护压力的均值和变异系数密切相关，支护压力的均值越大，变异系数越小，失效概率越小；提出了掌子面支护压力均值特征值的概念，并结合失效概率给出了确定方法。

Face stability analysis of shield tunnel considering variability of soil parameters and support pressure in clay

The probabilistic analysis of face stability of shield tunnel at present mostly focuses on the variability of soil parameters. However, few researches consider the variability of support pressure. In this paper, based on the K-L expansion, three dimensional random fields of soil parameters are generated to analyze the impact of variability of soil parameters on the failure mechanism of the tunnel face and the critical support pressure.Otherwise, the influence of mean value and the coefficient of variation of the support pressure on the failure probability has been discussed for determining the characteristic mean value of the critical support pressure. The results show that the spatial variability of cohesion and internal friction angle has an important influence on the tunnel face stability, and the influence of variability of internal friction angle is more significant.The failure mechanism of the tunnel face is closely related to the local distribution of random field. When the local random field of the tunnel face is dispersed, the local failure may occurs. The failure probability of the tunnel face is relevant with the mean value and the coefficient of variation of the support pressure. The failure probability decreases with the mean value of support pressure increase or the coefficient of variation of support pressure decrease. The concept of characteristic mean value of the critical support pressure has been proposed, and the determination procedure is given in combination with the failure probability.