Probabilistic Stability Analysis of Subway Tunnels Combining Multiple Failure Mechanisms and Response Surface Method

Abstract

A probabilistic approach is proposed for face stability analysis of subway tunnels, which begins with establishment of multiple failure mechanisms, including active failure and passive failure. In terms of the complex conditions during subway construction, the buried depth, surcharge load imposed on the ground, and pore water pressure are introduced to account for the extrinsic factors that probably affect the face stability. The probabilistic analysis is performed by consolidating the multiple failure mechanisms into response surface method (RSM). The cohesion and internal friction angle of soils are considered as random variables, and the remaining parameters are considered as nonrandom variables due to their low variability or determinacy for specific projects. The influence of nonrandom variables and random variables on failure probability is investigated in detail. Finally, a reliability-based design chart is provided to evaluate the target supporting pressure against tunnel face according to different coefficients of variation of random variables. In short, by taking into account of all the possible face failures in one performance function, the proposed approach has the virtue of catching the global behaviors of face failure when multiple failure mechanisms occur at tunnel face.