Active Stability Analysis of 3D Tunnel Face in Nonhomogeneous and Anisotropic Soils

摘要

Shield tunneling requires special attention to maintain the stability of tunnel faces. Many researchers have used the upper bound method to investigate the active stability of tunnel faces. Previous research with regards to the upper bound method has neglected the construction of 3D active failure modes in soils in which internal friction angles vary with the burial depth. In this paper, a 3D active failure mode is constructed through "double discrete technology", and the active limit support pressures of the tunnel face are compared using MATLAB and FLAC3D to verify that the method is effective. Based on the proposed method, the effects of nonhomogeneous and anisotropic soil on the active stability of tunnel faces are studied. Moreover, the presence of a weak interlayer and general three-layer soils were considered in a tunnel model, and the effect of weak interlayers and the parameters of each layer on the active stability of tunnel faces was investigated. The unit weight is the most significant factor affecting the active limit support pressures, followed by the internal friction angle, cohesion, and cohesion anisotropy coefficient. The critical failure shape is more influenced by the internal friction angle and less influenced by other parameters. The position, thickness, and parameter variation of each layer in the three soil layers have different effects on the critical failure shape and active limit support pressure. The method presented in this paper shows good applicability and flexibility in evaluating the active stability of tunnel faces in nonhomogeneous and anisotropic soils.