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

Abstract

This paper investigates the effect of the anisotropy and nonhomogeneity of soil on the three-dimensional stability of a pressurized tunnel face. A three-dimensional horn failure mechanism was constructed. The energy dissipation of the ultimate limit state was analyzed, and the upper bound solution of collapse pressure was obtained according to the limit analysis theory. The validity of the proposed method was demonstrated by comparing its results with those from other researchers. The difference in collapse pressures at linear variation cohesion and average equivalent cohesion was analyzed in detail. It was found that the anisotropy and nonhomogeneity of soil cohesion have a great impact on the collapse pressure and failure scope of a pressurized tunnel face and thus should be properly considered in the support design of pressurized tunnels. In addition, an approximate solution for the collapse pressure of a tunnel face in nonhomogeneous soils is proposed based on Terzaghi’s method, which provides a simple method to quickly and effectively assess the stability of a pressurized tunnel face.