A fully coupled hydraulic-mechanical model of deep tunnel considering permeability variation

Abstract

When the buried depth of underground engineering exceeds 1000 m, the deep surrounding rock will show typical nonlinear deformation characteristics due to the coupling effect of high in-situ stress, and high seepage pressure. The stress field of surrounding rock will change the distribution characteristics of seepage field, and in turn, the change of seepage field will affect the distribution of surrounding rock stress field, which is a process of mutual influence and interaction. Considering the variation of permeability coefficient of deep surrounding rock and non-Darcy flow movement of fluid, a fully coupled hydraulic-mechanical analytical model of deep tunnel was proposed based on Hoek-Brown criterion and effective stress principle, and the detailed application method of the model was also given. Through the triaxial compression test under hydro-mechanical coupling, the nonlinear softening model considering seepage pressure and permeability variation equation were established, which solved two key problems of the model. The corresponding numerical calculation program was compiled based on ABAQUS finite element platform, and the reliability of the calculation program was verified by comparing with the model test results. The influence of the thickness of the grouting layer, the permeability coefficient of the grouting layer, the number of drainage holes and the depth of drainage holes on tunnel surrounding rock seepage pressure and lining seepage pressure were calculated and analyzed, and the anti-seepage optimization design of Xianglushan tunnel was carried out.