Stability Analysis Of Surrounding Rock Of Deep-lying Tunnel In Water-rich Region

With the exploitation of hydropower resources in western region in China, long diversion tunnels are widely adopted .Since the mountains in western region are high and abundant in groundwater, some special geological hazards are encountered during the tunnel construction,such as high geostress, high external waterpressure, watergushing and so on,which have become problems demanding prompt solution in tunnel design and construction .In this paper ,the diversion tunnel in Jinping Cascade 2 Hydropower Station, which is located in the region abundance of groundwater,is taken as the engineering background. The stability of surounding rock under high geostress and high external waterpressure is studied in detail. The main contents are as follows:(1)Handling of geotechnical engineering and seepage analysis with ABAQUS-finite element analysis software are discussed,which provide theoretic basis and technological support for 3D nonlinear analysis of Jinping cascade 2 hydropower station.(2) Based on the modern design theory of tunnels construction that the surounding rock be regarded as primary load-bearing structure,seepage field,stress distribution and deformation of high geostress and high external waterpressure zone after excavation of tunnels are analyzed by the numerical simulation with ABAQUS. By this means, the relations between the different permeability coefficient, different depth of the grouting rock, different anchor structure installing time and stress distribution ,deformation, and plastic range of the surrounding rock are obtained. In addition, physical mechanics properties weakening behavior for surrounding rock which are in the plastic zones is taken into account through the user subroutine program,which make the calculation results provide more reference for surrounding rock stability evaluation.(3)To improve numerical simulation precision by enhancing the accuracy of the main parameters., the sensitivity of mechanical parameters of surrounding rocks is analyzed with the use of orthogonal test design method,which distinguish the main parameters from the secondary parameters.