Effects of Pore Pressure and Hydraulic- Mechanical Coupling on Stability of Under Ground Water Tunnels

In this paper an analytical-numerical method for hydraulic and mechanical analyses of tunnels below groundwater table excavated in a strain-softening Hoek–Brown rockmass is proposed. The problem is considered as axisymmetric, i.e. the initial stress state is assumed to be hydrostatic. In this method, the seepage body force and thesecondary permeability of rock mass due to the mechanical- hydraulic coupling are taken into account. As the strain dependent permeability and a nonlinear behaviormodel for the rock mass is used, the derived differential quations should be solvednumerically. Thus, the numerical method (the finite difference method) is utilized for these equations. The influence of seepage and the hydro-mechanical coupling, on the elasto-plastic solutions is also examined

Keywords:

Tunnel , Analytical-numerical solution , Seepage , hydraulic- mechanical coupling , Pore water pressure