Abstract: An analytical solution for the analysis of tunnels below a groundwater table in plane strain ax-symmetric conditions is presented. The seepage body force and secondary permeability of the rock mass due to the hydraulic-mechanical coupling, and external water pressure are taken into account. The Hoek-Brown empirical strength criterion for the rock mass is used in the analysis. The nonlinear solutions considering hydraulic-mechanical coupling are given in a pressurized flow tunnel. The results show that the stress field, displacement field and the plastic zone radius are larger than those of not accounting for coupling factors when the hydraulic coupling is taken into consideration. Thusly the tunnel excavation should take full account of the water - force coupling. The case analysis shows that the stress and plastic zone radius grows with the increases of m_i , the relation between plastic zone radius and parameter m_i is non-linear incremental.