The Effect of Groundwater Seepage on Stability of Tunnel by Using Strength Reduction Method Considering Fluid Solid Coupling

During the construction period of tunnels, groundwater seepage may lead to large deformation and even collapse of tunnel. To study the effect of groundwater seepage on stability of tunnel, the strength reduction method considering fluid solid coupling was employed to calculate safety factor of tunnel by using numerical simulation. Firstly, three working cases were established to investigate the effect of groundwater seepage and calculation mode on safety factor of tunnel. Then the fluid solid indirect coupling mode was adopted to investigate the relationship between safety factor and groundwater level. Numerical results show that safety factor considering groundwater seepage is about 20% less than that without considering groundwater seepage. Numerical results of two calculation modes are almost identical, but the computational time of fluid solid indirect coupling mode is far less compared with that of fluid solid coupling mode. Safety factor of tunnel linearly decreases with the increase of groundwater level, with the slope of 0.26. Moreover, tunnel crown settlement increases with the increase of groundwater level when the strength reduction factor is equal. Groundwater seepage is unfavorable to control tunnel deformation. In the watery zone, groundwater level should be lowered to improve stability of tunnel on condition that it does not seriously affect surrounding environment.