Effect of Seepage Force on Tunnel Face Stability Using Limit Analysis with SRM

The seepage force is of importance on tunnel face stability. The formulas to determine the seepage force are introduced based on Darcy's Law. The formula of the stability safety factor containing the tunnel face of the seepage force is derived and applied to the actual tunnel engineering using the upper bound limit analysis combining with the strength reduction method. The results show that: as the water level increases, the average seepage force increases, and the safety factor decreases. If the horizontal seepage force is considered only and the vertical seepage force is ignored, the result is unsafe. The stability of the tunnel face can be improved by reducing the excavation height and adopting some reinforcement, such as grouting or rock bolt to increase the cohesion and friction angle of the rock.