Influence of Pipe Roof Reinforcement on Face Stability of Underwater Tunnel

The effect of seepage force on tunnel face stability with pipe roof reinforcement was studied based on the kinematic method of limit analysis. This method can be employed to define the safety factor and its corresponding critical failure mechanism for a given tunnel. The studies revealed that the existence of groundwater may seriously affect the face stability. Under the steady-state groundwater flow condition, most part of the total support pressure is owing to the seepage pressure acting on the tunnel face. There was a relatively large reduction in the seepage pressure by adopting the pipe roof reinforcement technique.

Seepage force in a drained circular tunnel: An analytical approach

This study deals with the investigation of analytical solutions for the seepage forces acting on the lining in a drained circular tunnel under the steady-state groundwater flow condition. Two different boundary conditions (one for zero water pressure and the other for a constant total head) along the tunnel circumference are mentioned. Simple closed-form analytical solutions for seepage force along the tunnel circumference are derived in a theoretically consistent way for two different boundary conditions by using the conformal mapping technique. The seepage force predictions are compared to investigate the differences among the solutions. It is shown that the seepage forces acting on the lining should be considered for a drained tunnel and that the seepage forces greatly increase for a very deep tunnel.