Analysis on Seepage Stability of Subsea Tunnel in Rock Mass with Local Fracture Zones

The method of fluid-solid coupling stability analysis for subsea tunnels in rock mass with fracture zones under seawater seepage pressure is studied on basis of seepage finite element simulation method and rock strength reduction theory.The mentioned analysis method is applied in Qingdao-Huangdao subsea tunnel to analyze the seepage field of the rock mass with/without water-sealing consolidation and to analyze the seepage stability of the tunnel.Conclusions drawn are as follows: due to the fracture zones,the water head in the rock mass rises and the water seepage quantity increases;high hydraulic gradient occurs near the fracture zones,which dramatically reduces the safety coefficient of the tunnel;after water-sealing consolidation,the overall safety coefficient of the tunnel is improved and the seepage quantity in the rock mass is obviously reduced;at the water-sealing positions,however,the hydraulic gradient of the rock mass increases,therefore,the support at these positions should be strengthened.