Study on Water Pressure Reduction Measures Outside Hydraulic Tunnels in Water-Rich Areas
External water pressure is an important factor affecting the stability of the tunnel and the safety of the lining structure.Especially for the deep-buried hydraulic tunnel with rich water stratum,the high external water pressure brings great challenges to the lining design.At present,there is no unified standard of pressure reduction measures for tunnel drainage,and the main focus is on the influence of external water pressure on the lining,thus the influence analysis on the seepage field needs to be strengthened.Based on Songlin Tunnel of Central Yunnan Diversion Project,this paper carried out fluid-solid coupling analysis of surrounding rock and lining structure with ABAQUS software,and analyzed the changes of seepage field and external water pressure of lining under different grouting ring parameters and drainage layout schemes.The results show that the water pressure outside the lining can be effectively reduced and the influence of tunnel excavation on the seepage field can be reduced by changing the thickness of the grouting ring or reducing the permeability of the grouting ring.The layout of drainage holes can also effectively reduce the external water pressure of the lining,and the closer the distance from the drainage holes,the more significant the pressure reduction effect is,while the farther the distance from the drainage holes,the smaller the reduction range,and the greater the impact on the seepage field.It is suggested that the combination of plugging and drainage measures should be adopted in the actual project to reduce the external water pressure,and the optimal design of drainage holes and grout rings should be carried out to obtain the optimal pressure reduction effect.
tunnelsgrouting zonedrainage holeexternal water pressureseepage field
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