174 Sensitivity Analysis on the Effect of the Seepage from Underground Hydraulic Tunnel under High Internal Water Pressure

The seepage induced by high internal water pressure is a factor often ignored in the design of hydraulic tunnel, and its effects on external water flow is still unclear. The seepage-stress coupling analysis is used to investigate the influence of the seepage based on the Biot's consolidation theory and the entity mixed model, in which the variation of steel stress is used to represent the change of stress state in the structure.

Then sensitivity analysis is carried out to investigate the maximum water pressure acting on the exterior surface of tunnel liner. The impact factors include the crack width in concrete of tunnel liner, the permeability of surrounding rock and the dip angle of fault. The analysis results reveal that the tensile stress of rebar decreases in the coupling analysis step. The results also show that the maximum water pressure acting on the exterior surface of tunnel liner is the most sensitive to the crack width and insensitive to the dip angle of fault.