Research On Seepage Filed Of Tunnel And Rock Stability In Fractured Rock Mass

The hydraulic tunnel is usually long and large with deep buried depth, and will pass through a large number of fractured rocks. After excavation, the rock stress around the hole will be secondarily redistributed, while seepage field in fractured rock will be affected by stress environment, and in return, stress field will be influenced by seepage field changes (namely, fluid-solid coupled interaction). Those situations will have some impact on the stability of rock and seepage balance of groundwater. Particularly, if the area is rich in caves or underground water, these conditions are more serious. So it is necessary to discuss and analyze rock stability of tunnel, seepage influence and other issues considering the fluid-solid coupled interaction.In this paper, Muli river hydraulic tunnel is selected as the targeted project. First data research for tunnel excavation problem in fissured rock has been conducted. Then numerical simulation has been used for analysis of tunnel rock stability, seepage behavior and their impact factors considering the fluid-solid coupled interaction, and dynamics and behavior of tunnel grouting under fault fracture zone. The main work and results are as follows,(1) The impact of groundwater seepage (namely considering fluid-solid coupled interaction) on the rock stability and seepage is studied during hydraulic tunnel construction. The necessity of considering the fluid-solid interaction is proposed on the basis of comparative analysis of rock stress field and seepage field under three conditions. The first is to consider fluid-solid coupled interaction. The second is not to consider the fluid-solid interaction but involve hydraulic boundary conditions. And the third is not to consider fluid-solid interaction as well as not to involve hydraulic boundary conditions.(2) Effects of different stress, water level, normal stiffness and tangential stiffness on rock stability and seepage of hydraulic tunnel through fractured rock are studied. By changing a single variable, calculation results are obtained under different conditions and the stress field and seepage field are analyzed, and then the variation law is received under the single-factor impact, which can provide reference for design and construction.(3) The mechanical behaviors of rock under fault fracture zone after excavation are studied. Influence of fault fracture zone on the rock stability and seepage is obtained. Bingham fluid model is used to simulate the dynamic process of grouting, to analyze the mechanics and seepage characteristics of the process and to verify the improvement to rock stability by grouting.