The Study Of The Interlayer Pore Karst Water’s Effect On The Stability Of Surrounding Rock Of Hydraulic Tunnel

In this paper, with the tools include numerical simulation and theoretical analysis methods, numerical models of hydraulic pressure tunnel in the interlayer karst water area were established, which were based on the fluid solid coupling theory. Models were established to study the stability of surrounding rock of hydraulic pressure tunnel in three kinds of conditions, including excavation, operation and maintenance. The main research contents and achievements of this paper are as follows:(1) The article extracts the basic concept of the interlayer karst aquifer system,related generalization model and the corresponding mathematical model, in the foundation of the existing research of karst. Brief examples are cited.(2) Based on the basic percolation theory and corresponding water transport equation, analyzing the relationship between rock porosity and volume change, to propose the specific method of seepage-stress coupling. Through previous researches about the relationship between permeability coefficient, stress, strain and the porosity, establishing respectively coupling models and finite element models.(3) Based on analyzing the finite element model, this article established,calculated and analyzed the numerical analysis model on the effects of hydraulic tunnel surrounding rock of the fluid solid coupling theory on various conditions, through using ABAQUS software and the programming subroutine of permeability coefficient and volume strain.(4)The result for stress analysis of the calculation of the finite element models shows four conclusions. Firstly, stress concentration zone appears below tunnel tunnel in excavation, and its area is increasing with the tunnel dimater’s enlargement. Secondly, the stress of surrounding rock is incressing and the stress concentration zone is more prone to appear when the distance is decress between the tunnel and the junction of rock mass. Thirdly, the stress of surrounding rock is incressing with the tunnel dimater’s enlargement and it is also increesing when the part of tunnel in permeable layer is expanding. Finally, when the tunnel is crossing layers or the entire tunnel is in permeable layer, the stress of surrounding rock changes suddenly in complexity and varies instably.(5) The result for displacements analysis of the calculation of the finite element models shows that the changes of key points’ displacement in three main steps are: shrinking to the center?shrinking in vertical direction slightly, and expanding in horizontally?shrinking to the center. When the tunnel diameter unchangs and the entire tunnel is in one layer, the vault subsidence in different conditions are basically the same,but the tunnel’s level of convergence is smaller in the conditions that the tunnel is all in permeable layer.