Analysis of fluid-solid coupling mechanism of water-bearing weakly cemented surrounding rock-filling layer-drilling shaft lining in the west of China

The shaft drilling method has the advantages of intrinsic safety, high degree of mechanization,and good well completion quality. It is the development direction of automation and intelligence in deep shaft construction in China. The research on the interaction mechanism of drilling shaft lining, filling layer, and water-bearing weakly cemented surrounding rock was carried out to provide a basis for applying the shaft drilling method in deep and water-bearing weakly cemented strata in Western China. First,according to the working conditions of the drilling shaft lining in the employ stage, a fluid-solid coupling model of the interaction of water-bearing weakly cemented surrounding rock-filling layer-drilling shaft lining was constructed. The analytical solution of the seepage field and stress field were deduced based on the thick-walled cylinder theory, the generalized effective stress principle, and Darcy’s seepage law. Then, the north air shaft of the Taohutu Coal Mine to be built was taken as the engineering background, the distribution law of the seepage field and the stress field around the wellbore were obtained, and the analytical solution was verified by the method of numerical calculation. On this basis, the action mechanism of the filling layer was studied,and the influence of the filling layer on the long-term external load of the shaft lining was analyzed. The results show that: The radial effective stress distribution curve is similar to the pore water pressure distribution curve, and the closer to the wellbore center, the smaller the pore water pressure and effective radial stress; The hoop stress is generally greater as it is closer to the wellbore center,and the maximum value appears at the inner side of the wellbore. Reducing the permeability and increasing the thickness of the filling layer can improve the ability of the filling layer to distribute effective stress and pore water pressure, the effective stress and the pore water pressure transmitted to the shaft lining are reduced. Increasing the elastic modulus can improve the ability of the filling layer to distribute effective stress so that the effective stress transmitted to the shaft lining is reduced. The crushed stone filling should not be used in shaft drilling in western China,and high-performance cement mortar filling material should be developed. The deflection rate shall be controlled during drilling to increase the effective thickness of the filling layer. The research results of this paper reveal the mechanical mechanism of the drilling shaft lining in the western water-bearing weakly cemented strata in the employ stage and provide a basis for the long-term stress analysis of the drilling shaft lining. © 2023 China University of Mining and Technology. All rights reserved.