Abstract:
The movement patterns of rock strata in fault-structure zones remain unclear, and the influence range of fault structures is poorly defined. If surface gas drainage wells are deployed within fault-affected zones, premature well failure may occur, severely shortening the service life of the wells.To address these challenges, calculation formulas for vertical displacement were derived, horizontal displacement, and fault-plane displacement of overlying strata in fault-structure zones, based on the Winkler foundation beam theory, composite beam theory, and Mohr-Coulomb failure criterion. Combined with tensile test results of well casings, discriminant criteria for casing shear failure and tensile failure are proposed, providing a theoretical basis for analyzing failure modes of surface wells under mining disturbance. Using the 7703 working face of Zouzhuang Coal Mine as an engineering case, numerical simulations of strata movement in the fault-structure zone were conducted. The results show that the height of the shear failure zone exhibits phased growth as the working face advances, while the tensile failure zone height first increases and then decreases. The maximum shear and tensile failure heights for surface wells in the 7703 working face are 121.4 m and 53.9 m, respectively, validated by borehole wall imaging. Furthermore, based on the casing failure ranges predicted by numerical simulations and theoretical calculations, the structural design of surface wells was optimized. The optimized wells demonstrate stable gas drainage performance and improved operational reliability.