The huge, inclined goaf formed by the mining of steeply inclined and extra thick coal seams has the characteristics of occupying a large space and being subject to complex breaking behavior of its overlying rock structure, especially the rock block structure characteristics of the interface area between the goaf and the lower working face which is difficult to be characterized, leading to a hidden danger when mining the lower working face. In response to the aforementioned problems, the following conclusions are drawing as follows: (1) with the aid of the contradiction method, the critical condition governing instability of the triangular articulated structure was obtained to explain the correctness of the assumption of the triangular hinged structure; (2) three-point truss structure was composed of key layer blocks; (3) in the stabilization stage of the triangular hinged structure, the fracture network area was extracted, and the centerline intensive equivalent method of a single fracture segment was adopted to directly measure the equivalent length. Meanwhile, the value of equivalent average width with the equivalent length of a single crack was calculated by integral operation and equivalent figure calculation; (4) the mathematical expressions of permeability which was positively exponential function related to the ratio of equivalent average width to equivalent length were derived. Furthermore, the vectorized solution of seepage rate was carried out respectively for the goaf area and the extracted network area by using COMSOL software. The distribution of the strong seepage area of CBM and the ratio of equivalent average width to equivalent length is found to be consistent to a large extent, which provides theoretical support for subsequent CBM management.

With the help of mechanical models and numerical calculations, the research obtained: (1) the range of compressive shear stress in well bore is in the shape of “dam body” with the dip angle of a reverse fault, also, the magnitude of the compressive shear stress is related to the load factor and the maximum compressive principal stress which have an increasing relationship; (2) the superposition stress of lateral abutment stress and SZZ of a working face is σA, which is related to the distance between reverse faults; (3) the closer the distance to the reverse fault and the greater the vertical well displacement and deformation as the advancement length of the working face increases, the sensitivity to the effects of the reverse fault and mining is: XDISP > ZDISP > YDISP, and the sensitivity to the boundary is such that: ZDISP > YDISP > XIDSP; (4) the closer the distance to the reverse fault and the larger the length of the working face, the greater the displacement and deformation of the vertical well. In addition, the sensitivity to the effects of reverse faults and mining is: XDISP > ZDISP > YDISP; (5) when the working face continues to be mined, the shear stress on the well bore and the circumference of the hole is sensitive to the influences of reverse faults as follows: SXZ > SYZ > SXY; (7) the density of strain energy at the well bore is most sensitive to the lateral distance to the working face strike mining line. Based on these results, it is proposed to arrange large-diameter pressure relief boreholes around the hole and arrange layers to eliminate the influence of the well bore boundary and eliminate the accumulation of shear strain energy around such a well bore.