Abstract:
In view of the problem of special damage section in the cross-excavation roadway at the lower side of the residual coal pillar at the mining area boundary, taking the No.051606 tailentry along the gob-side of Lingxin Coal Mine as the background, the comprehensive analysis method of field investigation, theoretical analysis, numerical simulation and industrial test was adopted to study the on-site rock pressure behavior in the special failure section of the roadway. Based on the mechanical model of the influence of the residual coal pillar effect established by the half plane theory and the fine numerical simulation during the cross excavation and mining period, the repair and support design scheme of the special damaged section of the roadway was comprehensively studied and determined. The research results show that: under the influence of the legacy coal pillar effect, the surrounding rock of the cross-excavation roadway is mainly affected by the vertical stress below the axis of symmetry of the residual coal pillar, where the vertical stress is about 13.0-15.0 MPa. While the shear stress is mainly affected by the shear stress below the edge of the residual coal pillar, and the shear stress is about -6.5--5.0 MPa and 5.0-7.0 MPa; the maximum vertical stress at the roof is 14.4 MPa, the maximum vertical stress at the floor is 13.6 MPa, the maximum shear stress at the roof is 6.5 MPa, and the maximum shear stress at the floor is 5.3 MPa. The maximum vertical stress is directly below the central axis of symmetry of the residual coal pillar, and the maximum shear stress is located below the edge of both sides of the residual coal pillar; the disturbance effect on surrounding rock of special damaged section in No.051606 working face can be divided into non-stress influence section (more than 16 m away from the edge of residual coal pillar) and the advanced stress affected section (0 to 16 m away from the edge of residual coal pillar) and superimposed stress influence section (0 to 17.5 m away from the axis of symmetry of residual coal pillar). Due to the influence of mining disturbance, the concentration degree of deviatoric stress in coal pillar and roof close to the coal pillar is higher, and the surrounding rock is more prone to deformation and asymmetric damage; after the special damaged section of roadway was repaired by asymmetric anchor cable truss support system, the convergence of roof between floor and two ribs were 143 mm and 109 mm respectively, which were 4.3% and 2.2% respectively compared with the original section size of roadway. The overall control was within 5%, which could meet the needs of pedestrians and ventilation.