Research on ground stress characteristics of lower formation coal in Tengxian coalfield and stability control of limestone interlayer roof
In Jinqiu coal mine of Tengxian coalfield,there is a weak interlayer in the limestone of the 16th coal seam roof.Its thickness,failure pattern,and the physical and mechanical properties of the underlying hard rock layer affect the overall fracture pattern of the roadway roof.Additionally,the in-situ stress field is unclear and some surrounding mines have experienced roof falls for lack of consideration of this factor in support design.This study aims to address the roof fragmentation and significant deformation of the coal bodies on both sides of the roadway at 162-206 lower track of the 16th coal seam in Jinqiu coal mine.Using in-situ stress measurements,mechanical testing of the roof and floor,and roof borehole inspections,we explored the in-situ stress characteristics,limestone roof mechanics,and weak interlayer positions in the 16th coal seam of Tengxian coalfield to improve the support scheme.Numerical simulations were conducted to analyze the deformation characteristics of the surrounding rock under three improved support schemes,and the best support scheme was selected.The effectiveness of the optimal support scheme was evaluated through engineering monitoring.The results indicate that the limestone interlayer in the roof of the 16th coal seam is within a depth of 1～2 meters,particularly between 1.1～1.3 meters and 1.8～2.0 meters.The maximum principal stress in the 16th coal seam is nearly horizontal.The roof is more affected than the sides,leading to more severe shear failure and larger roof displacement.The maximum principal stresses are predominantly southeast oriented with values of 16 to 20 MPa.Considering the overall control effect,labor intensity,and support cost,Scheme 2 was chosen as the optimal support scheme for the lower track roadway.During engineering monitoring,the deformation of the surrounding rock in the roadway gradually stabilized 16 to 20 days after installing the measurement points.The maximum deformation of the roof and floor was 38 mm and the maximum deformation of the sides was 67 mm,thus verifying the effectiveness of the improved support scheme.
lower formation coal in Tengxian coalfieldground stress characteristicslimestone interlayer roofsur-rounding rock control
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