Roof stress evolution and failure mechanism of horizontal sublevel mining face in steeply pitching extra-thick coal seam

WANG Meng

doi:10.11799/ce202504015

Abstract：In order to explore the law of stress evolution and roof deformation of horizontal sublevel mining face in steeply pitching extra-thick coal seam,we took Baiyanzi Coal Mine in Gansu Province as the engineering background,analyzed the evolution law of stress field and displacement field of coal and rock in different sublevel mining processes through numerical calculation,and revealed the deformation and fracture characteristics of roof rock beam combining with theoretical analysis.The results demonstrate that the stress of surrounding rock in multi-sublevel stope of steeply pitching extra-thick coal seam distributes asymmetrically.With the increase of mining sublevels,the stress concentration of coal and rock on both sides of roof and floor occurs.Under the combined action of roof extrusion and goaf pressure relief,the stress concentration degree of coal rock on the roof side is further enhanced,and the stress peak area is close to the deep part of the working face on the roof side of the lower part of the goaf.Peak value of the concentrated stress increases linearly and positively,and the stress concentration coefficient reaches 2.56.The deformation mode of coal and rock changes from the settlement of coal above to the roof strata migration toward the goaf,and the fracture range of overlying strata gradually extends above the roof.The roof rock beam is constrained by the non-uniform filling of broken rock blocks,and the peak deflection is at the middle-upper region,which is prone to tensile deformation and failure,causing surrounding rock disasters.Roof pre-splitting blasting can alleviate the intensity of mine pressure behavior.