Research on Asymmetric Failure Mechanism and Control Technology of Roadway Along Gob in Extra Thick Coal Seam

Taking roadway along gob with narrow coal pillar in fully mechanized top coal caving face for extra thick coal seam as the research object, this paper systematically studies two key problems of asymmetric failure mechanism and control technology of gob side entry driving in extra thick coal seam by using comprehensive research methods such as theoretical analysis, numerical simulation and field measurement. Firstly, by establishing the mechanical model of overlying strata of gob side entry in fully mechanized top coal caving face of extra thick coal seam, the mechanical source of roof asymmetric failure of gob side entry is obtained. Secondly, the deflection stress invariant is selected to analyze the temporal and spatial evolution law of surrounding rock deformation and failure in the whole process of mining. Finally, the concept of asymmetric control and support technology of gob side entry in fully mechanized top coal caving face of extra thick coal seam are proposed, and the field engineering test is carried out. The research results show that: during the mining of extra thick coal seam, the overlying strata of gob side entry form a composite structure of “low cantilever beam + high hinged rock beam”, and the subsidence and rotation of cantilever beam is the fundamental reason for the roof asymmetric settlement and two sides asymmetric failure of gob side entry. During the mining, the bearing capacity of the narrow coal pillar and the roadway near the narrow coal pillar decreases, and the storage capacity of the distortion energy also further decreases, forcing the deviator stress to transfer to the deep part of the solid coal wall, resulting in more significant asymmetric deformation and failure on both sides of the roadway with the center line as the axis; The asymmetric control concept with asymmetric anchor cable truss and anchor cable channel steel composite structure as the core is constructed, and the supporting scheme of “anchor cable channel steel composite structure + asymmetric anchor cable truss structure + high strength anchor cable structure at the side” is put forward, and the field application effect is remarkable.