Structural Evolution and Stress Transfer Mechanisms of the Floor in Deep Roof-Cutting Gob-Side Entry Retaining

Based on the engineering background of roof-cutting and retaining roadway working face in Dingji Coal Mine of Huainan, the stress characteristics of the floor and the stress transfer mechanism caused by mining in the process of retaining roadway are studied. The stress in the roadway and the roadway after roof-cutting is relieved, and the floor stress is symmetrically distributed. During the first mining period, the stress at 5 m of the roadway side is concentrated, and the high stress is transmitted to the floor through the coal body. The stress on the solid coal side is restored, and the large-scale pressure relief on the goaf side forms an asymmetric stress field. The vertical stress is transmitted to the floor through the ‘short cantilever‘ structure of the roof, and the ‘short cantilever‘ structure is characterised by high tension and low compression. As the gangue collapses, the bending subsidence of the overburden rock causes the key parts of the roof to rotate and sink, and the high additional load is transmitted to the floor through the coal side and the supporting body in the roadway, resulting in an increase in the stress on the floor of the retained roadway. After the goaf is compacted, the floor fully touches the gangue and shares the load with the key parts of the coal body and the roof.