非均厚多层砂岩复合顶板结构特征及采动效应研究OA

A significant factor contributing to the increased difficulty in roof management and the in-ducement of rockbursts during the mining process is the presence of a thick,hard overlying roof above the coal seam.The main coal seams in the mine are often overlain by multiple layers of sandstone with non-uni-form thickness due to changes in the depositional environments and sedimentary facies,posing certain risks to the safe and efficient mining of the working face.A case study was conducted on the 11 139 working face in Zhangji coal mine,Huainan mining area to accurately understand the overlying rock structure and the dis-tribution pattern of sandstone layers in the working face roof,and to reveal the characteristics of the min-ing-induced effects under the condition of a non-uniform multi-layer sandstone composite roof.Drilling was performed on the working face roof to systematically investigate the thickness,lithological changes,and dis-tribution patterns of the sandstone layers within a 50-meter range of the working face roof.A heterogeneous model that conforms to the actual geological conditions was established using Rhino software and imported into FLAC3D software to conduct a study on the mining-induced effects of the working face.In line with the study results,three sandstone layers were found to be distributed within the surveyed range of the work-ing face roof.The sandstones were directly overlying the main coal seam,with the lithology from bottom to top being medium-fine sandstone,fine sandstone,and siltstone.The roof sedimentary structure exhibited a positive grain size sequence in the vertical direction,with the direct roof sandstone having a distribution pat-tern resembling a"lens"shape.The roof structure was a typical multi-layered sandstone body with non-uni-form thickness.In contrast with the uniform thickness model,the non-uniform thickness model was found to show a 35.92%increase in the maximum supporting stress at the coal wall,revealing that the stress con-centration was significantly enhanced due to the variation in sandstone thickness.Additionally,the stress dis-tribution in the surrounding rock of the mining area changed from an approximately symmetric distribution in the uniform thickness model to an asymmetric distribution.Furthermore,the maximum development height of the"two zones"and the roof subsidence after mining in the non-uniform thickness model were greater than those in the uniform thickness model.The findings provide a reference for studying mining-in-duced effects and managing hard roofs under similar conditions.