Study on Micro Deformation Features of Overburden Strata Above Longwall Coal Mining Face Under Goaf of Room and Pillar Mining

Based on the actual mining of the longwall coal mining face under the goaf of the room and pillar mining in Ordos Mining Area,a method combined with a theoretical analysis,site measurement and numerical simulation was applied to study the micro deformation features of the overburden strata above the coal mining face under the goaf of room and pillar mining.The results showed that the roof structure above the longwall coal mining face under the goaf of room and pillar coal mining would have a feature with a large structure in the top roof and small structure in the bottom roof.The reciprocal effect between the large structure and small structure would cause the circulated terminal resistance of the powered support and the roof pressurization judging data higher than at the bottom of the coal seam and at the bottom of the longwall mining goaf.There would be a stress concentrated abnormal zone existed in the coal wall of the longwall coal mining face under the coal pillar left in the goaf.Thus the spalling from the coal mining face and the roof breaking danger would be increased and the powered supports would lost its stability.