Research On Overburden Structure Evolution And Rock Burst Mechanism Of Fully Mechanized Caving Face In Shanzhai Coal Mine

Rock burst disasters frequently occur in fully-mechanized top-coal caving in extra-thick coal seams in Shanzhai Coal Mine,It is of great significance to master the characteristics of overburden structure in fully mechanized top coal caving mining,reveal the evolution law of overburden structure and the mechanism of induced rock burst,so as to provide basis for preventing rock burst disaster and ensure safe and efficient mining.Analysis of microseismic monitoring data and focal depth map in 1104 working face of Shanzhai coal mine,the strong mine earthquake in the fully mechanized top coal caving face mainly occurs in the return air channel of the working face,which is concentrated in the hard rock stratum of the roof and floor.Using physical similarity simulation,it is concluded that in Shanzhai coal mine,the overburden of the fully mechanized top coal caving face tends to break,which can cause the strong ore pressure of the surrounding coal and rock mass;after the failure of the interval pillars in the goaf,the key layers of the roof will be overall Fracture instability leads to large-scale overall fracture instability movement of overlying rocks,and strong coal pressure may be induced on the solid coal side.The caving angle of the roof after mining in the fully mechanized top coal caving face is 65?68° higher than that of the roof below 55?58°;The height of the slump of the roof is related to the width of the mining face.The drop height is between 36m and 60m.The coal pillars are subjected to large stresses between working faces,and the stress concentration is obvious.After the failure of coal pillars between working faces,the overburden fracture zone developed to the surface.According to the mechanical analysis,the first collapse steps of the main and sub key layers are 25m and 20m respectively,and the periodic compression steps are 10m and 8m.Synchronous and non-synchronous breaking of the composite key layer are the root causes of small and large periodic weighting on the working face.The numerical simulation found that the synchronous breaking of the composite key layer caused the synchronous breaking of the overlying weak rock layer to sink,causing the appearance of rock burst.The high stress near the working face is mainly concentrated in the roof rock layer of the upper part of the return airway.In the range of 150m in front of the working face,the stress in the coal seam of the floor of the two roadways is at a high level and the distribution range is also wide,these high stresses are the main source of the occurrence of rock burst on the working face.