Study On Strong Ground Pressure Behavior Characteristics And Presplitting Blasting Control Technology Of High-level Thick Sandstone Roof

In view of coal mining under the condition of overlying high-level thick sandstone roof,menkeqing coal mine is taken as the engineering background.The spatial structure of high-level thick sandstone roof is analyzed;the fracture deformation law of high-level thick sandstone roof under the influence of coal mining is revealed;the stress field and elasto-plastic zone distribution characteristics of high-level thick sandstone roof are studied;the presplitting blasting scheme is designed and the effect is analyzed.The following conclusions are obtained:According to the key layer theory,it is identified that there are four key layers above the 3102 working face.It is revealed that the structural form of the high-level thick sandstone roof in the dip direction is a symmetrical "t" type overburden structure,and the structural form change law in strike is: short masonry beam-"F" type cantilever beam-"F" type cantilever beam + masonry beam-"F" type cantilever beam.The mechanical analysis of F "cantilever beam is carried out.The peak value of the leading stress decreases with the decrease of the cantilever length.The fracture deformation law of high-level thick sandstone roof under the influence of coal mining is revealed.The first collapse step of the high-level thick sandstone roof is 130 m,which evolved from a long masonry beam structure to an "F" cantilever beam structure formed with the low-level thick sandstone roof.The maximum subsidence of the roof is 5.69 m,which is located in the middle of the goaf.The high-level thick sandstone roof is "pressured in a large period",with a step distance of 50～80m,and the low-level thick sandstone roof is "pressured in a small period",with a step distance of20～30m.Both of them work together,resulting in a relatively strong ground pressure in the working face.The stress field and elasto-plastic zone distribution characteristics of high-level thick sandstone roof are studied.With the coal seam excavation,the peak value of the advance abutment pressure gradually increases and gradually shifts to the front.The elasto-plastic failure area gradually expands from the low level thick sandstone roof to the high level thick sandstone roof.After presplitting blasting,the peak value of advance bearing pressure decreased,and shear failure occurred at the presplitting blasting position of high roof.According to the conditions of overlying high-level thick sandstone roof,a presplitting blasting scheme is designed.According to the field measurement results,after presplitting blasting,the periodic pressing step distance of the working face is shortened to 26.2m,the average working resistance of the support is reduced to 22.7MPa,the microseismic large energy events are reduced,and the total energy peak distance of microseismic is shortened from 148.5m to 84.7m.The safe mining of the working face was ensured.Figure 63 Table 18 Reference 84...