Research On Mining Effect And Crack Evolution Law Of Coal Seam Group Under The Influence Of Faul

The fault area in coal seam is an important area with frequent disasters in coal mines.The faults existing in coal and rock strata seriously affect the safe and efficient mining of coal mines.Based on the actual complex geological conditions of coal mines in Guizhou Province,this paper takes 151710 working face of Tucheng coal mine in Panjiang City,Guizhou Province as the research background,and studies the mining-induced rock stress distribution law and fracture evolution law of coal seam group under the action of faults by referring to relevant literature,theoretical,field measurement analysis and physical similarity simulation.In order to provide theoretical reference for safe mining of coal seam group in similar fault area.The main research contents and results are as follows :(1)Taking Tucheng coal Mine in Guizhou Province as the research background,the occurrence conditions of coal seams and faults in the study area are introduced.Based on Anderson and Huffler fault model,the stress state of fault formation is analyzed.By establishing the slip mechanical model of working face crossing the fault,it is obtained that the movement of structural instability in the fault is mainly determined by the combined action of vertical stress and horizontal stress on the fault surface.(2)Combined with the existing achievements and viewpoints,the main influencing factors of the dynamic evolution of the mining fracture zone and the main forms of the movement and failure of the overlying strata in the coal seam are analyzed.Based on the elliptic paraboloid zone of the mining fracture and the’ O ’ circle theory,a spatial structure similar to the trapezoid is established to replace the fracture morphology of the coal seam,which provides an effective theoretical basis and basis for the similar simulation and numerical simulation of the fault mining of the coal seam group.(3)Based on the similarity theorem,the similar simulation mining experiment of coal seam group under the action of faults was successfully carried out.The digital speckle measurement system was used to monitor and analyze the mining process of similar simulation experiment of coal seam group under the action of faults.The research shows that the stress distribution before and after the working face of the lower coal seam is significantly different from that of the upper coal seam.With the advance mining of No.9 coal seam(upper coal seam),No.12 coal seam(lower coal seam)is in the stress reduction zone,and the stress level in front of the working face is less than the peak stress in front of the working face of No.9 coal seam with the same mining distance,and the density of weathered rock fissures in the coal seam increases in waves.Finally,the growth trend of the total number of fractures tends to be flat.Coal seam excavation will affect the stability of the fault,and the fault will have a great impact on the roof collapse in the process of coal seam excavation.(4)Combined with the UDEC numerical simulation method,the stress distribution and fracture evolution model of overlying strata in coal seam group crossing faults were established,and the stress redistribution and fracture development state of overlying strata under the influence of mining were quantitatively described.The simulation shows that with the change of mining time,the vertical stress of No.12 coal seam(lower coal seam)is affected by the mining of the upper coal seam and the fault,and the vertical stress is also redistributed.The stress distribution characteristics of the working face are significantly different between the mining of the lower coal seam and the mining of the upper coal seam.The mining influence range of No.12 coal seam(lower coal seam)is less than that of No.9 coal seam(upper coal seam),and the peak value of the abutment pressure and the peak stress increase coefficient in the process of propulsion are lower than those of the upper coal seam.When the working face is close to the fault,the stress concentration of the overlying shale is more obvious.At the same time,when the working face passes through the fault,the fractures develop rapidly,and there is an obvious aboriginal separation between the strata,and various strata have different degrees of fracture.