Research On The Distribution Characteristics Of Mining Stress And Fault Mechanical Response Law Of Coal Seams With Fault

The geological conditions of coal mines in China are changeable and complex,especially in the areas affected by faults,and coal mine accidents and disasters occur frequently.The existence of faults will destroy the continuity of coal and rock mass,so that the surrounding energy field,stress field and displacement field are greatly different,and the risk of coal seam dynamic disaster increases.Therefore,this paper takes a mine in Guizhou as the research background,and uses theoretical analysis,similar simulation test and numerical simulation analysis to study the mining stress distribution characteristics and fault dynamic response law of fault-bearing coal seam group.The research results can a certain theoretical reference for coal seam mining in fault areas.(1)Based on the mechanical analysis model of the working face advancing along the fault,the mechanical mechanism of the working face mining along the upper and lower plates is summarized and studied.It is concluded that compared with the upper plate mining method,the overlying rock activity near the footwall mining fault is more intense,and dynamic disasters are more likely to occur in mining activities.Using a similar simulation test,it is found that after the footwall working face passes through the fault,it is cut by the fault,and the overlying rock collapse damage is more serious.(2)Through similar simulation experiments,it is found that the roof subsidence and overburden fracture development of the working face are discontinuously blocked by faults,and the stress change of the fault plane has obvious temporal and spatial characteristics.The high fault is first affected by mining,and the fault zone is subjected to tension and releases stress.During the excavation of No.12 coal seam,due to the influence of repeated mining,the relative sliding of the upper and lower plates of the fault occurred,the stability of the fault area was damaged,and the tensile failure of the fault occurred in advance.(3)Through numerical simulation,it is concluded that the distribution of mining stress is singular under the influence of fault.When the upper coal seam is mined,the stress distribution on both sides of the fault is obviously different,forming two pressure relief areas of’one high and one low’.The displacement expansion range of the roof and floor of the goaf is obviously blocked by the fault,and the floor near the fault has a large floor heave phenomenon along the fault plane.Under the influence of mining,shear dislocation occurred along the fault plane,and the fault zone slipped.After the excavation is completed,the stress concentration at the front end of No.12coal seam and the stress concentration at the front end of the upper coal seam are mutually disturbed and superimposed,and significant stress concentration occurs.(4)The analysis of the stress distribution characteristics of the upper and lower walls of the fault shows that the fault has a significant influence on the distribution law of the stope stress,and the vertical stress in the fault area is much lower than the original rock stress.During the mining of the hanging wall of the normal fault,the advanced support stress shows a trend of increasing first and then decreasing,while the mining of the footwall of the reverse fault shows a gradual increasing trend.When the footwall mining of reverse fault is close to the fault,the peak value of stress concentration is larger,the risk of floor heave in the roadway in front of the working face increases,and the risk of mining through the fault in the footwall of reverse fault is higher.(5)Using FLAC3 D software,it is found that the size effect of coal pillar has a significant effect on the stability and failure of fault plane.The smaller the width of remaining coal pillar,the greater the possibility of instability and failure of fault plane.When thrusting to the fault,the shear failure of the high fault occurs first,and the possibility of activation and shear failure of the low fault are higher.Before and after the footwall working face passes through the reverse fault,the relative slip between the upper and lower plates of the fault increases significantly,the possibility of fault activation increases significantly,and the risk of mining in the footwall of the reverse fault is also greater.