Study On Overlying Rock Structure And Stress Evolution Characteristics Of Mining Near Fault Under The Influence Of Coal-seam Inclination

Faults are a common geological structure in mining of coal mines.The existence of faults interrupts the continuous existence of the whole stratum and changes the stress distribution of the original rock in the vicinity.When excavation work is carried out near the fault,it may induce fault impact ground pressure.Up to now,many scholars have done a lot of research work on faults,but few have studied them in conjunction with inclined coal seams.Through theoretical analysis,similar material simulation experiments,and FLAC3D numerical simulation,this paper systematically analyzes the evolution of overburden structure and mining stress during the mining of inclined coal seams under the condition of fault structure,and the research results are verified by engineering examples.The main research results obtained in the end are as follows:(1)By establishing the stress model of the internal unit of the fault and the model of the fault-surrounding rock system,it is concluded that there are many and complicated factors affecting the activation instability of the fault.The danger of fault activation is directly proportional to the burial depth of the working face and the stress concentration factor of the stope,and inversely proportional to the lateral pressure coefficient and cohesion.The influence of the tilt angle of the fault on the activation of the fault is more complicated;Increasing shear stress in the fault or decreasing normal stress due to mining influence may cause fault slippage.By establishing a mechanical model of the inclined rock beam along the coal seam,it can be seen that the tangential force is a factor affecting the roof failure of the inclined long-wall face.(2)Similar material simulation experiments show that as the distance between the working face and the fault is getting shorter,the overlying strata and fault activity show a sharper and shorter advance step.And compared with the experiment under the condition of horizontal coal seam,in terms of the advancement step of the working face,compared with the experiment in this experiment,the fault and overburden strenuous activity occurred earlier in this experiment.It shows that the increase of coal seam dip angle does have an impact on the risk of impact,making it occur in advance.(3)It is found through numerical simulation experiments that the change of the coal seam inclination angle has an influence on the advance bearing stress of the working face.When the working face is close to the fault,when the leading bearing pressure begins to be affected by the fault and the maximum peak value of the leading bearing pressure occurs,the distance between the working face and the fault is proportional to the inclination of the coal seam;There is an inverse relationship between the rate at which the peak advance bearing stress decreases and the inclination of the coal seam.(4)The work faces the fault,and the upper fault area far from the coal seam is the first to be affected by shear.With the continuous advancement of the work face,the shear stress in the fault is directly proportional to the advancement distance of the work face and the inclination of the coal seam;At the near end of the fault from the coal seam,the magnitude of the normal stress is directly proportional to the advancement distance of the working face and the inclimation of the coal seam,while at the far end of the fault from the coal seam,the intermal normal stress is inversely proportional to the above two due to the influence of the lower disc rotation and subsidence.(5)Through the analysis and analysis of the microseismic data during the mining of two coal mining faces,it was found that as the coal seam inclination angle increased,the distance between the interruption layer and the mining face began to affect,and the distance between the two was Increased,preliminary verification of the research results of this article.