Study On The Prevention And Control Of Rock Burst In The Isolated Island Working Face Under The Irregular Pillar

There are a lot of researches on the working face under the coal pillar and the isolated working face.Stress concentration will occur under the coal pillar,which is easy to cause impact hazard accidents.Generally,the working face will not be set under the coal pillar;the impact hazard coefficient of isolated island working face is relatively high due to the gob on both sides.There are few isolated working faces under the coal pillars,and no one has studied the superposition of the two.Moreover,when the coal pillars are irregular,how the stress under them changes and how the impact risk changes when the coal pillars are mined to different positions.Therefore,based on the research background of the 29 isolated coal face in Nantun coal mine,through theoretical analysis,numerical simulation,field practice and other research methods,this paper analyzes the risk of Rockburst of 29 isolated coal face under irregular pillar in advance,and analyzes the stress distribution of the isolated coal face under irregular pillar in different mining positions.The main conclusions are as follows:(1)The stress concentration coefficient under the coal pillar is large.If the upper coal seam is not mined,the normal stress of the island working face is about 15 MPa,which is greater than 10 MPa of the original rock stress.After the upper coal seam is mined,the normal stress value of the protection layer is small,only 0.6MPa,but the stress in the area under the coal pillar can be more than 50 MPa.(2)When the isolated coal face is mined,from 75 m away from the coal pillar,the leading stress of the isolated coal face and the concentrated stress under the coal pillar will influence each other,which will gradually increase the leading stress;at 30 m away from the coal pillar,the stress curve will start to coincide;after entering the coal pillar,the peak stress will increase,which is obtained from the simulation from the minimum 60 MPa to the maximum 120MPa;after leaving the coal pillar,the leading stress will increase The stress slowly returned to normal.(3)According to the simulation,because of the irregularity of coal pillar,when the working face is not mined under the coal pillar,the stress peak value under the coal pillar along the side of the roadway is smaller than the stress peak value under the coal pillar across the working face due to the large width of the coal pillar near the solid coal body;but when the working face is mined under the coal pillar,the stress peak value ratio under the coal pillar across the working face The stress peak value of coal pillar is larger.(4)The microseismic data collected from the field shows that the microseismic frequency under the coal pillar is relatively high,the energy is relatively large,and the impact risk is large,so it is necessary to carry out the blasting and pressure relief treatment for the 3 upper coal pillar;the microseismic frequency and size of the roadways near the goaf are also larger than other locations,which is basically consistent with the results of the previous theoretical analysis and numerical simulation.The whole risk of the isolated island working face under the coal pillar is relatively large.The research of this paper can provide some reference value for the excavation and mining of the similar working face under 73 and 29 in the future.There are 60 figures,12 tables and 79 references in this paper.