Study On Prediction Of Rock Burst Risk In Coal Seam Mining In Magmatic Rock Intrusion Area

There are various causes of rock burst accidents in China.Some mine rock burst accidents occur near the magmatic rock intrusion area,but the current research on this kind of rock burst mostly focuses on taking the magmatic rock intrusion as the direct or basic roof of working face,and analyzing its breaking law and its influence on mining stress.However,there are few researches on the impact risk and control effect of magmatic intrusion area located in different strata on working face mining.In this paper,the distribution law of stress,displacement,energy and other parameters is studied when the igneous rock intrusion area is located in floor,coal seam and roof by theoretical analysis,similarity simulation experiment and Flac^3dnumerical simulation.The change of physical and mechanical properties of coal rock mass near the igneous rock intrusive area is analyzed,the physical model of coal body and igneous rock intrusive area is established,and the stress distribution of igneous rock in the igneous rock intrusive area is analyzed.It is found that the phenomenon of stress concentration occurs in the intrusive area and adjacent coal seam.Combined with the similar simulation experiment,the characteristics of overlying strata caving,stress concentration degree and displacement change of coal seam mining activities when the magmatic intrusive body is located in the roof are analyzed.Combined with numerical simulation,the stress and energy distribution characteristics of magmatic intrusion areas located in different strata are studied.According to the actual situation of No.3 coal seam in a mine in Shandong province,combined with the results of similar simulation and numerical simulation,the coal seam impact danger zone is divided.The results show that the phenomenon of stress concentration and energy accumulation occurs near the area of igneous rock intrusion,and as the igneous rock intrusion area gradually develops from floor to coal seam and roof,the scope of igneous rock intrusion into coal seam gradually increases,and the degree of stress concentration and energy accumulation of coal seam in the intrusion area increases,which increases the coal seam impact risk and thus increases the probability of coal seam rock burst.The similarity simulation experiment and numerical simulation analysis show that the stress concentration degree of coal seam gradually increases from 1.83 when there is no intrusion to 1.97,2.26 and 2.35 when the igneous rock intrusion area is located in floor,coal seam and roof.The degree of energy accumulation increased to 4.9 times,5.7 times and 8.1 times of that in the case that the igneous rock intrusion area was located in floor,coal seam and roof.Based on the analysis of similar simulation experiment and numerical simulation results,based on the probability index evaluation method of the impact of the macro 3coal seam in a mine in shandong province are analyzed,and the detailed division of the four level impact danger zone,think 15 m for strong shock after the magmatic intrusive devices for hazardous area,15 m-after the magmatic intrusive devices for 45 m for medium impact danger zone,Within 45 m to 60 m of the front and back of the magmatic intrusion is a weak impact danger zone,while beyond 60 m of the front and back of the magmatic intrusion is no impact danger zone.Based on the analysis of the mechanical model,simulation experiment and numerical simulation results,it can be seen that the stress concentration is the highest at the junction between the igneous rock intrusion area and the coal stratum.During coal seam mining,the concentrated stress in the magmatic intrusive area is superimposed with the advanced supporting stress in the working face,the stress concentration in the intrusive area increases significantly,and the rock burst risk of coal seam increases.The research results in this paper can better guide the safety production of No.3 coal seam in a mine in Shandong province,and also provide a certain technical basis for improving the safety and efficiency of similar mine working face mining.This paper has 42 figures,13 tables and 73 references.