| Rock burst was a kind of nonlinear dynamic response of coal and rock,which was one of the most serious mine dynamic disasters in deep coal mines.When fully mechanized caving working face was mined through fault,the possibility of rock burst induced by fault activation under the influence of mining was higher,therefore,it was of great significance to explore the impact risk degree and corresponding prevention measures in different areas of deep working face over-fault mining.In this paper,the actual situation of 14310 working face of Dongtan Coal Mine was taken as the engineering background,the impact risk and prevention measures in different areas of working face through fault mining was analyzed and discussed by means of theoretical analysis,numerical simulation and engineering practice.Firstly,according to the field measurement and experience analogy,the law of mine pressure appearance in this working face was deduced.The geological factors affecting rock burst,such as coal rock burst liability,original rock stress,hard roof and fault,were analyzed theoretically,it was identified that the 3 coal seam of this working face has strong impact risk,and the roof and floor have weak impact risk;the analysis shows that fault activation,fault coal pillar and fault dislocation were the main factors inducing rock burst.Then,numerical simulation was used to analyze the mining factors affecting the rockburst,such as the advance supporting stress of working face,the displacement of surrounding rock of working face,the plastic zone of working face,the slip trend of fault,the slip amount of fault and the variation rule of fault stress,the results show as follows:(1)the fault cutting is obvious,the maximum advance bearing stress is 50.8MPa,the maximum displacement is 0.21 m,maximum failure height of plastic area is 45 m,state on both sides of the fault is discontinuous,and the fault boundary is very obvious,influence range of the fault is 20 m on the advance working face;(2)The mechanism of fault slip is the sudden decrease of normal stress and shear stress,but the decrease of normal stress is greater than that of shear stress,according to the variation of fault normal stress and shear stress during the working face through the fault,fault slip mainly occurs in the high roof area of fault with reduced normal stress,and the maximum slip is 0.18 m.Finally,the comprehensive index method and multi-factor coupling method are used to classify the impact risk area and risk degree of working face,2 medium rock burst danger areas and 3 weak rock burst danger areas are divided in the tunneling stage,2 strong rock burst danger areas,2 medium rock burst danger areas and 1 weak rock burst danger areas are divided in the mining stage.For the above impact danger area,a comprehensive prevention and control scheme using microseismic area monitoring system and two active pre-pressure relief measures,large diameter drilling and hydraulic fracturing,has been developed,the pressure relief effect is tested by the drill cuttings method,It is concluded that the pressure relief measures of large diameter drilling and hydraulic fracturing are effective.The research on the risk and prevention of rock burst in deep working face through fault mining has certain guiding significance for 14310 working face through fault mining,At the same time,it also lays a certain technical foundation for safe mining of the working face with similar geological conditions to 14310 working face. |
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