Risk Assessment Of Rock Burst In Steeply Inclined Coal Seam

With the deepening of the mining depth,the quantity and the frequency of accidents in the impact pressure are increasing.Comparing with that on impact ground pressure of steep coal seam,there are fewer researches about risk assessment on upright and sharply inclined super thick coal seams.It's very important for production in safety,and also a prerequisite for preventing mining accidents to do some research about risk assessment on upright and sharply inclined super thick coal seams.In order to evaluate the rock burst risk of steep and extra thick coal seam in Urumqi mining area,this paper redivides the factors by comprehensive index method on the basis of previous research,so that it can be applied to the steep inclined coal seam,Meanwhile,it also aims to confirm the weight of each factor by adopting analytic hierarchy process.The main conclusions are as follows:(1)The soft coal seam clamping in hard roof and floor of coal seam is more likely to store large amounts of elasticity under the action of horizontal tectonic stress and gravity stress through analysis of the physical and mechanical properties of steeply-inclined coal and rock and the structural features of steeply-inclined coal seam;(2)The root causes of shallow source rock burst in Urumqi mining area are the peripheral thrust faults and folds in the geological conditions around the mining area.(3)According to the geological features of the rock burstin Urumqi mining area,the coefficient of stress difference is introduced to adjust the mining depth.And the theory of radius of power system scale is introduced to adjust the distance from hard rock stratum to the coal seam.What's more,when it comes to adjusting the hard rock strata thickness,three indicators of geological factors in the comprehensive index evaluation method will be amended according to the positions of micro-seismic events in recent years.According to the geological features of the rock burst in Urumqi mining area,the coefficient of stress difference is introduced to adjust the mining depth.And the theory of radius of power system scale is introduced to adjust the distance from hard rock stratum to the coal seam.What's more,when it comes to adjusting the hard rock strata thickness,three indicators of geological factors in the comprehensive index evaluation method will be amended according to the positions of micro-seismic events in recent years.under the support of the procedure of sub-level caving mining of steep coal seam,four indicators of geological factors in the comprehensive index evaluation method will be amended by introducing the number “n” in horizontal tectonic stress,the relational value between the adjoining mining area and working face of steep extra-thick coal seam,the width” Lm”of working face,and the distance “d” between adjoining mining area.At the same time,the irrelevant indicators will be removed so as toset up a new risk assessment model to impact rock pressure in steeply-inclined and extremely-thick coal seams;(4)The corresponding micro-seismic monitoring data proves that this new risk assessment method is not only accurate and reasonable but also applicable to the impact of the Urumqi mining area in risk assessment.And it also provides reference for the risk assessment of mine with the similar geological type on impact ground pressure.