Research On Roof Structure And Support Load Of Fully Mechanized Caving Mining In Steep Coal Seams Group

China's western mining area generally have steep coal seam,which angle between 35° to 55°.In contrast to near or slowly inclined coal seam,the steep coal seam working face can form hinged structures along the direction and inclination.The propensity structure and the strike structure of the roof have a significant effect on the support load,which belongs to the space structure problem.In view of the determination of the support load of the steep coal seam working face,it is generally accepted that the support will bear the partial load of the roof in addition to the top coal and the direct top load,but how to calculate the roof load is a difficult problem.The practice shows that after the direct top collapses of steep coal seam and rock blocks down along the working face,the lower roof is unevenly filled,resulting in the roof structure and the support load has a partition feature.And the research on roof structure and support load of fully-mechanized caving in steep coal seams group is less.In this paper,based on Wangjiashan coal mine engineering geological and mining technology.The relationship between the roof structure and the load of the fully mechanized caving mining in steep coal seams group is studied by using field measurement,physical simulation,numerical simulation and theoretical analysis and other means.On the basis of physical simulation,the mechanics model of the roof structure along the tendency and direction is established,and the 3DUC numerical simulation confirms the conclusion of the physical simulation.The calculation formula of the load in the middle of upper and lower coal seam face in the fully mechanized caving face of the steeply inclined coal seams group is obtained by theoretical analysis.The rated work resistance criterion of both the anti-skid and the anti-zone top pressure is given,and the reliability of the conclusion is verified by practice.The results show:After the upper coal seam mining,the key rock mass of the roof is formed along the inclined structure,which is affected by the roof hinge structure and the dip angle of the coal seam.The height of the roof collapse is reduced and the maximum load of the working face bracket is the middle pressure.After the lower coal seam mining,the interval layer as a whole occurred in the deflection sinking,but the key layer structure is still stable.Support work resistance to meet the premise of preventing the support side of the slide,the main commitment to the top coal,the separation layer and the roof of the collapse of the roof load.Define the load perpendicular to the top of the support as "top pressure",the load between the support along the tendency is "lateral pressure".There are partitioning characteristics of the top pressure and lateral pressures of the face.The upper support load is not large,stint prone to instability;Central support to resist the maximum top pressure,the rated working resistance needs to be greater than the top pressure,At the same time the initial support force to meet the conditions of self-stabilization;The filling of the lower zone is the best,the roof structure is stable and the support load is not large.Therefore,the working resistance of the lower coal seam is determined by the condition of balancing the pressure in the middle area.