Study On Coal-Gangue Flow Law And Caving Control In Horizontal Section Fully Mechanized Top-Coal Caving Mining Of Steeply Inclined Coal Seam

The low top-coal recovery rate is one of the major problems faced by fully mechanized top-coal caving mining in steeply inclined coal seam.This paper takes the 45#coal seam+575 horizontal working face in the north mining area of Wudong coal mine as the engineering background,and adopts the methods of field investigation,theoretical analysis and laboratory experiments to carry out the research on the flow law and the caving control technology of coal-gangue in the horizontal section fully mechanized top-coal caving mining of steeply inclined ultra-thick coal seam.Considering the geological occurrence and mining technical conditions of coal seam,the reasonable sectional height is obtained through theoretical analysis.The development and evolution law and standard equation of the drawing body,loose body and coal-gangue boundary in the initial and periodic coal caving stages are derived,and the relationship between loose body and drawing body is obtained.According to the derived standard equation,the calculation formula of roof and floor triangular coal loss,as well as the calculation formula of top-coal recovery rate and gangue mixed ratio are obtained.The similar simulation experiment method was used to study the different caving methods and process parameters of steeply inclined large section high fully mechanized top-coal caving mining,and the accuracy of theoretical analysis was verified.At the same time,the movement law of the loose top-coal was obtained,that is,the motion trajectory is approximate to a straight line,the closer to the drawing opening position and the central axis position,the faster the particle flow rate.Taking the top-coal recovery rate,gangue mixed ratio and the development degree of the drawing body as the measurement indexes,the optimal coal caving method and process parameters are obtained.Using the control principle of excessive coal caving,the top-coal caving control index is obtained when the gangue mixed ratio reaches a certain range.PFC2D software is used to simulate the optimized coal caving method and caving control index,verify the accuracy of theoretical analysis and similar simulation,and obtain the evolution process of coal-gangue boundary under different gangue mixed ratio.The displacement distribution of top coal presents an approximate elliptical ring,and the displacement in the ring is equal.The thicker the top coal is,the less the influence of the support on the top coal caving is.The prediction models of top-coal caving capability based on BP and GA-BP neural network are established respectively.GA-BP neural network is better than BP neural network in convergence speed and prediction accuracy.At the same time,through the comparison,it is concluded that the top-coal caving capability is better and the recovery rate is obviously improved by using the optimized coal caving method and caving control index.This study provides a reference for safe and efficient mining of large section high fully mechanized top-coal caving working face in steeply inclined coal seam.