Study On Top-coal Caving Property Of Extremely Thick Coal Seam With Dirt Bands In Laosangou Coal Mine

There are lots of extremely thick coal seam whose thickness is more than 8m with many dirt bands in Shanxi,Inner Mongolia,Shaanxi province and other places.When using fully mechanized caving mining,there are many phenomena,such as bad topcoal caving property,low production rate,small caving angle of top coal,rib spalling and so on because of influence of dirt bands.The exploitation of No.6 coal seam in Laosangou coal mine is the extremely thick coal seam whose average thickness of coal seam is about 20 m with lots of dirt bands.Due to the complex conditions of coal seam,in the use of fully mechanized caving mining,there is a need for top-coal caving property analysis and research.The No.6 coal seam of Laosangou coal mine as engineering background,using research methods of field investigation,experimental research,theoretical analysis,physical simulation and numerical simulation together analysed the top-coal caving property of the first mining area of Laosnagou mining area in extremely thick coal seam.The main contents are as follows:(1)Based on the geological conditions of Laosangou coal mine,using experimental test,the coal seam occurrence conditions and mechanical parameters of the coal and rock were mastered,and No.6 generalized model were gotten.(2)Based on the analysis of the crushing mechanism of top coal with dirt bands and the factors that dirt bands influence the top-coal caving property,with the process of work face,the top coal in the original rock stress area can be divided into four areas according to the stress state and the supporting pressure of top coal,fracture stress of top coal and dirt bands,the maximum thickness in the middle coal seam and the the fracture coefficient of the top coal and the dirt band are calculated.(3)On the basis of different generalizability models,using physical simulations and numerical simulations,combining with the theoretical calculation results,the topcoal caving property in the corresponding regions of different generalized models under different mining height are obtained and Reasonable ratio of mining to caving in the corresponding area;the overall top-coal caving property and the characteristics and regularities that top-coal caving property influenced by thickness of coal seam,quantity of dirt bands and the position of the dirt bands are obtained.the results of top-coal caving property in extremely thick coal seam can be used by Laosangou coal mining and other similar coal mining with full-mechanized caving mining.