The Effect Of Top-coal Thickness On Coal Caving Method And Characteristics In Tongxin Mine

Tongxin coal mine no.3-5 coal seam is a very thick coal seam.The thickness of the coal seam is between 7.28-19.98 m within the scope of the mine field,and the thickness of the coal seam changes greatly.In order to study the reasonable coal caving method and top coal caving rule under different coal seam thickness conditions,the numerical model of the inclined direction of the working face is established by using cdem numerical simulation software,and the mechanical mining height 4 is simulated m.Under the condition of top coal thickness of 4 ～ 16 m,there are three ways of coal caving: single round sequence,single round interval and four levels of "large-mediumsmall-micro".The evolution process of coal gangue boundary and top coal caving rate are analyzed.The numerical model of advancing direction of working face is established,and the evolution process of top coal caving body advancing with working face is inverted.The loss of top coal under different caving steps is simulated.Three kinds of on-site coal caving are compared According to the engineering geological conditions of Tongxin coal mine,the applicability of three coal caving methods under4 ～ 16 m top coal thickness is discussed and put forward.The numerical simulation results show that the thickness of top coal is 4 ～ 16 m Under the premise,the top coal recovery rate of the above three ways of caving decreases with the increase of the average top coal thickness;For the single round caving of extra-thick coal seam,the caving of this frame can significantly interfere with the top coal distribution of the adjacent supports,and it is easy to see gangue in advance under the sequential caving,and the coal rock boundary line can not sink evenly,so the top coal recovery rate is lower than that of the interval caving;Under the condition that the top coal thickness is 4-12 m,the "large-medium-small-micro" four-stage primary caving method is more reasonable,and the recovery rate of top coal is between 86.4%and 91.0%;When the top coal thickness is greater than 12 m,the single round interval caving method is better.With the increase of caving step distance from 0.8m to 2.4m,the dispersion degree of caving amount increases significantly,the coal rock interface is complex,some of the top coal is not released and left in the goaf,the recovery rate of top coal shows a decreasing trend;by comparing the recovery rate of coal and other indicators,it is found that it is better to adopt 0.8m caving step distance under the condition of 12 m top coal thickness in Tongxin coal mine.The field measurement shows that under the condition of top coal thickness of 9.86-11.96 m,the coal recovery rate of the working face with "large-medium-small-micro" four-stage coal caving method is 85.31%,11.1% and 8.7% higher than that of single round sequence and single round interval respectively.