Method of synergetic multi-windows caving in longwall top coal caving working face

In terms of the problems of low top coal recovery rate,high gangue mixing rate and low top coal caving effi- ciency in longwall top coal caving working face,the method of synergetic multi-windows caving was put forward in this paper. Based on the definition of synergetic multi-windows caving method,by means of theoretical analysis and numeri- cal simulation,the top coal caving method and the characteristics of coal rock mass interface at three stages top coal caving including initial stage top coal caving,intermediate stage top coal caving and end stage top coal caving were studied under the conditions of synergetic multi-windows top coal caving. The initial stage top coal caving method of “open window at the same time and close window in reverse” was proposed. According to the influence range of coal caving at the coal caving point,the velocity and movement equation of top coal particle during the caving process of top coal,an algorithm model for the initial stage top coal caving method was established,and the calculation method of the time intervals among caving windows in the initial stage caving process was deduced theoretically,which provides a method for the application of the initial stage top coal caving method. By analyzing the characteristics of fully mechanized caving face,it was concluded that roof stability,gas concentration,the transport capacity of rear scraper convey- or,dust concentration and coordination of mining and caving in longwall top coal caving working face are the main fac- tors affecting and limiting the number of caving windows which are opened at the same time with synergetic multi-win- dows caving method. Taking the coal seam conditions of the 8202 longwall top coal caving working face in Tongxin Coal Mine as an example,a numerical simulation model along the advance direction of the working face was set up to simulate and compare the top coal caving laws,top coal recovery rate and the top coal caving efficiency of the different top coal caving methods. It was concluded that under the condition of multi-windows top coal caving method,the coal- gangue interface is relatively smooth in the process of top coal caving,and the top coal recovery rate increases with the increase of the number of caving windows at the same time,and the efficiency of the multi-windows top coal caving method is 4-8 times as much as the single-window,and the top coal recovery rate of the multi-windows caving method is 5% higher than that of the single-window.