Research On Group Caving Technology In Fully Mechanized Caving Mining In Extra Thick Coal Seam Of Tashan Coal Mine

This paper aims at the problems of uncoordinated mining,easy to form arch above tailbeam,low caving rate,low caving efficiency and serious coal loss in the process of mining 20 m thick coal seam(3-5#)in Tashan Coal Mine of Datong mining area.According to the influence of intelligent mining on caving mining under the new situation,it makes it possible to automatically and intelligently control the tail beam of coal caving support.at the same time,it also provides a new opportunity for the innovation of coal caving technology.Therefore,this paper proposes a "group coal caving" method,that is,alone the direction of the working face,n(n?2)adjacent coal caving supports are regarded as a group,and under the coordinated action of each support in the group,the tail beam of support was opened in order and the tail beam was swung at a certain angular velocity,so that the interface between coal and gangue was slowly settled during the caving process,so as to improve the caving rate,caving efficiency and reduce the gangue rate.Focusing on the "group coal caving" method,this paper analyzes the feasibility of the group coal caving method applied in Tashan coal mine based on the analysis of geological and mining technology measured data and the combination of theoretical analysis and numerical calculation.this paper studies the effect of different coal caving methods,the combination number of caving support,top coal migration and coal gangue interface characteristics on top coal caving rate and caving efficiency under group coal caving method,and analyzes the results of coal caving under the condition of single coal caving and group coal caving.According to the actual production situation of Tashan Coal Mine,an industrial test was carried out in 8222 working face,and the reasonable group coal caving method suitable for Tashan coal mine has been determined.The test results are basically consistent with the theoretical analysis and numerical simulation results,at the same time,it also provides theoretical and technical support for the mining of extra thick-coal seam under similar geological conditions and the same coal group.The main research results are:1)This paper analyzes the feasibility of group caving method applied in Tashan Coal Mine,and in view of several factors affecting the caving ability of top coal,the influence of the development degree of top coal joints and fissures on top coal caving is analyzed quantitatively by using the fractal dimension of joint fissures distribution,it is concluded that the group drawing method is suitable for top coal caving operation in Tashan Coal Mine.2)According to the basic hypothesis of loose medium particle flow and the movement formula of coal-gangue particles,the mathematical model of top coal caving in group caving mode was established,and the mathematical expression of top coal caving body was obtained,revealed the development process of caving body in caving mining group,and deduced the equation of caving body by spatial coordinate relationship and fitting method under the condition of different combinations of support number.In the process of coal caving,the coal and gangue particles move along the least resistance path to the coal caving port with an approximate straight linear,and the interface of coal and gangue is an inverted normal distribution curve.3)The size of the coal caving port is small in the single-support caving mode.In the process of coal caving,it is easy to form a “coal caving arch” over the top of support which restricts the the top coal caving,and the top coal caving rate of the single-frame is less than 77%;and the coal discharging efficiency is extremely low;the thicker the top coal is,the more affected by the "coal caving arch",and the more coal left in the goaf with irregular block distribution.4)Multi frame simultaneous coal caving increases the size of coal caving opening,the lossening range of top coal is enlarged,and the mutual extrusion force between coal gangue particles is reduced,and the caving speed is accelerated.Therefore,it is difficult to form a stable "caving arch" structure;the more the number of coal drawing racks and the thicker the top coal,the longer the trace line of the coal-gangue interface,the larger the range of interaction influence between coal and gangue,the phenomenon of "local depression" is easy to occur,and the coal residue in the goaf increases;the top coal caving rate is in the range of 72.8%?83.4%,half of which can reach more than 80%,and the caving efficiency is increased by 2?9 times.5)The same amount of differential coal drawing makes the coal drawing mouth opening in an orderly and staggered manner,and the top coal to be caved is loosened in advance in the process of coal discharge,and the structure of "coal drawing arch" will not appear;the smaller the equivalent differential drawing "quantity" value is,the smoother the coal gangue interface is,the uniform settlement of the top coal to be caved,the smaller the thickness of coal and gangue interlayer,the least amount of coal left in the goaf,and the best coal drawing effect;the top coal caving rate is in the range of 77.6%?96.2%,60% of which can reach more than 90%,and the caving efficiency is increased by 2?7 times.6)Aiming at the actual mining of 20 m extra-thick coal seam in Tashan Coal Mine,two and three coal mining methods were used to carry out industrial tests in 8222 working face,which greatly improves the top coal caving quantity,top coal caving rate and efficiency;and it not only overcomes the production problems of the mine,but also provides group coal caving theoretical and technical support for fully mechanized top coal caving mines with the same geological conditions,and lays a foundation for the realization of intelligent top coal caving mining.