Suitable retention and recovery technology of floor coal at ends of fully mechanized face with great

Mining Science and Technology(China)21(2011)281-285Contents lists available at ScienceDirectMining Science and Technology( China)ELSEVIERjournalhomepagewww.elseviercom/locate/mstcSuitable retention and recovery technology of floor coal at ends of fullymechanized face with great mining heightsa bYuan Yong. Bai QingshengSchool of Mines, China University of Mining G Technology. Xuzhou 221116, ChinaXishan Coal Electricity Group Co Ltd. Taiyuan 030053, ChinaARTICLE IN OA BSTRACTateways at faces of great mining heights are mostly driven along the roof of coal seams. Forleaving a triangular floor coal at the face ends22 october 20a loss of coal. In order to improve coal recovery rates and to ensure efficiency of equipmeAccepted 28 November 2010mining faces, we investigated suitable retention methods and recovery technology of floorends. The upper floor coal can directly be recovered by a shearer with floor dinting. The lowerrecovered by shearer with floor dinting after advanced floor dinting and retaining a step forcoal sides in a haulage gateway. field practice shows that this method can improve the coal recoveryoor coal at face endsrates at fully mechanized working faces with great mining heights.Copyright o 2011, China University of Mining Technology. All rights reserved.Step for protecting coal sidefor keeping the machines working safely and efficiently and also forhe recovery of the floor coal.Compared to fully mechanized top coal caving, fully mechanizedmines with great mining heights have advantages of higher coaland management improves in China, fully mechanized mining face endf e retention methods and dimensions of floor coal atrecovery rates and smaller stone rates. As the level of equipment2. Suitabltechnology with great mining heights has become the main miningmethod for coal seams 3.5-6 m thick and mining heights increaseGateways of fully mechanized working faces with great miningyear by year 11-31. Because the coal seam is thicker than the height heights are driven along coal seam roofs: hence, the presence ofof the gateway at fully mechanized working faces with great floor coal at the ends of the working face seems inevitable. Theboth top coal and floor coal; ll Drive along the roof and retain floor the adaptability of supports to the slope of the floor (. l Hencecoal. To be of benefit for gateway construction and maintenancthe gateway layout is along the roof of the coal seam while face, causing the supports to be transferred from the ends of theretaining the floor coal. The three types of floor coal at the ends of working face to the mining height and keeping the scrapera working face are referred to as"C,"S"and compound (4]. The conveyor in a suitable state, are key conditions to excavate coalthickness of the floor coal under gateways and at the ends of thesafely and efficiently. When the floor coal is thick under theface increasesthickness of the coal seam, which causes gateway. the total amount of floor coal loss is high if a small angle ofloss of coal ahe stability of the machines at the face.especially thesupports, Decreasing the floor coal under supports may lose their stability and extrude seriously if a largegateways andof a suitable type of floor coal are beneficial angle of variation is used. The return airway is arranged at theCorresponding author. TeL: +86 15949048964.analy中国煤化工 e upper and lower facematter Copyright o 2011, China University of Mining TechCNMHGZ Nenghu et aL/ Mining Science and Technology( China)21(2011)281-285AFig. 1. Retention type of floor coal at the upper face end.The end of the upper face can be kept without a horizontal floor.The upper floor coal can be retained as a"c type for flat seamshs cos a sin(a s8)and an "s" type for coal seams with a larger dip angle,shown in Fig. 1.For the "C type floor coal, the following equations can bethe thickness of the floor coal under the outer edge of an"S"obtained from corresponding geometric relationsnd ns the number of supports in the face bending section;meters are similar to those of Eq (2). The dip angle of theb∑sin(i)= he cos ashould meet the condition: ns Bs /2+asy. the totalunder the supports in the bending section per unit strike length is then2he cos a sinSs=>bcos(iBs )hs cos a+BhgE arccos coh3 sin a cos a/2-B2tana/2where b is the supporting width of one support(m). B the A suitable height overlap between the scraper conveyor and theminimum angle between supports and floor in the face bending stage loader should be not less than 0.5 m at the lower end of a fullyection(o ).he the thickness of the floor coal under the outer edge of mechanized mining face [4, 6). The floor coal at the end of the lowerthe"C" type(m), ne the number of supports in the face bending face aids in reducing the dip angle and keeps the supports and scrapersection and a the coal seam pitch (.) The dip angle of the suppum conveyor, the floor coal at the end of the face is about 0.5 m higheradaptive dip angle of support( )than the floor of thhe haulage gateway. Two or three supports shouldWhen there are n supports in the bending section, the distance be kept horizontal for carrying the coal on the scraper conveyor.m the outer edge of i-th support to the floor is:The"C type floor coal could be retained at the lower end of theface as a coal seam with a large dip angle, as shown in Fig 2a. Thefollowing formula obtains the optimum number of supportsd时h如sprm-1ma(—2-2mas2of the first support to the floor in the bending section)The meanings of the parameters are similar to those of Eqs:-byan+h,)+助-The area of the floor coal under the supports is the sum of theof the floor coal of the bending section and that of the horizontalsection. For calculation of the total area, we refer to Eq. (4).sin a cos a/2-B tan a/2(4)The floor coal could be retained as an"s" or compound type fora nearly flat seam and thick floor coal. the size of the floor coal of an%a For an"S" type of floor coal, the following formula could be "stype is shown in Fig. 2b. The calculation of the number ofsupports is similar to that of Eq.(5). The inner floor coal ofb中国煤化工CNMHGFig. 2 Retention type of floor coal at the lower face end.Z Nenghu et aL/ Mining Science and Technology(China)21 (2011) 281-285a compound type is a"C type and an"S" type near the upper faceend. The number of supports in the bending section is the sum ofthe number in the C"and "s" sections the floor coal should beretained as a"C"or compound type for a coal seam with a dip angleof about 8, by a comprehensive and comparative analysis."C is the most simple type where the size of the floor coal cabe easily controlled. Both the"S" and compound types are relativelycomplex, where the size of the floor coal can be barely controlledThe area of the floor coal of the upper and lower face ends is thesum of the coal areas under supports and the gateways.The gap between the supports is t, and the maximum lateraldisplacement of the side guard plate is tz. t, is sealed by the sideguard plate through the jack or the spring when the floor is levelWhen the bottom surface is concave the top beams should be closeto each other, but the range of the lateral movement of the top beamsshould not exceed t. when the bottom surface is convex, the sideguard plate should ensure that waste rock is not escaping betweenthe supports. Hence, the supports should be adapted to the concaveFig 4 Floor dinting parameters in haulage gatewayand convex floor, and the variation angles (o, d )should satisfy [4:o< tan1∮stan-12-t(8) and loader, the advanced floor dinting can be used in thewhere the determination of the floor dinting height andSimultaneously, p should be less than 0, ie, the vertical rotating the major requirement. The haulage gateway after floorangle of the scraper conveyor line pans, so that B1≥0.7,m/cosa-h