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翻译部分英文原文Determination of the most effective longwall equipment combination in longwall top coal caving (LTCC) method by simulation modelingFerhan Simsir*, Muharrem Kemal OzfiratMining Engineering Department, Dokuz Eylul University, 35160 Buca, Izmir, TurkeyReceived 12 January 2007; received in revised form 2 November 2007; accepted 21 November 2007Available online 4 March 20081. IntroductionIn order to recover limited resources in underground efficiently, the most suitable production equipment and method must be applied to a colliery. Trying all alternatives and equipment combinations would be a very expensive challenge. Computer simulation, on the other hand, is a cost-effective tool for evaluating what-if scenarios in mine development and ore production. It is a useful tool for analysing complex systems such as factories, health care networks, logistics, and service-type operations. There are many different computer simulation types, such as discrete event, continuous, hybrid, and so forth. Discrete event simulations process discrete events that occur at random times through a central processing unit. In discrete event systems many events can occur simultaneously 1.Discrete event simulation languages, available since the 1960s, provide general facilities to model the operations involved in processing and manufacturing as discrete events occurring in time. The case under study, the fully mechanized longwall operation in Omerler, a colliery of the state-run Western Lignites Corporation, is suitable for discrete event simulation since movements of shearerloader and roof supports are occurring simultaneously.In Turkey, caving methods are mostly employed in mining of thick coal seams as long as the roof strata are suitable for their use. Longwall with caving is always preferred to stowing faces because of its simplicity, favourable economics, and high productivity. It is assumed that the upper bound of applying single-pass longwall (SPL) method as a mechanized system in thick coal seams is about 6m 2. If the thick coal seam cannot be mined by SPL, then multi slice longwall (MSL) can be employed. However, for thick seams, MSL is less convenient, less economic, and requires more labour compared to longwall top coal caving (LTCC) method. When choosing which method to employ, the features of the seam also need to be considered.The LTCC method offers a viable means of extracting up to 7580% of seams in the 59m thickness range. Suitable geomining conditions in Europe and many other countries have led to a wide range of applications of caving coal mining faces during underground working including sublevel caving of thick seams. The LTCC method is increasingly used in thick seam mining, for example, there are over 70 LTCC faces operating in China 3. In addition, in Australia, the LTCC method has successfully been used by several Chinese companies. The initial thickness, typically 3m, is cut and loaded conventionally with a shearer and front AFC. The remaining top thickness of coal, typically an additional 39 m, is allowed to cave into the rear AFC. By this way, coal recovery is increased to 85% from a 9m seam 4.In 1988, Senkal et al. found the coal loss to be 24.3% in the same underground mine. However, at that time, longwall equipment consisted of hydraulic props+steel roof bars as roof support, an AFC, and loosening blasting+pneumatic picks as winning method. The most important disadvantage of the LTCC method is that significant coal losses may appear when drawing the coal through the support window. Therefore, in this study, firstly the coal loss is figured out. After that, coal production sequence in the colliery is modelled dynamically by simulation. Real data collected from the system (i.e. the colliery itself) as well as the coal loss computed are used in the simulation model. The whole longwall operation is simulated using computer software, and daily production figures from face and the top are achieved.Here, the longwall, approx. 86m long, is set up on the floor part of the seam, and coal left on top is drawn through the roof support chute on the gob shield onto the front AFC. The thickness of the seam is variable due to layer formation, but it is 8.5m on average (Fig. 1). Of this 8.5, 3m is mined from the longwall, the rest 5.5m caves in. The longwall equipment used consists of a double-ranging shearer-loader (Eickhoff EDW-150-2L), an AFC (SGZ-730/264, Chinese manufacture) and 56 roof supports(CMEC ZYD 4000/18/32, Chinese manufacture) with chutes on the gob shield to draw the top coal. Fig. 2 gives the plan (a) and the cross-sectional views (b) of the longwall.In this study, equipment used in the longwall and effective on the whole panels operation have been changed in the simulation model one by one creating 320 distinct points to be executed. Sixty additional design points have been created by adding the cut numbers of the shearerloader to these two equipment, too. After executing these points in the model, best results for equipment combination and number of cuts of shearer-loader have been found out.2. SynopsisSimulation modelling turned out to be very suitable for this study since there is no chance to test alternative production methods during the ongoing work of the mine.It would be very costly to set up a pilot face to test alternatives, also. By the use of simulation, it is possible to test the effects of new methods and factors economically and quickly. Imitating the operations of real-life systems or processes is the main purpose of computer simulation.Operational scenarios can be tested and evaluated without the need or expense of physical experimentation. Applications have been developed to simulate the space and time relationships between mining equipment, mainly in connection with transport systems 68. Tsiflakos and Owen 9 discussed the philosophy, methodology, objectives,mining process logic, program structure and its stateof-the-art for a recently developed mine simulation model.By Connor et al. 10, a two-dimensional rigid block computer model was used to simulate discontinuities within the strata overlying a longwall coal mine. Hunt11 simulated the ore haulage in Henderson molybdenum mine. The purpose of the simulation was to demonstrate to mine management how simulation could be used to assist in optimizing ore transport using existing trains, trucks,and ore passes.Today, there exist specially designed high-level simulation programs. The most commonly used simulation languages are GPSS (General Purpose Simulation System),GPSS/H (event-driven version of GPSS) and ARENA.Also, Vagenas 12 and Sturgul 13,14 have applied discrete event simulation to both underground and openpit mining operations using GPSS and GPSS/H. SIMAN was used by Tan and Ramani to study belt networks. Kolonja 15 used SIMAN for studying the various dispatch criteria for open pit mines. Many of the mine simulations done using ARENA were proprietary in nature and did not appear in the literature.In addition to these studies, web-based simulation programs have also been made presenting a newly developed,user-friendly visual simulation computer tool which helps mine operators to plan the optimum mining sequence for different mine geometries and equipment layouts.Another study contributes to the body of knowledge by developing a robotization and stability control (RASC) model for operating dump trucks. Konyukh and Ramazanov 16 aimed in their study the optimal use of LHD vehicles working in underground by an operator at surface using the GPSS/H simulation language.When searching the studies carried out up to now, it can be seen that especially haulage equipment have been simulated at the underground mining methods room-and pillar and sublevel caving so far, and, longwall mining has not widely been subject to simulation.3. Calculation of coal loss In order to find out the coal loss, ash content of samples taken from face coal, top coal, and from the belt conveyor in the main gate to represent the whole panel, are analysed.To determine the real seam thickness and its properties,samples are taken from the face at 1015m intervals and every web. Also thickness of top coal is found by the help of samples taken from the beginning of top coal up to overlying roof strata (Fig. 3). To find out the ash content of top coal, and so to determine top coal recovery, samples are taken from belt conveyor in the main gate every 2 h. Samples taken from the face, top coal, and belt conveyor are separately brought together and mixed.These joined samples are quartered and 3040 kg of them is used to determine ash content and density. Totally six experiments are performed on samples and the outcomes are averaged to give the final result. In addition, samples taken from overlying roof strata are put into drying oven to find the ignition loss. Except tail and main gates, the length of longwall is 86 m. Since there is coal on top of both main and tail gates, the length of top coal including these ways is 93.2 m. It is assumed that coal from longwall face is mined with a recovery of 100%. Therefore, coal loss is caused during drawing of top coal only. To determine the coal loss, the weighted average of ash content of different materials is used. Five field experiments are carried out and the values are given in Table 1.4. Simulation study Simulation is setting up a model to represent a system.This model provides a chance to test operations that are infeasible to test on the real system. Simply, it can be defined as computer trials. Simulation has many applications in mining and mineral processing. In underground mining, its benefits include increased production,capital and operational cost savings, and improved prediction 17.Firstly, the flow chart of operations in the mine is figured out. Once the shearer-loader performs two cuts,AFC is pushed towards the face, and then, roof supportsstart moving forward. As the first roof support moves two webs forward, the top coal caves in and is drawn through the roof support chute. Then the second roof support starts moving, and this operation repeats until all roof supports are moved ahead, then the shearer-loader starts cutting a new web. The assumptions, parameters, variables, and attributes of the model are given in the following. In the real system, the shearer-loader moves continuously and hence feeds the AFC continuously. In this study, it is assumed that coal cut by shearer-loader is loaded onto the AFC once during one cut which takes place in the middle of the cut. The coal amount loaded onto the conveyor is equivalent to the coal produced by one cut of shearer-loader.The flow diagram is turned into a simulation model in ARENA 2.2. In the model, first of all, the motion is created(with the CREATE block) and the shearer-loader starts its first cut. Region I expresses the operations of shearerloader and the roof supports, in other words, coal production operations. During this cut, amount of coal produced is computed and assigned to a variable (AMOUNTCOAL1).When the shearer-loader finishes its first cut, it is released (RELEASE block) and it spends a certain time to set up its drum for a new cut. Then the program controls whether this was the first (CUTDIRECTION ? 1) or the second cut (CUTDIRECTION ? 2) of shearer-loader (BRANCH block). If it is the first cut, the motion goes back to the shearer-loader and makes the second cut. If it is already the second cut, the coal produced is sent out to belt conveyor. Region II expresses the movement through the chain conveyor, stage loader, crusher and belt conveyor,respectively.After the shearer-loader, the motion moves to roof supports and the first roof support moves forward. The chute is opened and top coal is drawn. At this point, the amount of coal drawn is assigned to a variable(TOPCOAL). Then, similar to face coal, top coal produced is sent out through conveyors. At this point, the program controls the number of roof supports (T) moved forward(BRANCH block). If 56 roof supports have finished their operation, then face-end and T-junction supports are moved. If not, the motion moves to the next roof support. After all roof supports are moved, the motion goes to the very beginning and the shearer-loader starts cutting again. The motion never stops since the mine works 24 h continuously. After creating the model,it is tested and compared with the current operating values. Average daily production value obtained by the model is 1046 tons and the real daily production of the mine is 922.93 tons. Since these results are close to each other, the model is verified. In addition, the model is tested with extreme values for parameters and its validity is proved.5. Creating the simulation modelWhile creating the frame of the experimental design, all equipment in the panel have been accepted as effective factors. As seen in Table 2, the shearer-loader has five different types including the existing one currently used, and the roof support has four different types including the existing one. For the remaining equipment (AFC, stage loader, crusher, belt conveyor), two different types have been investigated. All combinations of these values of longwall equipment give a total number of 5_4_2_2_2_2 ? 320 design points to be simulated.After first investigations it has been seen that different types of coal hauling equipment (AFC, stage loader, crusher, belt conveyor) are not effective on production figures. The reason for this is the low difference among the haulage durations and the capacities of these equipment, and that these values do not cause a bottleneck in coal production. In the second stage of the experimental design, the effects of shearer-loader and roof support types, including number of face cuts, have been investigated. In Table 3, it can be seen that the second stage comprises three distinct factors and 60 design points, which are simulated for a period of 30 days (Table 4). Tables 5 and 6 give the features of different roof support types used in the simulation, where shearer-loader features remain the same as in Table 2.6. Evaluation of computational resultsHaving determined the effective shearer-loaders and roof supports at design points, these are combined with number of cuts of shearer-loader. These design points have been computed for the three working rhythms (i.e. drawing the top coal after one, two or three shearer travels along the face) and results are obtained (Figs. 4 and 5). As can be seen in Fig.4, the design points delivering the biggest coal production figures are 6, 10, and 14 for the single-cut system, 26, 30 and 34 for the double-cut system, and, 46, 50 and 54 for the three-cut system, respectively. The equipment selected for these points and their features are given in Table 7 and in Table 3 in detail.The results indicate that the most efficient production system is the one in which top coal is drawn after two face cuts performed by shearer. In three cuts production system,top coal is left quite far from the roof support, and the overlying strata cave avoiding top coal to cave in through the roof support frame. On the other hand, in one cut production system, dilution of coal with dead rock increases and work organization within shifts becomes unstable.In all three types of production systems, RS1 turns out to be the roof support providing optimum production amounts. RS1 is similar to the current roof support but differs in terms of frame and support dimensions. Type of shearer-loader is not very decisive on the production amount, therefore, roof support is the primary factor effective on production efficiency of the LTCC method.7. Discussion and conclusionBy investigating the results it can be seen that equipment except the shearer-loader and the support units are not effective on the production amount, and the design points delivering the biggest coal production values are 26, 30 and 34. The shearer-loaders used at these points are SL1, SL2, SL3, whereas the best roof support unit has been RS1 in view of obtaining the highest value of top coal production.Drawing of top coal after two face cuts being currently applied in the colliery delivers bigger production values compared to other systems (drawing top coal after single or three face cuts). Therefore, also in case of alternative longwall equipment to be selected, this working rhythm should be kept in the mine. The coal production figures of this working style points to a high top coal recovery, which is a significant factor in applying this method efficiently.In the future research of this study, geomechanical properties of top coal and overlying strata should be included. So, whether the cavability properties and breaking distance of top coal and overlying strata are close to each other should be examined. In case the cavability values of top coal and overlying strata are close to each other, pressured-water injection can be applied to top coal in order to increase its cavability. By this way, loss of top coal can be decreased as well as decreasing dilution with dead rock. Also, the probability of roof support frame to be plugged by big coal blocks would be decreased.References1 Schriber T, Brunner DT. Inside discrete-event simulation software: how it works and why it matters. In: Proceedings of the winter simulation conference, Atlanta, 1997. p. 1422.2 Kose H, Tatar C. Underground mining methods. Izmir: DEU; 1997in Turkish.3 Hebblewhite B. Review of Chinese thick seam underground coalmining practice. Austral Coal Rev 2000;10:367.4 Kelly M, Balusu R, Hainsworth D. Status of longwall research in CSIRO. In: Proceedings of the 20th international conference on ground control in mining, Morgantown, 2001. p. 16.5 Destanoglu N, Taskin FB, Tastepe M, Ogretmen S. Omerler mechanized longwall application. Ankara: TKI; 2000 in Turkish.6 Topuz E, Nasuf E, Ramachandran D. Consim: an interactive microcomputer program for continuous mining systems. Blacksburg, Virginia: Virginia Tech; 1989.7 Zhao R, Suboleski S. Graphical simulation of continuous miner production systems. In: Proceedings of the 12th international symposium on applications on computers and mathematics in the mineral industry, Duncan, vol. 1, 1987.8 Ramachandran D. A simulation model for continuous mining Systems. Blacksburg, Virginia: Virginia Tech; 1983.9 Tsiflakos K, Owen D. Simulation of mining systems by objectoriented graphical modelling. Int J Rock Mech Min Sci 1993;30:A108.10 Connor O, Dowding KM, Engng CH. Hybrid discrete element code for simulation of mining induced strata movements. Int J Rock Mech Min Sci 1993;30:A67.11 Hunt C. Simulation model of ore transport at the Henderson mine. Comp Geosci J 1994;20:7584.12 Vagenas N. Applications of discrete-event simulation in Canadian mining operations in the nineties. Int J Surf Min 1999;13:778.13 Sturgul JR. Discrete mine system simulation in the US. Int J Surf Min 1999;13:3741.14 Sturgul JR. Mine design: examples using simulation. Colorado: SME,2000.15 Kolonja B. Simulation analysis of dispatching strategies for surface mining operations using SIMAN. MSc thesis, Penn State University,1992.16 Konyukh VL, Ramazanov RA. Control of underground loader-hauldumpers from the surface. J Min Sci 2004;40:3749.17 Hustrulid WA, Bullock RL. Underground mining methods. Colorado: SME; 2001.中文翻译在长壁放顶煤采煤法中通过仿真模型优化长壁工作面设备组合Ferhan Simsir*, Muharrem Kemal Ozfirat采矿工程系，Dokuz Eylul大学，35160 Buca,伊兹密尔,土耳其于2007年1月12日收到初稿；并于2007年11月2日收到修改文章；此后于2007年11月21日录用该文；2008年3月4日可上网查询1、简介为了有效地利用有限的地下资源，最合适的生产设备和采煤方法必须应用到煤矿。然而尝试所有可选择的设备组合将花费巨大。而另一方面，计算机模拟在矿山开发和控制生产成本方面非常有效地工具。这是一个在工厂、卫生系统、物流业以及服