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By G. E. Wasson

Coal in most refuse ponds including those owned by Consolidation Coal Company can be recovered by froth flotation techniques. Laboratory studies show that the flotation conditions required for coal recovery varied greatly from pond to pond. The variables found to be most important for high coal recovery and low product ash were: a) the amount and type of flotation reagents and b) the degree of conditioning before flotation. Coal recovery at a rate of 0.504 kg/s (2 tons/hr) was demonstrated at a pond site employing a mobile froth flotation unit.

Jan 1, 1988

By Qingming Feng, Jinhong Zhang

A study has been carried out to apply fly ash as a high strength, water-resistant precast construction material through geopolymerization. Experiment results show that the working conditions such as water content, the concentration of NaOH, curing temperature, and curing time significantly affect the mechanical property of geopolymermatrix. Through optimization, an above-100MPa compressive strength has been achieved with the geopolymerization products. The optimum working conditions involves 10MNaOH concentration, 14–15% water content, and curing at 90 °C in an oven for 1 day or at ambient condition for 3 weeks. Adding Ca(OH)2 does not help to increase the compressive strength of the specimen.Water soaking tests show that the geopolymerization product has a very high water resistance without losing noticeable compressive strength, even after a 1-month soaking time. To elucidate the geopolymerization mechanism, microscopic techniques such as SEM/EDS (scanning electron microscopy and energy-dispersive X-ray spectroscopy), XRD (X-ray diffraction) and ATR-FTIR (attenuated total reflectance Fourier transform infrared) are also applied to investigate the microstructure, the elemental and phase composition of geopolymerization products. The findings of the present work provide a novel method for applying fly ash as a high-strength water-resistant precast construction material.

Aug 17, 2020

By Charles F. Coleman

Kinetics studies and other rate measurements are reviewed in the amine extraction of uranium and of some other related and associated metal ions. Equilibration' is relatively fast in the uranium sulfate systems most important to uranium-hydrometallurgy. Significantly slow; equilibration-has ' been encountered' in some other systems. Most of the recorded rate information, both qualitative and quantitative; has come from exploratory and, process-development development work, while some kinetics studies have been directed specifically toward elucidation of, extraction mechanisms. In contrast to some other extraction systems, relatively little attention has been given to the kinetics of uranium extraction by amines. This is because investigators have not been troubled by slow extractions. Instead, when rate limitations have been of concern in amine extraction (Amex) process developments, they have been mainly from slow phase disengagement rather than from slow equilibration. Nevertheless, taking uranium together with several other elements that are closely related to it or associated with it in typical processes, a considerable body of rate information has been recorded.

Jan 1, 1979

By Edward Skolnik

The concept of using fluid dense media to separate heavy ore constituents from the lighter gangue dates back to 1858, when it was patented by Sir Henry Bessemer. Its use in coal did not begin until after 1917, however, when Chance invented a process (which bears his name) in which lighter coal floats in a suspension of fine sand in water while heavier refuse sinks. Conklin used fine magnetite in suspension as a medium for floating anthracite in 1922, DuPont designed a plant employing organic liquids in 1936, and Belknap used a solution of calcium chloride (which Bessemer had suggested, among other media) in 1937. Separation of magnetic media by magnetic separators from the suspensions in which they were carried was introduced in a Butler Brothers ore concentrator pilot plant in 1937. The media first used were crushed steel and various grades of ferrosilicon. Since 1940, when American Cyanamid used magnetic separators to recover and clean magnetite in a coal washing circuit, virtually all heavy medium circuits have been of that type. As long as static baths are employed, as they are in the processes above, coal smaller than 9.5 mm or 6.4 mm cannot be cleaned economically in heavy medium. The settling velocities of the fine material are very low, and consequently the time required to separate the lighter coal from the heavier refuse becomes excessive. In addition, stray currents in the vessel and the upward velocities induced to keep media solids in suspension affect the finer solids to the degree that physical size becomes a more important factor than specific gravity.

Jan 8, 1980

By S. Hearn, S. Boskovic, A. Smethurst

"The digestion of minerals in strong acids or at elevated temperatures can result in the release of large amounts of silicic acid which can polymerize in solution to form colloidal silica and gels. Colloidal silica can cause a number of problems including interfering with flocculation, initiating crud formation in solvent extraction (SX), decreasing SX extraction kinetics and increasing SX phase disengagement times. Huntsman’s POLYSIL® polyether coagulants have a “lock and key” relationship with the surface of colloidal silica to help lower the concentration of these particles in solution, improve process efficiency and reduce reagent losses by minimizing crud formation. This paper investigates some of the issues caused by colloidal silica in hydrometallurgy processes and illustrates how the use of POLYSIL® coagulants has helped to improve process outcomes. INTRODUCTION Coagulation differs from flocculation in a number of ways. Coagulants are relatively small molecules that modify the surfaces of fine particles, weakening repulsive forces between them and allowing particles to stick together, while flocculants are generally molecules that are large enough to bridge the boundary layers between the particles. With flocculation, addition rate and mixing all make a difference to the flocs formed. Coagulation, on the other hand, is an equilibrium process. With coagulation it is only necessary to achieve good mixing, and coagulates will form as Brownian motion pushes the particles into each other. In real systems, this process is complete within seconds. Huntsman’s POLYSIL® polyether based coagulants have a strong affinity with the surface of colloidal silica formed by the polymerization of silicic acid. While silica found in minerals has a low aqueous solubility, large amounts of silica as silicic acid can be released as these minerals are digested in strong acids at elevated temperatures. The solubility of free silicic acid is about 150 ppm under pH conditions typical in acid leach environments (1), so the bulk of the silica will polymerize in solution to form colloidal silica. Colloidal silica can pass through a hydrometallurgy process without affecting any of the operations. However, it can cause a number of problems. These include gelling in a leach, interfering with flocculation or crystallization, initiating crud formation (2,3,4), decreasing extraction kinetics and increasing phase disengagement times (5,6) in solvent extraction. In these cases, coagulating the silica with POLYSIL® coagulants can reduce or eliminate the problem by enabling these particles to be flocculated and removed from the solution."

Jan 1, 2015

By Richard Addison

Rosario Dominicana, S. A. operates an 8,500 tonne per dayopen pit gold/silver mine in the Dominican Republic on the Caribbean island of Hispaniola. The mine is located in an agricultural area which is also an earthquake and heavy rainfall zone. In the 64 years from 1910 to 1974 there were 19 earthquakes within 300 km of the mine in the range of 6 to 8 on the Richter scale and the most recent earthquake in this range occurred in March, 1979. Average annual rainfall in the area is 1.7 m and is distributed throughout the year. Safe and environmentally sound tailings disposal in such conditIons has demanded the buiIding of an extremely strong dam wall and use of a fail-safe system of tailings disposal and solution reclaim. The type of dam, the system of tailings disposal and solution reclaim comprise an interesting example of the manner of handling tailings for a medium tonnage mine. The system is relatively costly but does assure a long-term, safe and trouble free structure and operating system. General views of the dam wall and tailings pond are shown in Figures l through 4.

Jan 1, 1980

By Isabel F. Barton, Matthew J. Gabriel, CARSON ROBERTS, JOHN LYONS-BARAL, LEON DUPLESSIS, Mark D. Barton

Geometallurgical characterization is increasingly used in the mining industry to model ore types, predict process performance and identify potential recovery issues ahead of time. However, most geometallurgical assessments are based on bench- or laboratory-scale analyses of relatively sparse samples, leaving most of the orebody characteristics known only by inference until the rocks are actually mined. In this pilot study, we test drone- and tripod-based hyperspectral imaging for mapping mineralogy across mine highwalls, dumps and leach pads. The results show that hyperspectral imaging can successfully map the types and distribution patterns of key minerals (especially carbonates, sulfates, clays, other phyllosilicates) and other important features (such as lixiviant ponding on leach pads), bringing geometallurgy into the field to provide crucial inputs to process decisions.

By A. L. Ling, A. K. Janzen

"Design of effective mine water treatment plants depends on the ability to reliably predict treatment outcomes, but systems with multiple chemical and physical treatment processes and recycle loops can be difficult to model. GoldPHREEQC is a modeling framework that integrates mass and flow routing capabilities of GoldSim software and water quality calculations provided by PHREEQC, and is well-suited to modeling parameters of interest in the mining industry, especially metals and sulfate. Physical processes such as membrane separation and greensand filtration are modeled by defining mass rejections for each parameter and flow routing based on vendor projections and bench- or pilot-scale equipment testing. GoldPHREEQC models chemical precipitation processes such as HDS metals removal and gypsum precipitation by (1) performing surface-aging and solubility calculations in PHREEQC and (2) using the GoldSim framework to direct supernatant and precipitate to subsequent process steps. Users can apply this modeling framework to predict effluent water quality, chemical requirements, sludge production, and required equipment capacity to support design, troubleshooting, and cost estimating. INTRODUCTION Design of effective mine water treatment plants depends on the ability to reliably predict treatment outcomes, but systems with multiple chemical and physical treatment processes and recycle loops can be difficult to model. GoldPHREEQC is a modeling framework that integrates mass and flow routing capabilities of GoldSim software (1) and water quality calculations provided by PHREEQC (2), and is well-suited to modeling treatment of parameters of interest in the mining industry, especially metals and sulfate. GoldPHREEQC can also be applied to other water treatment scenarios using inorganic reactions and processes. The GoldPHREEQC model framework moves water and mass between specified model nodes and calculates specified reaction and water quality outcomes. It can be organized to provide flow, load, and concentration information for each location, including effluent and byproduct streams, and outputs can be adapted to include power and chemical costs."

Jan 1, 2018

By R. W. Fedors, S. T. Green, R. A. Hart, D. B. Walter

Computational fluid dynamic (CFD) modeling of a potential nuclear waste repository drift may be an important tool to estimate moisture redistribution caused by natural convection within the drift. To refine and support CFD techniques, a small laboratory cold-trap experiment was developed. Results from numerical modeling of the laboratory experiment show the sensitivity of the bulk air flow rate and average air temperature within the drift to several key parameters, including various boundary condition assumptions and surrounding porous media properties.

Jan 1, 2004

By Clark B. Risler

Conveyors constitute a critical artery, essential to the successful operation of most ore processing plants. Technological progress is permitting the recovery of metal from low grade ores which previously could not be worked economically. Significant in this progress are improved material handling techniques highlighted by the frequent and successful application of conveyors. From the standpoint of the plant manager the successful conveyors are those he never hears about. They continue to economically transport the loads applied to them, requiring only routine maintenance attention. When such conveyors are subjected to closer scrutiny you will find that they have been carefully selected and engineered to perform the required function under the anticipated conditions. Among the primary elements in a conveyor drive are the electrical motor and the speed reducer. The selection of these elements can be aided by the systematic consideration of several factors. These factors which focus attention on the critical operating conditions, will be individually evaluated and their effect upon the selection of the electrical drive system and speed reducer analyzed.

Jan 1, 1958

By Robert J. Hite, James P. Searls, Sherilyn C. Williams-Stroud

Potash is a generic term that includes potassium chloride, potassium magnesium sulfate, potassium sulfate, potassium nitrate, and sodium-potassium nitrate mixtures. In the ceramics industry, potash is also used to refer to potassium oxide. Potash, primarily in the form of potassium carbonate, was the first industrial mineral produced in the United States, and the first US patent issued was for an apparatus and process developed in 1790 for its production (Paynter, 1990). Prior to the 1860s, potash was primarily sold as an impure form of potassium carbonate produced by burning hard- wood trees and leaching the potassium salts from the ashes. The major early uses of potash include soap and glass making, dyeing fabrics, baking, and saltpeter for gunpowder. In 1859, the development of a purification process to remove the sodium and magnesium chlorides was developed for the carnallite found at Stassfurt, Germany, and mined potash became available. With the appearance of mined potash and the earlier (1840) discovery in Germany by Justus von Liebig that potash was a nutrient for crops, potash started to be used for high valued crops such as cotton and vegetables. The German potash companies quickly developed a manufacturing process for producing potassium sulfate for tobacco fertilization. German potash supplied nearly all American needs until the embargo of the First World War when imports from Germany were interrupted (Bateman, 1918). With the discovery of potash deposits in New Mexico in 1931, the United States became self-sufficient in potash. In 1962, the United States began importing potash from Canada, and two years later domestic apparent consumption began to exceed domestic production. Along with nitrogen and phosphorus, potassium is one of the three essential plant nutrients, the "K" of NPK terminology. As a result, 95% of potash production is used as plant fertilizer. In all plants, inadequate potassium diminishes growth, causes increased disease, stalk and stem breakage, and susceptibility to other stress conditions. Plants take up large quantities of potassium from the soil, and potash fertilization replaces this loss so that each new crop can be grown with the same vigor and productivity as the previous year's crop. The potassium depletion of the soil from growing repeated cotton and tobacco crops is well known in the history of southern agriculture in America. George Washington was known to have studied alternative crops that could be grown on soil that had been depleted by repeated tobacco crops. Most of the remaining 5% of potash consumption is by the chemical industry, as potassium hydroxide to produce soaps and detergents, glass and ceramic products, dyes, explosives, alkaline batteries, and medicines. Potash as chemical is used in oil field drilling mud, the aluminum recycling industry, and the electroplating industry. Additional minor uses for potassium chloride include water softener regeneration, sidewalk deicing, and salt substitution for human consumption. Potash is used in the food industry as potassium phosphate, and in production of glass products as potassium carbonate or nitrate. GEOLOGY Potassium is the seventh most abundant element in the earth's crust and the sixth most abundant element in seawater. It is found in silicate minerals of igneous, metamorphic, and sedimentary rocks and is also a major constituent of many surface and subsurface brines. The majority of world potash resources are found in subsurface bedded salt deposits which yield high grade, large tonnage ore bodies and are amenable to low cost mining and beneficiation. Because of the relatively high solubility of potassium minerals, potash from salt deposits is ideal for use as fertilizers. Some potash production is from evaporation of naturally occurring brines, but the vast majority of current domestic and international production is from bedded salt deposits. Sylvite, carnallite, kainite, and langbeinite are some of the more important potassium minerals (Table 1). Sylvinite, a mixture of KC1 and NaCl is the highest grade potash ore. Carnallite can be considered a potash ore when removal of magnesium chloride is included in the beneficiation, but it can also be considered a contaminant when mining for sylvite. Potassium sulfate and potassium nitrate are typically manufactured products. Potassium sulfate is produced from mined minerals through conversion processes in Italy, Germany, and Carlsbad, NM, and from brines in southern California and at the Great Salt Lake in Utah. Natural deposits of potassium nitrate occur only in small amounts in Chile. The majority of potash-bearing bedded salt deposits are believed to have originated from the evaporation of seawater or mixtures of seawater and other brines in restricted marine basins (Schmalz, 1969). The reflux depositional model for evaporite deposition was first described in the literature in 1888 by Ochsenius. A shallow bar, or sill, across the mouth of a basin lets in a restricted flow of seawater which evaporates into a salt-precipitating brine (Fig. 1). The density of the brine at the distal end increases with increased salinity, sinks to the bottom, and sets up a reflux current of higher density brine back toward the ocean. The sill, which restricts the inflow of seawater, allows inhibited flow of evaporation-concentrated brines back to the ocean. The least soluble salts are precipitated nearer the sill, and the most soluble components come out of solution in the deeper parts of the basin. The result is a lateral facies change in a tabular-shaped deposit that is due to the salinity gradients in the brine (Fig. 2A). The asymmetrical facies distribution of the Paradox Formation (Middle Pennsylvanian) Utah (Hite, 1970), the Prairie Formation (Middle Devonian) in Saskatchewan (Holter, 1972), and the Salado Formation (Upper Permian) in New Mexico (Lowenstein, 1988), might prompt explanation by such a model. Other deposits, such as the Salina Formation (Upper Silurian) in Michigan (Matthews and Egleson, 1974), show a facies distribution that could be described as a bull's eye pattern. Although some small subbasins of high grade sylvite are found near the margins, the potash is generally located in a central part of the basin surrounded by successively less soluble facies (Fig. 2B). The sparse

Jan 1, 1994

Several years ago, North American mining companies began to realize they needed to expand their spheres to remain viable. This strategy has been successful, according to Robert W. Schafer. Today, companies from other continents have also recognized the need for an international view for long-term growth and viability, he said. Schafer is vice president for exploration with Kinross Gold. He was the program chairman and moderator of the keynote session at the 1997 SME annual meeting, held in Denver, CO, Feb. 23-27. The theme of the meeting was "Minerals - Serving the Global Community." A record attendance of more than 6,000 people participated in the meeting, which featured 415 exhibitors occupying 582 booths. The title of the keynote session was "Corporate Perspectives on a Global Minerals Industry." Each of the three keynote speakers discussed a different perspective of a global minerals industry.

Jan 1, 1997

By F. A. Renninger

Limestone and dolomite are the most common rock types mined and quarried as industrial minerals in the United States. In 1993 over 720 million tons of limestone and dolomite valued at over 3.1 billion dollars were extracted and consumed throughout the nation. While the greatest volume of this vast production is used as aggregate for construction purposes, few people realize how critical limestone and dolomite are to our food chain and our national goals of clean air and water. Limestone, including dolomite, can truly be called nature's gift to the environment. Without a reliable, economical source of limestone the quality of our environment would be severely comprised and the standard of living of our citizens dramatically reduced.

Jan 1, 1995

By W. R. Reed, J. P. Rider

"The National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) has recently developed a series of models utilizing computational fluid dynamics (CFD) to study airflows and respirable dust distribution associated with a medium-sized surface blasthole drill shroud with a dry dust collector system. CFD models were constructed in ANSYS FLUENT Version 15. Previously run experiments conducted in the NIOSH full-scale drill shroud laboratory were utilized to validate the models. The setup values in CFD models were calculated using experimental data obtained from the drill shroud laboratory and measurements of test material particle size. Subsequent simulation results were compared with the experimental data for test scenarios, including 0.14 m3/s (300 cfm) bailing airflow with 2:1, 3:1, and 4:1 dust collector-to-bailing airflow ratios and 0.24 m3/s (500 cfm) bailing airflow cases with 2:1, 3:1 and 4:1 dust collector-to-bailing airflow ratios. For the 2:1 and 3:1 ratios, results showed the calculated dust concentrations from the CFD models were within the 95% confidence intervals of the lab experimental dust concentrations. This paper describes the methodology used to develop the CFD models, to calculate the model dust input, and to validate the models based on experimental data. Problem regions were identified and revealed by the simulation of a dry dust collector system. The simulation results could be used for future development of dust control methods for a surface mine blasthole drill shroud. INTRODUCTION In surface mines, production drilling is an essential process in blasting which fractures the hard rock overburden for removal. Holes with a predetermined pattern, diameter, and depth are drilled into the overburden to introduce explosives. During the drilling process, considerable amounts of respirable dust are produced. Past research conducting area sampling at blasthole drills has documented time-weighted average respirable dust concentrations ranging from 8.68 to 95.15 mg/m3 [1] and 1.04 to 52.30 mg/m3 [2]. These high dust concentrations, which may contain silica, can lead to respirable dust over-exposures for the drill operator, drill helper, and other personnel in the vicinity. These over-exposures can lead to silicosis, an occupational lung disease that has no cure and is ultimately fatal. In order to prevent the development of silicosis to mine workers, the Mine Safety and Health Administration (MSHA) regulates the exposure to respirable dust. For metal/nonmetal (M/NM) mines, MSHA has adopted the threshold limit values recommended in 1973 by the American Conference of Governmental Industrial Hygienists (ACGIH) [3]. The total airborne dust standard is 10 mg/m3. However, if the sample contains greater than 1 percent quartz (the most common form of crystalline silica), a respirable dust standard is calculated with the following equation: Respirable dust standard = (10 mg/m3) / (% respirable quartz + 2)"

Jan 1, 2016

By M. M. Nash

Since the late 19th Century, scholars have been concerned about finding proper methods of managing business. The search seems to be taking us full-circle to the time and motion studies of Taylor (Horn, 1987). It wasn't until the late 1970's, however, that systematic investigations were made in the mining industry. One of the first was a study by Sanders, Patterson, and Peay (1976). That project explored the relationship of attitudes and safety. Peay, Atkin, and Goodman (1977, then reviewed the whole area of Organizational Development, including the so-called Rushton experiment.

Jan 1, 1988

By James McNally, Adam Stremcha, John MacGregor

With 13.7km of TBM tunneling in Atlanta’s hard gneiss well under way, drill and shoot work continues on several sites throughout the city. In order for the City of Atlanta to meet the consent decree imposed by the federal government, an aggressive construction schedule was a necessity. Construction consists of two deep, large diameter tunnels, four construction shafts, a pumping station, one overflow shaft, three large intake structures, and two connecting tunnels. Due to the multitude of blasting insensitive urban environments, a high standard of seismic and air-overpressure criteria, coupled with time restrictions, was adopted for the project. At any given time, drill and blast operations were under way at four of the seven sites requiring a certain amount of coordination between the TBM excavation, surface work, and the forces of Mother Nature. This paper addresses the challenges faced and the techniques used to safely and successfully complete the rock excavation of the West Area CSO Tunnel and Pumping Station project.

Jan 1, 2007

By L. B. Hales

Expert control of grinding and flotation plants has been successfully used in the minerals industry since the 1970?s. The earliest of these systems were written in a hard-coded fashion in FORTRAN, BASIC or Pascal. Second generation systems were built using the first experimental expert system shells that were being developed in the artificial intelligence community. Later systems were deployed in expert system shells designed for real-time processing plants that also included the ability to model the process with neural network models and optimize setpoint selection through the use of genetic algorithms. Significant performance increases have been achieved using these systems, but in general, they suffer from the static nature of their rules and to a degree the process models also. Typical improvements quoted in the literature suggest throughput rate increases of 4 to 8 percent and recovery increases of 1 to 4 percentage points. In over 30 years of designing and installing expert systems we have never seen performance numbers less that these but have often seen numbers in excess of the high values. However, once the system has been installed and tuned up the performance usually does not improve much thereafter. Granted, the initial increases in throughput rate and recovery are significant but a question always lingers, that is, can the expert strategies be modified further to squeeze a little more improvement out of the system. The answer to this question is a resounding yes, however a complete understanding of what we do well as designers and operators of expert control systems is required as well as how we can improve upon our best practices is required to move us from the performance plateau we have been on for a number of years to a new higher level of performance.

Jan 1, 2009

By Neville T. Moxen, Stuart K. Nicol, Malcolm D. Engel

Ion flotation is a process in which ions of interest are complexed with a suitable surfactant molecule. A dilute solution containing these complexes is then aerated, under which circumstance the surface-active complex concentrates at the air-water interface and is transferred to a froth. The present work describes some of the phenomenology of this process and experimental work leading up to the design and use of a pilot scale laboratory facility. Early experiments suggest that selective recovery of gold can be obtained in a manner at least equivalent to conventional CIP processing at low capital cost. Under favourable conditions, upgrade ratios of gold ions of the order of 180: l have been achieved from reclaimed residue dam water with as low an initial gold level as 0.2ppm. Successful development of countercurrent ion flotation for concentrating solids-free gold solutions may offer a lower cost alternative to existing gold ore processing technologies, or in more secondary applications such as concentrating dilute gold solutions or heap leach runoff. The technology may also have more generalised applications to other heavy metal processing.

Jan 1, 1990

By Xiaolong Bi, Shaohua Luo, Longjiao Chang, Shiyuan Cao, Jianan Liu

iliary agent was proposed. The mineralogical transformation and silicon extraction kinetics of laterite nickel ore in alkaline hydrothermal treatment were studied. The effects of reaction temperature (175 ~ 250℃), molar ratios of sodium hydroxide to ore (1.05 ~ 1.2:1), and laterite nickel ore particle size (44 ~ 178 μm) on the extraction ratio of silica were investigated by using the shrinking core model. The results show that the extraction ratio of silica increases with the increase of reaction temperature, sodium hydroxide to ore molar ratio, reaction time, and the decrease of raw ore particle size. The kinetic analysis shows that the separation of silica in laterite ore can be described by internal diffusion model. The apparent activation energy (Ea) of the reaction was 8.87 kJ mol− 1, and the kinetic modeling was established.

Dec 2, 2021

By Weijie Wei, Jinwang Zhang, Jiachen Wang, Yang Li

"Longwall top-coal caving (LTCC) mining technique is one of the important methods for underground thick seam extraction in China. The coal seam in LTCC panel is divided into two parts: bottom-coal and top-coal. The bottom-coal is mined by conventional longwall method while the top-coal is mined by caving method. The top-coal caving process in LTCC and block caving process in metal mine are both gravity flow of loose ore/coal blocks. However, the presence of caving shield in LTCC makes the characteristics of drawing body shape in the two caving processes differ a lot. This paper discusses the influence of caving shields on the characteristics of drawing body shapes in light of recent studies of the top-coal drawing process. The theoretical model for describing the drawing body shape in LTCC is proposed both along the seam strike and seam inclination. Then, the experimental data are used to validate the correctness of the theoretical model. Furthermore, two examples of how the theoretical findings assist LTCC mining are given and discussed.INTRODUCTIONLongwall top-coal caving (LTCC) mining technique and large-cutting-height mining technique have been widely used for extracting thick coal seams in China. About 0.6–0.7 billion metric tons of coal come from longwall top-coal caving panels every year. The maximum annual production is 15 million metric tons per panel _The mining method employed in such panel is a combination of top-coal caving mining technique and large-cutting-height mining technique, which is suitable for seam height between 12–20 m, as shown in Figure 1. Apart from China, LTCC has also been employed in some coal mines in Australia and Vietnam (Le et al., 2017).The coal seam in a LTCC panel is divided into two parts: bottom coal and top coal. The bottom-coal is mined by the conventional longwall method, while the top coal is mined by the caving method. The top-coal caving process in LTCC and block caving process in metal mines are both gravity flows of loose coal/ore blocks, as shown in Figure 2. However, the presence of caving shields in LTCC causes the characteristics of the drawing body shapes in the two caving processes to differ significantly.There are two main differences between the blocking method and the top-coal caving method:"

Jan 1, 2019