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By I. B. Tulu, M. M. Sears

In 2015, 40 longwall mines provided nearly 60% of the US coal production from underground mining methods. This represents a substantial yet gradual increase from just under 50% over the last 5 years. As a result of this increased production share, the percentage of ground-fall-related fatalities in longwall mines has also increased when compared to all US underground coal mines. Additionally, about 80% of ground-fall-related fatalities have occurred in areas where the roof was supported. In an attempt to better understand the status quo of current US longwall support practices, a sample of 25 longwall mines were visited representing nearly 50% of the currently active longwall mines representing all of the major US longwall-producing regions. The resulting data was obtained from a wide variety of overburden depths, geologic conditions, mining heights, ground conditions, support practices, and gateroad configurations. The data collected is reported using both qualitative and quantitative methods. Results from the research update previous efforts in classifying mining accidents and injuries as well as current support practices presented by this author at the 2017 Society for Mining, Metallurgy, & Exploration Annual Meeting. This data provides a necessary background for future research aimed at further reduction of ground fall accidents and injuries.

By I. B. Tulu, M. M. Sears

In 2015, 40 longwall mines provided nearly 60% of the US coal production from underground mining methods. This represents a substantial yet gradual increase from just under 50% over the last 5 years. As a result of this increased production share, the percentage of ground-fall-related fatalities in longwall mines has also increased when compared to all US underground coal mines. Additionally, about 80% of ground-fall-related fatalities have occurred in areas where the roof was supported. In an attempt to better understand the status quo of current US longwall support practices, a sample of 25 longwall mines were visited representing nearly 50% of the currently active longwall mines representing all of the major US longwall-producing regions. The resulting data was obtained from a wide variety of overburden depths, geologic conditions, mining heights, ground conditions, support practices, and gateroad configurations. The data collected is reported using both qualitative and quantitative methods. Results from the research update previous efforts in classifying mining accidents and injuries as well as current support practices presented by this author at the 2017 Society for Mining, Metallurgy, & Exploration Annual Meeting. This data provides a necessary background for future research aimed at further reduction of ground fall accidents and injuries.

By P. R. Thomas

This paper addresses the relative long-term cost and resource position of new and existing ferrochromium production in selected Market Economy Countries (MEC'S). The market impact of new ferrochromium production in nations such as India and the Philippines and the continuing change in international trading patterns are also evaluated. This paper draws upon the data and analyses of a recent Bureau of Mines, Department of Interior, Minerals Availability Program appraisal that evaluated the cost and availability of chromite and ferrochromium production from the demonstrated resources of 80 producing or potential mining operations in 10 market economy countries.

Jan 1, 1984

By David W. Wisecarver

The U.S. Bureau of Mines, in cooperation with U.S. Borax and Chemical Corporation and the Kennecott Copper Corporation, has investigated the use of the microseismic method to evaluate the stability of large, open-pit slope walls. The method is based on the phenomenon that stressed rock normally emits subaudible rock noises, and the number of rock noises per unit time (noise rate) and the magnitude of the rock noises (amplitude) increase as the stresses in the rock approach the failure stress of the rock. Therefore, the detection and recording of those rock noises serve as a semiquantitative method of predicting the incipient failure of rock. This report briefly describes the three different types of microseismic apparatus, the procedures, and the results of microseismic investigations in the slope walls of the Boron Mine near Boron, California, and the Rimbley, Liberty, and Tripp-Veteran open-pit mines near Ely, Nevada. Microsesimic noise rates in stable inactive mining areas are between 0 and 10 noises/ hour; the rates in stable active mining areas are between 10 and 50 noises/hour; and the rate in unstable areas is as high as 2500 noises/ hour. High microseismic noise rates in the Liberty Pit correlate with the time of nearby earthquakes, indicating that the earthquakes affected the slope wall. The results provide evidence that the microseismic tech¬nique is applicable to large pit walls, and that the wide band, wide range microseismic equipment appears to be suitable for open-pit investigations.

Jan 1, 1969

By L. P. Meade

Dimension stone and salt are two of the oldest industrial minerals utilized. Salt has been and still is a necessity to the well being of man. Dimension stone on the other hand has been utilized by man to glorify conquests - both in the battlefield and corporate arena. Both commodities are important, but dimension stone has an additional use in that the survival lessons learned by the domestic industry can be applied to other contemporary industrial minerals, Specialization in the market place and customer service have allowed domestic producers to survive: subsidized foreign competition, obsolete equipment, and lack of capital.

Jan 1, 1986

By A. M. Whiting

Competition for coal producers and their primary customers has constantly increased during recent years. The effects of the Clean Air Act Amendments of 1990 on the electric utility industry, coupled with the normal complexities of coal production, quality control, transportation and contracting techniques have spurred both buyers and sellers to increase their level of sophistication. This paper will review the basic aspects of the U.S. coal business and explore the commercial approaches which have proven to be most successful.

Jan 1, 1994

By Dongjie Zhang, Zeyu Liu, Shuxin Liu, Yang Liu

Lateral pressure provided by caving rocks plays an important role in keeping the stability of the sidewall rock mass and controlling the rock movement. Taking Xilinhot Fluorite Mine as an engineering background, we studied the control mechanism of the granular media lateral pressure on the rock movement by combining physical experiments, theoretical analysis, and field monitoring. The results indicated that with the increase of the granular media depth, the lateral pressure provided by the static granular media presented two stages of rapid growth and slow growth. The lateral pressure on the footwall was negatively correlated with the dip angle of the orebody, and the lateral pressure on the hanging wall was positively correlated with the dip angle of the orebody. Ore drawing only caused the granular media lateral pressure near the drawing point to decrease. As the granular media moved, the granular media lateral pressure outside the pressure reduction area further increased, and this part of the granular media would play a key role in limiting surface rock movement. On this basis, the improved calculation formula of GLMP was given, which could be better applied to calculate the GLMP and critical granular media column with different dip angles. The action mechanism of the GLMP in the control of the surface rock movement was clarified. The granular body in the collapse pit was mainly composed of three parts: the bottom loose granular media column, the middle compaction granular media column, and the upper critical granular media column. The critical granular media column was the most important area to control surface subsidence and rock movement. Finally, through field practice, after effective filling of the collapse pit, the surface vertical displacement of the hanging wall and footwall was decreased by 56.8% and 55.6%, respectively, and the control effect of surface rock movement was remarkable.

Sep 18, 2023

By K. W. Lentz

The Maybell Mill of, Trace Elements Corporation, Unit of Union Carbide Corporation is located approximately five miles northeast of Maybell, Colorado, and twenty-five miles northwest of Craig. It is located in the midst of the uranium ore deposits whose presence, made it possible. In November 1953 Russel Cutter, Chief Geologist for the original Trace Elements Corporation, picked up high readings on a scintillometer while flying over this area. Later, with George Morehouse, Chief Engineer for the original. Trace Elements Corporation, he started a search for surface indications. In this search, they found an out crop which can be regarded as the discovery lode on this property. The actual locating of claims and acquiring free lands and state lands was begun in March 1954. During 1955 enough drilling was done to indicate that a sufficient tonnage of ore existed to make possible a mill. These ore deposits are located in the Browns Park formation which is an unconsolidated sandstone with a few hard lime ribs running through it. The geologists tell us that this region was once a vast basin which became filled with wind blown sand and volcanic tuff, Later on, ground waters brought uranium into the basin which precipitated out in the sand. During the late summer and fall of 1955, a small pilot plant was operated under the supervision of John L. Chapman testing these Browns Park ores. During the operation of the pilot plant, three small open pits were developed and the ore from these pits shipped to Union Carbide Nuclear Company, Division of Union Carbide Corporation, at Rifle. To date all ore is being mined from open ptis. In the fall of 1956 the original Trace Elements group signed a contract with: the AEC for a mill at Maybell and on November 5, 1956, Union Carbide acquired the Trace Elements Corporation properties and contract. During the next two months, intensive research was carried out on the Browns Park ores by our research lab at Rifle. They also checked some of the metallurgical results which had been obtained through the operation of the pilot plant by the original Trace Elements group. During this period, a report on Trace Elements Corporation ores was also prepared by the Colorado School of Mines Research Foundation. This report contained data on representative samples of the ore tested for the original Trace Elements group. From this research and study a flow sheet was decided upon.

Jan 1, 1959

By Xie Longshui

INTRODUCTION The gold production is from the state-owned gold mines, the local gold mines and the by-product of metal mines. Since 1975, the small gold mines have developed in rapid strides. Currently, there are about 3000 small gold mines in China. Most of them are operated by the local, and the production is about 50% of China's gold output. In the small gold mines, the normalized mining equipments are employed at most of mines, but some mines still use such backward tunnelling and mining tools as pick, shovel and hand hammer etc.. The mining techniques have developed from the primitive to the advanced, especially the methods of open stope, shrinkage and filling have been widely used. Such new mining techniques as bolting, vibrating draw, non-electric ignition and diamond drilling etc. are also introduced in the wall gold mines. In recent years, the development of small gold mines is very fast under the guidance of new mining policy which is ' rapid and great development of large-sized mines, helping small mines to develop, and quick mining for the existing mines; and encouraging the collective and the individual to operate a mine.' GEOLOGICAL FEATURES The gold veins are dominant, which are divided into two types, ie. the mesothermal deposit with altered rock in a crushed zone and the hypothermal deposit with quartz veins. The orebody distribution is not centralized, and the size of deposit and single minable orebody is small respectively. Most of deposit dip at 30° to 50°, characterized by expansion and shrinkage, ramification and compound, thinning out and reappearance, separation and composite at the parallel veins etc.. The ore grade is variable, and the factor of grade change is above 100%. The waste zones with lean or submarginal ore usually exist in deposits. As for the gold deposits with altered rock, the ore boundary is indistinct. Most of gold deposits, particularly the gold deposits with altered rock, are intruded by the late structural rock, thus the faults and joints are developed, and the rock and ore are crushed, especially the host rock of roof wall is very crushed. It ie obvious that the conditions of both formation of deposit and mining are considerably complicated. HISTORY With a long mining history and rich experiences, the local gold sectors are small, but they play an important role in China's gold mining industry. Dated from Xia and Shang Dynasty, the gold goods was made. In the Tang Dynasty, the development of gold mining industry was very fast. A Chinese poem , written by Liu Yuxi -- one of famous poets in the Tang Dynasty, says: As sun is shining over Dengzhou land, The fog on river slowly goes away, The panning girls together meet at bay, The beauty's jewels and stamps of king are gold from river sand. This poem shows the local gold mining was flourishing at that time. In 1888, the local gold mining sectors were all the rage at the moment, and the annual output of gold was as high as 21.5 tons. Since the founding of New China, the development of local gold mining was subjected to several back- sets, but certain advances are made on the whole, especially since 1970. Round about 1970,the simple, backward and indigenous mining was dominant in the small gold mines; for instance, the hand-hammer drilling, the hand-operated winch hoisting and the hand haulage etc.were main methods of gold mining . Up until the late 1970s,great changes took place in stoping, haulage and so on. Currently, some advanced technology and large-sized equipments are adopted in the local gold mines. Generally, the local small gold mining sectors play an important role in development of China's gold mining industry, and are important and attractive sectors. PRESENT DEVELOPMENT

Jan 1, 1987

By R. L. Pozzo

A previous investigation showed that corrosion currents estimated from polarization curves for the pyrrhotite-grinding media system under abrasion correlated well with corrosion currents estimated from marked ball wear test data by applying the Faraday's Law. Freshly abraded metal debris were magnetically attracted to pyrrhotite and lowered the rest potentials of the mineral particles, thereby affecting the corrosive wear. The investigation was extended to explore the interactions between a nonmagnetic sulfide mineral, pyrite, and abraded metal debris and their effects on the corrosive wear mechanism. The electrochemical behavior of a three-electrode system involving pyrrhotite, pyrite and grinding media was also investigated as a first step towards elucidating the nature of interactions that occur in the grinding of complex sulfide ores.

Jan 1, 1987

By W. E. Bardelmeier

The high speed conveyor type self unloading bulk carrier concept has been around for about 70 years. Although the design was developed, refined and steadily improved in the Great Lakes, to date limited numbers of such vessels have emerged in the bulk ocean trades, and these have tended to concentrate within specific mineral trades. For example, North American gypsum companies have embraced conveyor self unloaders to the point where such vessels almost exclusively carry the gypsum requirements of this part of the world. One major aluminum company has developed an impressive fleet capability in self unloaders. Application of other ships tends to be fragmented through several mineral trades. A few years ago a new phenomonen began to appear on the Great Lakes. Whereas it had historically been accepted in that region that self unloaders were effective vessels for the minor bulk trades including limestone, coal, salt, gravel and sand; they had seldom been employed heavily in the big volume iron ore trades. Suddenly, however, the new generation of 60,000 ton Lakers which emerged were all designed as high speed self unloaders. The new vessels intended to trade especially in ore, or alternatively especially in coal, have somewhat different internal features, but the important point is that all are self unloaders.

Jan 1, 1979

By HASAN SERKAN GOKCEN, SERKAN CAYIRLI

The purpose of this study was to investigate the dry grindability of calcite powders in a vertically and horizontally orientable laboratory batch type stirred mill. The experimental results were evaluated using stress intensity analysis. The performance was also compared in terms of mill orientation. The results showed that the d50 values decreased with increasing stress energy down to a certain point and then increased for both milling orientations. Even though the optimum stress energies for both vertical and horizontal orientations were in the range of 1*10−3 to 5*10−3 Nm at 750 and 1500 kJ/kg energy consumption, the product size was finer for the horizontal orientation at the same stress energy value. Additionally, to the best of the authors’ knowledge, this is the first study to compare mill orientation (vertical vs. horizontal) for the same mill and under the same test conditions.

Apr 21, 2021

By Wendell E. Bearce

At the, Crescent Valley Mine of the Hanna Coal Company, several 10,000 ton unit trains of 41" x 0 strip coal are loaded per week during the lake season. This is accomplished without the use of any accumulation of prepared coal. A large raw coal pile is built up during the winter months adjacent to two truck dump bins. This is added to whenever trucks are coming in from the pits and trains are not being loaded. During the loading of trains, trucks from several pits dump into the truck hoppers and coal is also dozed in from the pile. At a rate up to 3200 tons per hour this coal is screened, the plus 6" hand picked, the plus 4" crushed, and' all weighed and sampled as it goes directly to railroad cars being handled on two tracks by car retarders. With such an arrangement it is possible to exercise some control over coal quality, if it can be assessed rapidly. For instance, if the moisture rises to a level where it seems probable the BTU per pound will be reduced to the point where the contract calls for penalties, the trucks from, the wettest pit may be stopped, more or less coal may be moved in from the stockpile, or other measures taken to assure that the average BTU of the trainload will be satisfactory.

Jan 1, 1967

By James H. Barks

Exploration for ore deposits in southeastern Missouri in the 1950's resulted in the important discovery of lead, zinc, copper and silver in 1955. Further discoveries in the area led to the naming of the Viburnum trend. It has sometimes been referred to as the "New Lead belt" to distinguish it from older lead-producing areas to the east. As presently developed, the "trend" is 35 miles long, running north and south about 50 miles west of the Lead belt. Galena (lead) is the principal ore mined, with lesser quantities of sphalerite (zinc), chalcopyrite (copper) and silver recovered as economic by-products. The ore body is as much as 140 feet thick and 1,200 feet wide, and is found in the Bonneterre Dolomite (Upper Cambrian) at depths ranging from 700 to 1,200 feet. Since its discovery many companies have engaged in exploration and several major companies have developed new mines and constructed mills and a smelter in the area. The first mine in the Viburnum trend came on stream in 1960, but as more mines came on stream and others reached capacity, lead production increased to the point that the Southeast Missouri Lead district produced 432,576 tons of lead in 1970 to become the world's largest lead-producing region (Missouri Geological Survey and Water Resources, 1971). The Viburnum trend area with its rolling, heavily forested hills and numerous clear running streams is in the Clark National Forest of the Missouri Ozarks. Until the recent development of its mineral resources, the area was sparsely populated and nearly unmarked by the activities of man. Industrial development is almost certain to be accompanied by environmental changes. In a day of growing awareness of the need to preserve the quality of the

Jan 1, 1971

By K. L. Purdy

Electron spectroscopy for chemical analysis (ESCA) was used to determine the-surface characteristics of products from operating Pb-Zn-Cu concentrators on the New Lead Belt of southeast Missouri and pure galena and sphalerite samples treated-with flotation reagents in concentrations similar to those used in the mills. The emphasis was on the action of surface modifiers such as Na2Cr207, starch, SO2, CuSO4 and NaCN in sphalerite flotation and in the galena-chalcopyrite separation. The objective of the investigation was to monitor the relative oxidation states of the mineral and reagent constituents and correlate these surface concentrations and oxidation states with flotation theory and practice. ESCA was able to follow the action of all the modifiers except NaCN. The existence of PbCrO4 on the surface of galena conditioned with Na2Cr207 was verified. The Pb in the bulk PbS-CuFeS2 scavenger concentrate was found to be significantly more oxidized than the Pb in the bulk PbS-CuFeS2 rougher concentrate. ESCA was found to be most useful for investigating the actions of modifiers rather than collectors due to the large amounts of sulfur and background carbon already present on the mineral surfaces. After calibration for the particular chemical system of interest, ESCA can yield semi-quantitative analyses of the oxidation states of many elements (except hydrogen, and helium) present in the outer 10 to 25 A of a sulfide mineral surface.

Jan 1, 1975

By B. J. Arnold

Utility coal specifications usually contain a requirement for a maximum moisture content in order to prevent coal handling problems and to minimize evaporative losses in the boiler. As most coal cleaning processes are water-based, dewatering and sometimes drying steps are required to meet moisture specifications. Screens are often used for dewatering, with centrifuges and filters used to further reduce moisture in many cases. Algorithms to predict the performance of screens were developed for the Coal Cleaning Simulator running under Aspen Plus during a project sponsored by the U.S. Department of Energy and the Electric Power Research Institute. These algorithms include calculations for the size separation and a calculation for moisture content of the oversize product based on particle size and specific gravity distribution. This paper discusses the algorithm for predicting the moisture content of coal dewatered by screens.

Jan 1, 1997

By John C. Ferm

The role of geology in coal exploration, mine planning and mine development has, in the past, been relatively small. The primary reason for this lies in. the simplicity of geologic concepts that were necessary to bring these operations about. These concepts can be briefly stated as follows: 1) coal occurs in the beds or layers and is overlain and underlain by shales, sandstone or limestone in varying porportions, 2) each coal bed has been given a name and certain quality characteristics can often be associated with a named bed and 3) coal beds (and their adjoining rocks) are often folded into broad anticlines or synclines and, in some places, displaced or faulted. In actual practice, however, these simple principles have been found wanting. Thickening, thinning, pinch outs or changes in coal quality occurred but the occurrence was apparently unpredictable and the only real solution to such problems seemed to be practice and experience. This combined with ingeneous engineering solutions have provided answers to most questions. Perhaps a more fundamental reason that geology could offer so little input to coal mining is that the thickest, most persistant and best quality coal seams followed the above stated rules fairly well. In many areas, however, such seams are now nearing exhaustion and the increased demand for clean, non-polluting, safe energy is quickly bringing a need for techniques of exploration and mining procedures that will make development of formerly unminable seams a profitable venture. For the past 20 years some considerable body of knowledge has been added to the framework of the geology of sedimentary rocks and it is the purpose of this paper to present some of these newer ideas that will be useful in solving some of the present problems of coal exploration and development.

Jan 1, 1976

By T. A. Toney

A sampling program was conducted in 2008 to determine the run of mine characteristics of 5 coal seams. The sampling program included size analyses and float sink determinations. The samples were analyzed for ash and mercury concentrations for each size and gravity fraction. This paper will report on the sampling program, the analytical results, and the correlations determined in the data set investigated.

Jan 1, 2010

By Joseph W. Leonard

Much progress has been made in the application of geostatistics to hard rock ore deposits.1,2,3 4,8 Progress in the application of geostatistics to coal deposits has developed over a period of time out of hard rock technology.5,7 Exploratory drilling in many hard rock deposits is frequently significantly more productive than exploratory drilling in coal deposits. For example, hundreds of feet of drilling and/or many drill setups are frequently necessary to obtain a few samples from a typical 4 to 6 foot thick coal seam. With hard rock deposits, which are frequently thick or volumetric, less drilling dead work is involved in sampling the deposit. To produce a variogram, which is the basic element needed for geostatistical analysis, a few well positioned holes drilled into a hard rock deposit where the core(s) can be divided into many sections can produce a detailed variogram. To produce a similar type variogram in coal, it is necessary to drill many dozens of holes with much of the core length consisting of overburden data which is frequently of only secondary importance. To apply geostatistics to coal, not only are many separate sample sites needed, but frequently a problem exists in that the interval distance between samples cannot be controlled with the ease that hard rock drilling intervals can be controlled where it is only necessary to cut core segments according to some preassigned interval of distance. Because the uses of existing coal deposit samples are frequently handicapped by irregular sample distances and lack of sampling density along certain directions needed for the development of variograms, the application of geostatistics to coal deposits frequently does not proceed with the same efficiency and rapidity as when these techniques are applied to ore deposits. Grid-fitting was developed by the writers, as a logical and evolutionary improvement over the long and successful application of geostatistics to coal seams.6,9 Grid-fitting combines the trending of variance as well as other aspects of probability theory to optimize informational yields from the commonly less productive data derived from coal exploratory programs. Grid-fitting is basically a technique where a hypothesis involving numerous grid patterns, where each pattern is of a given geometry, size and direction is repeatedly matched against actual sample data to determine which match results in the closest fit of the hypothesis to the data. To determine the closest fit, a special index known as a selectivity index was developed. The selectivity index is basically the product of the mean and variance of the variances contained within each of the grids. hence, if SI is the selectivity index then [SI = Xs E (S i - Xs) /N] where [X]s is the mean of individual grid variances Si2 for any pattern of given geometry, direction and size.

Jan 1, 1984

By C. A. Rowland

When studying the feasibility of using autogenous or semi-autogenous grinding, operating and engineering companies frequently request assistance from the mill manufacturers in three areas - 1. Recommendations for studying the suitability of autogenous or semi-autogenous grinding for the specific ore. 2. Mill sizing, to accomplish required grind. 3. Recommendations on mill design and operation. Rod mills and ball mills are selected by the use of bench scale standard grindability tests and established calculation procedures, of which the most frequently used are the Bond Grindability tests and the Bond Work Index equation(1). The accuracy of these have been reviewed by C. A. Rowland in his papers, showing the correlation of work indices calculated from plant operating data and laboratory grindability tests(2)(3). The selection of autogenous and semi-autogenous primary mills has not reached the stage where mill size selection can be made from bench scale tests. Considerably more extensive testing will be necessary than required for selecting rod mills and ball mills.

Jan 1, 1974