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By Otto Braach, Wolfgang Frietzsche, Erdogan Gürkan

The Westerschelde Tunnel is located in the south of the Netherlands and links the two parts of the Provinces of Zeeland, Zeeuws-Vlaanderen and Zuid-Beveland, which are separated by the Westerschelde. Road traf?c has up till now taken the detour via Belgium or crossed by ferry. This unsatisfactory transport link signifies major economic disadvantages above all for Zeeuws-Vlaanderen. The first fixed link for road traffic between the communities of Terneuzen and Borsele are to be created by means of the two 6.6 km long tunnel tubes down to 65 m below sea level.

Jan 1, 2003

By Joseph T. Matoney, Okley B. Bucklen, Claude A. Goode, Philip G. Meikle

INRTODUCTION Annual coal production rose to over 1.03 billion st (931 Mt) in 1990. At the same time the number of mines producing this increased tonnage has decreased over 60% in a 30-year period, from 9230 mines in 1960.1 The great increase in production made possible through continued mechanization requires greatly improved loading facilities just to get coal away from the mine. Also the trend to combine production from more than one mine and cleaning it in a single preparation plant continues. A recent census of US coal preparation plants indicated that 310 plants were in operation.2 In addition to increased loading capacity, storage and blending facilities are more necessary both at the producer and user end. In this climate of rapidly changing technology, any written account is faced with the possibility of obsolescence before its appearance. Thus, this chapter seeks to define the common and current practice in coal loading and storage facilities with the full knowledge that this practice is an ever-moving target. FUNDAMENTALS OF COAL STORAGE Storage of coal is becoming an increasingly important part of coal handling systems at mines, particularly since the advent of the unit-train concept in transportation. In order to take advantage of reduced transportation rates on trainload shipments of coal offered by unit-train movement, operators have found that storage is an economic necessity. In unit-train practice, large predetermined quantities must be loaded in relatively short periods of time, as opposed to conventional practice where coal is loaded at a speed dependent on the production capacity of the mine and/or the cleaning capacity of the preparation plant. Clean coal storage is generally practiced in order to accomplish one, or a combination, of the following objectives: 1. To load out promptly and economically. 2. To facilitate blending in order to even out chemical and physical inconsistencies and to prepare desired products or to attain maximum product uniformity. 3. To store certain sizes whose prices and market demand fluctuate with seasons and to permit shipping in good weather. Coal storage, then, is necessary and desirable, both from production and utilization standpoints. There are, however, several undesirable aspects attendant to the storage of coal, the most important of which are oxidation and spontaneous combustion, changes in properties which may affect utilization of the coal, degradation of coal due to rehandling, and the added cost of handling and storage facilities.

Jan 1, 1991

By Rambabu Pothina, Rajive Ganguli

The economics of a mineral-processing circuit is dependent on the numerous sensors that are critical to optimization and control systems. When a sensor goes off calibration, it results in errors that can have a severe impact on plant economics. Classical statistical approaches fail to detect when errors are “subtle,” unless they grow and become large enough to be “gross,” whereas methods based on signal processing and artificial intelligence fail in dealing with the complexity of process fluctuations. Due to the sheer volume of sensors, undetected errors are not remedied until the next calibration, which on average are a year apart across all industries [1]. This research aims to detect such subtle errors (2 percent bias) in shorter time spans of about a month — rather than wait for errors to grow — using innovative data-mining techniques and algorithms.

By Mark E. Gershon

Extensive efforts are under way to- ward applying computer techniques to mine production scheduling problems. These efforts are concentrated in four areas: optimization, computerization of traditional methods, heuristics and simulations. These areas complement each other rather than compete. Characteristics of each are discussed toward enabling the engineer to evaluate specific systems that may be encountered. Alternative approaches within each classification are described as well as the motivation for each.

Jan 1, 1985

By Siddhartha Roy, Hemant Agrawal, Ram Madhab Bhattacharjee, Devi Prasad Mishra

The paper addresses heat stress in underground coal mines, which poses significant threats to miners’ health, safety, and productivity. It involves a comprehensive ventilation survey in three deep and mechanized underground coal mines in India. Using VentSim software, 3D simulation models were developed to predict heat stress conditions and explore the application of auxiliary ventilation and spot coolers to reduce heat stress.

Oct 1, 2023

"One of the major issues that the Rare Earth Elements Mining Industry has to deal with is the legislation vacuum that exists in many countries around the world. Among these, are countries which have long history and tradition in mining. In many cases the lack of direct legislation for REE mine management as well as for other potentially polluting industries can be a barrier to sustainable development. Moreover, the case of lax legislation in China has led to environmental pollution problems and extended smuggling of rare earth elements. This paper looks into the current regulatory status on the mining of REEs, identifies the loopholes and suggests some elements for a new global legislation framework for sustainable development in the REE mining industry. The setting of this regulatory framework will be in line with the present and future challenges of the rare earths market as well as with the policy strategies that are defined internationally. The aim of such a legislative framework will be to strengthen the global rare earth elements supply chain, appease social concerns and ensure the preservation and conservation of the environment. INTRODUCTION The general public received their first introduction to rare earth elements (REEs) in 2010, when the previously inconspicuous commodities became the subjects of front-page headlines. It was when China created a furore in global high-tech markets after imposing an embargo on Japan following a minor marine dispute (Barakos et al. 2015b). Soon enough the Chinese embargo was extended on REE export restrictions all over the world and thus aroused concerns to many countries over potential supply disruptions. The world had suddenly realized that these wonder materials underpin products that they care about. Governmental and industry executives, policymakers and material scientists voiced concerns and conducted numerous reports stating the situation and the risks of a supply crisis. The price spike of 2011 intensified the crisis and the public turmoil, yet the drama did not last for long as the prices declined significantly in 2012. Nevertheless, the world was nonplussed by the fact that China has the total control of the market with more or less the 90% of the global production. More potential entrants became interested, thus initiating an exploration boom during the recent years that has resulted in a significant increase in known global REE reserves that could have potentials for exploitation."

Jan 1, 2016

By Michael M. Kimberley

Gold is sufficiently valuable that concentrations as small as 1 p.p.m. may support low-cost mining. Mindful of this, Sunoco Energy Development Company (Sunedco) obtained fire-assay analyses on some sulfide-rich sandstone encountered during routine drilling. Initial fire-assay values from independent laboratories indicated some significant gold values and independent analysis by atomic-absorption spectroscopy also indicated detectable gold at economically interesting concentrations. Sunoco geologists realized the potential for spurious results inherent in both fire assaying and atomic-absorption spectroscopy. Fire assaying that relies on gold measurement by weight requires perfect separation of gold from all other elements, Imperfect separation may artificially enhance apparent gold concentrations. Atomic-absorption-spectroscopy (AAS) measurements are potentially subject to interferences from other elements. For example, Beamish and Van Loon (1977, p.4) report AAS measurements of 4 p.p.m. Au to be characteristic of completely barren soil samples when samples are prepared by standard dissolution in HC1 to form solutions of about 10,000 p.p.m. total cations (mostly Na, Ca, Mg, Al, and Fe) .

Jan 1, 1981

By Jonisha P. Pollard, F. Nasarwanji, Lydia M. Kocher

This study identifies nonfatal injury incidence rates, nature of injury, work activities, glove usage, and sources of hand and finger injuries in the U.S. mining industry, as reported to the Mine Safety and Health Administration (MSHA) from 2011 to 2017. Hand and finger injuries occur at a rate of 6.53 per 1000 full-time employees, which is nearly double the rate of the next highest affected body part, the back.

Feb 24, 2022

By Jonathan Baggett, Nino Ripepi, Amin Abbasi, Richard Bishop, Juan Monsalve, John Hole

This work focuses on the operational and safety issues associated with karst voids in large opening underground mines. Issues include water inrush, structural instability, and engineering uncertainty in these environments. Coupled with the fracturing prevalent in folded sedimentary rocks, karst voids are complex and challenging ground-control risks. Traditional methods of predicting karst void locations, such as probe drilling, are impeded by the inconsistent spatial distribution and variable sizes of the features as reported by Li et al. (J Rock Mechan Geotech Eng:232–242, 2010) and Hassan et al. (Procedia Chem 19:737–742, 2016). Ground-penetrating radar (GPR) is a geophysical technique that transmits radio waves into a medium and subsequently detects reflected waves via a receiver. The travel time and energy of received signals are then processed and interpreted. The difference in conductivity and dielectric permittivity between limestone and open karst cavities causes strong reflections. GPR is frequently used as a geophysical surveying technique in several industries; however, there is a lack of published research on underground mining GPR applications as reported by Zhao et al. (2015a; Geophys J Int:62–71, 2015b) and Eskelinen and Pellinen (Constr Build Mater:888–898, 2018). The purpose of this work is to demonstrate the use of GPR in an underground stone mine and to discuss the importance of karst void detection ahead of mining.

By William R. Bush

This paper is a presentation of findings based upon an econometric model of the world zinc industry. The model was developed as a simple but useful aid for long-run forecasting and planning purposes. A structure was developed for both simulating real zinc price effects on production and consumption, and for forecasting long-run annual zinc prices and supply/ demand levels. Moreover, a methodology is provided to incorporate the effects of: (1) historic technological advances in zinc supply, and (2) the development of the competitive plastics industry. Finally, reduced form equations are used to generate ex post forecasts to evaluate the model's performance.

Jan 1, 1979

By Wilson W. Zoogah, Joel G. Burken, Abdullah Al Moinee, Mariam K. Al-Lami, Kwame Awuah-Offei

Soil CO2 flux serves a critical indicator of ecosystem function and carbon cycling in disturbed landscapes. This study measured and quantified temporal patterns and environmental drivers of soil respiration across fifteen revegetated treatment plots over a 12-week period (July-October 2025). Utilizing automated CO2 flux measurements, we investigated differences between treatments and quantified their relationships with soil temperature, moisture, and atmospheric pressure. One-way ANOVA revealed significant treatment effects on CO2 flux (F4, 442 =14.1, p < 0.001, η2=0.113), with amended plots exhibiting 40–50% higher mean fluxes than control plots. Weekly temporal analysis demonstrated distinct temporal patterns, with peak fluxes registering in mid-August before a gradual decline. Multiple regression analyses showed that soil temperature (β=0.043, p < 0.001) and moisture (β=2.31, p < 0.001) are the primary flux drivers, together accounting for 18.2% of total variability (adjusted R2=0.182). Atmospheric pressure had a moderate effect (β=1.13, p < 0.001), detectable only in multivariable analysis. Variance partitioning indicated that environmental factors explained more variability (18.7%) than treatment effect (10.5%), with approximately 71% of flux variability attributed to finer spatial or temporal variability. These results demonstrate that revegetation amendments enhance soil biological activity and impact geochemical cycling, and that temperature and moisture are dominant controls on respiration dynamics in reclaimed mine soils. The findings provide quantifiable benchmarks for ecosystem recovery through altering soil biology and geochemistry and for quantifying carbon sequestration potential in post-mining landscapes.

Feb 22, 2026

By Eduardo Pimenta de Melo, Rambabu Pothina, Rajive Ganguli

Sensors are everywhere in the mining industry, with sensor information being used to monitor and operate processes. Therefore, when sensor information is wrong, economic losses can occur. Unfortunately, sensor errors are usually not detected till they become large. This is problematic as most calibrate their sensors no more than once a year (Beamex, n.d.). Using principles of data mining, where all relevant information is tapped to glean hidden information, Pothina [8] designed an algorithm to detect errors in temperature sensors in gold stripping circuit in Pogo mine, Alaska. This paper continued his work by analyzing the behavior of the algorithm on baseline data and testing the algorithm in new data and under more rigorous conditions. It also made a change to the algorithm. The modified algorithm performed very well in the new data. It also worked well under the new error conditions. Three types of errors were seeded, a fixed additive error (+ 2%), a fixed subtractive error (− 2%), and a noisy, normally distributed error, with a mean value of + 2%. Artificially seeded errors were detected within about 20 gold stripping cycles. Inherent bias in operation impacted algorithm performance by increasing the number of cycles needed to detect errors. This paper reinforced Pothina’s [8] conclusion that when data mining approach is used, sensor errors can be detected even when they are pretty low. Significant economic losses can thus be minimized.

By E. Topuz, M. J. McPherson, I. M. Konduri

The research is carried out to investigate the flow mechanics and effectiveness of face ventilation using induction fans, as an effort to provide a more efficient alternative to conventional auxiliary duct or brattice ventilation systems. The induction effects and plume longevity of fluid jets are being studied with the help of a plexi-glass model, using water as the fluid medium and creating a system that is dynamically similar to the flow in mine headings. This scaled model represents a typical 1.5m x 6m x 25m heading connecting to a crosscut. Reynolds Number criteria are used to obtain dynamic similarity of the flow in the designed model to simulate real mining conditions. The role of various parameters such as nozzle position in three dimensions, airway roughness, nozzle geometry, and flow rate in the jet are studied. During the laboratory tests, flow visualization techniques, coupled with still and video photography, were employed to identify the flow patterns. The results indicate that in typical coal mine headings, jet fans can produce effective face ventilation for distance up to 30 meters.

Jan 1, 1995

By Kenneth A. Rogers, Richard F. Hill

Introduction A number of processes for deriving more convenient liquid and gaseous fuels from coal are commercially available or in final stages of development. Generally, synfuels from coal processes have efficiencies ranging from 50 to 70%. Considerable engineering design and development work are necessary to bring forth commercial plants using the various technologies-but technological breakthroughs are not expected or needed. Gasification While a variety of solids handling, gas contacting, and gas quality upgrading techniques may be employed in the various gasification processes, the primary goal is the same-to convert a sulfur-containing solid to an essentially sulfur-free gaseous product. The gaseous product may be a mixture of hydrogen and carbon monoxide with nitrogen. Definitions are not rigorous, but high-Btu gas is generally over 900 Btu/scf(33 534 kJ/m3) and low-Btu gas is generally below 350 Btu/scf(13 041 kJ/m3). Medium or intermediate gas falls between these values. High-Btu production is more difficult, as it requires additional upgrading of a low- or intermediate-Btu gas stream to produce a commercially acceptable product. The carbon/ hydrogen ratio is adjusted either by rejecting a portion of the carbon, increasing the hydrogen, or a combination of both. The chemical processing steps include production processing gas containing carbon oxides and hydrogen by the reaction of carbon and steam (gasification); reaction of hydrogen and coal to form methane (a hydrogasification process); reaction of hydrogen and carbon monoxide to produce methane (methanation); and the removal of impurities. The gasification processes share a number of common techniques. The coal received at the plant site must be further cleaned and crushed or ground before it can enter the gasifier. Conventional cleaning methods are used to remove extraneous materials such as metal, rocks, etc. For some processes the coal must be finely ground so it may be fluidized or entrained in a flowing gas stream. For other processes crushing and sizing only are required. Agglomerating coals may be pretreated by heating, mild oxidation with air, or other procedures to assure smooth gasifier operation and to avoid reactor plugging. Nonagglomerating coals Such as lignite and subbituminous coal normally do not require pretreatment. Feeding a solid material such as coal to a higher pressure reactor is a difficult task. Dry feeders using a series of pressurized lock hoppers, or wet systems in which a slurry is pumped into the reactor, are used. The gasification step is the heart of the process. Here, the solid feed material is contacted with synthesis gas (carbon monoxide and hydrogen). The coal is devolatilized and a portion of the fixed carbon converted to methane. The gas-solids contacting methods used include fixed beds, fluidized beds, moving beds, entrained beds, and free-fall systems. The gasification process, overall, is endothermic and the heat required to maintain reaction rates is usually supplied by burning a portion of the coal feed. External heat sources such as electric resistance heating, molten salt or solid heat carriers, and the introduction of a hot hydrogen stream also have been tested. Following the gasification step the particulate materials and heavy hydrocarbons contained in the reactor effluent are removed by a water quench and solids separation system. If low-Btu gas or synthesis gas is the desired product, the raw gas is scrubbed to remove carbon dioxide and sulfur compounds and then is used directly. However, if high-Btu gas is desired, methanation is necessary. In most gasification processes, the hydrogen content of the gasifier

Jan 2, 1980

By R. L. Weigel

As Florida phosphate mining gradually moves from the Bone Valley formation to the Hawthorn formation, a greater portion of the minable deposit contains dolomitic diluents which result in lower product grades that can be detrimental to the production of phosphoric acid for fertilizer uses. One beneficiation technique found applicable to the phosphate pebble size range (3 X 16 mesh) is heavy media separation using suspensions of magnetite and ferrosilicon. As part of an ongoing investigation of dolomite removal technology, a pilot heavy media cyclone system was constructed by IMC and used in the testing of a variety of drill core composites and hulk samples. The results of these tests were used to develop a predictive model for heavy media cyclone separation based on pebble fraction assays and heavy media operating parameters. This model is currently being used in the evaluation of specific future mining areas.

Jan 1, 1984

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 Z. Jin, D. DePaoli, P. Zhang

"Phosphate beneficiation in Florida generates more than one tonne of phosphatic clay, or slime, per tonne of phosphate rock produced. Since the start of the practice of large-scale washing and desliming for phosphate beneficiation, more than 2 Gt of slime has accumulated, containing approximately 600 Mt of phosphate rock, 600 kt of rare earth elements (REEs) and 80 million kilograms of uranium. The recovery of these valuable elements from the phosphatic clay is one of the most challenging endeavors in mineral processing, because the clay is extremely dilute, with an average solids concentration of 3 percent, and fine in size, with more than 50 percent having particle size smaller than 2 µm, and it contains nearly 50 percent clay minerals as well as large amounts of magnesium, iron and aluminum. With industry support and under funding from the Critical Materials Institute, the Florida Industrial and Phosphate Research Institute in conjunction with the Oak Ridge National Laboratory undertook the task to recover phosphorus, rare earths and uranium from Florida phosphatic clay. This paper presents the results from the preliminary testing of two approaches. The first approach involves three-stage cycloning using cyclones with diameters of 12.4 cm (5 in.), 5.08 cm (2 in.) and 2.54 cm (1 in.), respectively, to remove clay minerals followed by flotation and leaching. The second approach is a two-step leaching process. In the first step, selective leaching was conducted to remove magnesium, thus allowing the production of phosphoric acid suitable for the manufacture of diammonium phosphate (DAP) in the second leaching step. The results showed that multistage cycloning with small cyclones is necessary to remove clay minerals. Selective leaching at about pH 3.2 using sulfuric acid was found to be effective for removing more than 80 percent of magnesium from the feed with minimal loss of phosphorus.IntroductionFlorida phosphate ore, or “matrix,” as it is called locally, contains three different mineral groups that have to be separated from each other: (1) phosphate minerals, (2) clay minerals and (3) quartz, or sand. As mined, the phosphate and sand particles are embedded in compacted mud, or clay-balls. Before separation can begin, all of the particles must be liberated from the matrix of mud. The very first unit operation in the beneficiation process is to disaggregate the various particles. This actually starts while the matrix is flowing through the multimile pipeline from the mine to the beneficiation plant. While in the pipeline, the matrix is exposed to shear forces as it passes through the various centrifugal pumps along the pipeline. These intense shear forces cause a significant percentage of the sand and phosphate particles to be liberated from the clay-balls by the time they arrive at the plant. Once they reach the plant, the first goal is to finish disaggregating the clay, and follow that by making a size separation at 1 mm. This processing is conducted in the washer, consisting of a large rotating trammel screen and a few stages of log washer, screens and hydrocyclones. In all of the currently operating beneficiation plants, the washer is a large structure that receives the matrix, screens it and then discharges a pebble phosphate product sized larger than 1.0 mm and a slurry of liberated clay, sand and phosphate particles that are smaller than 1.0 mm."

Jan 1, 2017

By Paul R. Thomas

This paper addresses two issues affecting the international ferrochromium market as they pertain to the changing pattern of U. S. chromium import dependency. These issues are 1) the long-term ferrochromium production cost differential between the United States and the Republic of South Africa and 2) the ability of Zimbabwe to expand ferrochromium production and exportation. This paper draws upon the data and analyses of a recent Bureau of Mines Minerals availability Program appraisal that evaluated the international availability of chromium in the form of chromite and ferrochromium from 10 market economy countries. South African ferrochromium producers are shown to have a long-term production cost advantage over U.S. producers of $0.03 to $0.04 per pound of contained chromium, in 1981 dollars. Zimbabwean ferrochromium production and exportation are expected to increase in the future. Major expansions of production capacity will be dependent upon alleviating potentially serious constraints in electric power, rail, and port facilities. In the long term, ferrochromium production costs in Zimbabwe are expected to increase faster than the rate of inflation, because as chromite mining from the podiform resources in Zimbabwe decreases, production from the Great Dyke resources will increase.

Jan 1, 1984

By Warnie Flint

According to statistics compiled by the National Safety Council, US Bureau of Mines, American Medical Association, and other agencies, accidental injuries cause more deaths than all the leading diseases. No one is immune to an accident. Probably the best way to describe an accident is to say that it is an unexpected happening. The automobile driver is not expecting a terrifying crash, the electrician does not expect to be electrocuted, nor is the coal miner expecting the roof to fall on him. All personal injuries will not result in death. There is a multitude of victims who are living proof of what accidents can mean to an individual-victims who are blind, paralytic, missing arms, legs, etc. In most instances the earning power of these individuals is gone, and they are utterly dependent upon family or welfare. For many years there seemed to be an attitude that prevailed in industrial America that accidents were inevitable, and that so many fatalities and injuries should be expected. This, of course, was utter nonsense. Since the birth of such organizations as The National Safety Council, American Society of Safety Engineers, and. the US Bureau of Mines, much progress has been made in reducing accidents. The enactment of compensation laws greatly contributed to the progress that has been made. Does this mean that all accidents can be prevented? Unfortunately, it does not. Human psychology indicates that men will work unsafely or perform unsafe acts for the following reasons : 1) Lack of knowledge or skill. 2) Conflicting motivations, such as: (a) to be more comfortable, (b) to save time or effort, (c) to be accepted by a group. 3) Physical or mental condition. Nearly everyone desires his own safety, but not all individuals are willing to do what they know to do to insure their own safety.

Jan 1, 1981

By Richard L. Bullock

OPEN STOPING An open stope is an underground cavity from which the initial ore has been mined. Caving of the opening is prevented (at least temporarily) by support from the unmined ore or waste left in the stope, in the form of pillars, and the stope walls (also called ribs or abutments). In addition to this primary support system of open stoping, some secondary support may also be required using rockbolts, reinforcing rods, split pipes, or shotcrete to stabilize the rock surface immediately adjacent to the opening. The secondary reinforcement procedure does not preclude the method classified as open stoping. There are many forms of open-stope mining used to extract the initial material from a mine. Having once established that the mineral and waste rock are competent enough to use an open-stoping method, and assuming that the reserve is not classified as gassy, the Form which the method will take is primarily determined by the dip and thickness of the reserve. How these two factors affect the selection of the open-stope mining is discussed in a later chapter. At this point it will suffice to say that the classification of the open-stopes mining system which follows is based on whether dry&apos; broken materials flows by gravity or whether it must be moved by nongravity methods where energy must be supplied to move the material. Room-and Pillar-Mining Room-and-pillar mining is an open-stoping method where mining progresses in a nearly horizontal or low angle direction by opening multiple stopes or rooms, leaving solid material to act as pillars to support the vertical load. Since the direction of excavation (angle of dip) is below that which would cause the dry material to flow by gravity to a drawpoint or gathering point, the material must be loaded in the room where it was extracted and transported to a point where it will flow, either by gravity or mechanical means, to a central gathering point to be taken out of the mine. This is an important aspect of room-and-pillar mining which differentiates the system from other open-stope mining methods which rely heavily upon gravity to transport ore from where it was broken to a lower elevation, usually through a drawpoint. There are many variations of the method which go by a number of names in local districts: breast stoping, breast-and-bench stoping, board-and-pillar, stall-and-pillar, and panel-and-pillar are all basically open-stope room-and-pillar mining. In some instances detailed stope planning is almost nonexistent; i.e., the operator simply follows the visual pay values, leaves pillars only where necessary, and tries to locate them in the zones of lower value. This method of mining is as old as the beginning of underground mining itself, dating back thousands of years. Early in the history of mining in this country, the term "gophering" was used to describe this method (Peek 1941). The term is appropriate, for it brings to mind the exact results of this type of system-a random and irregular room-and-pillar mine. In other instances where the mineral values are consistent both in physical dimensions and quality, the mine layout can be planned to the last detail, resulting in a uniform room-and-pillar mine. Coal, trona, gilsonite, potash, oil shale, salt, limestone, and sandstone mines can usually follow such a system. Today, most metal mines using a room-and-pillar operation try to mine as regular a pattern as possible but deviation in height, width, thickness, dip, and grade of the ore results in comparable deviation in the mine plan. Variations of the Room-and-pillar System It is necessary to briefly describe some of the many variations of the room-and-pillar system of mining, enabling the reader to fully explore the concepts and become familiar with the terminology used before going on to the details of mine design. Full-Face Slicing: If in the process of opening the rooms the total vertical extent of the mineral values of the particular seam or strata are extracted from the advance of one vertical face, the term used to describe this is full-face slicing. This face is also known as the "breast." There is no mineral of economic value intentionally left either in the floor or the roof (back) to be mined later. To be able to extract the full-face height in one pass, the mining equipment must obviously be designed to reach as high as the back. In an Appalachian coal mine, this may be all of 660.4 mm (26 in.); for a future oil shale property it might be 15.24 m (50 ft). Normally, however, in a majority of mines where the mining face gets over 6.09 to 6.7 m (20 to 22 ft), the tendency is to divide the face into more than one pass. Over this height, it becomes difficult to properly see and remove loose rock from the back with a hand "mining bar." Where the process of taking down loose rock has become mechanized, higher full-face mining can be safely practiced. Most eastern and midwestern coal seams and western uranium, trona, and potash seams in the United States are easily reached in a single face; many limestone, lead, and zinc mines must resort, at least in part, to "multiple-slicing" to remove all the minerals of value. Multiple Slicing (also known as multiple-pass mining): In many cases it is not practical to carry the full vertical height of the mining horizon as a full face. The face is divided into parts known as the breast, bench, and/or brow. Ideally, if the operator knows the vertical extent of the mineralized zone, he will drill and blast the first pass at the top of the zone, thereby

Jan 1, 1982