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By Carl Erickson, James Hislop

INTRODUCTION As practiced today, longwall mining is a mechanical version of an established mining system. The equipment for longwall mining consists of four basic units: roof supports, face conveyor, winning or mineral-getting ma¬chine, and stage-loader conveyor. The system mines relatively thin slices of mineral across a predetermined face length in a virtually continuous sequence. As the winning machine cuts, the mineral is loaded automatically onto the face conveyor. In turn, the face conveyor is pushed over into the newly cut track by hydraulic rams attached to the conveyor and the roof supports. The roof supports then are lowered individu¬ally from the roof, advanced to the repositioned con¬veyor, and reset to the roof. At the end of the pass, the longwall cutter is pushed over, and a slice is taken in the opposite direction, so the system repeats itself. Fig. I illustrates a typical longwall mining system. The principle behind the longwall mining system is that the roof is supported only immediately adjacent to the worked seam, keeping the blocks of immediate roof clamped securely from the face to the rear of the sup¬ports. At the rear of the supports, the roof is allowed to fall and break up, with the swell of the broken material eventually establishing an equilibrium in the strata be¬hind the mined area. Fig. 2 illustrates the principle of longwall support. There are two distinct types of longwall mining. The longwall retreating system is the most common in the United States, South Africa, and Australia. The longwall advancing system is the most common in the re¬maining industrialized countries such as Britain, Ger¬many, Poland, and the Soviet Union. The longwall retreating system comprises a mining panel, where the roadways that form the head entry (end at which mineral is delivered from the face con¬veyor to a stage-loader conveyor) and the tail entry are predriven before the longwall units starts production. In the longwall advancing system, the longwall unit makes the head and tail entries as the face advances, utilizing various techniques to prevent the entries from being destroyed as they are left in a consolidating gob area. Fig. 3 illustrates the comparative approaches of the longwall retreating and advancing operations. As with most other underground mining systems, there are many variations on these two basic systems, using combinations of the systems that are dictated by

Jan 1, 1982

By B. DANIEL MARJAVAARA, I. A. SOFIA LARSSON, ANNA-LENA LJUNG

One way to upgrade iron ore is to process it into pellets. The pelletizing process is multifaceted, involving complex fluid dynamics with highly turbulent, high-temperature flow in intricate geometries. This makes it hard to perform measurements during operation, so a useful tool for better process understanding is computational fluid dynamics (CFD), where the challenge is to perform efficient and trustful simulations of complicated problems. A validated simulation model can be valuable for increased process control and development. In this paper, the flow field and coal combustion process in a pilot-scale iron-ore pelletizing kiln is simulated using a CFD model. The objective of this work is to apply a coal combustion model to enable an investigation of thermal effects from the flame on the surrounding flow field.

By P. M. Krishna

A five-year effort by the ASTM subcommittee E10.14 on Uranium Resource Evaluation has culminated in the approval of E901-82, Classification System for Uranium Resources. The standard classification was prepared with participation of representatives from the Dept. of Energy, the Dept. of Interior's Geological Survey and Bureau of Mines, utilities, and consultants. The classification of a resource is based on level of knowledge and the economic producibility of the resource at a given time. Alpha-numeric identifiers are used rather than words to avoid confusion with existing terms, definitions, and classifications. An effort is underway to develop estimation criteria to guide users in classifying a resource according to the above format.

Jan 1, 1983

By I. Meliadis

This study presents the methodology and proposals for the restoration of an abandoned quarry in the Greek island of Milos. The local data (soil, vegetation etc.) of the island were collected, analysed and compiled into thematic maps using Geographical Information Systems. The restoration plan was based on the G.I.S. database and suggested the revegetation of the disturbed lands with herbaceous (grasses and legumes) or woody (shrubs and trees) plants. Plants should be indigenous or from other areas with the same vegetation type. Herbaceous plants establish and grow easily protecting the soil from surface erosion. The revegetation success depends on the seed quality, planting season and methods as well as local environmental conditions. Our proposals aim to restore the abandoned quarry with methods that follow the natural succession of vegetation, have minimal environmental impact, low cost and the expected result will be similar to the surrounding undisturbed land.

Jan 1, 2002

By Ted Budd, Vladimir Goubanov

The East Central Interceptor Sewer, commonly known as the ECIS Project, is the largest public works construction project awarded by the City of Los Angeles. The complexity of this $240 million project, together with the challenge created by the mandated 1,000 calendar days for construction completion, make this project a major interest for the tunneling industry. This paper will describe the ECIS tunnel project, currently under construction by the Joint Venture of Kenny (Sponsor) / Shea / Traylor / Frontier-Kemper. Mining of the18.5 km (about 11 miles) long and 4.7 m (15ft-4in) diameter tunnel is underway with four Tunnel Boring Machines mining at the same time. Details on the mining machines, muck handling systems, innovative construction sequence, together with mining progress will be given.

Jan 1, 2003

By Robert Stefanko

Longwall mining appears very attractive from an engineering standpoint because of its simplicity. The use of one long, continuous face can simplify power distribution, ventilation, and supervision, and minimizes or prevents lost time associated with the tramming of equipment in room-and-pillar systems. Since the longwall system is more amenable to automation, it is inherently safer than room and pillar. Remote control of all face equipment from gate roads will obviate the exposure of men in the face area. Considering what has been said, it seems a paradox that more longwall installations are not found in the United States. However, with favorable mining conditions in relatively level seams of adequate height under shallow cover, it has been possible to develop highly productive, mechanized, room-and-pillar systems. Thus there has been no real incentive to employ longwall in the United States. In Europe, mining companies usually have very little choice between the two systems. Pitching seams of low height located at great depth dictate the use of longwall methods. With depletion of its readily accessible reserves, mining conditions will be similar to those now prevailing in Europe, and an increase in the use of longwall in the United States can be anticipated.

Jan 1, 1963

By Byron C. Hardinge, E. R. Palowitch, Albert W. Deurbrouck, David J. Akers, Edward R. Torak

During 1983, 42.2% of the 686.0 (624.3 Mt) million tons of coal reported, 289.6 (263.5 Mt) million tons were mechanically cleaned, of which 107 (97.4 Mt) million tons were cleaned by dense media (magnetite and sand) processes.' The percentage of bituminous coal and lignite cleaned mechanically by dense medium processes increased from 7 to 38% between 1938 and 1983. The Electric Power Research Institute estimates that 150 million tons (137 Mt) of coal were cleaned by heavy-media processes in 1986, and that this number may increase to 265 million tons (241 Mt) by 1990.2 Dense medium separations include those coal preparation processes that clean raw coal by immersing it in a fluid having a density intermediate between clean coal and reject. As there is a general correlation between ash content and specific gravity, it is possible to achieve the required degree of removal of ash-forming impurities from a raw coal by regulating the specific gravity of the separating fluid. Dense medium processes generally offer the following advantages over other coal cleaning processes: • Ability to make sharp separations at any specific gravity within the range normally required even in the presence of high percentages of raw coal whose specific gravity is near the specific gravity of separation. • Ability to maintain a separating gravity that can be controlled within + 0.005 sp gr units. • Ability to handle a wide range of coal sizes. • Ability to change specific gravity of separation to meet varying market requirements. • Ability to handle fluctuations in feed, in terms of both quantity and quality. Unfortunately, dense medium processes can have the following disadvantages: • Relatively high capital costs caused primarily by the need for equipment to collect and recycle the medium. Relatively high operating costs caused primarily by operation of medium recycle equipment and loss of medium.

Jan 1, 1991

By S. D. Michaelson

Open pits and quarries are the major sources of all "hard rock" tonnage mined today. Normally, ore is fractured from the pit face by blasting and then truck-hauled to a primary crusher where processing begins; over- burden (or waste) is generally truck-hauled from the pit to dump areas. Truck haulage of blasted ore and overburden accounts for some 25 to 50 percent of total mining costs in a typical open pit and commonly is the largest single cost factor. Obviously then, cost reduction efforts should properly focus on improving existing haulage systems and developing new breakthrough techniques for material transport. Continuous flow systems for large tonnages ordinarily will result in a lower cost than batch systems such as truck or rail haulage. Continuous flow with pipelines for liquids and slurries, or conveyors for medium to coarse dry materials (in the -8 in. range) are the accepted economic answers for bulk materials handling over reasonable distances.

Jan 1, 1968

By Patrick Shea

Old mine workings are found throughout the Western United Sates on lands administered by the U.S. Bureau of Land Management, U.S. Forest Service and private lands. Some of these mine workings date back to the late 1800s. There may be as many as 100,000 sites on lands administered by the National Park Service, U.S. Forest Service and Bureau of Land Management. The U.S. Department of the Interior has worked with the U.S. Geological Survey, the U.S. Forest Service, the U.S. Environmental Protection Agency, and western state governments to identify and prioritize these sites on Bureau of Land Management, National Park Service and U.S. Forest Service administered lands. This presentation will discuss the accomplishments we have made to date to clean up inactive and abandoned mine sites, focusing primarily on lands administered by the Bureau of Land Management.

Jan 1, 2000

By Raúl Castro, René Gómez

In underground mining, rock fragment size is a key variable for productivity because it impacts equipment selection and mining structure design. This study characterizes granular material fragmentation during its flow to understand its characteristics and mechanisms. Tests were conducted using a laboratory setup to emulate various heights where material is drawn. The fragment-size distribution was measured before and after tests for clay, concrete fragments, and gravel. Results showed that fragmentation mainly occurs in minor sizes, with significant increases in fine material as travel distance increases.

Jan 10, 2022

By M. Dayne Aldridge

A discussion of the definition of automation in mine ventilation applications is presented. The results of theoretical studies, experiments and practical experience from work in the United Kingdom, Belgium, Poland, the Soviet Union and the United States are summarized. Conclusions are drawn from these efforts and the prospects for the future development of automatic mine ventilation systems are explored.

Jan 1, 1978

By Orris C. Herfindahl

Every few years we are treated to a battle over trade policy when the Reciprocal Trade Agreements Act comes up for consideration. In 1962 it is especially appropriate to consider the problem of mineral import -policy and the closely related problem of general import policy, for this year's struggle is different from those of the past in two ways. First, proposals have been made which are a substantial departure from past trade agreements legislation, and second, the formation and growth of the Europe Economic is Community may have an important bearing on the kind of legislation that is adopted. But this anticipates what is to come later. My task is to examine the problem of mineral import policy, although we shall find soon enough that general trade policy must be considered in order to get an indication of what is in store for minerals.

Jan 1, 1962

By Ashish Kumar, Khadija Said, Ulupi Mishra, Sekhar Bhattacharyya

Using battery-powered equipment in underground mining can improve safety, advance automation, and reduce greenhouse emissions. In this context, rechargeable lithium- ion batteries (LIBs) have a competitive edge due to their high Coulombic efficiency, superior energy density, and extended cycling stability. However, several conditions must be met for their safe operation. Their failure can cause thermal runaway (TR), which poses a significant safety risk in underground mines. Despite studies having investigated this phenomenon using physics-based models, limited research has used deep learning to predict its implications. This study aims to bridge this gap by characterizing LIB TR under dynamic airflow through simulations and predicting temperatures using two of the most common recurrent neural networks: long short-term memory (LSTM) and gated recurrent units (GRU).

Feb 22, 2026

By George D. Brunton

The past and present argillaceous rock studies for the U.S. National Waste Terminal Storage Program consist of: (1) evaluation of the geological characteristics of several wide- spread argillaceous formations in the United States; (2) laboratory studies of the physical and chemical properties of selected argillaceous rock samples; and (3) two full-scale in situ surface heater experiments that simulate the emplacement of heat-generating radioactive waste in argillaceous rock.

Jan 1, 1981

By James Wm. White

Calculation of consistent steady-state mass balances in operating metallurgical plants and pilot plants is of interest for many reasons. In general, enough data can - and should - be collected to overdefine the system, i.e., permit calculation of nonmeasured quantities via more than one path. In such cases, resulting steady-state metallurgical mass balances rarely close due to sampling, analysis and/ or instrument error. Indeed, determination of a valid calculational sequence for complicated process flowsheets with multiple recycle streams can prove quite difficult. Here we present and discuss a method that has proven useful in analysis of numerous grinding circuit flowsheets of varying-degrees of complexity our technique requires only a consistent process flowsheet with appropriate associated data and arbitrary numbering of streams and equipments. Process topology and user data are decoded to yield a set of "search" or base variables and a set of "calculated" variables in solids, water, particle size and splitter parameter space. This procedure greatly speeds subsequent actual mass balance adjustment calculations since perturing certain variables (e.g., a solids value) does not require recalculation of other variables (e.g., the water balance). Finally, internal search and calculated variables are back converted to User units and used in a Sum-of-Squares criterion. Global minimization of this performance functional then yields a consistent mass balance in a least, squares sense. Weighting factors of choice can be used. Examples illustrate application of these methods.

Jan 1, 1979

By R. Bhaskar

The results of an experimental study on the dispersion and deposition characteristics of fine coal dust in mine airways are presented. Experiments were conducted at various flow velocities using bituminous and semi-anthracite-coal dust which had a large proportion of dust in the respirable size range. Cross sectional variations in the concentration of dust at various points in the airway were also measured. Instruments used in the experiments included gravimetric samplers and impactors. Concentration measurements were made both for the respirable and total airborne dust. The experimental design, sampling procedures and results are discussed. The study is aimed at providing a better understanding of the temporal and spatial behavior of dust particles in underground mine airways.

Jan 1, 1986

By Gabriele Eccher, Michele Caponero, Paolo Cucino, Roberto D’Angelis

"This paper describes the optic fiber structural monitoring system implemented for Pavoncelli Bis tunnel. The paper highlights the optic fiber sensors customization capabilities, how they smoothly fit precast concrete lining processes and TBM operations, and how a lifelong service monitoring can be achieved. An overview of readings’ evolution during excavation concludes the paper.INTRODUCTIONPavoncelli Bis is a 10 km hydraulic tunnel designed to by-pass the existing Pavoncelli tunnel which experienced severe damages during the 1980 Irpino-Lucano earthquake, in south of Italy (Barla 2009). Pavoncelli Bis excavation work commenced in 1988-90, however, when excavation approached pk. 0+583 in 1992, water percolations became more and more consistent and resulted in work suspension. The tunnel was eventually sealed at pk. 0+383, leaving a flooded section between pk. 0.383 and pk. 0+583. Work resumed in 2012 where EPB-TBM excavation was adopted to cross the flooded section and to overcome complex hydro-geological conditions in various lito-types and, in particular, in the Varicolori Clay-shales area (Figure 1).Consequently, stress evolution monitoring is extremely important during construction and during the service life of tunnel lining in clay-shales and in faults areas. In particular, the paper focuses on the monitoring system proposed for the newly EPB-TBM excavated portion from pk 0+583 onwards where optic fiber sensing technology was chosen for its reading stability and reliability in presence of water and its ability to be connected in series and remotely interrogated at kilometers of distance. FBGS OPTICAL FIBER SENSOR TECHNOLOGYFiber Bragg Grating Sensors (FBGS) are gaining increasing attention in the field of experimental stress analysis. Basically, Fiber Optic Bragg Sensors are strain-measuring devices and therefore provide many of the advantages of the well-known metal foil strain gages (Kreuzer 2007).Bragg gratings are written into so called single-mode fibers. These fibers consist of a very small inner core of 4 to 9 µm diameter and an outer part (cladding) of pure glass (SiO2) of 125 µm diameter. The difference of refraction indexes between inner core and cladding causes the light to propagate only inside the small core."

Jan 1, 2016

By F. Arslan

Gold extraction from refractory ores is still a problem. Gold losses in the cyanidation process are mainly due to the presence of sulfides and carbonaceous materials. Oxidation of carbon and sulfide minerals by sodium hypochlorite is a possible method to render the ore amenable to cyanidation, and earlier work by the USBM indicates that electrochemical generation of hypochlorite is promising. Laboratory work was carried out on the oxidation of pyrite and carbon in an electrochemical cell with a sodium chloride electrolyte. The results of preliminary tests are discussed in relation to the mechanism of electrooxidation of refractory gold ores and the estimation of current efficiency.

Jan 1, 1991

By KOKOWSKI J., RUDZIŃSKI Ł.

The LUMINEOS network was established in 2013 to monitor mining-induced seismicity in Legnica-Głogów Copper District (LGCD), located in south-western Poland. Since the starting time, the network was improved and today consists of 17 seismometers and 10 accelerometers. Up to now, the strongest recorded earthquake in the region had Mw4.0. Both raw seismic data and earthquakes catalog for events recorded by the LUMINEOS network are fully open and available on the EPISODES platform (https://tcs.ah-epos.eu/#episode:LGCD). During the last 7 years, the network improvements gave us a possibility to increase location accuracy for shallow mining events. This accuracy is influenced by factors such as the configuration of seismic stations, noise level at seismic stations, and the influence of the velocity model. Here we encountered two main issues which are worth to discuss. The first one is the low detection threshold of two seismic stations and their significant impact on the location errors. The second one is the large uncertainty in the S-wave picking. Even though S-waves are not so clearly visible on seismograms, they are very helpful in the estimation of source location and strength of seismic events in the region. In our work, we present the history of LUMINEOS network and corresponding improvement on location accuracy as well as the influence of noisy stations on the error distribution and how it is connected with location results. We also investigate the effect of the S-wave phases and how they are related to the accuracy of the earthquakes locations in the network.

Apr 26, 2022

By G. F. Joklik

Although the mineral shortages of twelve to eighteen months ago have given way to oversupply, their memory lingers on. These problems were man-made: booming demand throughout the industrial world, political and industrial unrest and the oil embargo all contributed. But in the minds of many, the shortages conjured up visions of the depletion of the world's mineral resources, a disaster that could be staved off only by drastic curbs on consumption and therefore, curbs on economic growth. A little historical research shows that fears such as this are not inventions of the 1970's. A hundred years ago, for example, the imminent exhaustion of the world's coal supplies was being predicted in Great Britain. The English economist, John Stuart Mill, who was usually more perceptive, wrote a few years earlier that "it is only in the backward countries of the world that increased production is still an important object". And later there was Franklin Roosevelt who said in 1932, "Our industrial plant is built; the problem just now is whether under existing conditions, it is not overbuilt". His concern, in other words, was not with the discovery and exploitation of new natural resources, but with the administration of known resources and with seeking foreign markets for surplus production. In light of copper prices at the time -- just under 6¢ a pound -- that was understandable. These instances illustrate how, throughout the world's industrial history, concern about surpluses of raw materials has alternated with alarm about the adequacy of supplies and with calls for restricting growth.

Jan 1, 1975