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The gases transportation and adsorption in the coal are greatly dependent on the pore-crack parameters, such as the porosity, the pore distribution, as well as the number and size of the pores. What?s more, the pore parameters of the coal are always changing with the temperature. However, the pore characteristics and their changes are extremely difficult to quantify. In this case, Fractal Theory provides a good tool to address this issue. Based on this theory, the pore distribution coupled with the size of the pores can be quantitatively described. In this paper, the equation used to calculate the Fractal Dimension of coal pores was deduced and Mercury Porosimetry was employed to test the pores distributions of coal samples at different temperature. The experimental data excellently verified the Fractal characteristics of coal pores. In addition, the experiments also indicate that the Fractal Dimension of the coal pores linearly increases with the temperature.

Jan 1, 2012

By André Vervoort

The roof behaviour in room and pillar panels during the development of roadways and the subsequent pillar extraction was monitored underground and numerical simulations were conducted. For several underground sites, a satisfactory, correlation was found between underground measurements and three-dimensional numerical simulations using a boundary element code in the linear elastic domain. However, to simulate bed separation, and roof block collapses more complex models were required, of which examples are presented.

Jan 1, 1992

By J. Patrick Powers, Joel Miller, Arthur B. Corwin

A combination of a slurry trench with dewatering successfully controlled groundwater for a large sloped excavation immediately adjacent to the Arkansas River. The Murray Hydro Electric Project required excavation through sand and gravel to bedrock, 85 feet below high water in the River. The perimeter system of deep wells pumping up to 25,000 GPM (1,600 1/sec) lowered the water level to 15 feet (4.6 m) above bedrock. A short soil/bentonite slurry trench near the toe of the slope cut off the residual head. The method cut six weeks from the critical path. Design of the slopes and the dewatering system demanded high safety factors because of risk to existing Lock and Dam No. 7. A localized pocket of soft organic clay was supported by a rock filled bolster. A major flood event was successfully withstood. The method can be applied to large civil excavations and open pit mines.

Jan 1, 1989

By C. DeRossett, K. F. Unrug

Sedimentary rock fractures commonly occur in the vicinity of outcrops. Mine highwalls and highway cuts provide excellent views of these near-surface joint systems. This paper explains the origin, characterization, distribution and extent of the these joint systems with reference to the lithologic composition of the rocks. The practical implications of these joint systems on the operation of a mine are described. Included are discussions of the discontinuous deformation that results from surface subsidence, the stability of mine portals and near-outcrop underground operations, and the stability of highwalls when using highwall miners and strip operations. Some design procedures are recommended to minimize the problems encountered within mining areas having intense joint systems.

Jan 1, 1996

By Y. M. Jiang, R. L. Sanford, D. W. Park

Artificial intelligence has emerged over the past two decades as an important problem-solving tool. Techniques include expert systems, neural networks, free classification, fuzzy logic and genetic algorithm. These methods can be employed to solve rock mechanics and ground-control problems associated with the highly complex nature of rock masses and ground conditions. A current study focuses on the development of an artificial-intelligence system for real-time interpretation of data collected from longwall monitoring stations and on the development of an early warning system for the prediction of undesired conditions and the prevention of longwall-mine instability problems. The successful application of these artificial-intelligence techniques will contribute to a safer and healthier mining environment.

Jan 1, 1997

By R. V. Ramani, R. Srikanth

A three-part study was conducted to relate the dust generation propensity of a coal sample, defined here as the dust generation rate (grams of dust generated per tonne of coal broken), to its characteristics, in order to rank coal seams according to their respirable dust generation potential. In this paper, the results of a single breakage study on a variety of coal samples encompassing all coal ranks, and samples from operating mines are discussed. Further, where data are available, the primary dust generation rates of coal samples collected from underground coal mines are compared with the in-mine dust generation rates. The results of this analysis are then used to apply the results of this study to longwall face ventilation design. Vitrinite reflectance, and level of organic metamorphism are highly correlated with primary respirable dust generation rates of bituminous coal samples. The dust generation rates in underground coal mines are an order of magnitude higher than the primary dust generation rates in the laboratory. Depending on the type of coal, production rates, and dust control procedures, the air quantity required for airborne dust control can vary significantly. The air quantities on some high production longwalls are approaching the limits beyond which it may not be possible to reduce ambient ARD concentrations to less than 2 mg/m3 by dilution ventilation alone. In these cases, the miner's exposure should be controlled through the use of personal protective de- vices and administrative practices.

Jan 1, 1997

By William M. Hartzler

The Powder River Basin (PRB) refers to the coal deposits located in southeastern Montana and the northeastern Wyoming counties of Campbell, Converse, Hot Springs and Sheridian (Wyoming PRB). In 1993, there were 20 active surface mines with 3109 employees in the Wyoming PRB (Annual Report, The State Inspector Of Mines Of Wyoming, 1993). Early PRB production growth was primarily in response to the passage of the Clean Air Act of 1970. The disproportionate growth in Wyoming as compared to Montana can be attributed to the differing coal taxation policies of the two states. The state severance and production taxes were significantly lower in Wyoming. However, Montana passed legislation in 1987 reducing the severance tax rate, substantially narrowing the severance tax gap. Campbell and Converse counties in Wyoming have benefited the most from the production growth in the region. Cyprus Amax's Belle Ayr Mine, south of Gillette, in Campbell County, was the first modern commercial coal mine to be developed.

Jan 1, 1994

By Pedro Marques Bernardo, Carlos Dinis da Gama

This paper presents a methodology for design and simulation of underground ventilation networks, based on the analysis of real situations, followed by the careful interpretation of the obtained results in order to implement their optimization. The method involves two basic steps: the construction of a complete ventilation data base for the mine, upon a series of care- fully previous surveying studies in order to determine the values of its ventilation parameters, and the simulation of relevant situations for the ventilation system optimisation. A simulation model, modified after the Hardy Cross method, allows the testing of various mechanical means located at different points of the network, aiming to determine the technical-economical feasibility of each solution. These simulations obey the directions of air flow in each point of the mine, as determined by the directions of the natural ventilation flow established in the data base that represents the network. The methodology was validated upon studies developed in ventilation network of the Panasqueira Mine (Portugal), in two situations: regular production (mechanical ventilation) and care- maintenance (natural ventilation).

Jan 1, 1997

By J. A. Herbst, C Lo. Y, Z. Rogovin

The identification and quantification of incipient overload conditions in mills have recently been found to be very significant in the design of tumbling grinding mills. To investigate these phenomena, a series of experiments was conducted in a Plexiglas mill operated in both dry and wet modes. For on-stream measurement of the mill charge weight, volumetric filling, dynamic angle of repose, and mill power, an electronic system was developed. The mill was filled to various levels with 19.1-mm (3/4-in.) ceramic balls as grinding media. As feed material, grindable limestone or 3.2-mm (1/8-in.) nongrinding ceramic balls were fed at various steady-state rates to determine the incipient overload conditions. The prediction of overload has apparently been reduced to predicting the feed rate that results in 50% mill filling.

Jan 1, 1988

By R. L. Pozzo, A. S. Malicsi, I. Iwasaki

The electrochemical nature of mineral-grinding media interaction in the wet grinding of one and two sulfide mineral ores was investigated with regard to the flotation behaviors of the minerals. Two iron sulfides (pyrite and pyrrhorite) and mild steel were used to represent the sulfide minerals and the grinding media, respectively. Galvanic currents in two- and three-electrode combinations under abrasive and non abrasive conditions were correlated with the floatabilities of these minerals under corresponding conditions.

Jan 1, 1991

By Glenn P. Jones

Laterization of syenite and other rocks in north Alabama produced material which was picked up and carried by streams to southeast Alabama. These streams deposited the aluminum rich material in the sinkholes of a karst topography developed on the Clayton Limestone. Measurement of the bearing of the long axis of each deposit in the Screamer area, along with plotting the location of these deposits on a map, indicate a depositional pattern controlled by local fractures or solution zones in the Clayton Limestone. The sinkholes and channels dictated the original structure of the deposits. Additional structure changes have resulted since compaction of the deposits by continued solution of the underlying limestone. The original material in these deposits was enriched by the removal of silica to form bausite and bauxitic kaolin during deposition and compaction. Subsequent ground water action has reintroduced silica into the deposit leaving a core of bauxite.

Jan 1, 1972

By H. T. Miller, L. M. Scott

Radiation exposures in Uranium operations may result from external beta-gamma radiation emitted by Uranium and its progeny, internal exposure to alpha and beta radiation due to the inhalation and ingestion of Uranium ores, Radon gas, and Radon progeny in mine, mill, and laboratory atmospheres and from the contamination of environmental working surfaces and clothing by Uranium-bearing compounds and ore. This paper summarizes occupational experience with reference to the exploration, surface mining, underground mining, milling and transport of Uranium by one company in the U.S. and Canada.

Jan 1, 1981

By Rudrajit Mitra, Wesley B. Johnson, Erik C. Westman

The ability to understand stress redistribution within a mine allows greater extraction efficiency with reduced safety concerns. Stress redistribution has been examined at the laboratory scale using ultrasonic tomography and numerical modeling using PFC3D. A data acquisition system was built to obtain tomograms as samples are loaded in uniaxial compression. Limestone samples were loaded to failure. Three-dimensional tomograms of the samples correlate to various stress distributions. The tomograms are compared to analytical and PFC3D results.

Jan 1, 2005

By Alberto Sarmentero

Venezuela, once a world's top gold producer until 1886 Witwatersrand discovery, did let fall its role then because of a serious lack of infrastructure and population, and lately (since World war II times), because of discouraging mining and taxation laws, laying upon an oil prizes bonanza. Recent research leading to estimates of about 5.000 mt. of gold, mainly related to the greenstone belts of the Guiana Precambrian shield outcropping in Venezuela, are opening the scope for both Government and international investing and mining companies, for gold exploration and development projects in the country. This paper overviews Venezuelan Gold mining industry, as seen from the point of view of a participating mining company.

Jan 1, 1989

By I. Michalakis

A geological and geophysical study was con-ducted at the area of Stylos, Hania in order to study the possible mechanisms of saltwater contamination. A new detailed geologic map in scale 1:5,000 was combined with the results of a time lapse geophysical survey using seismic and electrical methods. A fault system in the N-NE direction possibly favors the saltwater intrusion.

Jan 1, 2006

By Donald A. Dahlstrom, Soumitro Nagpal, Timothy Oolman

Bacterial oxidation of a pyrite/ arsenopyritic gold-ore concentrate was carried out with continuous flow operation in 14 liter (1.4x10-2 m3) mechanically agitated reactors. 02 and C02 uptakes were determined at varying residence times. Bacterial concentrations were measured using a protein assay. A sharp optimum in biooxidation rates was observed with increasing steady-state residence times. Growth of the bacteria and biooxidation of the mineral were both shown to be strongly dependent on dissolved 02 levels in the liquor.

Jan 1, 1990

By John K. Kellis, Fazley Azhar

Advancements in AC drive technology offer conveyor designers a viable drive alternative for conveyor systems which require accurate load sharing as well as multiple drive systems. Recently developed AC drives have the ability to accurately control the output torque of AC motor. These AC drives, compared to current DC drives, offer superior performance characteristics while enjoying the benefits of an AC motor. Conveyor applications and case studies incorporating this AC drive technology are presented for review.

Jan 1, 1998

By Hassan El-Shall, Abbas A. Zaman, Brij M. Moudgil

The addition of organic and inorganic dispersants to aqueous suspensions of heterogeneous particles (kaolin) was found to significantly affect the solubility of metal ions from kaolin particles and stability of the dispersion. In most of the industrial applications of kaolin, highly concentrated slurries of controlled stability and fluidity are required. The solubility of kaolin particles in terms of aluminum and silicon ions and its effect on the stability of the slurry was investigated. The main objectives of this study were (1) to study the effect of the extracted metals on the properties and performance of the slurry, (2) to understand the reaction mechanism of dissolution of metals from kaolin, and (3) to understand the interaction mechanism of dispersants with kaolin particles. The controlling variables were dispersant dosage, slurry pH, solids loading, and aging.

Jan 1, 2003

By Liuhuai Ding

Background of Ocean Mining Research Inspired by the 1970?s deep seabed mining activities of other nations, China started ocean mining research work within the framework of the International Law of the Sea Treaty (UNCLOS) and the subsequent establishment of the International Seabed Authority in the 1990?s. This work has been carried out mainly with the cooperation of the Changsha Research Institute of Mining And Metallurgy. We have been committed to this work to fulfill our responsibilities and obligations as a Pioneer investor under UNCLOS and also to support the much needed development of deep-sea technology in China. Exciting recent advances by Nautilus Minerals in the development of seafloor massive sulfide deposit exploitation has led us to a new perspective of ocean mining and some re-evaluation of ocean mining economics. This has provided us with an opportunity to support more efforts in ocean mining research. We will not delay the development of our ocean mining system and corresponding technology, although commercial mining in the deep-sea area may not occur for many years.

Jan 1, 2008

By SAMUEL A. LOLON, ADITYA JUGANDA, JURGEN F. BRUNE, JR. GREGORY E. BOGIN

Historically, there have been many events of mine fires and explosions recorded in the United States and other countries that have demonstrated the existence of explosive methane-air mixtures, herein referred to as explosive gas zones (EGZs) [1]. The risk of mine explosions can increase if these EGZs migrate out from the gob into the surrounding mine entries — a phenomenon known as gob breathing. A number of 3D computational fluid dynamics (CFD) simulations using various magnitudes and periods of barometric pressure variation have indicated that the EGZ outgassing potentially occurs due to lags in pressure, which are strongly influenced by mine conditions and ventilation systems. Early-warning systems with real-time pressure monitoring and the application of gob ventilation boreholes are recommended to detect and mitigate explosion hazards from gob outgassing.