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By J. A. Oraniscak

Longwall mining operations continue to increase extraction rates and the potential to generate higher amounts of airborne respirable dust (ARD). The National Institute for Occupational Safety and Health (NIOSH) has gathered data from underground longwall surveys and laboratory crushing tests to identify the important factors influencing the amount of ARD levels generated. Coal-seam characteristics, operational parameters (i.e.,cut sequence, mining height, etc.), extraction rates and dust-control parameters (i.e., airflow, water flow, etc.) were examined to determine their influence on ARD levels measured at longwalls during actual mining operations. ARD generated by a laboratory crusher while crushing bituminous coal samples collected from underground longwalls was also examined to determine if there were cor relations with coal-seam properties. Results from the longwall and laboratory data collected indicated that low-ash, high-volatile coals (low moist fuel ratio or MFR coals) generate higher amounts of ARD. It was found that face ventilation and water application to the coal product are essential elements to controlling longwall ARD levels.

Jan 1, 2000

By J. A. McKeown, B. M. Sanders, A. Dadgar, R. H. Sergent

This paper describes the leaching of gold with Geobrom® 3400 from a very rich (6.2 kg/tonne) black sand concentrate and its subsequent recovery by ion exchange resins and solvent extraction. The dissolution of gold from black sand ranged from 94 to 96%. Gold loadings and recoveries of nearly 100% were achieved by both ion exchange and solvent extraction methods. The kinetics and equilibrium of loading gold onto ion exchange resins and its elution from the resin were studied. The commercial ion exchange resins PAZ®- 4, DOVEX®- 21K, and Amberlite® XAD- 7, and Great Lakes Chemical experimental GLR-30 were evaluated in this work. Diethylene glycol dibutyl ether was used in all the solvent extraction work for gold recovery from Geobrom leach solution. The consumption of Geobrom was about 130 kg per tonne of the concentrate processed. Therefore, the cost of lixiviant to extract 3.11 x l0-2 kg of gold from the black sand was only about $1.00. Based on the electrochemical regeneration of bromine, the economics of bromine process vs. cyanidation were investigated.

Jan 1, 1990

By D. Dolinar, T. P. Mucho

Horizontal stresses are caused by global platetectonic forces. During 1995 alone they were largely responsible for the closing of two longwall mines in the United States. This paper presents six case histories from Pennsylvania, West Virginia, Kentucky and Alabama. In each case, a mine encountered roof falls or difficult ground conditions at the headgate caused by horizontal-stress concentrations. The problems are detailed, and the control measures adopted are described. In most cases, nearby longwall panels without stress concentrations were trouble free. The paper also discusses detailed measurements that were made at two adjacent Pennsylvania longwalls. One headgate was oriented to avoid a horizontal-stress concentration, and the other was not. Eliminating the stress concentration dramatically reduced roof support loads and roof deformation. The paper concludes that proper panel orientation and sequence is the key to maintaining headgate ground control. The optimum orientation is not parallel to the maximum horizontal stress, as previously thought, but rather it is 20o in the stress shadow of the gob. Other stress-control techniques, including artificial support, are briefly discussed

Jan 1, 1999

By Noris Del Be1 Belluz

Drilling underground in the Grasberg dewatering drifts has routinely hit water aquifers with high flow rates and pressures. Two types of holes are used. Pilot holes probe ahead of the tunnel development to intersect aquifers ahead of the face. And dewatering holes dewater rock formations that will drain water from the Grasberg pit and allow tunnel development to proceed safely. Recently, static pressures of >8.3 MPa (> 1,200 psi) have been recorded with flows from a 100 mm (4 in.) HQ core hole measured at 5,700 L/min (1,500 gpm). The waterflows can be slightly acidic, necessitating the use of stainless-steel collar gear to resist corrosion. These rates were anticipated and contingencies were planned early on to deal with these conditions. PT Freeport Indonesia (PTFI) established procedures to maintain the safety of the drill crews, to enable coring of the rock, and to maintain the safety of the miners driving the drifts. The collar gear controls the waterflows because these drill holes are a vital source of water for the concentrator.

Jan 1, 1998

By Arafat Ghosheh, Yousuf Abu-Rish, Darwish Amara, Mohammed Baderkhan

The Jordan Phosphate Mines Company is one of the world's major phosphate rock and phosphatic fertilizers producers (the second largest phosphate rock exporter), with ore reserves exceeding 2 billion tonnes, mainly located in the Eshidiya area. The Eshidiya phosphate deposits, 120 km north-east of Aqaba, are of sedimentary origin (as are all phosphate ore in Jordan). Three exploitable beds (Al, A2, and A3) with variable content of P205, CaO, SiO2, etc., are processed in order to produce 68-70,73-75, and 75-77% TCP grades. The A3 bed, which is characterized as the most siliceous containing 40-48% TCP, requires physical beneficiation using wet scrubbing, screening, and desliming by hydrocylone, followed by anionic conventional flotation to achieve 75- 77% TCP grade. For the last 15 years extensive laboratory and pilot tests (including physical, chemical, and mineralogical studies) were carried out. After operating the industrial plant, certain modifications were deemed necessary to adjust the operational parameters and the final flowsheet, which was followed to obtain the targeted quantity and quality of concentrate.

Jan 1, 1999

By [Miroslaw] M. Hajdasinski

The Payback Period (PBP) is one of the most widely applied project evaluation criteria 'in the mineral industry. As much as this criterion is liked by practitioners, it is also criticized by academicians who seriously question its validity. Inspired by this criticism, the author of this paper examines the classical definition of the PBP criterion, and formulates a new one designed for both investment and borrowing projects. It is demonstrated that the PBP, in its revised version, is free from all the shortcommings of the old one, and is fully compatible with the Net Present Value (NPV) criterion, as well as with all the other NPV compatible project evaluation criteria. Since the traditional approach to the comparison of mutually exclusive projects (MEP1s) by means of the PBP criterion has been incorrect, the paper also outlines the correct approach to this problem. Finally, owing to the fact that the PBP depends on the assumed interest rate, and using a specially developed computer program, the PBP is graphically presented, in six numerical examples, as a function of the interest rate.

Jan 1, 1989

By R. J. Sweigard, R. V. Ramani

The effects of postmining land use planning are addressed in this paper. These effects may include savings in reclamation costs and increased value of reclaimed land. However, this may result in greater planning costs and possible delays in production. Therefore, an economic analysis was undertaken in an effort to determine the importance of each potential result and to quantify the overall economic impact of postmining land use planning. A discounted cash flow analysis was performed using a surface mine cost model to analyze the sensitivity of selling price to changes in various postmining land use planning parameters. As a result of this analysis, it was determined that the profitability of a project is most sensitive to delays in production, particularly if the delay occurs after major investments have been made. Many methods have been proposed for evaluating postmining land use alternatives (Sweigard and Ramani, 1981). Both quantitative methods, such as benefit-cost analysis (Brock and Brooks, 1968), and nonquantitative methods have been proposed. The application of one specific analytical method is pursued in this paper.

Jan 1, 1988

By R. E. Johnson, J. E. Dutrizac, B. R. Palmer

Silver sulphide (acanthite) and lead sulphide (galena) dissolve relatively rapidly in FeCl3 media with the formation of elemental sulphur and soluble silver and lead chlorides. Parabolic kinetics are observed, and the leaching rates are controlled by the outward diffusion of the AgCl and PbCl2 reaction products through the constantly thickening elemental sulphur layer formed on the sulphide. Hence, both leaching rates are strongly dependent on those variables which affect the solubility of AgCl or PbCl2 at the reaction interface. The rates therefore increase with increasing temperature and total chloride ion concentration, but decrease in the presence of elevated concentrations of AgCl or PbCl2. By contrast, neither sulphide is significantly attacked by ferric sulphate media, even at high Eh values. Although the reasons for the refractory behaviour of Ag2S in sulphate media remain unknown, the low rate of PbS attack is attributable to the passivating layer of PbSO4 and elemental sulphur formed on the surface of the galena.

Jan 1, 1993

By M. T. Holroyd

Digital computer applications to minerals exploration remained largely an experimental alternative to manual techniques until well into the 1960's. Due to the high cost of computer time, and the lack of digital data and appropriate software, the most favoured applications in the early days were computationally intense tasks - those which produced the most results with the least demands for programing and data input, e.g. forward modeling. When large digitisers and plotters became affordable, the computer took over simple labour intensive tasks such as data transcription, and when software caught up, more complex tasks such as contouring. Digital data acquisition systems and superminicomputers made total computerisation of geophysical compilation and cartography possible and affordable. Applications continued to develop into areas of much greater logical complexity. Software, the new labour intensive process, still lagged behind. The microcomputer made computer applications potentially available everywhere to everyone. Desk-top micros as powerful as the minis of ten years ago can take on any geophysical exploration task currently done by computer - when the software becomes available.

Jan 1, 1989

By C. A. Pickles, S. J. Splinter

Silicon oxynitride, Si2N20, has many of the intrinsic properties of a potential high temperature engineering ceramic material. Some of these properties are similar to those of silicon nitride, which has been more intensively studied. However, although silicon nitride ceramics are approaching a state of microstructural refinement for various engineering applications, silicon oxynitride has received little attention. This has been mainly due to a lack of an economical and reproducible method of producing pure crystalline Si2N2O. Several reports exist on the preparation of crystalline Si2N2O from SiO2 and Si3N4, yet very little kinetic data exist. Even less is known about the carbothermic reduction of SiO2 in a nitrogen atmosphere to produce Si2N2O. In this paper, a review of the properties and methods of preparing silicon oxynitride will be presented. In addition, results obtained by reactively sintering SiO2 and Si3N4 will be discussed. The overall reaction is as follows:

Jan 1, 1990

By M. Charles Gilbert

Basement rocks in southern Oklahoma are divided into two groups. One group is the Lower Cambrian Wichita Igneous Province, a diverse igneous suite that crops out in the western Arbuckle Mountains and in the Wichita Mountains. These largely bimodal igneous rocks were emplaced in an intracratonic-rift environment. The other group, the older, is a set of Precambrian rocks of the Eastern Arbuckle Province, yielding ages between 1,350 and 1,400 Ma, exposed in the core of the eastern Arbuckle Mountains. These are deeply eroded mesozonal granitic rocks and associated granitic gneisses cut by numerous dikes ranging in composition from diabase to rhyolite. The southern Oklahoma igneous rocks have long been utilized mostly as dimension and crushed stone. Most of the early quarries were in granite of various red hues for monuments and facing stones. Large crushed-stone quarries are now exploiting both granite and rhyolite, which is used chiefly as aggregate and railroad ballast. The exposed basement rocks in Oklahoma represent an underdeveloped and accessible resource.

Jan 1, 1999

By S. Triantafyllidis

The tailings produced from the Kirki (Agios Filippos) high sulfidation epithermal deposit processing plant are laminated, weakly cemented and their particle size ranges from fine sand to fine silt. They are mainly composed of milling residues of gangue (quartz, dickite/kaolinite, pyrophyllite, illite); sulfides and secondary minerals (jarosite group minerals, butlerite, anglesite, beudantite and gypsum) are present to a lesser extent. They have high Pb and Zn (average 0.75 % and 0.57 % respectively) and low S (1.04 to 2.92 %), Cu, As, Cd, Ni and Sb content (average 248, 163, 59, 27, 20 g/t respectively). Stagnant waters forming small ponds on the surface of the impoundments exhibit low pH and high heavy metal and sulfate concentrations. Negative Net Neutralization Potential (NNP) characterizes the tailings, indicating moderate to high potential for acid generation. Application of the TCLP test revealed that the tailings are characterized as toxic because of the increased solubility of Pb and Cd. On the other hand, As TCLP solubility is very low.

Jan 1, 2006

By Curtis A. Pledger, H. Lee Wimmer, I. Michael Gowring

The Upper Diamond Fork Project, as part of the Central Utah Project Completion Act, conveys water six miles from the existing Sixth Water Aqueduct to the Diamond Fork Pipeline. During design, a Value Engineering team proposed a single-tunnel alignment that would be less destructive on the environment and might have a lower life cycle cost than the proposed design of two tunnels connected by two pipelines on steep hillsides. A decision was made to include this option in the bid process as a design-build alternative. The bid for this option was the lowest and a contract was awarded. During the TBM excavation a segment of tunnel wall caved in containing large quantities of water saturated with extremely high levels of hydrogen sul?de (H2S)gas (measured at 380 to 520 ppm in the air). The Central Utah Water Conservancy District (District) in consultation with Obayashi/Clyde (Contractor) quickly developed anew plan to finish the system by incorporating parts of the original tunnel/pipeline concept and re-bid the remainder of the project as a Phase 2 Design-Build contract.

Jan 1, 2003

By Biao Qiu

Longwall and/or room-and-pillar mining operations in multiple coal seams could not only induce subsurface and surface subsidence but also cause interactions between these mined coal seams. The interaction might destabilize mine structures and subsequently induce additional strata movements. Mechanical models to utilize the predicted subsurface deformations to assess the interactions and the consequences have been developed. The models are incorporated into a computer program, CISPM-MS, for predicting the final surface movements and deformations as well as the mining interactions associated with multi-seam coal mining operations. It predicts final surface movements and deformations caused by the individual mining operations and by the interactive effects. The program can also be used to assess mine structural stability in multi-seam mining operations. The paper presents the developed interaction models and their application in surface subsidence prediction caused by multi-seam mining operations. A case study involving mining in two coal seams, using longwall and room-and-pillar mining methods, respectively, will be used to validate the program.

Jan 1, 2013

By Dell H. Adams

Coal exploration may be defined as the acquisition of data necessary to define and acquire a block of coal which can be mined at a profit. Unlike ore minerals, coal resources are widespread and relatively abundant with supply exceeding demand in almost every case. Thus simple discovery of coal is generally not enough. The chemical and physical variability of individual coal seams, the capital intensive nature of coal mine development, and the changing patterns of utilization require that a multiphase, three-dimensional evaluation be made of each potential reserve. Factors which must be investigated include not only the quantity and quality of the coal but also the geologic, hydrologic, and engineering characteristics of the seam and its surrounding strata. Acquisition of property to provide a secure base for exploration and mine development is equal in importance to the geologic and engineering programs. The successful development of a coal reserve requires that control of coal and, in the case of a strip mine, the surface be in the form of contiguous blocks of sufficient size to support mining.

Jan 1, 1981

By Richard E. Gray

Virtually all structures show some signs of distress due to deterioration of the building components, to changed loads, or to changed support conditions. Changed support conditions result from ground movements. In mining regions many cases of structural distress are attributed to mining without considering alternative causes. This is particularly true of coal mining since it occurs under extensive areas. Coal mining is estimated to have already undermined more than eight million acres and may eventually undermine 40 million acres in the United States (HRB Singer, Inc., 1977). Other nonmetal and metal underground mines impact much smaller areas. Although it is sometimes difficult, even with careful study, to identify the actual cause of damage, persons responsible for underground coal mining should at least be aware of possible causes of building stress other than mine subsidence. This paper presents information on distress to structures and briefly reviews a number of causes of ground movements other than subsidence: Mass movements, dissolution, erosion, frost action, shrinking and swelling, yield into excavations and compressibility

Jan 1, 1986

By William H. Bird

Over the past 14 years, the efforts of 2 companies and several individuals have outlined a major solfataric gold ore body in the Summitville district in the southeast San Juan Mountains of Colorado. The hard work of these years could not have flowered without a dedication to modern exploration methods, an intense interest in new theories of ore genesis, and a relentless discontent with the accepted geology of the Summitville area. To set the stage for this discovery period, it must be noted that it began 100 years after gold was first found at Summitville. It was the height of the "porphyry copper" era and gold was still not a part of the explorationists' portfolio. It was also a time of great intellectual stimulation. Theories were rapidly developing to relate different types of ore deposition and to place ore genesis within the fabric of plate tectonics. Summitville itself had just been linked to the newly discovered Platoro caldera complex and the Platoro lineament. This in turn related Summitville to the other San Juan volcanic field caldera ore deposits.

Jan 1, 1990

By Frederick K. A1lgaier

The Bureau of Mines' Denver Research Center initiated a subsidence research program in 1978. The short ten goals of the program were to determine practical methods and equipment for measuring subsidence and demonstrate these methods by monitoring subsidence at several mines having mining, geologic and topographic variables typical of those encountered in the western United States. Data from the monitoring program would be supplied to cooperating mining companies and used by the Bureau to accomplish the long term objective of developing and validating subsidence prediction techniques applicable to mines in the West. Subsidence monitoring is being conducted at five mines in Colorado and Utah with substantially different mine plans, mining methods, depths of cover, and topography. The monitoring procedures used at each site are similar and include designing the monitoring network layout, installing the subsidence monuments, initial and periodic surveying of the monuments, and processing the survey data. The network layout, surveying methods, and types of monuments vary according to the conditions at the individual sites and the type of data being collected.

Jan 1, 1982

By Robert J. Whiteley, Colin Parker

Two major tunnel projects with a combined value of about $US700 million have been recently completed in Sydney using both soft ground and hard rock Tunnel Boring Machines. The first of these and the main entry in Australia for the Year 2000 Olympics was the New Southern Railway. This is 10 km of mainly soft ground tunnel linking the Sydney’s International Airport with the Central Business District. The second tunnel was designed to alleviate major stormwater pollution of Sydney Harbour and involved construction of the Northside Storage Tunnel. This is19 km of hard rock tunnel at depths exceeding 90 m that connects many of the northern Sydney suburbs of Sydney with the North Head Ocean Outfall. Case studies of these projects describe the use of innovative geophysical technologies comprising gravity and seismic tomographic imaging with geotechnical testing at the feasibility and design stages. This approach minimised construction and financial risk by effectively quantifying the significant geological and hydrogeological issues along these tunnel routes that exerted major controls on these projects.

Jan 1, 2001

By Dennis S. Kostick

Introduction Soda ash is known chemically as sodium carbonate, an important inorganic chemical. It has been produced for several centuries by processing certain vegetation and minerals. The US soda ash industry has evolved from several small sodium carbonate mining operations in the West. Now, a nucleus of six companies produce about one-fourth of the world's annual soda ash output US producers currently dominate the world market. But certain international events are occurring that will reshape the domestic soda ash industry in the next decade. Historical perspective Soda ash is used mainly in the manufacture of glass, soap, dyes and pigments, textiles, and other chemical preparations. All of these are the first basic consumer products produced by developing societies. About 3500 BC, the Egyptians became the first society to use crude soda ash. The soda ash was used to make glass containers. It was most likely obtained from dried mineral incrustations around alkaline lakes. Soda deposits were virtually nonexistent in western Europe. So people resorted to burning seaweed to obtain the ashes. The ashes were then leached with hot water and the solute was recovered after evaporating the solution to dryness. The solute, a crude "soda ash" was impure. But, it could be used to make glass and soap. These two products and industries were important to the population and economic growth of the region. About 11.5 t (13 st) of seaweed ash was required to produce about 0.9 t (1 st) of soda ash. Along the coasts of England, France, and Spain, seaweeds with varying alkali contents became important items of commerce and sources of soda ash before the 18th century. The LeBlanc process used salt, sulfuric acid, coal, and limestone. It became the major method of production from about 1823 to 1885. In the early 1860s, Ernest and Alfred Solvay, two Belgian brothers, successfully commercialized an ammonia-soda process to synthesize soda ash. It used salt, coke, limestone, and ammonia. The Solvay process produced a better quality product than the LeBlanc method. In 1879, Oswald J. Heinrich presented to the Baltimore meeting of AIME, a paper entitled "The manufacture of soda by the ammonia process." The paper compared the two processes and foretold the demise of the LeBlanc technique. World production of soda ash in 1880 was 680 kt (750,000 st). Of that, 544 kt (600,000 st) was produced by the LeBlanc process. Of the 2.8 Mt (3.1 million st) of soda ash produced worldwide in 1913, only about 50 kt (55,000 st) was by the LeBlanc method. The LeBlanc process was never used successfully in the US, except for a brief period from July 1884 to January 1885 in Laramie, WY. Previously, soda ash had been produced by burning certain plants, as exemplified by the early Jamestown colonists, or by recovering small quantities of natural sodium carbonate found in alkaline lakes, such as those found near Fallon, NV, and Independence Rock, WY. Before the 1884 startup of the first synthetic soda ash plant in the US at Syracuse, NY, most of the domestic soda ash demand in the East was met by imports, primarily from England. Large-scale commercial production of natural soda ash began in California in 1887 from surface crystalline material at Owens Lake. Production from sodium carbonate-bearing brines at Searles Lake began in 1927 (Fig. 1). In 1938, during exploration for oil and gas in southwestern Wyoming, a massive buried trona deposit, presumably the world's largest, was accidentally discovered. Recent mineral resource evaluation by the US Geological Survey and the US Bureau of Mines indicates that the Wyoming trona deposit contains 86 Gt (93 billion st) of identified trona resource in beds 1.2 m (4 ft) thick or greater. Additionally, there is about 61 Gt (67 billion st) of reserve base trona. Of this 36 Gt (40 billion st) is in halite-free trona beds and 24 Gt (27 billion st) is in mixed trona and halite beds. In 1953, the Food Machinery and Chemical Corp. (later shortened to FMC Corp.) became the first company to mine trona in Wyoming. Soda ash demand increased.

Jan 10, 1985