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By E. A. Laurila

During last years many different types of X-ray fluorescence analysers have appeared in the market most of these instruments being designed for laboratory use. The instruments applied ins continuous processes are usually modifications of these laboratory types. The application of these instruments to the analysis of heavier elements seems to be quite satisfactory. By lighter elements difficulties are caused by the strong absorption of the characteristic fluorescence radiation, which sometimes makes the use of vacuum or helium chambers necessary. In the following an instrument of another type will be described. It has been developed exclusively for the analysis of titanium in ilmenite concentrate, where the content of Ti02 varies between 43 - 46%. Preliminary measurements have shown that in this interval absolute change of 1% in the Ti02 concentration causes a relative change of about 2% in the intensity. Because: the accuracy of 0.5 % Ti02 is sufficient, 1% relative accuracy should be, attained in intensity measurement. The problem is not very easy to solve due to the fact that Ti K radiation is rather soft and the requirement's for accuracy are rather high. Being applied to the analysis during a continuous process may statistically fluctuating variables in connection of sampling and disturbances of many kind set special requirements for the instrument design.

Jan 1, 1960

By P-M. Dupond, S. Lowrie, C. Tauziéde, Z. Pokryszka, A. D. Jones

A physical model has been developed to simulate the flows and mixing of gases in the waste of a longwall retreat coalface. The model is used in conjunction with computational modelling, and the distributions of permeability and gas emission in the model waste follow those in computer simulations (Pokryszka et al 1996). The physical model represents at 1170th scale a 200 m long, 3 m high coalface with a waste extending up to 280 m to the face start line. The model is tilted to the same seam slopes as the real face, e.g. 22° ascensional ventilation along the face and 7" slope to the dip. The purpose is to investigate the flow of three components: ventilation seepage flow through the waste; methane; and nitrogen injected to quell spontaneous combustion. A heavier-than-air surrogate gas (SF,) is used in place of methane, and therefore the model is inverted so that gas layers form along the 'roof". The main forces driving the flows in the waste (pressure gradients due to ventilation and the density difference of gas layers) are kept in proportion by appropriate scaling of the permeability. Calibration and validation used data from a coalface at a mine in the Lorraine coalfield. The model is now in operational use.

Jan 1, 1997

By AKIHIRO YOSHIMURA, HIDEKAZU KATO, KOTA TAKATORI, YASUNARI MATSUNO

Chalcopyrite (CuFeS2) is the most refractory copper mineral when treated in conventional sulfate media leaching systems. This is the first study to examine the use of a dimethyl sulfoxide (CH3SOCH3, DMSO) solution containing copper chloride (CuCl2) for the leaching of chalcopyrite. Leaching experiments for a copper concentrate composed mainly of chalcopyrite were conducted at ambient pressure at 313–413 K. The leaching fractions of Cu, Fe, S, Au, and As were investigated. It was found that 90% of the Cu was extracted in 2 h, and 94% was extracted in 4 h at 373 K, which is competitive with other conventional processes. A DMSO solution containing CuCl2 could selectively dissolve the valuable metals Cu and Au from chalcopyrite, but leave minerals with little economic value such as pyrite (FeS2) and As in the residue. Chalcopyrite is oxidized by cupric ion in proportion to the stoichiometric ratio of Cu in the concentrate to the initial cupric ion in the DMSO solution, which is enhanced by the presence of oxygen below 373 K.

Mar 12, 2021

By Onuralp Yücel, Kağan Benzeşik, Ömür Can Odabaş, Selçuk Kan

Extraction and processing constitute an important area in the metallurgy of molybdenum. Molybdenum trioxide (MoO3) production is one of the most important stages in molybdenum production. In this study, the effects of different furnace types on MoO3 production were investigated by using molybdenum concentrate as a raw material obtained during the enrichment of copper ores. Preliminary experiments have been made using a chamber type furnace, and a transition to a pilot-scale has been carried out with rotary kiln experiments. The effects of a different time and atmospheric conditions on MoO3 roasting kinetics were investigated by experimental studies conducted in the temperature range of 500–650°C. It was determined that the optimum temperature and time for sulfur (S) removal was 625°C and 180 min in the studies carried out in the rotary kiln, and it was determined that 0.61%S content was reached with an average removal efficiency of 98%. The activation energy in these sets was calculated as 89.519 kJ/mol.

May 3, 2021

By Iain M. Mason

Linear meridional zones of bad roof conditions have been frequently encountered in producing collieries working the Permian age Lithgow seam in the western coalfield of New South Wales. The prediction of such zones ahead of mining is desirable for reasons of both safety and economics. In March, 1981, we carried out an experimental, three-component in-seam seismic survey at Invincible Colliery to discover whether such zones have any unambiguous seismic effect. The underground survey was the first of its kind to be attempted in an Australian mine. The data quality was excellent with the spectra broadband and clear. Polarisation analysis disclosed two modes: one compressional; the other shear horizontal. The SH model was clearly dispersive and well gound to the plane of the seam. Modal velocities decreased by up to 15% at the fracture-swarm site. There is a strong suggestion on the RLS maps obtained here that the distributed fault zone is acting as a composite scatterer of channel waves. The P-SV and SH wave tomograms obtained show, in a general way, the distribution of stress in the coal panel.

Jan 1, 1982

By R. V. Ramani, C. J. Bise

INTRODUCTION Classification of coal seams as thin, medium, and thick is both subjective and relative and is more a reflection of the statistical mode of the thicknesses en- countered in a mining region. A geological factor more precisely understood as defined than thickness is the inclination of the seams to the horizontal, commonly referred to as the pitch or the dip of the seam. Thick and steeply pitching seams present far more challenges to the ingenuity of the mining men to devise methods for their extraction than the thick and less steeply inclined ones. In a marginal case, where a thick coal seam may be minable by surface or underground methods, the decision bears a close relationship to the technological developments in the mining scene. Near surface thick coal seams are a special gift of nature and are not as wide- spread as the ones that call for the application of under- ground methods. Recent advancements in surface mining equipment have made it possible to surface mine to great depths. Stripping ratios of 30: 1 (cu yd of over- burden removed per ton of coal) have been achieved. The extraction of thick seams which preclude the use of surface methods is the concern of this chapter. Specifically, the objective here is to outline the special technological factors in underground mining of thick coal seams and to illustrate through several case histories the methods that are practiced in the North American continent. For the purposes of this chapter, a thick seam is defined as one which is not readily minable with currently available equipment without modifications to the extraction method or the equipment. At the present time, a thickness of 4.8 m (16 ft) can be considered as the lower limit, although developments in equipment and methods can be expected to push this limit upwards. The data for the case histories were collected from two extended mine visits in 1975 and 1978, and from other published accounts of the mines visited. Reference is drawn particularly to reports by Bise, Ramani, and Stefanko (1976) and Rarnani and Kenzy (1979). THICK SEAM MINING METHODS The various methods of mining thick seams can generally be grouped into three major categories: full face methods, where the entire thickness of the seam is re- covered in a single pass; slicing methods, where the seam is extracted to its full thickness by horizontal or inclined slices either in an ascending or descending order; and caving methods, where the seam is undercut and the en- tire coal seam is recovered by caving the top coal into the excavated cut, or some variations of the basic sub- level caving method. As shown in Table 1, in each of these methods, the coal is removed by either room-and-pillar or longwall methods. Hydraulic mining and transport of the coal in open flumes or in pipelines are also practiced. Addition- ally, the void created by the removal of coal may be filled with a packing material (stowing) except in the caving methods. The pitch (dip) of the seam, particularly when it is greater than 0.26 rad (150), imposes severe operational limitations on mobile equipment. A more detailed general discussion of the methods can be found in Bise et al. (1976) and Vorobjev and Deshmukh (1964). Specific discussion on the many variations of the three basic methods can be found in the papers presented at the international symposia that were held in

Jan 1, 1982

By N. S. Aouad

"Gaseous explosions are one of the most hazardous incidents in process and mining industries. Experimental research in this area is shown to be high risk and expensive. Computational Fluid Dynamics (CFD) techniques are reasonable alternatives to experiments; specifically when testing large scale gaseous explosions such as methane explosion in underground mines. The dimensions of a confined space where explosions could occur vary significantly. Thus, the scaling effect on explosion parameters is worth to be investigated using CFD tools. In this research paper, the impact of scaling on the explosion overpressures is investigated by employing two scaling factors. These two factors are the Gas-fill Length scaling factor (FLSF) and the Hydraulic Diameter scaling factor (HDSF). The combinations of eight HDSFs (1, 2, 4, 8, 16, 32, 64, and 100) and five HDSFs (0.5, 1, 2, 4, and 8) will cover a wide range of space dimensions where flammable gas could accumulate. Experiments were conducted to evaluate the selected premixed combustion and turbulence models. Large Eddy Simulation (LES) turbulence model was used because it shows accuracy compared to the widely used Reynolds’ averaged models for the scenarios investigated in the experiments. Researchers also simulated methane explosions in both deflagration and detonation regimes using different numerical schemes. Three major conclusions can be drawn from the simulation results. (1) The overpressure increases with both FLSF and HDSF within the deflagration regime; (2) in an explosion duct with length to diameter ratio greater than 54, detonation is more likely to be triggered for stoichiometric methane/air mixture; (3) overpressure increases as an increment hydraulic diameter of a geometry within deflagration regime. INTRODUCTION The most typical category of gaseous explosion accidents is methane explosion accidents in the mining industry. It normally leads to significant economic loss and massive amount of casualties (McPherson, 1993). It could occur in unconfined spaces, such as combustion due to flammable gas leakage, as well as confined spaces, such as inner-combustion in process equipment and methane explosions in airways of underground mines. Gaseous explosions in confined spaces are more intensive compared to unconfined spaces provided that the total energy of explosives is the same. In addition, explosion characteristics are also affected by the geometry of a selected confined space. The size of confined spaces commonly encountered in process and mining industries could differ as much as an order of four (Catlin & Johnson, 1992). A better understanding of the scaling effect on gaseous explosions could contribute to explosion mitigation and prevent operation activities within high risk regions. This research paper has investigated this scaling effect and its impact on explosion propagation. The approach to investigate explosions is either experimental or numerical. Large scale explosion experiments are often costly and dangerous (Catlin, 1991; Zhang, Pang, & Zhang, 2011). Lab scale experiments and numerical methods are common alternatives. However, it is not yet clear if the findings in lab scale experiments can be used to represent the explosion characteristics or not. On the other hand, CFD modeling has been used to simulate chemical combustions and, thus, can be used to evaluate the scaling effects in methane explosions."

Jan 1, 2015

By Terry L. Logan, Arfon H. Jones, James C. Seccombe

Deeply buried coal seams [greater than 3000 ft (914 m)] are difficult and sometimes hazardous to test and complete due to coal sloughing, formation pressure anomalies and coal fine generation. Data collected while stimulating two deep coalbed methane wells located at the Gas Research Institute/Resource Enter¬prises, Inc. "Deep Coal Sean Project" test site in the Piceance Basin, Colorado, is presented in this paper. A single thick coal seam was completed openhole in each well. Core data, reservoir data, in-situ stress measurements, and pre-stimulation calibration test data were collected at the site to use in the design of the fracture stimulation treatments for both wells. A nitrogen foam fracture fluid treatment was selected for the first well and a linear gelled water for the second well. Treatment pressures were monitored with a downhole quartz pressure transducer. Atypically high treating pressures were observed, possibly indicating coal fines plugging at the fracture tip or increase in fluid viscosity caused by interaction of the generated coal fines with the fracturefl uid. In addition, a comprehensive fracture diagnostic effort was employed during the fracturing of the second well; namely, triaxial borehole seismic, seismic televiewer, hydraulic impedance monitoring, gamma ray log (in conjunction with radioactive additives in the sand), and temperature log. The results indicate a vertical fracture was created parallel to the face cleat as expected.

Jan 1, 1986

By Douglas G. Brookins

Clay mineralogic studies of ore versus barren rocks in the Grants mineral belt show that some combination of chlorite (rosette form), illite, mixed layer illite-montmorillonite, (- Mg-montmorillonite) are penecontemporaneous with uranium minerals in trend ore; these same clay minerals plus kaolinite are related to the roll type ore near the main redox front of the Grants mineral belt. Clay minerals from barren rocks are characterized by a greater abundance of Na-montmorillonite, kaolinite, and face-to-edge form chlorite. Chlorites from ore zones contain much more vanadium than do chlorites from barren rocks. Trend ore probably formed from southeasterly flowing waters following paleochannels in the Late Jurassic. These deposits are found almost entirely in reduced rocks, and organic carbon may have been an important reductant to remove U-V-Se-Mo from solution as carbonate from ore zones contains some organic carbon based on stable iso¬tope studies. Uplift, remobilization and reprecipitation of some of the trend ore resulted in the formation of redistributed ore, some of which possesses a roll type geometry. Mineralization for the roll type ore was apparently controlled by sulfide-sulfate equilibria at or near the main redox front in the Grants mineral belt. Trend and roll type ore possess different assemblages of clay minerals and different trace element abundances. Laramide faults cut both trend and some roll type ore. Stack ore is found in Laramide fault zones. Limited oxygen isotopic data from clay minerals in two mines at Ambrosia Lake in reduced rocks indicate probable preservation of ancient, formational waters and no evidence for infiltration by young meteoric waters. This information, plus the pre-Laramide faults, suggest, but do not unequivocally prove, that the main redox front has been relatively stable since its formation, probably some time in the Cretaceous. Younger encroachment of the redox front in post-Laramide is proposed by others, however, and the problem is unresolved. Uranium for the deposits was most likely carried in solution as an oxyion, probably as (UO2(CO3)2.2H2O)2- or (UO2(HPO4)2)2-, although organic transport cannot be entirely ruled out. Oxyions of vanadium, selenium, molybdenum and possibly arsenic and antimony, are interpreted from Eh-pH diagrams to have been segregated and transported with U6+ soluble species and precipitated when a chemically reducing environment was reached. The rare earth elements are also enriched in ore zones, but it is not clear if they were transported with the U-V-Se-Mo-(As)-(Sb) suite or derived from a more local source.

Jan 1, 1980

By R. L. Peyton

Risk analysis is used extensively in many engineering applications. Although its use in the field of dam safety has been limited in practice, it has received considerable attention in recent years in the dam safety literature. Thus far, it has been shown that risk analysis in the evaluation of existing dams has the potential for providing a more rational basis for decision- making because of its focus on the direct issues--likelihood of failure, likelihood of loss of life, and risk cost of damages. It provides for a logical balance between the risk a dam imposes and the degree to which rehabilitation is required, compared to traditional evaluations based on somewhat arbitrarily chosen design events applied to large classes of dams. Dam owners could benefit by optimizing the cost of remedial measures. Downstream landowners could benefit by minimizing the likelihood of flood damages. However, it is also clear that significant technical and policy issues remain to be resolved before risk analysis in dam safety is accepted and routinely implemented in engineering practice. An obvious and important potential application of risk analysis is its use by the state regulatory agency as an in-house evaluation tool, or even as part of regulatory policy, in the implementation of its state dam safety program. Adoption of such a policy would have an important impact on the mining industry. .Although no state dam safety programs are known by the writers to have officially incorporated risk analysis into their regulations, there appears to be considerable interest in the concept. In recent surveys 47 states agreed that the development and promotion of a risk assessment methodology for state dam safety programs should be encouraged (Tschantz, 1983; Tschantz, 1984). The issue has also received important attention within the Association of State Dam Safety Officials (1986). One state-Illinois-proposed regulations during 1986 to allow risk analysis to justify lower spillway requirements for existing dams (Illinois Department of Transportation, 1986). At the Federal level, the National Research Council has found risk analysis especially appropriate for assessing dam safety at high-hazard dams (National Research Council, 19851, the Bureau of Reclamation has published guidelines for incorporating risk analysis into their dam safety grogram (U.S. Department of the Interior, 1986), and the Federal Emergency Management Agency has recently sponsored workshops and supported research related to risk analysis in dam safety (Federal Emergency Management Agency, 1985a ; Federal Emergency Management Agency, 1985b; - - McCann, et. al., 1985a, 1985b).

Jan 1, 1986

By R. Tanaskovic

Unfavourable climatic conditions in stopes are of significant economic and social importance due to the following reasons: - Working effect is much lower leading to decreased output and work productivity disregarding implementation of mechanization. - Manpower operating capability decreases much faster under unsatisfactory climatic conditions. Under normal climatic conditions a workman would expend much less effort in line with a shorter effective time for the achievement of identical production effects since the work would be more efficacious. The objective of study of problems and climatic conditions is to make the working environment in mines suitable for normal development of operations. Lowering of mining works to increasing depths and winning of a growing number of small orebodies over a broad area makes the problem of creating suitable climatic circumstances more complex. Mining costs are growing due to bench conditions in line with decreasing metal content in the ore, so frequently the investments required for creating favourable climatic conditions represent, in addition to the selection of mining technology, a very important parameter when making decisions regarding exploitation. As known, the basic factors affecting climatic operating conditions in mines-are: temperature, humidity and speed of air flow, implying that the climatic operating conditions are closely related to mine ventilation. Usually, the concept of unfavourable climatic operating conditions includes increased mine air temperature and humidity and low air flow velocity so that heat exchange between human organism and the working environment is impeded or reduced to minimum. Metal mines in Yugoslavia are characterized by the existence of a large number of active faces - stopes and horizons and lowering of mining operations to increasing depths, so that face ventilation solutions are more and more complex. Since its foundation (1961), our Institute is engaged in investigation of factors influencing climatic circumstances improvement of calculations for air distribution and distribution control in complex ventilation networks and study of problems related to ventilation of large volume and irregular configuration faces, as well as application of gained knowledge in our mines. The paper presents the knowledge and experience gained in the case of Lead and Zinc Mine "Trepca" - Stari Trg.

Jan 1, 1980

By Karen M. Kessen

The isotopic variations of lead from Mississippi Valley galenas have long been used to place constraints on the sources of the lead, and on the residence the of the lead in crustal reservoirs prior to its emplacement in the Mississippi Valley province. Similar studies based on strontium isotope variations in gangue minerals associated with the lead-zinc sulphides have been neglected until Haden's (1) study of such minerals from several localities in northwestern Ohio. His work revealed two things about the mineralization. Firstly, it shoved that the average isotope composition of lead from galenas from northwestern Ohio lies on the anamalous lead line characterizing Mississippi Valley-type leads, albeit at the least radiogenic end of the entire data array. This confirm earlier assignments of the Ohio mineralization as Mississippi Valley-type (Hey1 and others (2)). Secondly, Haden (I) showed that the strontium in the calcite, strontianite and fluorite is broadly similar in isotopic composition to the strontium in the host Silurian to Devonian marine carbonates within which these minerals arc emplaced. He concluded that the mineral strontium my have been very locally derived, from the carbonate hosts.

Jan 1, 1979

By Corey Vaughan

Unplanned shutdowns from abrasive wear part failure in crushers, chutes, and slurry pipe assets can cost millions in lost production and reactive maintenance. 2Censor patented sensor technology enables real time abrasive wear monitoring of mineral processing equipment, turning passive assets into smart, data driven components. Wireless sensors embedded in liners and pipework transmit wear data live to operators, allowing for predictive maintenance, safer scheduling, and optimized asset life. This paper will present global case studies showing reductions in downtime, increased throughput, and improved maintenance accuracy. The system is ready to retrofit, neutral to original equipment manufacturers, and proven across more than twelve countries in abrasive wear liners and slurry pipe applications.

Feb 22, 2026

By J. W. Markham, M. Atiemo, K. Yoshida

INTRODUCTION In open-pit mining of high grade ores, operators of mining equipment in a pressurized cab are protected from inhaling radioactive aerosols by the use of filtered air through a pre-impactor and a HEPA (high efficiency particulate air) filter. At present, a limited amount of scientific information is available on the worker exposure to airborne alpha emitters in the mining of high-grade ores. (Miller, 1977, Nielson, et al, 1979). Factors affecting the worker exposure to alpha radiation are: the grade of uranium containing ores, the environmental conditions inside the mine pit, the protection factor of the cab filter system, the workers' attitude towards the hazards of radioactivity and the adopted contamination control in the cabs. Four series of field samplings were conducted during the fall of 1980 and the summer of 1981 at a mining site in northern Saskatchewan to investigate the extent of protection an equipment operator has against cab internal exposure to airborne alpha emitters with short and long half-life radionuclides. The variation in the breathing zone concentrationnof aerosols as a result of resuspension is discussed, however no attempt was made to isolate and investigate the factors and the associated parameters of the aerosol resuspension phenomenon. AEROSOL RESUSPENSION IN A CAB Mechanisms of Resuspension [Sources]: The presence of radioactive aerosols inside a cab and in the breathing zone of an operator may be due to initial concentration inside [(CO)], concentration in the filtered (HEPA) air (CC, at the flow rate [QC]), the concentration of the aerosol through resuspension ([CR]), the aerosol concentration in the air outside the cab ([CE]) and the concentration of the aerosol in the leaking air [(CL)], at the flow rate of [(QL)]. [Volumetric Equilibrium]: Assuming a uniform concentration of the aerosol in the cab, the aerosol concentration in the breathing zone[ (CBZ)] may be expressed as, [CBZ+CO+CC+CR-CL] If [QC] remains greater than [QL], there is pressurization in the cab. There is particle loss as a result of the leaking air from the tight cab, however the condition of adequate pressurization ensures that [CL ~ CC]. Also for dust particles filtered through HEPA [CC – 0] thus [CBZ + CO + CR] For the radioactive gases, [CBZ - CO + CC] Over long periods,[ CBZ – CE] but if [CBZ] exceeds the value of CE then the aerosol build-up in the cab has, occurred. [Resuspension]: Turbulent bursts are generated within the core region of a cab confinement, such that the down sweeps and the up sweeps of the air bursts cause resuspension of dust from the surfaces. Particles initiate resuspension by four major modes: namely, sliding, rocking, rolling, bouncing or sudden ejection or by combinations of these. Nevertheless the adhesion force between the particles and the surface must be overcome by ejection forces before ejection takes place (Kline et al, 1967, Corino and Bradkey 1969, Kim et al 1971). The phenomenon of particle resuspension from a surface may be expressed in a generalized form as: CR =f (Uz . R . D . H) where CR = Rate of particle resuspension UZ = Surface shear velocity R = Surface roughness parameter D = Aerodynamic diameter of particle H = Frequency of surface airburst A detailed discussion of the individual parameters was attempted for the case of farm tractor cabs by Atiemo (1981), such a treatment is out of the scope of this study. Only the effects of the properties of surface roughness will be discussed. Effect of Surface Properties The roughness of the surface from which dust particles are ejected plays a significant role in the deposition and resuspension of the dust. The roughness or the amount of protrusions greatly influence the intensity of air turbulence in the immediate vicinity of the surface (Schmel 1976). For most roughened surfaces therefore, larger particles may be dislodged in greater quantities than smaller particles. The deposition and the resuspension of dust particles from different surface materials of glass, cloth, metal and rubber have been studied in a wind tunnel (Atiemo, 1981). Field Conditions Mining equipments used are: a backhoe, a bulldozer with ripper attachment and two dumptrucks for high-grade ore operations; a payloader and two dumptrucks for waste handling; and a jumbo drill which drills dynamite holes for ore blasting. All this

Jan 1, 1981

By John K. Hollmann

The use of the direct method of determining coal methane content has grown in the last decade from a research technique into a practical coal exploration tool. However, the literature available on the subject is somewhat lacking in site-specific guidance and observations on the conduct of the method and the use of the resulting data. This study discusses some practical lessons learned in conducting a large scale direct measurement project at an operating mine, describes the initia1 interpretations and uses of data from the project, and presents observations from subsequent mine operations into the success and limitations of using direct measurement data in mine planning. The site studied is in central Pennsylvania on the Appalachian Plateau and includes coal seams in the Allegheny series.

Jan 1, 1987

By DING TANG, JINGHE CHEN, Shuiping Zhong, CHEN KUANG

The Zijinshan gold-copper mine, located in Shanghang County, China, is a porphyry-type, low-grade ore deposit with a geological profile of upper gold and lower copper. Despite its low-grade nature, it has become one of the largest in production scale and most profitable nonferrous metal mines in China, which can be attributed to the successful application of hydrometallurgy as well as proper engineering design. A large-scale, open-air cyanide heap leach has been successfully implemented to recover gold under the humid and rainy weather conditions of southern China. Furthermore, according to the gold ore characteristics, a combination of gravity separation, carbon-in-leach and heap leaching processes was developed to improve gold recovery. In terms of copper extraction, copper ore of a grade higher than 0.25 percent is fed to the flotation plants to produce copper concentrate (gold is also enriched here), while copper ore of a grade lower than 0.25 percent undergoes heap bioleaching followed by solvent extraction and electrowinning to produce cathode copper. Additionally, a unique bioleaching system has been established at the Zijinshan Mine: low operating pH (0.8~1.0), high concentration of total soluble iron (~50 g/L), high temperatures (45~60 °C) and low activity of microorganism (~104/mL) in the pregnant leach solution (PLS). This review paper summarizes the practical experience acquired in developing the Zijinshan gold-copper mine and could be of use in other gold and/or copper plants.

By R. V. Hunter, J. F. T. Agapito

Introduction Significant increases in extraction ratio on the order of 6% to 8%, equivalent to as much as 142 t/m (48 st per ft) of panel, have occurred at the Big Island trona mine during the last five years with the help of a practical rock mechanics program. This increase in resource recovery also has contributed to improvements in productivity. Both conventional and continuous machine mining have been used to mine two flat-lying trona beds at depths of 250 m and 260 m (820 ft and 853 ft) in the Green River Formation in southwestern Wyoming. Conventional room-and-pillarmining originally was conducted in panels with extractions of 5 8% to 60%. The use of yield pillars has allowed the panel extraction in increase to 66%. Continuous machine mining was introduced, with a 64% extraction ratio using long, narrow pillars and wide rooms. Further improvements in resource recovery seem feasible in light of present mining experience. The rock mechanics program consisted of field instrumentation to determine the pillar and roof response hole locations. to mining and computer modeling to evaluate the stability of various layouts, which were then adopted for mining. Mining background Stauffer Chemical Co.'s Big Island mine and refinery are located 40 km (25 miles) northwest of Green River, WY. Underground mining operations supply trona, a sodium mineral, to the refinery to produce soda ash. The room-and-pillar method is used to mine two 3 to 3.6 m (10 to 12 ft) thick, flat-laying seams at depths of about 250 to 260 m (820 to 850 ft). Mine production in 1986 was 2.3 Mt (2.5 million st). These were supplied through both conventional and continuous machine mining sec-

Jan 1, 1989

By Y. Xi

This paper offers an algorithm to determine the optimal panel size with the objective of minimizing the overall stripping cost. The approach is presented both in analytical form for regular layers of coal and overburden, and in graphical form for the cases of irregular and multiple coal seams. When the optimal panel width needs to be changed due to some circumstance, we prove in general that increasing the panel width is better than reducing it in both economics and operational efficiency.

Jan 1, 1994

By M. K. Patel, K. C. Wade, M. Cross

In the past decade a good deal of effort has gone into the computer simulation of the heat distribution of pellet induration systems. The major uncertainty in the analysis of such systems is the gas flow distribution and, in particular, the role of leakage. Evaluation of the leakage into or out of a zone has proved to be very difficult, as has the cross-flow from one zone to another when adjoining zones have gas flows which change direction from up draft to down draft for example. This paper describes an initial model to calculate the gas flow distribution in a variety of practical situations of interest to those involved in pellet induration. The model is based upon a multiphase CFD code called CASCADE which is used in conjunction with the pellet induration simulation INDSYS.

Jan 1, 1990

By S. J. Knoll, D. F. Scott, T. J. Williams

Highly stressed rock in stopes continues to be a primary safety risk for miners in underground mines because it can result in failures of ground that lead to both injuries and death. Spokane Research Laboratory personnel investigated electromagnetic (EM) emissions in a deep under-ground mine in an effort to determine if these emissions could be used as indicators of impending catastrophic ground failure. Results suggest that (1) there is no increase in the number of EM emissions prior to recorded seismic activity, (2) some EM signals are generated during blasting, (3) interference from mine electrical sources mask seismic-generated EM signals, (4) EM emissions do not give enough warning (compared to seismic monitoring) to permit miners to leave a stope, (5) the distance an EM signal can travel in the rock is between 17.7 and 39.6 m (58 and 130 ft), and (6) current data acquisition systems do not differentiate between EM signals generated from seismic activity and random mine electrical noise. These results preclude monitoring EM emissions as precursors of impending catastrophic ground failure.

Jan 1, 2004