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By Thomas Camus

"STATE OF THE ART The current situation of ground prediction in TBM is of great concern for tunnelling contractors, and the subject has been quite widely addressed over recent years, for instance by the French Eupalinos 2000 programme, which tested a variety of technological approaches. A number of interesting projects were executed, such as the SOUND and OnSITE projects, part of the German Geotechnologien programme: these projects are focused on seismics, while other techniques such as radar are not considered. Little information and even less industrial applications have been released apart from lab simulations and numerical modelling. A number of field tests in different configurations have been carried out for compression waves, but the results were often not reliable or convincing, and therefore little has been reported in open literature. The advances seem somewhat promising as far as hard rock tunnels are concerned, but ignore the problem raised by concrete lined tunnels such as those bored by a TBM in soft ground. In such tunnels, sending and receiving seismic waves reliably through the lining (and the grouting behind) is quite illusory. A careful analysis of the seismic prediction research results show that the main problem is the source which is poorly controlled and poorly coupled (for instance in concrete lined tunnels, or in approaches that use the TBM cutter head vibrations as a source). Generating waves perpendicular to the tunnel axis is also a problem: aligning with the tunnel axis makes more sense. Radar (Ground Penetrating Radar - GPR) has been used in geotechnical surveys for decades, and also for tunnel inspection. Attempts have been made at using it on a TBM (for example in Japan by Taisei) but mainly using off-the-shelf GPRs, which are not adapted to work in the specific environment of a TBM (because of its huge mass of metal, to start with). Very few results have been published, probably due to the somewhat disappointing performance of such implementations. At present, no TBM has a GPR incorporated in its cutter head that is able to predict ground characteristics while drilling. Another characteristic and drawback of most current methods is that they require dedicated periods of time during which other tunnel construction activities must be stopped. Due to the duration of such operations this leads to performing ground prediction on a weekly basis only, and therefore to a requirement for an investigation range of 100 metres approximately (in order to cover the TBM advance over the coming week). This is not achievable with boreholes made from the TBM, even less if a reasonable accuracy is required, as is usually the case."

Jan 1, 2016

By H. Simpson

Middelburg mine is an opencast export mine operating in the Eastern Transvaal Coalfields of the Republic of South Africa (Figure 1). The mine was commissioned in 1983, to its original design capacity of 4.25 million sales tonnes which was subsequently raised to 5.5 million sales tonnes in 1989. This increase in export tonnage was brought about through an increase in the mines export allocation and the revision of management strategies. The maintenance of this increased tonnage with minimal additional capital has been achieved through improved operational efficiencies and the upgrading of planning operations through the purchase of an Enhanced Mine Scheduling Software Package (EMSSP/MINESTAR). Simultaneously with this requirement were additional factors that contributed to the implementation of the EMSSP. The mine was owned by a joint venture of two partners and is operated by Middelburg Mine services (Rand Mines Pty. Ltd) (Figure 2). This structure of ownership required the evaluation of numerous planning options to be under-taken concurrently and hence the need for an efficient streamlined scheduling pack-age that could fulfill this requirement. Compounding the EMSSP needs further, were the problems experienced in the export market, these being the external pressure from current and new suppliers in the market place which obliged management to provide solutions to rapidly changing market conditions. These fluctuating market conditions have had a direct effect upon the mine's planning strategies because of the large percentage of the mine?s sales sold on the international spot market. The sanction factor for all South African exporters has had a negative effect upon price and this was compounded further through internal competition in 1987 via suppliers attempting to maintain the market position.

Jan 1, 1991

By P. Geoffrey Feiss

The Piedmont province of the southern Appalachians is becoming the focus of interest for many exploration geologists. In the past, only those deposits with significant surface exposure have been exploited. Thus, few deposits have been found and relatively little exploration has been conducted in recent years. Modern geochemical and geophysical techniques can alleviate this problem of concentrating on exposed ore bodies by allowing us to "look through" the soil and saprolite to detect the presence of significant mineralization at depth. This paper will attempt to evaluate the feasibility and effectiveness of several geo¬chemical exploration techniques in the Piedmont, of Cabarrus and Stanly Counties, North Carolina. The area chosen for the study is shown in Figure 1, lying almost wholly within the Mt. Pleasant quadrangle, North Carolina. The area is on the eastern boundary between the Charlotte belt, a zone of plutonic and intermediate grade metamorphic rocks, and the Carolina Slate belt, a series of complexly interbedded volcanic and sedimentary rocks of predominantly low grade metamorphism. The area is now considered to be a 500 million year old active, continental margin.1 As is typical of most of the piedmont, outcrop is sparse. Figure 2 is a sketch map of the general geology of the area under study, showing the Charlotte belt rocks in the northwestern quadrant and slate belt rocks, to the east. Within the area are a number of old mines and prospects, the most famous of which are the Furniss and the Phoenix mines in Cabarrus County. All are reported to have contained Au and Cu. Ag and Pb were reported from some. A summary of the deposits is given in Table 1. Data used in this study are from three Master's theses conducted at the University of North Carolina at Chapel Hill. 3,3,6 In separate studies, well waters5, B-zone soils3, and vein and float quartz6 from the area described were sampled and analyzed. Each study concluded separately that geochemical anomalies in the vicinity of the ores justify use of that specific sample type in a geo-chemical exploration program. However, no comparative study of the methods has

Jan 1, 1977

By Richard Thomas Newcomb

The trend towards proportionately rising volumes of surface mining through- out the world and especially in the United States has led some observers to predict that the future of underground mining is quite limited. Certainly, the simple extrapolation of current trends1 gives evidence of a compelling sort for the hypothesis that technological progress is proceeding at a faster pace in surface than in underground mining. This paper attempts to examine the basis for these predictions by searching the historical record on differential rates of productivity as these are observed in iron ore and coal mining. In recent years economists have discussed "technology gaps" among industries or segments of the same industry, by which they mean that mechanisms for invention and its diffusion are faulty or retarded in such a way that feasible cost-cutting innovations are not applied or developed, even though technicians regard them as practical.2

Jan 1, 1968

By Donald E. Scheck

Blasting practices based on sound engineering principles are well established but the successful application of these practices requires accurate information about the overburden geology and close supervision of the drilling and blasting operations. Good design alone is not sufficient to insure good results, but the process may be difficult to control unless steps are taken to measure the variables and to provide management and the operators with the information they need to establish and maintain control. Satisfactory blasting can be defined as loosening and fragmenting the rock so that it can be handled by the excavating equipment, while at the same time, governmental regulations on air blast and ground vibrations are not violated. Optimum practices achieve these objectives at the lowest combined cost of the drilling and loading operations and the blasting materials. Total system optimization, that is, taking into consideration the effect of fragmentation on the cost of operating and maintaining excavating equipment as well as drilling and blasting costs, probably is not a reasonable goal at the present time.

Jan 1, 1984

By R. C. Milici

Historical production data and reserve decline rates can be used both to predict future coal production rates and to estimate when the reserve will be depleted. Reserve estimates inferred herein from historical production data and decline rates are commonly lower than estimates made from geologic data. The latter include significant amounts of lower quality (deeper, thinner, higher sulfur) coal which may be mined when the better deposits are depleted.

Jan 1, 1997

By Charles L. Allie

In June, 1980, Reserve Mining Company completed a 370 million dollar construction project which included process modifications required to reduce the silica content from nine to five percent by weight and increase the iron con- tent of Reserve's pellets from 62.5 to 65.8 percent by weight (dry basis); process modifications and additions required to implement "best available technology" water quality controls; and installation of "best available technology" air emission controls. The new process began operation on June 24, 1980 and is being optimized to meet design objectives. Dry cobbing, fine screening and flotation additions to the concentrating process have reduced the silica content of Reserve's pellet from nine percent to five percent by weight. The process reclaims and reuses all process waters, stores all tailings in a zero discharge tailings basin and meets all air emission standards.

Jan 1, 1980

By Ashis Bhattacherjee, Rahul Upadhyay, Nearkasen Chau, Aditya Kumar Patra, Dhanjee Kumar Chaudhary

Heavy earth-moving machineries used in openpit mines intensively expose drill operators to whole-body vibration and shocks, and thus to musculoskeletal disorders. The roles of individual, machine and rock-related factors in their exposure remain poorly understood. This cross-sectional study investigated their roles in 39 drill operators from Indian iron ore mines. It shows that 70 percent of the operators were exposed to high levels of vibration, above the limit values recommended by ISO 2631-1 (1997). Multiple linear regression models showed that the whole-body vibration and shock exposures were strongly associated with operator’s age, drill-machine model and rock hardness, uniaxial compressive strength and density. The role of body mass index was close to significance (p = 0.08). Univariate analyses found the drill’s age, seat-pad thickness and seat backrest height were also strong predictors. These results help in identifying risky operators, materials and occupational situations, and in implementing appropriate prevention and intervention strategies to reduce and monitor the exposures and health risk. In addition, during the planning stage of acquisition of new equipment, anthropometric data of the operators should be considered for the ergonomic design of the seat.

By T. Bauerle, G. Poplin, Z. Dugdale

"The issue of mine worker fatigue is as complex as it is understudied. Generally, worker fatigue lies somewhere on a continuum between psychology and physiology, which makes the measurement and management of it difficult with no easy solutions for operators or workers. Answers to even basic questions remain elusive—such as what is fatigue, how is it measured, and how can organizational resources reduce fatigue—and answers seem to present no single, clear path to action for the health and safety of the worker. This manuscript supplements the growing body of interest in the problems of fatigue in the mining industry by reviewing some of what is known about worker fatigue in general and in the mining industry in particular. The material covered here includes basic topics of the hows and whys of worker fatigue; an overview of fatigue models, findings, and evidence-based solutions with a focus on mining; and potential future directions aimed at mitigating miner fatigue. INTRODUCTION “It is recommended that the whole fatigue test problem be stated in a form the nature of which may be indicated by the following suggestions: that the term fatigue be absolutely banished from precise scientific discussion, and consequently that attempts to obtain a fatigue test be abandoned [emphasis added].” – Bernard Muscio, Pioneer Australian Philosopher and Industrial Psychologist, in a 1921 Report to the Cambridge Industrial Fatigue Research Board Fatigue presents several challenges for the mining industry. Depending on the specific occupation, daily work, or operational setup on any given mine site, mining jobs can have a fair amount of labor-intensive tasks mixed with monotonous and repetative duties. Combined with the long working hours and shift-work schedules of mining work, the prevalence of fatigue in mine workers may seem rather unsurprising. On the one hand, mining is certainly not alone in facing the challenge of addressing worker fatigue. Indeed, many of the characteristics above mirror the similarities of fatigue in other industries, such as health care, aviation, and security. To the extent that fatigue in mining acts like fatigue in any other industry, then any fatigue management applications, trainings, or interventions in existence can be borrowed from other industries and applied to mining in a “cookie-cutter” approach. On the other hand, some have argued that mining in particular is especially susceptible to increases in the prevalence of fatigue beyond the characteristics listed above due to the multifaceted combination of factors in mining environments associated with fatigue: dim lighting; limited visual acuity; hot temperatures; loud noise; highly repetitive, sustained, and monotonous tasks; shiftwork; long work hours; early morning awakenings; and generally poor sleep habits (Canadian Centre for Occupational Health and Safety, 2012; Legault, 2011). Legault (2011) in particular argues that it is the combination of these factors simultaneously that can make mineworkers particularly susceptible to sleep deprivation and fatigue in comparison to other industries where these factors are often not present alltogether. If fatigue looks and acts different in mining, as others have argued, more research is needed to determine if, how, and why worker fatigue might need to be managed differently in mining."

Jan 1, 2018

By Tony Walsh

Australian Stock Exchange Limited (ASX) -ASX is ranked 9th in the Morgan Stanley Capital International (MSCI) Index – only 2.02% of that Index. -1520 companies – 400+ mining & mining exploration. -Over 50% of Australians own shares in ASX listed co.s -Disclosure standards play a vital part in providing investors with confidence, thereby building depth and liquidity in the market.

Jan 1, 2003

By Susanne Pignolet

Ore microscopy has been applied to the complex lead-zinc-copper-cobalt-nickel ores from the Madison Mire in the Fredericktown subdistrict of the Southeast Missouri Lead District to predict potential beneficiation problems. It has been found that in some portions of the ore deposits, textures are present which may result in metal losses. In ores from the Bonneterre Transition Zone the intimate association of siegenite with chalcopyrite may result in cobalt and nickel losses to the copper concentrate. In ores from higher stratigraphic horizons, this association is relatively uncommon, and siegenite is commonly associated with bravoite. This latter association will increase the recovery of the cobalt and nickel in bravoite, even though some of the fine-grained bravoite will not be recoverable. Other textures which may result in potential beneficiation problems include coatings of covellite on chalcopyrite and inclusions of sphalerite in galena.

Jan 1, 1983

By Lyle A. Hale

The subject area known as upper Dry Valley is located 15 miles due east of Soda Springs in Sections 14 and 23, Township 9 South, Range 44 East, Caribou County, Idaho. The railroad extending from Soda Springs to its terminus at El Paso's Maybe Canyon mine is 8z miles to the north in lower Dry Valley. Initial data derived from trench work in 1962 revealed a variety of econom¬ically significant alterations of the phosphatic beds related to the rather unique geomorphic development in the northern part of phosphate lease 1-012989. It was apparent that such conditions, while valid for near-surface beds in a strike direction, would be misleading if projected to the proposed depth limits of strip mining. Consequently, a subsurface mapping program was initiated in 1963 to determine: (1) the depth and horizontal extent of weathering and related phe¬nomena, (2) the depth, thickness, and quality of ore beds and intervening strata, and (3) structural geology as a guide for mining procedures. Successful use of a scintillometer in 1956 to detect the subcrop position of phosphate beds in the Smokey Canyon area of southeastern Idaho led to the conclusion that gamma radiation surveys of drill holes could be a useful aid in subsurface mapping. The objectives of this paper are: (1) briefly to describe geologic features characteristic of the phosphate lease area and (2) to demonstrate the practical application and theory behind gamma radiation logging as an effective tool in the economic evaluation of a phosphate lease.

Jan 1, 1969

By Thomas A. Earl

Strip mining of coal, and to a lesser extent limestone, gravel and other mineral deposits in the Appalachian region of the eastern United States has left many large and small areas of devastated land where mining predated reclamation requirements. In Pennsylvania alone, there are between 250,000 and 370,000 acres of strip-mined land 1,2/. A higher percentage, and a greater total acreage of land in Pennsylvania is in need of some form of reclamation than any other state, with the neighboring states of Ohio and Nest Virginia also having nearly the same magnitude of mining.2/ Recent legislation governing strip mining of coal proposed royalties to cover reclamation of such presently unusable land. However, in Pennsylvania and other states some progress has already been realized by utilizing abandoned strip mines and gravel pits for waste disposal sites. Given acceptable hydrogeologic settings, such use of these mined areas for landfilling has provided the incentive for ultimately restoring unreclaimed land to beneficial use, at no cost to the general public.

Jan 1, 1975

By Jr. Winters

The United States continues to be the largest producer and consumer of copper in the world. Table 1 on the following page shows several production statistics for 1974, the most recent year which the non-communist world copper industry might consider a good year, and for 1976 and 1977. In 1974 an estimated 24 percent of the non-communist world's newly mined copper was mined in the United States, and. 87 to 89 percent of that was from the western porphyry coppers. In 1976 U. S. new mine production was down to 22 percent of the non-communist world's newly mined copper, and the percentage of U. S. new mine production supplied by the porphyry coppers had risen to 89 to 91 percent. In 1977 the statistics remained the same as in 1976. U. S. porphyry copper production represented about 65 percent of U. S. refined copper consumption in 1974, rose to 75 percent in 1976, and dropped back to 61 percent in 1977 as imports of foreign copper into the United States began to swell.

Jan 1, 1978

By Clifford O. Hamilton

In both mature and young maintenance workforces, the workforce commonly lacks some of the skills required for their assigned work. We call this the "skills gap." This skills gap usually exists in a new operation because although you may hire qualified maintenance personnel, they more often than not have little if any experience with the specific equipment at the facility. Performance Associates International, Inc., has developed and proven a technique to address the maintenance skills gap that is usually found in a new operation.

Jan 1, 2001

By J. R. Allan

Loki Gold Corporation of Vancouver, B.C. is developing the Brewery Creek Mine, an open pit heap leach gold mine, 55 km East of Dawson City in Yukon, Canada. Mineable reserves are 17.1 million tonnes of ore grading 1.45 grams/tonne, containing 24.8 tonnes (797 000 oz) of gold. Ore processing will employ a cyanide heap leach using run of mine ore. Permitting this mine has drawn significant attention because the heap leach technology, while proven in other jurisdictions, has not been used in Yukon. Engineering design of the heap leach was similar to that for heaps in more temperate climates, with the added issues of permafrost and cold weather operations. Solution balance with seasonal placement of ore and year -round leaching requires very large pond capacity for spring thaw conditions.

Jan 1, 1996

By Keith G. Wallace

The effect of face resistance on ventilation air leakage through stoppings was measured in a twin development heading. Face resistance was varied by alternately tightening or loosening the face line brattice to change the line brattice leakage. Results indicated that tight brattice lines are necessary to maintain acceptable airflow at the face but result in higher leakage throughout the entire system, reduced overall ventilation efficiency, and higher operating costs. Conversely, a low face resistance which simulated an auxiliary fan/duct system gave reduced stopping leakage losses, higher quantities of air at the last open cross-cut and greater entire system efficiencies

Jan 1, 1984

By Clinton A. Hollingsworth

The Flotaire Flotation Cell is a simple, efficient hydraulic/pneumatic Flotation Cell that has no moving parts. It is normally used in conjunction with a surfactant (frother) in which case the combination is known as "The Flotaire System". On many ores, metallurgical efficiencies are substantially increased and operating costs reduce. For example, in floating phosphate rock, it is not unusual for BPL recovery to be increased more than 10%, the major increase being due to floating coarse phosphate, up to 14 mesh, and the difficult to float phosphate. Substantial improvements have also been made on coal, mica, vermiculite, kaolin, barite, copper, etc.

Jan 1, 1981

By VIVEK KASHYAP, PATRICK TAYLOR

The presence of iron in sphalerite induces the formation of zinc ferrite (ZF) during roasting. Zinc refinery residues (ZRR) and electric arc furnace dust (EAFD) contain a significant amount of zinc ferrite and are difficult to treat. According to the literature, up to 71% ZF has been found to be present in ZRR. The dissolution of zinc ferrite is inefficient even in aqua regia. The Waelz process is an existing process to recover zinc from electric arc furnace dust by reduction using carbon monoxide followed by the volatilization of zinc. In this study, zinc was selectively extracted from zinc ferrite by partial reduction of zinc ferrite at relatively low temperature followed by leaching in dilute sulfuric acid (20 g/L). Pure zinc ferrite samples were partially reduced to zinc oxide and magnetite by using H2 gas as a reductant. The presence of magnetite and zinc oxide was confirmed by X-ray diffraction (XRD) technique. A maximum of 95%zinc extraction was achieved after leaching with sulfuric acid on the reacted samples. The paper also discusses the effect of time, temperature, and concentration of H2 in the reducing gas on the extraction of zinc and iron from ZF.

Sep 16, 2020

By D. A. Dahlstrom

With today's high energy costs per million BTU's, far greater emphasis is placed on increasing thermodynamic efficiency in the use of energy. America has long since discarded its previous golden age of "low cost energy" in the past ten years. Energy costs are now a very significant percentage of operating expense in industrial operations. Public utilities have felt the same influences of increasing costs in energy for the generation of electricity. Not only has the input energy expense increased seriously, but as pointed out by Blackmore in a paper, fuel costs were 53.4% of the total operating costs for American Electric Power Company.

Jan 1, 1983