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By Norman E. Breslow, John A. Montgomery, Sanford W. Horstman

Reconstruction of historical exposures to silica dust is required in an ongoing cohort mortality study of workers in the diatomaceous earth (DE) industry. However, historical data were collected using three different sampling methods. This study was conducted to derive empirical quantitative relationships from linear regression equations between the three methods: standard impinger, total mass, and respirable mass. Dust from one diatomaceous earth processing plant was sampled simultaneously by all three methods. Results from 61 clusters of the three sampling devices indicate that the phcle size distribution of the dust varies with the two parent products sampled. baghouse product and main product. The relationships between particle counts and respirable mass are: Respirable mass (mg/m3) = 0.064 (mppd) impinger count for baghouse product dust, and respirable mass (mg/m3) = 0.018 (mppcf) impinger count for main product dust. The relationships between particle counts and total mass are: Total mass (mg/m3) = 0.837 (mppcf) impinger count for baghouse product, and total mass (mg/m3) = 1.21 (mppcf) for main product dust. In all four euuations, the intercept did not differ significantly from zero, and the correlation coefficients ranged from 0.90 to 0.95. Results are compared with data from four previously published studies.

Jan 1, 1991

By Axel Nitschke, Josef Arnold

Bochum’s Underground Lot 306 was characterised by a confined site and unique tunnelling methods. A highly mechanized construction concept was developed to achieve high progress rates. Bespoke backup systems for muck disposal and material supply were used. For the first time in suburban tunnelling, wet shotcrete, batched onsite, was applied. A three-storey underground car park had to be undermined with only1.5 m of overburden and had to be lifted several times by “compensation grout in.” An existing operational two-lane metro tunnel was enlarged without any major impact on train operation.

Jan 1, 2005

By Charles H. Wells

This paper presents a review of the state of the art in coal preparation plant instrumentation and a discussion of automation practice that could be applied based on current mineral beneficiation experience and demonstrated foreign technology in coal washing plants. Specific e-mules of applications of remotely controlled slurry values, pneumatic and electronic field transmitters, computers for control and data logging, and on-line analytical instrumentation are given. A program, to demonstrate this technology is described.

Jan 1, 1980

By Jessica M. Wempen, Dallan J. Coons, Bailey S. Simmons, Michael K. McCarter

Gate-road yield pillars are subject to increases in stress as the longwall face advances toward the pillars. Abutment loading conditions are important to gate-road layout and support design in longwall mining systems. Ground support systems are often designed based on mine experience [1,2]. Convergence monitoring is one method of ground support monitoring that can be used to infer increases in pillar stress. Convergence of a yield pillar was measured regularly over the course of six months as the longwall face approached and passed the pillar. Measurements were collected at eight locations surrounding the pillar. The convergence measurements contribute to the knowledge of when yield pillar abutment loading, caused by the encroaching longwall, is first detected. Knowing when abutment loading begins to yield the pillars can help define when standing secondary roof supports are required for head-gate entry access for specific geologic and mining conditions. 

The Canadian mining industry is one of the strongest in the world. Not only does the country produce a sizable amount of minerals and metals, Canada plays host to hundreds of global mining companies, large and small. The country, for the most part, recognizes the importance of natural resource development, particularly mining, to its economic well being. Like any country, though, there are federal and provincial regulations on the books that the industry takes issue with. But there are also certain economic incentive programs in place to encourage exploration and mine investment. And, unlike the industry and the United States government, the Canadian government and mining industry appear to have a reasonable working relationship.

Jan 4, 2010

By C. J. Myers, D. L. McKinnon, A. A. Dasys

In 1988, the National Institute of Occupational Health and Safety (NIOSH) published an information bulletin stating that whole diesel exhaust should be considered a probable carcinogen. Since then, regulations across Canada and the United States (Mine Safety and Health Administration, MSHA) have looked at appropriate exposure limits for underground mine workers. In Canada, an interim standard of 1.5 mg/m3 Respirable Combustible Dust (RCD) has been adopted by some provinces and is being looked at by others. MSHA is considering levels as low as 0.5 mg/m3 soot. Golden Giant, being aware of regulatory developments, decided to look at means of reducing diesel particulate on thier large production machinery. This machinery (LHDs and haulage trucks) is powered by Detroit Diesel 71N Series engines and is used to produce 3000 tonnes of ore/day with a longhole mining technique. Having looked at the various control technologies, it was decided to evaluate the potential of using diesel particulate filters with a copper-based fuel additive for regeneration (the process by which collected particulate is burned off). This paper outlines the control technology used and the results of the field evaluation indicating the benefits to the underground mine worker.

Jan 1, 1993

By J. H. Bassarear

Conventional crushing and grinding circuits are compared to semiautogenous circuits. Recent installations of each circuit are reviewed and seven methods of using autogenous or semi- autogenous techniques are described. Steel and power consmption data are reported and benefits of a dedicated digital computer are discussed.

Jan 1, 1981

By Allan J. Breitenbach

Heap leach operations provide a low-cost method for recovering gold, silver, and copper metals from low grade ore materials. The processed ore materials are stacked in controlled lifts on a lined pad facility for heap leaching. A controlled barren solution is applied to the heap ore surface by sprinkler or drip emitter irrigation, and ore metals are leached into the solution for collection and extraction in plant process facilities. The leach pad and solution collection facilities are lined with impervious materials for containment of all process solutions. The liner system typically includes a composite geomembrane and clayey soil liner with a protective drain cover fill to maximize solution recovery and protect the underlying groundwater conditions. This paper discusses the types of pad liner systems currently used by the mining industry and the "good, bad, and ugly" lessons learned in engineering practice over the last 10 years in the design and construction of heap leach pads.

Jan 1, 1999

By C. Opoku-Ware, M. Kukay, P. Conrad, F. Inkoom, R. Pal

Researchers at Montana Tech are investigating the potential for developing trees tolerable to degraded un-reclaimed mine site tailings and soils as a solution to re-establishing long-term tree growth on those sites. This project involves growing tree seedlings from seeds planted in the degraded mine tailings and soils in which they will eventually be planted. The outcome of the project is expected to lead to a successful solution for re-establishing tree growth in degraded tailings and soils in Butte, Montana with minimal post-planting human intervention. Work conducted on the project to date has shown successful growth of seedlings in degraded tailings and soils. INTRODUCTION In an effort to improve Butte Area One natural resources, this research project is working to help restore tree growth in the Butte Priority Soils Operable Unit Boundary (BPSOU) (Opoku-Ware, et al 2018). Research by Blicker, et al (2003) found that, the BPSOU, which is part of the Silver Bow Creek/Butte Area National Priorities List (Superfund) Site within and near Butte, Montana has multiple historic mining sites situated entirely within the urban setting of Butte. Mine wastes and mill tailings, accumulated from over 100 years of gold, silver, and especially copper mining are dispersed throughout Butte, posing health risks to human and environmental receptors. Stabilization of tailings sites is needed to control fugitive dust, prevent run-off of toxic material resulting in subsequent sediment deposition in streams, reducing the volume of water seepage through acidic and heavy metal contaminated material, and improving land productivity and aesthetic values (Watkin and Watkin, 1982). If successful, the project will help restore water quality and maintain stream flow in Silver Bow Creek where it flows through Butte Area One. Trees native to Butte are being grown to seedlings in a greenhouse located on Montana Tech’s campus which will be planted in degraded soils located within the BPSOU. Growing trees is expected to help restore vegetative ground cover within the watershed contributing to stream flow in Silver Bow Creek. The trees will prevent soil and tailings from eroding and being deposited in Silver Bow Creek where they could degrade water quality and choke stream flow. The project combines research with tree seedling growth to provide a resource for Butte that could produce thousands of tree seedlings each year adapted to the harsh climate, soil, and tailings conditions that exist in the BPSOU where they will grow. It is anticipated that the trees developed by the project will have the capability for long-term survival and growth because they will be germinated and grown into seedlings in the degraded soils and tailings collected from the BPSOU where they will be planted. Soils and tailings collected for the project have been evaluated to determine if they lack nutrients or contain substances potentially toxic to the long-term growth and survival of the trees. Toxic levels of metals, high concentrations of soluble salts, extremes in pH, nutrient deficiencies and imbalances, surface crusting, high bulk density, low infiltration rates, high surface temperatures, low cation exchange capacity, restricted microbial activity, low water retention, harsh climatic conditions and surface particle movement are some of the traits of mine tailings sites that restrict revegetation efforts (Barth, 1986).

Jan 1, 2019

By A. J. Romeo

The Old Hickory heavy mineral ore body, which lies within the Fall Zone of south central Virginia, has been mined since 1997. There are many differences in this deposit when compared to humate-laden mineral sands mines of southern Georgia and Florida. These differences include an abundance of kaolin-rich clayey sands, highly concentrated and iron-colored heavy mineral sand units, and a base of mineralization that is undulating. For these reasons, the selective approach of dry mining with track excavators is ideal. Grade control in this deposit uses traditional panning techniques and requires an intimate working knowledge of near-by drilling data. Mine geologists train equipment operators to recognize the base of mineralization by such characteristics as a stark color change, significant changes in grain size, and/or considerable, recognizable shifts in the concentration of heavy minerals. The regular pattern of mine site drilling does not always prepare the geologist and digging crews for occurrences of near-vertical contacts between the saprolite basement and the ore sands. These deformed areas, combined with undulating and pinching ore zones, require close monitoring and flexibility by the geologist and the mine operators.

Jan 1, 2005

By B. Oraee

Tunnels as any other structures are affected by different loads and stresses. Generally, the loads on tunnels consist of both static and dynamic loads. These loads must both be considered in the tunnel design process. In this paper, the stability state of Jiroft water-transform tunnel is evaluated. Firstly, the in-situ stresses and then using Kirsch?s equations the induced stresses due to static loads in walls and crown of tunnel are calculated. Consequently, the strain caused by probable earthquake without considering the interaction between the concrete lining of tunnel and rock mass using seismic analysis is calculated based on free-field deformation. When the strain is determined, the simplified method of closed-form solution, Wang?s equations and Penzien?s equations are used to estimate the applied forces on the tunnel due to earthquake such as axial force and bending moment on a tunnel section taking into account the interaction of the tunnel concrete lining and rock mass. Results of this study show that the loads applied to the tunnel as a result of earthquake waves can be affect the stability of underground structures, especially long structures such as tunnels.

Jan 1, 2011

By Luiz Roberto Amaral, Peter Frobenius

Construction of the first phase of the Sao Paulo Metro, the North-South Line, will be completed late in 1974. The downtown section of this line consists of 2.2 miles of 19.6-foot diameter soft ground tunnels and 3 subway stations. The entire tunnel - station package was let to one contractor. A plan and profile of the tunnels and stations is shown on Figure 1. Passage of the tunnels under Boa Vista Street in the Sao Paulo Financial District was one of the major challenges. The street is only 50 feet wide from building line to building line and flanked by 10 to 20 story buildings. The tunnels pass within 4 feet of adjacent footings. Further south, the tunnels run 13 feet below the flat foundations of the Caixa Economica, a massive 11 to 14 story building. Surface settlement had to he limited to less than .07 feet/tunnel and good face control and grouting procedures were essential. For this reason, full face cutting wheel tunneling machines were selected to drive the tunnels south of the Access Shaft Prestes Maia which included Boa Vista Street and the Caixa Economica. The tunnels north of the Access Shaft Prestes Maia were driven under a fairly wide Avenue and greater settlements were permitted. Open face shields were selected to drive these tunnels. Most of the work has now been completed and analyzed. Here are some of the results - Careful planning and execution of tunneling procedures kept surface settlement over the tunnels below a magnitude of .05 feet, allowing tunneling adjacent

Jan 1, 1974

By S. M. Hsiung

This paper presents the results of an extensive study concerning a series of roof falls in a room-and-pillar coal mine located in West Virginia. Three dimensional finite element modeling was employed to identify the possible causes for the roof falls. The effectiveness of possible roof control measures for alleviating or eliminating the adverse roof conditions is analyzed, discussed, and compared. The best mining alternatives are recommended. It has been found that large overburden depth and typical roof geology are the major reasons for the roof falls. Angle bolting may not solve the problem encountered in the mine studied. Changing the mine layout currently used in the mine appears to be the best alternative. The recommended pillar size and entry width which will eliminate the problem completely are 90 ft. x 90 ft. and 14 it., respectively.

Jan 1, 1985

By Gus L. Maciula

Although I will briefly review the current status of coal slurry pipeline technology, I wish to make it clear that this is not a technical paper. It is intended instead to review the current situation on energy resources and requirements, and the environmental, political and economic considerations that mandate a serious consideration of Slurry pipelines as a viable mode of coal transportation into the Georgia and Florida markets. In order to more fully appreciate our current energy situation, it will be helpful to go back a few years and review the evolution of our so-called energy "problem." It was about two decades ago that the first and only major natural gas transmission pipeline was built into the State of Florida by Florida Gas Company. This line was conceived and implemented during a time when gas was plentiful and cheap, and it appeared at that time that unlimited gas reserves were continually being discovered, thus assuring the availability of a clean, cheap fuel and the ,viability of the pipeline system. One of the major factors justifying the original pipeline construction as well as subsequent expansions was a series of long-term commitments under which Florida Gas transported natural gas owned by electric utilities for use as boiler fuel. Thus for the past 20 years Florida industry, commerce, and domestic fuel requirements have been met either directly or indirectly through clean, cheap natural gas which would not have been otherwise available without the pipeline system.

Jan 1, 1978

By Wallace Jarman

Introduction As with many gravity concentration processes, pneumatic concen¬tration traces its origin in antiquity. The use of winnowing to separate chaff from grain has long been known, and such procedures were undoubtedly practiced in ancient civilizations for the concentration of ores and the separation of slag from metal whenever specific gravity, size, and shape differences were favorable. Taggart142 has reported on the use of dry rockers and dry panning techniques for use with gold ores in arid regions such as Western Australia. The present day air table was developed in the last century for this purpose. Devices and Processes Classification. All classifiers make a separation on the basis of size, shape, and specific gravity. In addition to specific gravity and size, particle shape factor is often particularly important to pneumatic processes, and advantage is taken of the fact that both flat and fibrous particles settle at velocities substantially lower than that of their equiv¬alent spheres. Another factor of importance in this process is the bulk density of the material since substances such as exfoliated ver¬miculite or partially opened fibrils of asbestos have bulk densities significantly lower than those of the pure in situ mineral. Winnowing takes advantage of all of these physical factors to affect a separation starting with a closely sized feed, and vermiculite has been separated from rock by this process.142 When air classifiers are used to size minerals, the separation will often not be perfect because heavy particles will respond similarly to somewhat coarser light particles while flat, elongated, and low bulk density particles will act as would particles finer than the cut size. An example of a classification process that also results in concentration is the zig-zag classifier"' used to separate paper from glass, metal bottles, and cans during the recycle of municipal solid waste. Application of this process to minerals showing the proper specific gravity, size, and shape differ¬ences is obvious. An important device of this type is an air-aspirated screen used to remove asbestos from its associated rock during the dry processing of that mineral.144 The raw ore is crushed and screened and the asbes¬tos removed by aspiration from the surface of the screen by virtue of its shape and low bulk density. Hindered Settling. Based on the discussion in the section on "Hindered Settling Concentration and Jigging," the use of air devices could be anticipated in desert areas or where moisture may be deleteri¬ous to the product to be separated. Such processes have three major defects: (1) dust may be difficult to contain, (2) fines are difficult to process, and (3) the process is inherently less efficient than are wet processes as may be seen from Eqs. 3 and 4 in the section on "Hindered Settling Concentration and Jigging p. 4-47." Taggart142 has reported on the use of both dry panning and a dry rocker for gold separation in and regions. The dry panning makes use of winnowing, defection on the basis of specific gravity and shape during fall, and hindered settling. Prescreened placer material is poured from one pan to another as air blows across the falling stream. The process is repeated many times with hand picking to produce a rough concentrate. Magnetic minerals are then removed, and the residue, one grain deep in the pan, is air blown. In dry rocking the gravel is sized on a steeply inclined screen with the undersize fed to a riffle box with a porous bottom which is blown from underneath."' This device was the forerunner of the present-day air table. Air Tables and Jigs.145. 146 At least nine types of these devices have been developed, all but two of them for coal. While the devices used for coal may be characterized as pneumatic jigs, pneumatic tables, and pneumatic landers,145 only pneumatic jigs survive today. The same is true for ores.'" In these devices presized particles are fed to the separator which consists of an inclined vibrating conveyor with a porous surface through which air is carefully introduced to form a fluid bed. The lighter particles are lifted by the air out of uphill conveyance and float downhill, while the heavier particles in contact with the surface are conveyed uphill by the vibrator. Typically both transverse and longitudinal slopes are used. A plan view of a Triple S air table and the type of separation made is shown in Fig. 44.147 Because of its external appearance, the device has been called an air table, although it functions essentially as a jig. However, some of the asymetrical acceleration conveying function of a standard shak¬ing table is also performed by the eccentric vibrator incorporated into this device. Low pressure air is admitted below the vibrating table surface consisting of cloth (e.g., canvas), porous plastic, woven wire, or punched metal supported on a wire mesh or grid. As with a shaking table, the device produces a concentrate, middlings, and tailings. The middlings are recycled or are subsequently treated on another concentrating device. As with many wet separations, presizing by screening is necessary. The oft-repeated admonition of Professor Richards, "Separation without classification is damnation," is cer¬tainly true here. In this way a small heavy particle which might weigh the same as a large light particle and thus report to the same place on the air table has already been removed in the sizing step. Air tables are almost universally encased with a canopy to remove dust by aspiration. Some concentration may also be achieved in this step when favorable specific gravity, size, and shape differences are present. Applications Ore Separations. Air tables were originally developed for ore separations, and they find application in and regions or where water is deleterious or inconvenient to use or remove (e.g., small tonnage materials already dried). They have been used for asbestos, bauxite, calcite, cassiterite, columbite-tentalite, diatomaceous earth, fluorite, gilsonite, graphite, kyanite, manganese minerals, mica, managite, perlite, pyrite, pyrrhotite, vermiculite, and uraninite ores. More recently, air tables have found favor in separating a wide variety of secondary materials such as abrasive grains, bone char, catalysts, fiberglass, scrap glass, scrap wire from its insulation, prills from slag, dross and coke from metal or from each other, metal from crushed crucibles, lead from plastic in old batteries, and cubic particles from flat ones. The devices also finds considerable application in the preparation of food¬stuffs. As stated before close sizing before separation is desirable, and if the specific gravity difference is slight, very tight

Jan 1, 1985

By A. Bascetin

Waste materials caused by mining activities are an important environmental problem. Paste technology is a good alternative for waste management because it has many benefits in the aspects of environment, cost and safety. Disposal of process wastes in paste form is an attractive option for waste management, as it eliminates or reduces the risks associated with conventional methods. Due to the geotechnical characteristics of the paste, it is very similar to soil materials. So determining the geotechnical properties of the paste material is essential to durability of the paste. The some important geotechnical properties are compressive strength, porosity, shear strength, hydraulic conductivity, water content, consolidation, etc. In this study, the important parameters and the relation between them were investigated and obtained some results which will affect for optimum design of waste management.

Jan 1, 2012

By K. G. Kebkal, R. Bannasch

"Because the operation of tethered underwater vehicles in the deep ocean or under drifting ice areas is very complicated or impossible, the application of autonomous underwater vehicles (AUV) is preferred or even the only possible solution. However, this implies the possibility of a direct and real-time control over all AUV functions, which is only achievable with the availability of accurate positioning/navigation and a high-speed communication link. This paper presents a flexible bottom- or surface-based solution enabling high positioning accuracy of underwater objects (harvester, AUVs, bottom nodes); specifically, a multifunctional system that combines Ultra Short Baseline (USBL) transceivers and Long BaseLine (LBL) stations deployed at a large depth. Moreover, each baseline transponder is equipped with a high-speed communication device to provide the means for real-time AUV control based on the information about its current position, e.g. navigate it with direct commands and operating its actuators and other mechanisms. Moreover a communication link with a high data rate can provide valuable visual information from the operation area.Depending on how many nodes the LBL grid comprise has, target transponder positions can be estimated with an accuracy of several to tens of centimetres. The purpose of the paper is to present the experiments with all key elements of the multifunctional Hydro-Acoustic USBL-aided LBL Positioning and Communication System."

Sep 1, 2014

By Nural Kuyucak

Several thousand years ago, metallurgists discovered that by combining two relatively soft metals, copper and tin, they could make a new material, bronze, that was stronger than either metal separately. Bronze and other alloys show how different materials can be integrated to create something new and better. Today?s mining industry can likewise find benefit in an integrated approach to managing the external impacts it has through its waste materials and its use of water. Just as using bronze gave ancient nations an economic and military advantage, mining companies can gain competitive advantage through finding better ways to manage water and waste. Trends pushing this include: ? Environmental ? Regulations on water-taking and the quality of discharged water are becoming more stringent. Net zero discharge requirements are often imposed by regulators. Mining companies also come under pressure to manage environmental impacts of mine waste, including minimizing the area occupied by waste and seepage amount resulting from infiltration of water from a smaller surface area. ? Social ? Particularly in arid parts of the world, there are multiple possible uses for each gallon of water. Local residents do not want to see a reduction in supplies of water for agricultural, domestic, manufacturing and other purposes. They get suspicious about any potential impact of water being mixed with their water reservoirs if it comes from a mining site, even if it would be treated. Such suspicions may cause conflicts among the stake-holders and delays in project approval processes.

Jan 1, 2009

By R. Washnock, P. James

"INTRODUCTION Abstract Tankhouse iron control through application of new treatment technology to mitigate conventional bleeding losses is considered. Implementation is discussed and the treatment economics explored. A representative case is assessed. Treatment benefits and application drivers for specific scenarios are noted. Background Hydrometallurgical ore processing has become a significant metal extraction/production avenue in recent decades. In copper mining; the focus for this examination, around 25% of global primary copper production and nearly 50% of US production result from various hydrothermal leaching extraction approaches coupled to Solvent Extraction/Electrowinning (SX/EW) metal production. Generally such processing is favored over pyrometallurgical processes for lower ore grades and as such is finding growing use and is expected to remain a key processing route looking forward with average world-wide ore grades falling as known ore reserves become exhausted. Target Problem And Motivation In hydrometallurgical processing the production circuit may be thought of as a chain of interlocked recirculation loops (Figure 1). Leaching dissolves the target metal from the ore along with other ore components which contaminate the Pregnant Leach Solution (PLS). Iron is a common component in copper ores and, as a result, occurs fairly ubiquitously in copper Pregnant Leach Solutions (PLS) generated by leaching. Leached components migrate through the production circuit from left to right (Figure 1) through a net combination of chemical and mechanical transport mechanisms. Selectivity at the recirculation loop interfaces tends to retard rejected component migration through the production process. As a result, overall relative contaminant migration fluxes are slower than the target metal (copper) and the contaminants tend to build up relative to copper in the more upstream portions of the processing circuit over time with iron often being a significant contaminant. Further, while copper is continuously removed from the system in appreciable amounts, little contaminant exit occurs and the absolute contaminant amounts and concentrations also increase throughout the EW circuit over time."

Jan 1, 2018

By Andreas Eberhorn

The evaluation criteria for cost comparison of the Gearless Drive, also called Ringmotor or wrap-around motor, as variable-speed drive with a Twin Drive System using synchronous motors are reviewed. Both mechanical and electrical components of the drive system are considered. The evaluation criteria are described and for the cost comparison the applicable method is demonstrated. The cost comparison is based on a medium and large sized mill system. Each drive package will display cost details with regard to capital cost, maintenance, power losses, overall efficiency, overhead and loss of production. As conclusion the benefits and disadvantages of the two drive/mill packages will be presented together with a payback diagram.

Jan 1, 1996