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By V. C. Rogers, K. K. Nielson

INTRODUCTION An evaluation of the radiological health risks from uranium mining and milling requires the determination of several key parameters. As shown in Figure 1, the first step is the estimation of the radioactive source term. The radionuclides in the ore consist of the 238U decay series nuclides shown in Figure 2, the 235U series nuclides, and 40K. The 238U decay series isotopes dominate the source term, with the 235U series isotopes causing less concern and 40K remaining at background levels. [ ] Specifically, the risks from uranium mining and milling are mainly associated with 230Th, 226Ra, 222Rn, and its short-lived daughters. These radioisotopes are mainly alpha-particle emitters; hence, some dispersion mechanism is necessary to bring them into intimate contact with man so that they can be inhaled or ingested For water pathways, the leaching of the isotopes from [ ] the solid ore or tailings provides a measure of the amount of contaminant initially available to the environment. For the air pathway, dust-creation mechanisms such as blasting, crushing or general resuspension processes dominate for 226Ra and 230Th. However, 222Rn, being a chemically inert gas generated from the decay of 226Ra, can migrate through the ore, overburden and tailings over considerable distances. As shown in Figure 1, the next step in the pathway to man is environmental dilution and delay. For the water transport mechanism, the delay in the isotopes reaching an accessible water supply may be considerable (several thousand years or more), but for airborne nuclides the dispersion in the atmosphere is rapid and constitutes the main mitigating factor. Considerable ventilation is provided in underground mines to dilute and remove radon and its daughters in order to keep their concentrations low and thereby minimize their inhalation by miners. The rate of uptake by both the workers and the general public is often difficult to ascertain. It involves breathing rates, rates of water consumption and other poorly-defined parameters. The final steps are the risk estimators used to predict doses and cancer rates from the inhaled radon daughters and ingested or inhaled radium. Many

Jan 1, 1981

By K. N. Han, Y. Guan

[The dissolution behavior of copper and gold from their pure state and from Au-Cu alloys in cyanide solutions has been investigated using a rotating disc. Oxygen was used as an oxidant. The effect of the alloy composition, stirring speed of the disc. [lixiviant] concentration, solution pH and temperature on the overall dissolution kinetics has been studied. An-Cu alloys of three compositions were used in this study. The atomic percent of gold in these alloys was 75, 50 and25, respectively. The dissolution behavior of these three alloys was compared, under the same chemical conditions, with that of pure gold and pure copper. In general, the dissolution of copper and old from alloys is controlled partially by surface chemical reaction and largely mass transfer.]

Jan 1, 1994

By Olivier Kraft, Olaf Kortz

"Project-specific optimized tunnel boring machines represent the spearhead of technological progress in tunneling because with their use, very long-lasting, high quality tunnel structures in almost any geology, depth and topography can be produced with a high degree of automation. The mechanized excavation of tunnel structures ensures the greatest possible environmental protection during tunneling itself. Professional, systematic and high quality rebuilds and reuse of already proven equipment also ensures maximum efficiency in the use of materials and energy resources. It offers an enormous potential for a highly optimized environmental balance. Here the manufacturers of tunnel boring machines and their users in particular have a duty to ensure transparent, high quality and binding standards in the entire rebuild cycle and in the refurbishment management of innovative tunneling technology. This paper deals with the comprehensive processes with rebuild levels of tunnel boring machines and highlights some exemplarily implemented projects. 1 INTRODUCTION All over the world, the number of tunnel boring machines (TBM) in which equipment rebuilds from previous projects are re-used has increased over the last few years. This text presents the technical and economical aspects of this market development. It also takes a look at the practical implementation of rebuild measures. The ""ITAtech Guidelines on Rebuilds of Machinery for Mechanized Tunnel Excavation"" from 2015 lay down the requirements that the machine manufacturers must meet. 2 ECONOMICAL AND ECOLOGICAL ASPECTS OF RE-USING COMPONENTS The globalization of the construction sector and the consideration of environmental aspects promote an increased re-use of machines and machine components. Nowadays, large-scale construction projects are often carried out by international joint ventures of several individual companies that are established specifically for this purpose. After the completion of the project, the joint ventures are dissolved and they liquidate their project-specific equipment, such as tunnel boring machines. Today, it is much more uncommon for such machines to remain permanently in the possession of construction companies. Joint ventures offer TBMs on the free market, or they exercise contractually agreed repurchase options with the manufacturer. On the whole, this increases the number of re-usable components or complete tunneling systems available on the market."

Jan 1, 2016

By R. Tanaskovic

The objective of study of climatic conditions in underground mines is to create a working environment suitable for normal development of operations. Disregarding the fact that the development of equipment and technology, especially during the past decade, made the work in underground mines much easier, it is observed, according to the number of professional publications, that increasing attention is devoted to the study of climatic operating conditions in mines of many countries. This indicates that the climatic operating conditions are closely connected with productivity, and in turn with mine production profitability, in addition to the protection of manpower health and working capabilities. Usually, the concept of unfavourable climatic conditions of operation implies increased mine air temperature and humidity and low air flow rate, resulting in impeded heat exhange between human organism and working environment. As known, above phenomena are present in deep underground mines where the heat problem exceeds the-problems related to other features of natural conditions of mining. On the contrary, unsuitability of climatic operating conditions in mines with shallower mining depths is manifested by inadequate heat, particularly during the cold winter period. The two stated aspects of unsuitable climatic operating conditions are not solvable only by mine ventilation, so the former case requires cooling and the later one heating of the air used to ventilate the pit, or part there of where the phenomena are manifested. Study of climatic operating conditions in mines is, due to the number of factors involved, a complex and time consuming task, and this was, among others, one of the reasons for inadequate study of these problems in many mines. However, it is evident that further development of mine production imposes the need to make the climatic operating conditions in mines similar to those existing in other activities, where increasing attention is being devoted to the improvement of these conditions. Development of mining industry in Yugoslavia, particularly over the past decades, caused several of our mines to approach mining depths where the heat regime has a major influence on climatic operating conditions. This imposed the need to determine and investigate heat regime parameters, especially those that cause unsuitable operating conditions. The results of such investigations in the case of the deep part of Lead and Zinc Mine "Trepca" - Stari Trg are briefly reported in this paper.

Jan 1, 1980

By Graeme Lyall, Oy Leuangthong, Clayton V. Deutsch

There are many variables to consider in the evaluation of nickel laterite deposits including the concentrations of nickel, iron, silica, and magnesia. These variables show complex relationships with each other such as mineralogical constraints, non-linear correlation, and heteroscedasticity. The complex multivariate relationship between the variables cannot be reproduced by conventional Gaussian or indicator geostatistical techniques. We introduce the stepwise conditional transformation method as a pre- and post-processing multivariate transform for the stochastic simulation of a nickel laterite deposit. Transformed data are multiGaussian and independent at h = 0; thus, cosimulation can be avoided after verification that variables are independent at all lag distances. Back transformation restores the features of the input multivariate distribution to the simulated realizations. The complex multivariate correlations are reproduced and sensitivity issues are addressed.

Jan 1, 2002

By Y. C. Kim

Three rock fracture parameters define three points along empirical cumulative size (of rock fragments) distribution curves at Inspiration copper mine. These parameters are: rock quality designation (RQD), longest piece of intact rock and % of +1 inch. The RQD and the longest piece are actually measured on drill hole cores whereas % of +1 inch is visually estimated on the same cores. These size distribution curves are then utilized in a variety of engineering applications such as; slope instability analysis, blast design, copper recovery prediction from heap leaching, etc. The three rock fracture parameters for two dominant rock types (porphyry and schist) in the pit had to be estimated separately due to different rock fracture characteristics.' Both ordinary kriging (OK) with measured hard data only and soft kriging (SFTK) with hard and soft data were used to estimate each parameter. The cross validation of 100 measured sample values served as the-basis for evaluating the potential benefits of SFTK over OK. Use of subjective information during SFTK required obtaining (prior) probability distributions for all three rock fracture parameters. These distributions were obtained from the typical rock fracture parameters observed in drill hole cores falling inside the geologically interpreted structural domains with varying degrees. of fracture intensity and also through direct mapping along the exposed bench faces. Two different types of soft information were developed for this study; namely, Type "A" and Type "K". The former is based on sample distribution of fracture parameters whereas the latter is based on two step estimation designed to narrow the range of variation observed in data Type "A". The results of the cross validation were analyzed using a linear regression of actual values versus estimated values. The results confirm an improvement on the estimates made by SFTK with hard and. both types of soft data over those produced by OK with hard data only.

Jan 1, 1989

By James A. Everts

Calcined bauxites are classified by their major end uses - abrasives and refractories. Target properties are dictated by application and processing requirements. The chemical and physical properties of premium grade calcined bauxites are far more stringent than metallurgical bauxite and this limits the sources and availability. Premium grade calcined bauxites are considered to be strategically critical to the industrialized countries of the world. Subject to disruptions in the key source countries, adequate supplies of premium grade calcined bauxites are anticipated in the foreseeable future.

Jan 1, 1984

By O. E. Etheridge Jr., R. A. Lowe, C. I. Basilio, J. M. Randolph, S. W. Sheppard

The low-shear viscosity of kaolin slurries is one of the principal characteristics that determine whether a clay can be utilized for paper and ceramic applications. In this work, the causes of high low-shear viscosity and methods for improving the rheological behavior of the slurries were investigated. The presence of fine-grained smectite impurities within the kaolin was shown to detrimentally affect the low-shear rheology of the slurries produced from these clays. It was also shown that mechanically working (i.e., pugging) a crude kaolin followed by desliming to remove these impurities can reduce the low-shear viscosity.

Jan 1, 2000

By R. Gong, R. Bhaskar

The development of a three-dimensional mathematical model for evaluating airflow fields at a continuous miner face is described. The model utilizes three-dimensional incompressible flow, mass continuity, and momentum (Navier-Stokes) equations to predict the airflow velocity at the face. Obstacles and equipment in the face area are modeled using appropriate boundary conditions. Parameters such as flow velocity and face dimensions can be modified and evaluated for various schemes, such as exhausting and blowing ventilation, using either brattice or tubing. A model such as the one described, with additions for local effects, can be used to evaluate novel face ventilation ideas before initiating expensive full-scale tests or field studies. The model described is a step in the direction of advanced predictor models.

Jan 1, 1993

By R. L. Bleifuss, S. Zhong, H. E. Geotzman

Microwave heating of iron ore was investigated as an alternative to conventional reduction processes to solve the problem of slow heat transfer. Microwave heating and reduction tests were run on composite green balls made from coal and magnetite concentrate. Benchscale tests were run on both powdered and pelletized feeds using a 15 kW microwave generator. A significant increase in the reduction rate was obtained. With 20% excess stoichiometric carbon in the mix, more than 90% reduction of the iron ore can be achieved in about 10 min at temperatures of around 1,000°C. The reduction of iron ore with coal by microwave heating produces a pure, dust free, high-Btu flue gas that can be used in related thermal operations. Depending on the purity, the reduced iron product could be fed directly to an electric arc furnace for melting. In some cases, the removal of a slag phase may be required to eliminate excess silica and alumina.

Jan 1, 1997

By M. S. J. Leary, M. J. McPherson, O&apos

This paper introduces a computer simulation that extends the use of microcomputer systems for mine ventilation planning. The program was developed as part of an ongoing study to produce a simulation model that would determine the optimum duties of a main fan and a booster fan without requiring the trial-and-error runs that are necessary with currently available programs. To use the new program, the user specifies the location of one main fan and one booster fan, and the minimum required airflows in any number of working places. The computer determines the fan duties that will maintain the required airflows at the lowest operating costs without causing undesired recirculation. The methodology of the program and an example showing how it can be applied are presented.

Jan 1, 1990

By R. L. Grayson

As a followup to a USBM-sponsored research project, the authors utilized the knowledge-base structure and system concepts from a Sun Sparcstation-based worker-scheduling system of the mine-management support system to develop a PC-based application. The new software adopts the nested-window concept to facilitate data collection and modification on personnel, including their availability and work priorities during a shift. The system can optimally allocate manpower on a work shift and can delineate supervisory training responsibilities. The various components of the software, including enhancements made to the original system, are described in detail.

Jan 1, 1997

By Hill McDonald

Sand and gravel deposits may be explored by many different methods. The methods used by The Standard Slag Company are primarily two in nature. One is using an auger which is limited in depth by various soil conditions. The other is a heavy wall dry sampler and a heavy wall wet sampler. The heavy wall dry sampler takes continuous uncontaminated samples up to seven inches in diameter. The heavy wall wet sampler takes continuous uncontaminated samples up to six inches in diameter. For us, the maximum depth of the heavy wall samplers has been two hundred fifty feet of which one hundred feet was above the water table and one hundred fifty feet was below the water table.

Jan 1, 1972

By J. F. Cuderman

In situ experiments at the Department of Energy's Nevada Test Site (NTS) have extended the technology of propellant-based fracturing to include liquid- filled, uncased boreholes. Previous work had developed the technology for liquid-free, uncased wellbores. Test results show that fracturing behavior is considerably more complex in liquid- filled boreholes than in the liquid-free case. Compared to liquid-free boreholes, liquid-filled boreholes have faster pressure risetimes and lower peak pressures, large hydraulic-type fractures propagating several meters beyond the end of the test zone, numerous oscillations in the pressure history, and variable types of fracturing within a single test region. Multiple fracturing is initiated in the wellbore of a fluid-filled borehole when the proper propellant mixture is used but, unlike fluid-free wellbores where up to eight fractures propagate, only one to three hydraulic- and/or shear-type fractures propagate. Hydrodynamic effects involving liquid compression during borehole pressurization appear to be responsible for the differing phenomena observed in fluid- filled boreholes.

Jan 1, 1986

By D. Mannino, M. Townsend, E. Daniloff, E. Petsonk

Nonspecific airway hyperresponsiveness is a central feature of chronic obstructive pulmonary disease and has been associated with atopy in the presence of environmental exposures such as smoking. Coal miners may develop emphysema and lung function decrements related to their dust exposure. To investigate the roles of airway responsiveness and atopy in these effects, we evaluated the relationships among smoking, a history of hay fever or seasonal rhinitis, and airway responsiveness (AR) in a group of underground bituminous coal miners and nonmining controls. All subjects had a normal baseline percent predicted FEV1. Increased airway responsiveness was defined as a 15% or greater decrease in FEV1 following methacholine inhalation. 85 miners (45%) and 99 controls (46%) were current smokers, 59 miners (31%) and 55 controls (26%) were lifetime nonsmokers; former smokers were excluded from further analysis. Overall, 25% of 144 miners included in this analysis had increased AR, as opposed to 29% of 155 controls. Thirty-seven percent of both miners and controls had a history of seasonal rhinitis. Significantly fewer miners (15%) had a history of hay fever compared to controls (25%, p< 0.05). Figure 1 shows the prevalence of increased airway responsiveness in miners and controls in association with hay fever. In both smoking and non smoking miners the presence of a hay fever history was significantly (p < 0.05) associated with a higher prevalence of increased AR. Little effect was seen in smoking (p = 0.827) and nonsmoking (p = 0.940) controls. Figure 2 shows a similar higher prevalence of increased AR associated with symptoms of seasonal rhinitis in the mining group. This was significant (p < 0.01) only in the smoking miners. No effect was noted in the controls. These data suggest that the association of a history of hay fever or seasonal rhinitis symptoms with increased airway responsiveness may be more common in coal mining, compared to non-dusty occupations. Although the implication of these data are unclear, further study of miners with a history of hay fever or seasonal rhinitis is warranted. (Supported in part by Grants G1135142 and G1105142, US Bureau of Mines, Generic Mineral Technology Center for Respirable Dust)

Jan 1, 1991

By Winfield G. Wright, Greg P. Meeker, Philip L. Verplanck, Douglas B. Yager, Dana J. Bove, M. Alisa Mast

A really extensive acid sulfate-altered and mineralized rock in the southeast Red Mountains area is noted for its association with naturally occurring and mine-related acidic and metal-rich waters. Integrated geologic and aqueous geochemical studies demonstrate that the degree of metal mobilization and acid production in natural waters correlates well with the type of hydrothermally altered rock and structural features in which these water interact. Quartz-sericite-pyrite, quartz-alunite, and argillic alteration assemblages are associated with some of the most naturally acidic, high-metal waters in the study area; calcite-bearing propylitic rocks are related to the most pristine waters and buffer sulfate-rich, acidic waters produced by pyrite oxidation. Trace metals in natural waters are mostly derived from enargite, zinc-rich tetrahedrite and sphalerite. Pyrite oxidation contributes very little with respect to base-metals in these natural waters.

Jan 1, 2000

By F. D. Mendes, A. H. Martins

The high copper grade in the Igarapé Bahia (Brazil) gold-copper ore restricts the direct application of the classical cyanidation process. Copper oxide and sulfide minerals react with cyanides in solution, causing high leach-reagent consumption, raising processing costs and decreasing gold recovery. According to studies, a feasible solution would be to pretreat the ore to remove copper minerals prior to cyanidation. The goal of this experimental work was to study the conditions for the removal of copper from the Igarapé Bahia gold-copper ore by sulfuric acid leaching, applying a statistical approach to the experimental design. By using the Plackett Burman method, it was possible to select the variables that exhibited the largest influence on copper extraction at the sulfuric acid leaching stage. These variables were leach solution temperature, stirring speed, sulfuric acid concentration in the leach solution and ore particle size. The individual effect of these variables and their interaction influences on the experimental response were analyzed by applying the replicated full-factorial design method. Finally, the selected variables were optimized by the ascending-path statistical method, which determined the best leach experimental conditions for maximum copper extraction. The optimized leaching conditions resulted in a copper extraction of 75.5%. Keywords: Copper, Gold, Extraction, Sulfuric leaching, Optimization

Jan 1, 2003

By K. Deaton

"INTRODUCTION A packaged cooling system is being developed for refuge alternatives (RAs) that meets MSHA qualification guidelines for deployment in coal mines. This system will allow full occupancy ratings of deployed Refuge Alternatives (RAs) to be maintained by keeping the apparent temperature inside the RA from exceeding 95°F. Research investigations sponsored by NIOSH have shown that heat buildup caused by occupants in mobile RAs will result in apparent temperatures that exceed the 95°F limit established in 30 CFR 7.504. Figure 1 shows the temperature rise in an inflatable RA having an occupancy rating of 23 people at an 81°F mine air temperature. This plot shows the need for either heat mitigation or occupancy derating in warmer mines. The RAECS will be designed to provide enough heat mitigation to eliminate occupancy derating due to heat buildup over the 96 hour refuge period.This paper describes testing of a prototype cooling system that uses proven vapor compression technology powered by batteries to keep the RA interior below the 95° limit for a minimum of 96 hours. Testing of this prototype cooling system was conducted in December of 2015 and January of 2016 at the NIOSH test mine in Bruceton, PA. December testing was conducted at the prevailing mine ambient temperature – approximately 60°F. The January testing was done with the mine ambient temperature in the immediate vicinity of the RA artificially elevated to 85°F. Realistic heat gain from RA occupants was provided by human simulators developed by NIOSH. These simulators add sensible heat corresponding to human metabolic processes and latent heat generated by respiration and perspiration. Heat generated by CO2 scrubbers was also added. Results of cooling system performance using these simulated loads at the two ambient conditions are described. A comparison of the apparent temperature in the RA using two different control techniques is also presented. This work documents the ability of the cooling system to meet the established apparent temperature limit at the full occupancy rating of a six person RA. A new cooling system intended for use with existing RA deployments and having greater cooling capacity is currently in development and will be described."

Jan 1, 2017

By M. J. McPherson, P. Mousset-Jones, G. Danko, F. Calizaya, K. You

The friction factor is one of the more difficult parameters to determine in ventilation planning. In practice, this can be estimated from published factors such as those of McElroy. The problem with this approach is that the selection requires some judgement, and the estimated values offer no more than guideline accuracy. This study, examines the effects of four factors on the coefficient of friction for a simulated mine airway. The factors are: airway cross-section, asperity height, flow direction, and cross-cut spacing. The study includes the modeling of a mine airway and the evaluation of the results from 13 experiments on flows of air over rough surfaces. The model, physically represented by a wind tunnel, includes a rough surface section which can be modified to simulate mine airways of various shape and asperity height. Most of the experiments were performed under controlled flow conditions during which the Reynolds number was varied between 50,000 and 300,0000. Based on this study, the friction factor for a mine opening was found to depend not only on the size and shape of the surface asperities but is also affected by the orientation of them in relation to the flow direction.

Jan 1, 1991

A parametric study was conducted to establish the optimum operating conditions for the column flotation of fine coal. The parameters examined in this investigation included collector and frother dosages, feed solids content, and the volumetric flow rates of feed slurry, air and wash water. Despite the wide range of conditions studied the experimental data were found to fall along single grade-recovery curves, just below the maximum separation predicted by the release analysis technique. The deviation of the parametric test data from the release curve was attributed to the nonselective entrainment of mineral matter associated with poor froth washing. The operating point on the characteristic recovery-grade curve was found to be primarily determined by feed rate and aeration rate.

Jan 1, 1992