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By C. J. Pritchard, R. D. Jacksha, K. V. Raj, C. Sunderman

"In underground metal/nonmetal mines, repeated short-term exposure to high levels of airborne contaminants can become a serious health issue. Currently there are no common mechanisms to control or mitigate these localized short-term high exposures to contaminants. To improve miners’ health and safety, the National Institute for Occupational Safety and Health (NIOSH) Spokane Mining Research Division (SMRD) is developing a Smart Monitoring and Control (SMAC) system for real-time monitoring of mine air quality, with integrated countermeasures to reduce these high concentrations of airborne contaminants in localized sections of mines. To develop and test a SMAC system that could be implemented in an underground mine, researchers at SMRD built a test apparatus incorporating a fan, louver, ducting, and sensors combined with atmospheric monitoring and control software. This system will institute effective countermeasures to reduce contaminant levels, improving miner safety and health. INTRODUCTION Underground metal/nonmetal mines continue to expand production by employing large equipment in greater numbers and by mining into hotter and more challenging environments which are typically further away from fresh air sources. This challenges the ventilation system to provide adequate quantities of fresh air to the workplace and increases the potential for air contamination that could result in immediate and long-term health and safety issues to miners. Currently, airflow and contaminant concentration in mines are typically based on full-shift sampling which may not identify repeated short-term exposures to high levels of airborne contaminants such as NO2, CO, diesel particulate matter (DPM), and dust with high silica contents. Repeated short-term exposure to these high levels of airborne contaminants over long periods can lead to serious health issues which are documented in several studies [1-3]. Based on data from ventilation surveys and contaminant measurements, mines often attempt to minimize exposures by sending more fresh air to the working areas where contaminant concentrations are found to be high. Real-time monitoring and control allows mines the option to monitor contaminants and implement controls in real-time. Real-time monitoring and control of the underground mine atmosphere has been a subject of research since its beginning in Finland at Outokumpu’s Pyhäsalmi Mine in 1969 [4]. More recently, the real-time monitoring and control problem has been addressed using ventilation on demand (VOD) systems [5, 6]. A VOD system attempts to deal with this issue on a global level by controlling fans, louvers, and doors to increase airflow to active work areas and reduce contamination. However, a VOD system only controls the distribution of airflow and may not be helpful in mines where the airflow is at maximum capacity. Researchers at SMRD are developing a SMAC system for real-time monitoring of mine air quality with an integrated ability to trigger countermeasures to reduce high concentrations of airborne contaminants in localized sections of mines. The SMAC system will be designed, tested, and refined in the laboratory environment before being demonstrated in an underground mine. This system will not only try to minimize the gaseous contaminants by regulating the airflow locally, but will also potentially employ a filtration system to reduce the airborne contaminants in case the maximum airflow capacity is reached. This paper presents development of the test apparatus for the SMAC system."

Jan 1, 2017

By J. D. Miller, J. Hupka

Environmental applications of the air-sparged hydrocyclone (ASH) technology are presented. The original ASH design used porous sintered steel or porous polyethylene tubes as spargers. To diminish/prevent plugging and to reduce pressure head loss in the gas path a wire screen sparger and new hydrocyclone design have been developed, which allows for wide application of the technology to solve environmental problems and to be used as a chemical reactor. Field and laboratory trials have shown that the ASH technology might be preferred for the stripping of volatile organic compounds WOC) from contaminated water. The ASH has also been developed for absorption of SO2, toluene vapors, and for the recovery of cyanide.

Jan 1, 2005

By R. J. Lutton

The suitability of large-stone materials continues to present occasional problems in US construction. Distinctive modes of rock deterioration cracking, spalling, delaminating. disaggregating, disintegrating, and dissolving help to distinguish causes of deterioration. Design requirements, costs, and environmental factors remain critical to performance. The rating of material quality from superior hypes such as granite to marginal types such as conglomerate is too simplistic but may be useful in a preliminary way. Regardless, the market is dominated by limestone/dolomite material types because of their widespread availability. Certain tests that have been standardized are widely accepted and used for evaluating stone as riprap and armor. These tests are adapted from those used extensively for concrete aggregate; they explore the resistance of the rock to destructive processes such as abrasion, freeze-thaw, and wet-dry environmental attack. The field evaluation of the rock source is often as important as testing. Important limitations imposed by natural jointing and variations of bedding are documented in this manner. The field examination also supports the testing by estimating how much of the quarry is rep¬resented by each of the samples to be tested. Finally, quarrying and processing methods and transportation are carefully considered in regard to stone quality, average size, size gradation, and cost.

Jan 1, 1990

By Kenneth K. Humphreys

INTRODUCTION At the time the 4th edition of this book was published in 1979, the coal industry had experienced a sharp upturn in prices for its product. From 1950 throgh 1969, steam coal prices had held almost flat at about $5 US per st (about $5.50/t). Thus, when considering the effects of inflation, the price of coal had actually been declining for two decades. The passage of the Coal Mine Health and Safety Act in 1969 and its cost effects started an upward trend in coal prices which was rapidly accelerated by the effects of the Mid-East oil embargo in 1972. Prices of steam coal on the spot market eventually climbed to over $30 US per st ($33/t) and higher in some cases. Metallurgical coal prices skyrocketed in a similar manner and the industry at long last appeared assured of an adequate return on investment. Many companies did expend large sums of money to upgrade and expand their mining and preparation facilities. Unfortunately the bubble eventually burst, in great measure due to the downturn in the US domestic steel industry and the resultant decline in metallurgical coal demand, loss of export markets to other nations and even imports of large amounts of foreign coal to the United States, and more stringent environmental regulations which made many high sulfur coal measures uneconomical to mine. Compounding the problem was the rapid world decline in oil prices in the mid-1980s which encouraged many consumers to utilize oil rather than coal. During the 1980s, metallurgical coal dropped over 20% in price, which, when considering inflation, actually amounted to about a 40% decrease in value. Export coal decreased a similar amount in price. Steam coal prices held nearly constant, thus also losing considerable value when inflation is considered. All of these factors make it even more imperative than ever that the industry do everything in its power to make wise economic decisions and to examine carefully all existing operations and planned future expenditures to be certain that their full cost implications are understood and that they can be justified on the basis of an adequate return on investment. It cannot be assumed that the price of coal will increase. To the contrary, as indicated previously, when considering inflation, coal decreased in value in the 1980s, just as it also did in the 1950s and 1960s. The price surges in the 1970s merely were a catchup game, and in truth the true market value of coal is in reality even lower than it was in 1950. CAPITAL AND OPERATING COST ESTIMATION Prior to constructing a new plant or expanding existing facilities, a detailed preliminary cost estimate is necessary to determine the capital investment

Jan 1, 1991

By J. B. Cabezas

The metallurgical processes that are frequently applied today use strong solutions and are of alkaline, acidic, or organic nature. These play a very important part in recovery of values from many ores. These solutions are of such a chemical nature that they are generally corrosive, flammable, and contaminating. In most cases, they are highly dangerous to the environment. Within the extractive metallurgical industry, it is also very common to have to deal with the handling of contaminating solutions with a high content of cyanide, arsenic, mercury, lead, copper kerosene, acid and many other components whose temporary or permanent confinement within the process must be adequate and absolute.

Jan 1, 1986

By Subhash Sethi

The WIPP (Waste Isolation Pilot Plant) Project near Carlsbad, New Mexico. is a research and development project sponsored by the U.S. Department of Energy, designed to demonstrate the safe disposal of radioactive waste. A mine (repository) is being developed 2150 feet below the surface in a thick salt bed, which will serve as the disposal medium. The underground ventilation system for the WIPP project was originally designed based on a fixed project scope. The design criteria and ventilation requirements were developed for the performance of various activities as then envisioned towards the achievement of this goal. However, in light of new information and actual site-specific experience at WIPP leading to a clearer definition of the scope-related programs and activities, it was realized that the existing ventilation system may need to be modified. A re-assessment of the ventilation requirements--based on the current status of the facility and a clearer definition of the scope of the experimental programs, waste storage methodology, mine developmental activities. and current equipment list--indicates a two- fold increase in underground airflows from 210,000 cubic feet per minute (cfm) to 425,000 cfm. Various options to provide the increased airflow to the underground facility were considered and analyzed. Based on the techno-economic analysis, safety and environ- mental considerations, and other conditions unique to a facility like WIPP, it was decided to construct a new shaft to serve as the primary fresh air intake, along with the installation of additional fans in parallel with the existing set up. Low cost and the ease with which the new design could be implemented and integrated into the existing ventilation system with minimum impact on current activities and projected schedules were the guiding factors in designing the shaft and related ventilation modifications.

Jan 1, 1987

By R. G. Eggert, M. R. Walls

A mining CEO's willingness to participate in risky investment opportunities significantly affects a company's strategic-investment decisions. Decision-analysis techniques provide a mechanism for measuring a CEO's risk tolerance and ability to make formal comparisons of risk propensity among mining firms. The authors developed a methodology for measuring CEO risk tolerance. The findings from a confidential survey of mining CEOs are presented. The results from the survey suggest that: •mining CEOs are overwhelmingly risk averse when considering investment decisions; •CEOs of small mining firms are significantly more risk averse than CEOs of large mining firms; and •there appears to be some differences between Australian and non-Australian CEOs regarding their willingness to participate in risky investments. The results of this survey suggest that CEOs are pursuing objectives other than, or in addition to, maximizing shareholder wealth and that they act to reduce the financial exposure associated with strategic investments.

Jan 1, 1997

By J. A. Brierley, R. Y. Wan

Newmont Gold has advantageously used the capabilities of mineral oxidizing bacteria to develop a process for the pretreatment of low-grade sulfidic and carbonaceous-sulfidic refractory gold ores. The biooxidation process results in the oxidation of the sulfidic minerals with increased exposure of gold for subsequent gold recovery. The biooxidized carbonaceous-sulfidic ores cannot be heap leached with cyanide because of the preg-robbing characteristics of the carbonaceous matter in the ores. Therefore, an alternative heapleach process using ammonium thiosulfate was developed to extract gold from these preg-robbing biooxidized ores. The ammonium thiosulfate leach process was successfully applied in both laboratory and pilot plant tests. Satisfactory test results were achieved, encouraging the continuation of process development.

Jan 1, 1998

By A. J. Hendron, B. Mohraz, R. B. Peck

INTRODUCTION The state of the art of soft-ground tunneling was discussed in detail by the senior author at the 7th International Conference on Soil Mechanics and Foundation Engineering held in Mexico City in 1969. Little can be gained by repeating the information assembled at that time. Hence, in this report, only the briefest summary will be given of the overall state of the art and attention will be concentrated on trends and developments since 1969. A characteristic of recent developments is the continued trend toward use of shields and excavating machines. The implications of this trend with respect to design and construction, and particularly with respect to the treatment of unfavorable ground conditions, will be examined. Settlement associated with lost ground, a subject as old as tunneling itself, will be reviewed and methods will be considered for its reduction. Design of tunnel supports was discussed in detail in 1969 with respect to essentially rigid or essentially flexible types of linings. In this report, a definition of flexibility will be considered and design procedures suggested for linings of flexibility intermediate between the two extremes.

Jan 1, 1997

Little knowledge is available that considers the effects of continuous miner position on the possible respirable dust exposure of the remote mining-machine operator. Such information could be very useful for increasing the awareness of the remote operator as to those parts of an extended cut that generate higher levels of respirable dust. This data could be used to develop guidelines for positioning the remote operator to reduce his potential exposure. This work details the effects of continuous miner position on dust levels measured on the machine and at the remote continuous miner operator location.

Jan 1, 2000

By Daniele Martinelli, Rodrigo Winderholler, Daniele Peila

"This paper presents a technical description of an experimental procedure developed for the geotechnical characterization of granular soils conditioned for EPB tunneling using a modified direct shear box. As the main concerning parameters of the conditioned soil mass were their undrained properties, in order to preserve its pseudo-fluid characteristics, a watertight direct shear apparatus was constructed. A comparison between the results obtained under dry, saturated and conditioned conditions is presented. INTRODUCTION EPB shield machines have been used for tunneling excavation in many different types of soils thanks to the use of soil conditioning agents. These modify the properties of the soil into that of a plastic paste, thus permitting the homogeneous flow of the excavated soil from the tunnel face through the bulk chamber, the screw conveyor and finally the conveyor belt. Moreover this technique allows controlling the face pressure and its regulation in the bulk chamber, preventing water inflow when tunneling below the water table. Further advantages are a drop of the cutter head and screw conveyor torque and reduction of the friction between metallic parts and the soil, consequently reducing wear phenomena (Merritt & Mair, 2006; Vinai et al., 2007; Borio et al., 2010; Thewes & Budach, 2010; Herrenknecht et al., 2011; Barbero et al., 2012; Peila, 2014). Several studies have investigated the possibility of conditioning and the chemical materials to be used in different types of soils, mainly subdivided into three groups: cohesionless soils (sand and gravel), silts and clays, and rock masses. This various researches have set up several laboratory procedures for these achievements before and after soil conditioning, as stated in Thewes & Budach (2010) and Peila (2014) (for cohesionless soils), in Thewes & Burger (2005), Hollmann & Thewes (2013), Zumsteg et al.(2012) (for clay), in Peila et al. (2013) and Martinelli et al. (2015a) (for rock mass). Such tests should be simple to execute, reliable and easy to interpret at the in-situ excavation step. The reduction of shear strength is necessary in EPB operations, since it allows an effective transmission of the pressure from the material itself to the front. In some cases the slump is not sufficient to return a reliable result on the shear strength reduction, as in some cases some materials are behaving differently. Therefore this research is aimed to study this aspect more in detail, in order to show the effectiveness of the soil conditioning process on the material to be excavated."

Jan 1, 2016

By S. R. Clifford

Organic contaminants can be removed from river sediment using conventional flotation methods. Organic contamination in sediments is one of the most significant pollution problems facing the Great Lakes region. Using conventional flotation, the majority of the organic contamination can be collected in a concentrate, leaving a "clean" tailings. This provides a cost savings by reducing the amount of material requiring further treatment. The concentrate can then undergo additional flotation stages, or other contamination removal procedures, to further remove the organic contaminants.

Jan 1, 1994

By Charles H. Arnold

This topic addresses historic and current techniques of excavating, supporting and lining tunnels of 4 m (13.1 ft) and smaller. Special considerations relate to the economics of working in close quarters and the sizes of tunnel which achieve the required facility in the optimum economic manner are discussed. The excavation discussion includes TBM, conventional and special techniques for hard rock, soft ground, subaqueous, free and compressed air tunnels. Internal and external support methods discusses timbering, steel ribs, bolting, strapping, shotcreting, grouting, and freezing. Lining methods include cast-in-place concrete, concrete pipe, segmented linings, shotcrete, and others.

Jan 1, 1981

By Anthony Harding, Rodolfo D. Aradas, Juan M. Fernandez, Darío Tsingas

"The adoption of tunneled combined sewerage interceptors and outfalls leads to design linings which are often subject to internal pressures that are larger than the external pressures, resulting in significant tension loads. The need to meet stringent durability conditions for the normal design life of 100 years often drives client specifications to require a double pass solution with a cast in situ secondary concrete lining. However, improvements in concrete technology and the need to seek efficiency in terms of time and costs, have driven designers to consider single pass segmental linings. The Riachuelo Sanitation project in Buenos Aires is subject to these constraints both upstream and downstream of a sewage treatment plant. This paper describes how the challenges of up to 2 bar pressure differential have been addressed by careful analysis of soil structure interaction to ensure that the full benefit of external ground pressure is realized, resulting in a more optimal design for the constructor both in terms of cost and time. INTRODUCTION The construction of long sewerage interceptors and outfalls is becoming an increasingly common piece of infrastructure for modern urban cities facing a large water front and estuarine conditions, which are under a significant environmental burden imposed by decades of sustained growth. Such works intercept most of the distributed sewage discharges to then divert them to a central treatment point from which it will be finally diffused via an outfall into a water body capable to accept these discharges under acceptable environmental conditions. Depending on the magnitude of the sewage load to be handled, the configuration of the urban environment and the conditions of the receiving water body, both in terms of oceanography forces and seabed conditions, these schemes will vary in length, conveyance capacity and design and construction requirements. When conditions permit, the current trend is the execution of long outfalls using flexible solutions (such as the use of HDPE pipes) which usually require some form of concrete ballasted weights to resist off shore dynamic forces when directly laid over the sea bed. However, this concept faces limitations when the conveyance requirements indicate the need for large diameters (typically above 3000 m) and also when the outfall needs to avoid deep features off shore such as navigation channels. When this occurs, tunneling, particularly segmentally lined tunnel constructed by TBM emerges as the most feasible approach for large diameter, long deep outfalls. The operating conditions often result in internal pressures that are larger than the external pressures, resulting in significant tension loads in the lining. The need to meet stringent durability conditions for the normal design life of 100 years often drives client specifications to require a double pass solution with a cast in situ secondary concrete lining."

Jan 1, 2016

By Allan E. Hall, Kuda R. Mutama

Jet fan (ductless fan) ventilation in underground mines and tunnels is a subject requiring further attention. At present there are no accepted procedures or guidelines for this type of ventilation. The main reason has been the absence of sufficient general data, which has hampered the development of rules. There is great potential for using jet fans in terms of both effectiveness and economics because they eliminate the need for ventilation tubing. In the present studies a procedure is described and results are presented from a jet fan modeled in a square section wind tunnel. The major purpose of the studies was to provide fundamental data on jet fan performance after it was realized that previous work had been limited and too site specific. The jet fan position in relation to the tunnel walls was varied in order to study the influence of confining walls on entrainment rates and the resulting aerodynamics. A clearer understanding of the fundamental principles of jet fan applications was obtained.

Jan 1, 1995

By Jack M. Jodrey, Neil D. O’Donnell, R. A. Metz

Bituminous sands of the Lower Cretaceous McMurray Formation in northern Alberta constitute the ore for the surface mining operation at Syncrude Canada Ltd. These sediments represent a complex succession of fluvial, estuarine and marine depositional environments. Grade prediction is realized through a combination of geological interpretation, computer modeling, and reference to past mining experience. Accurate forecasts of feed grade permit reliable predictions of volumes for removal to meet budgeted synthetic crude oil production. This planning facilitates efficient allocation of mining equipment and resources. The feed grade to the Extraction Plant is monitored at various points along the delivery system.

Jan 1, 1992

By Jeffery H. Stricklin

Jim Walter Resources operates five underground coal mines with longwall faces in operation in four of the mines. Due to high air velocities (1000-1200 fpm) needed for methane control together with the friability of the coal, dust control on JWR longwalls offers unique challenges. We have tested many innovative measures to reduce respirable dust concentrations on longwalls with varying degrees of success. These measures include the "shearer clearer" system, different drum water spray configurations, sprays on the longwall belt, stageloader and crusher sprays, wetting agents in the spray water system, and homotropal ventilation. Water infusion of deactivated horizontal methane drainage holes in longwall panels is now being evaluated. A study was completed in November 1986 where water was infused into two horizontal de-gas holes. Personal gravimetric samplers were used to measure respirable dust concentrations and showed a significant reduction in the infused zone. A more in depth study will be conducted. This paper will describe the dust control measures presently used on JWR longwalls, give the results of past studies, and discuss new methods proposed to control longwall dust.

Jan 1, 1987

By Brenda J. Wolfe

Following successful laboratory and pilot plant investigation of dewatering characteristics of molybdenum concentrate produced by a Chilean copper/moly producer, two (2) DENVER SALA 500 Series Tube Press Filters were installed in 1994 to handle the total production volume. Moisture requirements in the filter cake have been consistently met, eliminating the need for thermal drying after filtration. Operating data and Tube Press Filter are described herein.

Jan 1, 1995

By Roshan B. Bhappu

In situ mining and extraction is one of the Frontier Technologies that is destined to play an increasingly important role in the recovery of metals and minerals in the future. This premise is based on increasing costs of labor and energy, increasing awareness of environmental considerations and decreasing ore grades in the United States. Up to now, in situ mining has been successfully applied to a few favorable situations for the extraction of some evaporites, copper and uranium. However, because of its unique technical, environmental and economic advantages, this versa tile technology will find broader applications for the recovery of above commodities as well as for others which are currently extracted by hydrometallurgical means. This paper traces the development of in situ mining and extraction; stresses its dependence on interdisciplinary science and engineering; discusses its theoretical, practical and economic aspects; and finally presents potential applications of this Frontier Technology.

Jan 1, 1985

By George J. Dvorznak, Robert W. Waytulonis

The Bureau of Mines is conducting a research project in cooperation with the Mine Safety and Health Administration (MSHA). Mining companies, and equipment manufacturers are also participating through the Colorado Mining Association (CMA). The objectives of this cooperative research project are to determine the practicality of coupling a dry exhaust conditioning system (dry system) and diesel particulate filter (DPF) to make an integrated control system, and to determine the effectiveness and durability of the integrated system in an underground coal mine. Diesel-powered mining machines must be equipped with control devices to reduce surface and exhaust temperatures to safe levels and prevent flames and sparks from being emitted to the mine atmosphere. Diesel exhaust-gas water scrubbers have been successfully used for many years but they have several disadvantages; they are large, consume large quantities of water, and require frequent maintenance to remain functional. Additionally, diesel exhaust is a source of noxious gases and particulate matter. Particulate emissions are composed primarily of small carbon particles with absorbed hydrocarbons and they are almost entirely respirable in size. Even an engine in good mechanical condition can emit up to 400 mg/cu m of respirable particulate matter. A dry system for control of diesel fire and explosion hazards, coupled to a DPF, promises to be a complete control system for diesel engines. The dry system cools the exhaust and suppresses sparks and flame with a heat exchanger and flame and spark traps. The conditioner is smaller, consumes no water, and requires less maintenance than a comparable water scrubber. The DPF uses a ceramic substrate as a wall-flow filter and is very efficient at collecting exhaust particles. Average particulate mass collection efficiency is 90%. This report describes a cooperative research project to combine the dry system with the DPF, conduct performance tests on the integrated system at Bureau and MSHA 1aboratory facilities, and conduct field tests of the system on a production machine in an underground coal mine.

Jan 1, 1987