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By Richard Giffen, Martha Gross, Luca Pellegrini, Pa Ousman Njie

The Hampton Roads Bridge-Tunnel (HRBT) Expansion project in Virginia includes parallel 1.5- mile (2.4 km) tunnels constructed using a tunnel boring machine (TBM). The TBM launching and receiving shafts were excavated within the footprint of two reclaimed islands abutting the navigation channel for the Port of Virginia. The shaft excavations—a circular tri-cell shaft at South Island, and a circular-rectangular twin-cell shaft at North Island—were supported by slurry walls up to 190 feet (58 meters) below the island surfaces. This paper describes specic design considerations for these shafts, as well as construction and uality-oversight aspects of their excavation and construction.

Jun 23, 2024

By T. W. Beck, J. A. Organiscak

The U.S. National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) has recently studied several redirected scrubber discharge configurations in its full-scale continuous miner gallery for both dust and gas control when using an exhaust face ventilation system. Dust and gas measurements around the continuous mining machine in the laboratory showed that the conventional scrubber discharge directed outby the face with a 12.2-m (40-ft) exhaust curtain setback appeared to be one of the better configurations for controlling dust and gas. Redirecting all the air toward the face equally up both sides of the machine increased the dust and gas concentrations around the machine. When all of the air was redirected toward the face on the off-curtain side of the machine, gas accumulations tended to be reduced at the face, at the expense of increased dust levels in the return and on the curtain side of the mining machine. A 6.1-m (20-ft) exhaust curtain setback without the scrubber operating resulted in the lowest dust levels around the continuous mining machine, but this configuration resulted in some of the highest levels of dust in the return and gas on the off-curtain side of the mining face. Two field studies showed some similarities to the laboratory findings, with elevated dust levels at the rear corners of the continuous miner when all of the scrubber exhaust was redirected toward the face either up the off-tubing side or equally up both sides of the mining machine.

Jan 1, 2013

By W. W. Simpson, S. A. N. Sheya

A procedure was developed by the U.S. Bureau of Mines for recovering gold, silver, cobalt, copper, and zinc from a massive sulfide ore by a hydro-metallurgical process. The procedure consists of (1) oxygen pressure leaching; (2) iron, arsenic, and copper removal from the leach solution by precipitation; (3) selective extraction of cobalt and zinc from solution; (4) electrodeposition of the cobalt and zinc from the strip liquor; and (5) cyanidation of the pressure leach residue to recover gold and silver. The results are discussed in terms of efficiency of metal recovery and conclusions drawn as to possible benefits and broad applications of the process.

Jan 1, 1990

By G. Roberts, S. S. Klima, W. R. Reed, J. Deluzio, G. Ross, A. Mazzella

The abstract discusses the problem of silicosis among roof bolter operators in coal mines due to respirable quartz dust (RCS) exposure. It presents a study comparing a new wet box collection system to the traditional dry box system. The wet box system uses water to saturate collected material, reducing RCS exposure during cleaning. The study found that the wet box system significantly reduced RCS exposures and quartz content in samples compared to the dry box system.

May 11, 2022

By LUKAS FAHLE, Andrew J. Petruska, JURGEN F. BRUNE, Gabriel Walton, Elizabeth A. Holley

Adverse ground behavior events, such as convergence and ground falls, pose critical risks to underground mine safety and productivity. Today, monitoring of such failures is primarily conducted using legacy techniques with low spatial and temporal resolution while exposing workers to hazardous environments. This study assesses the potential of novel simultaneous localization and mapping (SLAM)-based light detection and ranging (Lidar) data quality for rapid, digital, and eventually autonomous mine-wide underground geotechnical monitoring. We derive a comprehensive suite of quality metrics based on tests in two underground mines for two state-of-the-art mobile laser scanning (MLS) systems. Our results provide evidence that SLAM-based MLS provides data of the quality required to detect geotechnically relevant changes while being significantly more efficient for large mine layouts when compared to traditional static systems. Additionally, we show that SLAM-specific processing can achieve an order of magnitude better relative accuracy relevant for change detection than quality metrics derived from traditionally deployed tests would suggest while reducing SLAM drift error by up to 90%. In collaboration with an operating block cave mine, we confirm these capabilities in field tests on a mine-wide scale and, for the first time, demonstrate methods of rockfall detection using MLS data. While more work is required to investigate optimal collection, processing, and utilization of MLS data, we demonstrate its potential to become an effective and widely applicable data source for rapid, accurate, and comprehensive geotechnical inspections.

Aug 16, 2022

By Leonard B. Rothfeld

For many years, pulverized coal (PC) boilers in utility power plants have been the dominant market for domestic coal. Today, two new coal utilization technologies challenge the PC boiler's dominance. Atmospheric fluidized bed combustion (AFBC) and "coal gasification/combined cycle" (GCC) stand on the verge of commercial demonstration in the utility environment at a scale of 100 MW. Developed over the past decade, these technologies respond to the demands for cleaner ways to burn coal and for more flexibility in fuel supply. In the near term, these are the "clean coal" technologies most likely to have a significant impact, because they are ready for commercial application. As for environmental acceptability, consider that just a few years ago one of the environmental slogans was "no coal in California." Indeed, the only large quantities of coal above ground in California at that time were in transit on the way to Asia. Today, thanks to new technology, we can point to two operational coal-burning plants in California and one in the works: * Cool Water GCC demonstration plant (100 MW) * California Portland Cement AFBC commercial cogeneration, near Riverside (190 000 lb/hr steam) * Energy Factors AFBC commercial cogeneration at Stockton, to be operational 1988 (44 MW)

Jan 1, 1987

By B. N. Thompson

The main industrial minerals produced are non-metallic - clay, dolomite, limestone, pumice, salt, serpentine, and silica sand. The other minerals, some with minor production, include diatomite, feldspar, magnesite, sulphur, asbestos, and perlite. Energy and metallic minerals and aggregate are excluded from this account. These industrial minerals occur in a wide range of rock types and geological ages. For example clays are known from the weathering products of Cretaceous rhyolite and leaching of Eocene coal measures; from Quaternary weathering of contemporary loess and shallow marine sediments, and of greywacke of Triassic-Jurassic age; and from the hydrothermal alteration of Late Cenozoic acidic volcanic rocks.

Jan 1, 1982

By R. H. Roberts

The Environment Weipa is located at 12° south latitude on the west coast of Cape York Peninsula, North Queensland, Australia. The climate is tropical with most of the 1 600 mm. average annual rainfall falling between November and March. During the short winter months (May/ August) the weather is clear and pleasant, with temperatures seldom exceeding 27°C.Throughout the remainder of the year, conditions are frequently oppressive due to consistent high ambient temperatures accompanied by high humidity. The terrain is of low relief, and generally not more than 6 to 10m. above mean sea level adjacent to the coast. The coastline features numerous short estuaries which discharge run-off from the heavy rains collected by creeks and rivers. The whole area is covered by an open forest, the predominant species of which is Eucalyptus tetradonta. These eucalypts have only limited commercial value and are heavily infested with termites. Despite the fact that Weipa is close to the location of the first reported sighting of the Australian coastline by a European (William Janz - 1606), it remains very isolated. There is no developed road or rail connection to centres of population, so that transport of practically all products, personnel and materials to and from Weipa is by sea and air. Cairns (population 49 000) is 580 km. by air and 670 nautical miles by sea; Brisbane, the

Jan 1, 1977

By G. A. Irdi

An automated method of microscopy for determining the pyrite size distribution on two base coals that were crushed to 28 mesh x 0 has been developed. Polished epoxy-bound coal pellets were prepared and examined by a Zeiss IBAS image analyzer utilizing a program developed from provided software. Pyrite size distribution determination is considered a necessary first step in pyrite characterization that could lead to successful predictions, by microscopy, of a coal's theoretical pyritic sulfur removal. Our research efforts to date have indicated that the IBP-S can be a reliable instrument for determining pyrite size distribution in crushed coal. A program was also developed to convert pyrite size data to a weight basis for comparisons to the results from chemical analyses. The problems encountered in our research and their solutions will be presented in the discussion.

Jan 1, 1986

By Robert C. Edmiston

"Further, we search for the veins by observing the hoar-frosts, which whiten all herbage except that growing over the veins, because the veins emit a warm dry exhalation which hinders the freezing of the moisture, for which reasons such plants appear rather wet than whitened by the frost," Georgius Agricola, De Re Metallica, 1556 In view of Agricola's statement, made in 1556, the concept of using the heat released by oxidizing sulfides as an ore guide can hardly be considered a product of twentieth-century technology. In fact, thermal exploration has received relatively little attention in modern times compared to other potential field geophysical methods. There have evolved, however, two basic approaches to thermal exploration for subsurface heat sources. These are 1) the measurement of surface temperatures by infrared, thermal imagery and 2) the measurement of geothermal gradients in exploratory drill holes.

Jan 1, 1974

By Shawn Benner, David Blowes, Carol Ptacek

A full-scale reactive barrier was installed into an aquifer impacted by acid mine drainage in August 1995 at the Nickel Rim mine site near Sudbury, Ontario. The primary mechanism of water quality improvement is bacterially mediated sulfate reduction and metal sulfide precipitation. Dramatic changes in the groundwater chemistry are observed with up to 90% decline in Fe (from >18 to <2 mmol L-1) and increases in alkalinity from <1 to >10 mmol L-1 (as CaCO3). Over a 3 year period, the rate of Fe removal declines by approximately 35%. Primary controls on barrier performance are organic carbon reactivity, groundwater temperature, and variable residence time within the barrier.

Jan 1, 2000

By M. A. Cornachione

The west central upper Peninsula of Michigan contains a large resource of graphitic slate. The slate has potential industrial use as a substitute for shale currently used in the production of portland cement. Some of the unweathered slate, however, has a high concentration of pyritic sulfur which can create emission problems when processed in a kiln. A low cost method to reduce the sulfur content of the slate through the optimization of pyrite oxidation in a bio-heap leaching operation was investigated.

Jan 1, 1992

By F. Calizaya

This paper explains and discusses a computer program developed to determine the ventilation design parameters for complex auxiliary ventilation systems such as those found in the construction of long excavations with multiple headings. The program is based on the principle of partitioning the system into segments of finite length, and formulating and solving the resulting networks recursively. The application of the program is illustrated by the detailed solution of an auxiliary ventilation system proposed for the Exploratory Studies Facility (ESF) at the Yucca Mountain project, Nevada.

Jan 1, 1994

By Felicia F. Peng

The manganese removal from aqueous solution containing high Mn2+ concentration by adsorption and oxidation was studied using manganese oxide particles as the adsorbent. The operating parameters including pH, flow rate, initial manganese concentrations, and oxidant dosage affect the performance of Mn2+ removal were evaluated in a laboratory packed column. In the multi-column adsorption tests, each additional column doubled the time for complete manganese removal. No further decrease of pH was also observed once it was lowered to pH 4.5 to 5. This finding implied the possibility of complete high manganese removal without further pH adjustment during adsorption. Oxidation of Mn2+ by dissolved oxygen was found to be insignificant for manganese removal for high Mn2+ concentration. Adsorption was the predominated mechanism involved with manganese removal. Extremely low H+/Mn2+ stoichiometry compared to the reported values was measured. These low values suggested that different adsorption mechanisms such as chemisorption other than H+/Mn2+ ion exchange might play an important role at low pH. This paper presents the quantity and explanation of the results obtained for the mechanism of adsorption and oxidation of high concentration manganese on the manganese ore particles.

Jan 1, 1997

By Setareh Afrouz, Emily Sarver, Cigdem Keles

The resurgence of severe lung disease among US coal miners since the mid-1990s has led to efforts to better characterize and monitor respirable dust exposures, particularly focusing on mineral constituents from rock strata surrounding the coal. A rapid analysis method for silica (quartz) mass using direct-on-filter Fourier transform infrared (FTIR) spectroscopy has been developed, which can also estimate kaolinite, a primary silicate mineral in many coal mines.

Feb 24, 2022

By M. D. Flavel

My paper relates to bond&apos;s third theory of comminution and suggests work be used as a basis for designing crushing and screening plants, this will give more accuracy than existing methods, As stated in the abstract, this paper is only a synopsis of my official paper, many of the questions that might arise in this brief address will be answered by referring to the detail i n the main paper $ Because of the limited time available and the fact that many people here do not need to study the aspects of crushing and screening in depth, i will highlight-those sections of the paper which show how major capital, operating and energy cost savings can be achieved in the process, I will develop the theme in the following manner, Firstly, pointing out, why a new approach is needed to the fundamentals of crushing and screening, Secondly, by setting forth some theory to describe what we are trying to accomplish, Thirdly, by looking at important factors which need to be observed in designing plants and applying machines to comply with this theory, Lastly, i will put forth some ideas on how we might develop this theory to make the industry more efficient, At the outset, i have to say my approach to this process is entirely new, for those used to applying machines and designing plants on existing criteria, they will find this theory easier

Jan 1, 1977

By Robert D. Schmidt

The US Bureau of Mines is cooperating with Cyprus Mineral Park Mining Co., Columbia University, and the US Geological Survey in investigating the feasibility of applying in situ leach mining methods to fracture-hosted, supergene copper sulfide (chalcocite) ores. This paper presents the initial findings of mineralogical, hydrogeological, and geochemical characterization studies conducted at the Mineral Park mine, located in the Wallapai mining district of northern Arizona. A design for in situ leaching is proposed that would minimize the need for blasting prior to leaching, and would enable economical development of deep reserves at the Mineral Park mine. The in situ leaching design would also reduce the potential for long term acid rock drainage.

Jan 1, 1995

By T. Karlkvist, H. R. Kota, F. Andreas, B. I. Pålsson

"Separation of different calcium minerals have long been an interesting and challenging problem. In this investigation calcium mineral separation is examined by: microflotation, zeta potential measurement and adsorption, using novel collectors having two functional groups instead of one. In theory, by varying the distance between the functional groups, it could be possible to preferentially target one calcium mineral by matching the spatial distance between the sites on the mineral surface. In this investigation two new surfactants have been tested to estimate their ability to float apatite and/or calcite. Preliminary findings show that an increase in distance between the functional groups favors one mineral over the other, and this might be due to differences in the mineral surface structure. INTRODUCTION Apatite is a strategically important mineral which has both great value for industrial use as a precursor to phosphoric acid; and in the agricultural industry as an important source of phosphorous in fertilizers. This has led both the European Union and the United States to recognize it as an important resource for the future. Currently there is no lack of apatite in the world, but it is important to develop the beneficiation to ensure future supply. A common problem in apatite flotation is the selectivity towards calcite, which it is commonly associated with. Although calcite is an important industrial mineral its abundance makes it not usually worth to extract from apatite ores unless it is easy to separate1,2. Both apatite and calcite are semi soluble minerals with calcium as one of their constituents. The most common way to separate apatite and calcite is to use flotation. A process that involves making the mineral particles to extract from the system hydrophobic by adsorbing a collector on the mineral surface. One way to study collector adsorption on a mineral surface is by zeta potential measurements. The zeta potential is the charge at a slip plane a short distance from the surface. By measuring the zeta potential with and without the presence of collector it is possible to investigate if the collector is present at the surface or not, a change is indicative of collector adsorption. The zeta potential of fluorite, apatite and calcite without collector can be seen in Figure 1. The small difference in zeta potential between apatite and calcite shows the similarity in their surface properties and gives an indication of their separation difficulty. One additional problem with semi soluble minerals is their tendency to slightly dissolve in the pulp and thereby change the ionic composition of the solution. This makes separation and research problematic as the freed ions may readsorb on the mineral surface and interfere with the collector adsorption on the mineral surfaces3–5."

Jan 1, 2016

Reaction kinetics for gold dissolution in acid thiourea solutions were investigated using formamidine disulfide as an oxidant. For the conditions studied it appears that a surface reaction limits the rate of gold dissolution. The rate was found to be first order with respect to thiourea concentration and half order with respect to the concentration of formamidine disulfide; the apparent activation energy for the reaction was 10.40 kcal/mol (43.40 kJ/mol); and the reaction rate was independent of pH for the pH range 1.0 to 3.0.

Jan 1, 1999

By Levent Ozdemir

An extensive study involving laboratory testing and computer modeling has been performed to assess the technical and economic feasibility of utilizing the recently developed minidisc cutters on roadheaders for hard rock mining. The results show that heavy duty roadheaders fitted with minidiscs can excavate hard rock formations at acceptable production rates and cutter costs. This paper presents and discusses the results of this study together with the ongoing developmental efforts of this technology, which include laboratory testing of a roadheader cutting drum with minidiscs and full scale field testing of a machine in hard rock

Jan 1, 1995