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By G. Bulut

The recovery of copper and cobalt from ancient copper slags from the Küre region of Turkey was investigated. A fayalitic-type of ancient copper slag containing 1.24% Cu, 0.53% Co and 53.16% Fe were subjected to an experimental study. Two different routes were followed to recover the metal values. The first route was roasting the slag with pyrite followed by leaching. The second route was flotation of the slags, roasting of the flotation tailings with pyrite and leaching. The second route was found to be suitable for the treatment of the copper slag studied. In the flotation step, a copper concentrate containing approximately 11% Cu was produced with a 77% recovery while 93% of the cobalt stayed in the tailings. In the roasting experiments, the effects of roasting time, pyrite: slag ratio and roasting temperature on the dissolution efficiencies of Cu and Co were investigated, and the optimum conditions were determined. In the tests, 87% of the cobalt dissolution was observed after one hour of roasting at 500°C with a pyrite: slag ratio of 3:1. The copper dissolution in the tests was 31%. Based on the results of this study, a process flowsheet is proposed for the evaluation of these slags.

Jan 1, 2007

By Bob Rautenberg

The Construction of Tunnel and Edison Force Mains contract involves the installation of two new force mains to provide a redundant means for sewage conveyance from Middlesex County Utility Authority?s (MCUA) Edison Pump Station on the northern shore of the Raritan River to the Central Wastewater Treatment Plant on the southern shore. The force mains will be installed in a 1,192 m (3,910 lineal foot) long tunnel with a 4.09 m (13'-5') inside diameter, fully gasketed precast concrete segmental lining, which is to be tunneled underneath the Raritan River utilizing an Earth Pressure Balance TBM. The tunnel is anticipated to encounter flowing soils near and beneath the river. Two new 60-inch diameter Centrifugal Cast Fiberglass Reinforced Polymer Mortar force mains will be installed within the tunnel leaving an open utility corridor above the force mains for future consideration. The project also includes the design and construction of two slurry wall shafts with associated piping. The paper will provide an overview of design and provide a case history of the construction of the tunnel and highlights of the construction methods implemented to date.

The extraction and processing of minerals from surface mines and quarries can produce significant fugitive emissions as a result of site activities such as blasting, unpaved road haulage, loading, primary crushing and stockpiling. Uncontrolled fugitive dust emissions can present serious environmental, health, safety and operational issues impacting both site personnel and the wider community. Simulation technology is finding increasing use for the purposes of advanced warning of potential problem emissions in addition to providing a basis for future planning applications where demonstrable compliance with regulatory requirements are necessary. The initial re-entrainment and subsequent dispersion of fugitive dust presents a process complicated by the combination of the in pit topography, the surrounding natural topography and the dynamic nature of emissions from these sites. These factors impact upon the accuracy and reliability of the conventional Gaussian plume based computational prediction methods employed for regulatory compliance and IPPC applications. This paper proposes that optimal modelling of open pit emissions may be more accurately achieved by the use of a multi-scale predictive modelling approach utilizing computational fluid dynamics (CFD) methods for high resolution near source dispersion and conventional Gaussian based methods for far field dispersion modeling. This paper presents a numerical based flow and dispersion analysis of a typical UK based open pit utilizing CFD in conjunction with a conventional Gaussian plume based methods. Typical operating emissions and meteorological conditions are obtained from long term data records collected at a large operating quarry extraction operation in the UK. Emissions are modelled using a Lagrangian framework within conventional atmospheric boundary layer (ABL) profiles expressed as functions of turbulence and velocity parameters under assumed neutral conditions. Results are presented in terms of the impact of site topography on in pit retention as compared to the Gaussian based method.

Jan 1, 2009

By Wei Victor Liu, Na Zhang, Chengkai Fan, Bei Jiang

The truck haulage data from open-pit mine sites are usually massive and multidimensional with multi-peak Gaussian distributions. Artificial neural networks (ANNs) are well-known machine learning algorithms to handle massive and multidimensional data for building models. Moreover, Gaussian mixture modeling (GMM) is a suitable option for processing the data under multi-peak Gaussian distributions and improving model accuracy. For the first time, this study used a back propagation neural network (BPNN), an extreme learning machine (ELM), and a Bayesian regularized neural network (BRNN) coupled with GMM to deal with the complex truck haulage data and build three weighted ensemble models (WE-BPNN, WE-ELM, and WE-BRNN models) to predict truck productivity at mine sites. Decision tree (DT), random forest (RF), gradient boosting machine (GBM), and extreme gradient boosting (XGBoost) were used to build models to be compared with the weighted ensemble models. The results showed that the WE-BRNN had a higher accuracy than the WE-BPNN and WE-ELM models. The proposed weighted ensemble models performed better than the benchmark models in predicting truck productivity, indicating that a weighted ensemble approach based on the GMM analysis significantly improved the model accuracy. Based on the relative importance analysis, haul distance was the most crucial input variable for predicting truck productivity. This study provides a new approach to predicting truck productivity, which will help mining companies make sound budget decisions and improve mine planning.

Mar 2, 2023

By Robert E. Mazurak

Mines and plants for sale, downsizing, bankruptcies, consolidation, slab imports, minimill growth displacing traditional integrated steel-making. These are some issues for North American iron ore and integrated steel producers. But the blast furnace still remains the workhorse of the ironmaking industry. And direct reduction and other alternate ironmaking technologies have yet to make any serious inroads in North America. How come? This article addresses the current state of primary ironmaking in the changing North American steel industry, the direct reduction market and new technologies under development that may hold some promise.

Jan 1, 2003

By M. S. Ellis, D. J. Nichols

In 1999, 1,100 million short tons of coal were produced in the United States, 38 percent from the Northern Rocky Mountains and Great Plains region. This coal has low ash content, and has sulfur content in compliance with Clean Air Act standards (U.S. Statutes at Large, 1990). The National Coal Resource Assessment for this region includes geologic, stratigraphic, palynologic, and geochemical studies and resource calculations for 18 major coal zones in the Powder River, Williston, Green River, Hanna, and Carbon Basins. Calculated resources are 660,000 million short tons. Results of the study are available in U.S. Geological Survey Professional Paper 1625-A (Fort Union Coal Assessment Team, 1999) and Open-File Report 99-376 (Flores and others, 1999) in CD-ROM format.

Jan 1, 2001

By R. K. McLimans, C. Knudsen, S. Bernstein, D. Frei

Computer Controlled Scanning Electron Microscopy (CCSEM) is used to analyze indivdual mineral fractions in heavy mineral sands. CCSEM is a fully automated particle analysis technique for the determination of physical and chemical properties of a large number of individual particles. CCSEM enables the precise and accurate determination of the modal abundances of individual mineral fractions (e.g. ilmenite, rutile, zircon, or garnet), their average chemical composition (and compositional variation), as well as their physical properties such as size (e.g. diameter and perimeter length) and shape (aspect ratio and circularity). A unique sample preparation procedure is used to produce representative polished sections from cylinders of raw sand samples such that thousands of grains are present in a polished cross section, but grains are not touching. The combination of this sample preparation technique with CCSEM enables the fully automated analysis of individual grains without the application of de-agglomeration or erosion steps to separate touching particles. Hence, CCSEM yields information representative of the entire area of analyzed grains without systematic bias due to neglect of rim areas by de-agglomeration or erosion steps. Therefore, the resulting data are determined with high accuracy, precision and statistical validity. Because the sample preparation is relatively straightforward, using raw sand samples, and all chemical and physical properties are determined in one analytical session per sample, CCSEM is a powerful cost and time efficient tool for characterizing chemical and physical properties of minerals in heavy mineral sand deposits.

Jan 1, 2005

By A. Martin

Detailed porewater profiles of arsenic and other interstitial metabolites were used to assess the relationship between trophic status, sediment redox chemistry and arsenic mobility in a historic tailings repository. The results demonstrate that in eutrophied systems which exhibit greater sediment oxygen demand, the depth of the Fe(III) redoxcline, and hence depth of arsenic release, may lie in close proximity to the sediment-water interface. As a result, arsenic scavenging mechanisms are significantly reduced, resulting in a greater flux of arsenic to the water column. Such considerations have important implications for the management of pit lakes, tailings ponds and contaminated lakes which may consider: 1) the discharge of sewage to the water body during operations; and/or 2) post-closure fertilization as a remediation strategy.

Jan 1, 2002

By Douglas D. Campbell, Alan S. Imrie

INTRODUCTION Mica Dam is located on the Columbia River just downstream of the "big bend" of the Columbia, where it leaves the Rocky Mountain Trench and begins to flow southwards, approximately 85 miles north of Revelstoke, B.C. (Fig.l). The dam was built as one of three Columbia River Treaty dams in British Columbia which regulate the flow of the river and provide flood control downstream in Washington and Oregon. In addition, the three Canadian dams make possible greatly increased power generation at existing power plants in the United States and further development along the Columbia and its tributaries in British Columbia. History Mica Dam, constructed during the period 1967 to 1973, is a zoned earthfill embankment 650 feet high, which has 12,000,000 acre feet of live storage and an available head of 550 feet. Power intakes which would serve either a six-unit surface or underground plant were incorporated into the design and construction of the right abutment of the dam (Fig. 2). Prior to 1971 alternative 2500 MW capacity surface and underground powerplant arrangements were studied. Cost estimates for the two alternatives were the same within the limits of estimating procedures. However, it was believed there was a certain continuing risk in locating a surface plant at the toe of a steep canyon wall. Therefore, in 1971 a tentative decision was made to proceed with an underground plant, provided that additional exploration confirmed assumptions of

Jan 1, 1976

By Daniel N. Adams

The University Link project extends Seattle?s light rail from downtown to University of Washington (UW). It includes 5.0 kilometers (3.15 miles) of twin-bored, 6.4 meters (21 feet) excavated diameter tunnels, and two cut-and-cover stations. The Capitol Hill Station (CHS) requires an excavation 170.7 meters (560 feet) long, 22.6 meters (74 feet) wide, and 22.9 meters (75 feet) deep. The University of Washington Station (UWS) requires an excavation of about 238.4 meters (782 feet) long, 21.3 meters (70 feet) wide, and 33.5 meters (110 feet) deep. The project is within the glacially diverse soils of the Puget Sound region, below groundwater. This paper highlights major station and tunnel design elements, including the approach to support of excavation at both station boxes, and the site staging requirements.

Jan 1, 2008

By M. Superfesky, P. Michael

Introduction The US Office of Surface Mining (OSM) is proposing changes to the Code of Federal Regulations in the interest of minimizing the adverse effects of excess-spoil-fill construction on the “prevailing hydrologic balance, fish, wildlife and other environmental values” (70 FR 35112). The proposed changes will require: (1) minimization the amount of excess spoil generated at a mine site; (2) minimization of the size of the fills constructed; (3) consideration of alternative configurations for disposal; and (4) development of a disposal plan that would minimize adverse impacts to the environment.1 To achieve those objectives, mining companies operating in steep-sloped Appalachia will likely build excess spoil fills (also called valley fills) that toe out at higher elevations in the hollows (i.e. to prevent or limit burial of streams). Consequently, the slopes of fill foundations will generally be steeper. Whereas the authors of this paper support these measures to protect the hydrologic balance and general environment, we wish to point out that placement of fills on steeper foundations can negatively impact the stability of the fills if proper care is not taken during their construction. It is important to note that in addition to impairing human safety, valley fill instability can negatively impact streams, the riparian habitat etc., and thus defeat the very purpose of the spoil minimization measures proposed. We do not, however, propose additional regulatory requirements pertaining to valley fill stability. Rather, we intend to emphasize the importance of engineering requirements already on the books, especially as they apply to the predominant type of valley fill constructed: the durable rock fill. We believe that the practice of restricting valley fills, to higher elevations in the watershed leaves less room for error in the design and construction of stable structures. This paper gives a quick review of the nature of excess spoil generation; methods and requirements of excess spoil fill construction, and the to-date stability record of the fills. The interest in excess spoil minimization and how it affects valley fill construction is also discussed. Most importantly, we will review long-standing issues pertaining to proper design and construction measures with respect to durable rock fills and discuss how they will become more critical as spoil minimization is practiced.

Jan 1, 2007

By R. W. Fedors, S. T. Green, G. R. Adams, C. Manepally, L. B. Browning

This paper provides estimates of large-scale temperature gradients that can be used to support modeling of natural convection and cold-trap processes in thermally perturbed drifts. Temperature influences estimates of the quantity and chemistry of water contacting engineered components (e.g., drip shields and waste packages) in a potential high-level waste repository at Yucca Mountain, Nevada. Temperature gradients drive natural convection and cold-trap processes, which could affect the distribution, quantity, and chemistry of liquid-phase water contacting drip shields (waste packages).The confluence of high temperatures, liquid-phase water, and high chloride may lead to corrosion of drip shields and waste packages. An overview of the evolution of environmental conditions in thermally perturbed drifts is presented to provide a context for the estimates of temperature gradients. A mountain-scale conduction-only model is used to estimate temperature gradients and temperature differences for a drift located at the center of a potential repository. Thermohydrologic models and heat transfer algorithms are used to evaluate the reasonableness of the conduction-only results. Estimates of temperature using an in-drift heat transfer algorithm account for the possibility of drift degradation and formation of a rubble pile on the drip shield. Temperature differences between the center and ends of the drift are estimated to rapidly increase to 80 °C soon after repository closure. That temperature difference decreases over time to 15 °C after 10,000 years. Local temperature gradients are generally estimated to be less than 0.2°C/m, though the gradients can be much larger near changes in lithology and near the end of the drift. The estimates of temperature gradients do not account for intermediate- and small-scale variations, such as those influenced by differences in heat loads between waste packages, intra-layer variations in thermal properties of the surrounding fractured rock, or localized drift degradation.

Jan 1, 2004

By Christopher Mark

Sixty years ago, underground coal mining was the most hazardous job in the United States. Roof falls were a big part of the problem. They killed about 100 miners every year, more than all other causes put together. Fast forward half a century to 2016, which is the first year ever with zero roof fall fatalities. Just three miners were killed by roof falls during the following 6 years. How was this historic goal achieved? This paper starts with a modern analysis of the causes of the roof fall fatalities in 1968. Then it follows the reductions over time by category, using snapshots of the fatalities occurring in subsequent decades. Along the way, it evaluates the influence of the regulatory environment, changing mining methods, and better ground control technology. The paper shows that in 1968, more than half of roof fall fatalities at large mines were attributable to an inadequate safety culture. The immediate effect of the 1969 Coal Mine Health and Safety Act was to reduce the riskiest activities, like needlessly going under unsupported roof. Other hazards, like large roof falls, required technological developments before they were brought under control. Roof control plans, which the U.S. Bureau of Mines had been advocating since the 1920s, played a significant role throughout the process.

Jul 1, 2023

By T. McKeon, G. Luttrell

Spiral separators are commonly used to upgrade sand-sized particles in both the coal and mineral processing industries. Many plants utilize multiple stages of cleaning and/or scavenging spirals to improve recovery and/or final product grade. Field studies suggest, however, that the layout of industrial spiral circuits is often less than optimal. This oversight can usually be attributed to a failure by plant designers to consider fundamental process engineering rules that govern the layout of complex separation circuits. This article reviews some of these important rules as specifically applied to multistage spiral circuit design. Two industrial case studies, one involving the upgrading of heavy mineral sands and a second involving the cleaning of fine coal, are presented to illustrate the impact of good design protocols on spiral circuit performance.

Jan 1, 2007

By William R. Yernberg

What a difference a year makes. One year ago, the iron mining industry and the steelmaking industry in the United States were in trouble. Many companies were in bankruptcy, and talk of plant and mine shutdowns was rampant. At that time, it seemed difficult, if not impossible, to remain competitive with imported steel. In addition, the World Trade Organization declared as illegal the tariffs placed on imported steel. And many questioned the viability of the ironmining and steel industry in the United States. At that time, global economic conditions were the main contributors to the industry’s problems. However, since last year’s meeting, changes in global economics have actually helped the steel industry in the United States. Heavy global demand for steel has caused raw-material shortages worldwide. Much of the increased demand is a result of the economic boom in China. In addition, because of a weak U.S. dollar and higher international freight rates, steel imports into the United States have been reduced to about 50 percent of recent levels. These factors have contributed to a rebirth of the U.S. iron mining and steel industries.

Jan 1, 2004

By Morteza Gharouni Nik

Flexible Dilatometer Test (FDT) is one of the in-situ test methods for determining the deformational characteristics of rock masses. In this study, several dilatometer tests have been conducted in different geotechnical phases of site investigations by means of two types of FDTs. The purpose of this paper is comparison of the performance of these two types of dilatometers and analysis of the differences in the results of the tests.

Jan 1, 2008

Impala Platinum?s No.16 Shaft mine is currently under construction and is expected to reach full production of 256 500 tons per month by 2014. Mining will start at 1 260 m below surface with a maximum mining depth of 1 535 m where virgin rock temperatures of 56.6°C will be experienced. As a result of depth, high virgin rock temperature and narrow reef mining, an expected total of 31.5 MW[R] of air cooling capacity will be required to achieve acceptable underground conditions. This will be achieved by cooling mine intake air in a single dedicated air cooling installation located on surface. The compact installation includes air cooling spray chamber, refrigeration machines, condenser cooling towers, evaporator and condenser water reticulation as well as all electrical and control systems. Construction and commissioning of the first phase of this air cooling installation has recently been completed on a turn-key contract basis.

Jan 1, 2009

In 1991, Placer Dome Venezuela established a 70% stake in Minera Las Cristinas, to mine the Las Cristinas gold deposits in Bolivar. This case study examines the multi-sectoral partnership arrangement that was developed to improve health services near the proposed Las Cristinas gold mine. The investment climate in Venezuela is uncertain and the socio-economic circumstances are potentially hostile. Despite that, the partnership between the mining company, local communities, government agencies and an international health nongovernmental organization (NGO) collectively leveraged nearly $2.5 million to build and operate a community health center.

Jan 1, 2002

By H. S. Rathor

NTPC (National Thermal Power Corporation), a multi-unit organization, is generating 26% of India’s total power. This power is produced from its 14 coal based stations and 7 gas based stations. NTPC is entering into the business of power-distribution, power-trading, setting up of coal mines and diversification in non-conventional energy sector as well. For achieving the goal of the country “Power for All” NTPC has taken a giant stride by entering into Hydro Power generation which is also the cheapest and the cleanest renewable source of energy. In its pursuit for excellence, 800 MW Koldam Hydro Power Project is NTPC’s first venture in hydro sector. In Koldam, hydropower potential will be harnessed by constructing a 163m high earth and rock fill dam in a narrow gorge at upstream end of Bhakra reservoir. The river diversion is envisaged through two parallel, 14m finished diameter ‘horseshoe’ tunnels of length 901m and 934m at village Kian on the right bank, where the river forms a 180° loop. The diversion tunnels are designed to accommodate a flood of 6500m3/sec, taking into account the maximum probable discharge of 200 years return period. The tunnels pass through dolomite and limestone rock formations. The excavation of tunnels was done with drill and blast method. The excavation was attempted from both inlet and outlet faces. During geological investigation a rock fault was located at the outlet area. The location of the fault was such that it was passing through the edge of the Tunnel-1portal and around 30m away from the face of the Tunnel-2 portal. The quality of the rock at Inlet was also poor. To save the portals from slips, excavation of the tunnels was planned to start after the completion of the open excavation and its support system both at inlet and outlet. The tunnel excavation at inlet was envisaged by approaching the tunnels’ portal by constructing a road through 540EL bench and meeting the inlet portals on the upstream end, which would have been ready by mid2003, only after completion of the open excavation and its support system. To save time and cost, it was felt necessary to modify the planning by starting the tunnel excavation simultaneously along with open works both at inlet and outlet. The excavation at the inlet face of the tunnels started in December 2002 after rerouting the approach road to inlet portals through haulage road on the downstream and similarly Tunnel-1 at the outlet was started in the low cover area before completion of open area works. Thus the tunnel—heading excavation was started nearly 06 months early with the change of methodology.

Jan 1, 2005

By R. D. Hagni, P. A. Shivdasan

Cathodoluminescence microscopy (CLM) is uniquely applicable to the study of carbonatite-related fluorspar ore deposits. The mineralogy of the carbonatites, sodic and potassic fenites, marbles, quartzites, and fluorite ores are readily determined and characterized. Calcite, dolomite, apatite, fluorite were deposited dominantly under high temperature conditions and they exhibit strong cathodoluminescence (CL). Three types of carbonatites have been recognized at the Okorusu, Namibia carbonatite complex and fluorspar mines by field mapping and laboratory CLM. The main carbonatite intrusion is fine grained and consists mainly of calcite. A later phase of pegmatitic carbonatite consists of calcite, magnetite, Fe-rich pyroxene, apatite, and pyrochlore. Pyroxene carbonatites were recognized mainly through their study by CLM.

Jan 1, 2001