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By Ahmet Gursoy

Maryland, will be the widest vehicular tunnel ever built by the trench tube method. Careful coordination and planning were required to meet the tight and fast design and construction schedules. During the preliminary design, traditional design drawings were bypassed in favor of 25 preliminary design reports representing major work breakdown structures (tasks). For each task, alternative design solutions were examined and analyzed by means of trade-off studies on the basis of engineering, constructibility, and economic considerations, thus providing an overall conceptual value engineering approach for the entire project. So far, total value engineering proposed by the contractor for Contract I I (largest contract of the project at $245 million) is less than 1.5 percent of the contract value. This is an important indication of the success of the design phase planning.

Jan 1, 1983

By Douglas R. Malicoat, Christopher J. Pritchard

Tg Soda Ash operates an underground trona mine located In southwestern Wyoming, which utilizes continuous mining machinery to produce 2.OM tpy (2.2M stpy) by shortwall and room and pillar methods. As the mine developed, the Increasing distance from the shafts caused travel times to be a significant factor in planning for mine emergencies. It was decided to construct a barricade chamber, a modified refuge chamber, to Increase safety and to provide an additional escape option in the case of a mine emergency. Fortunately, there has been no need to use these facilities during the last 9 years, but mine emergency planning has been greatly improved.

Jan 1, 1993

By W. J. Cieslewicz

Geologically, northeastern Siberia is a region occupied by a folded belt of Triassic and Jurassic sediments and volcanics. Gold mineralization is of Upper Jurassic age. Most of the stream placers formed during the Quaternary. Placer gold was first discovered in 1916. Between 1930 and 1957, mining was carried out by the "Dal 'stroi," a Russian concentration camp organization. Since 1966, the mines have been worked mechanically. About 10 mining districts are now active, producing, altogether, 110 to 135 t (120 to 150 st) of gold annually.

Jan 1, 1987

By J. G. Groppo, B. K. Parekh

Column flotation testing was conducted on the flotation feed slurry obtained from a preparation plant located in the Southern Illinois coal basin. The column flotation tests were conducted using three different bubble generating devices: a static sparger, a gas saver and a foam jet. Each of these devices was tested with three different types of frother and various column operating variables to provide maximum combustible recovery, minimum product ash and maximum pyrite rejection. The results show that column flotation provided improved flotation performance, in terms of combustible recovery as well as ash and pyrite rejection, for each of the bubble generating devices. However, the effectiveness of each bubble generating device was dependent on the type of frother used. Alcohol frothers were most effective for use with the static sparger, somewhat less effective for the foam jet and ineffective for the gas saver. Glycol frothers were effective for all three bubble generating systems, providing high combustible recovery (>90%); low clean-coal ash (4-6% ash) and high pyrite rejection (70-80%).

Jan 1, 1994

By Y. Q. Zhang, Y. Luo, S. S. Peng

Burrier pillars in underground coal mines could eventually be subjected to a water head due to the build-up of mine water in the old workings. The water head could not only act ns a force to destabilize the pillar, but it could also cause seepage flow through the pillar and its surrounding strata. Excessive seepage flow could induce piping failure that, ill turn, could accelerate the mechanical failure process of the barrier pillars. In this paper, a finite element simulation approach was employed in the evaluation of the barrier pillars. Both the stress distribution and the seepage flow pattern in and around a barrier pillar have been simulated numerically. The effects of ground stress on rock permeability to water seepage has been taken into consideration in these simulations,

Jan 1, 2002

By F. C. Loughnan, Shane B. Sadleir

Bauxite is currently produced at three centres in Australia: - Weipa in northern Queensland; Gove on the northeastern tip of Northern Territory; and in the Darling Range near Perth, Western Australia. At each of these centres the bauxite is of Tertiary age and occurs as blanket-like, lateritic crusts in which gibbsite is the predominant mineral. Development was essentially in situ although possibly the deposits, particularly at Gove, are in part of transported origin. All of the deposits formed from quartz-rich parent rocks with those at Weipa and Gove being derived from kaolinitic sands while in the Darling Range, granite and other crystalline rocks of Precambrian age immediately underline the lateritic bauxite.

Jan 1, 1984

By D. W. Hendrickson

Cliffs views the process as extending from mine planning to cargo loading including auxiliary systems such as material handling and plant utilities. Process automation is recognized as an area that can provide significant improvement opportunities with less capital requirement than major flowsheet modifications. This paper discusses the development and results of a strategy to allow and promote implementation of process automation improvements at individual mines based on their economic priorities taking advantage of common systems and concepts for use at multiple mines where practical. Specific process control upgrade projects a Hibbing Taconite Company and the Empire Mine are reviewed in detail.

Jan 1, 1998

By Y. H. Alghamdi, A. D. S. Gillies

"INTRODUCTION Background Diesel Particulate Matter (DPM) has been a critical issue during the last decade in underground mines. This problem is threatening the health of mine workers, as well as the mine’s productivity. It has been confirmed that the diesel engine exhaust is the main source for the diesel particulate matter (DPM), and that it has the highest impact in raising carbon monoxide, carbon dioxide, oxide of nitrogen, and hydrocarbons in the underground environment. Miners who are exposed to this kind of emission are at high risk for developing lung cancer and other lung diseases. The Mine Safety and Health Administration (MSHA) has issued standard rules to regulate diesel emissions in underground mines. The final ruling confirmed in 2008 that the total carbon should not exceed 160 µg/m3. (MISHA, 2008) Monitoring DPM in underground mines has become important to ensure compliance with the MSHA regulations. There are many different types of DPM monitoring systems that are currently being used in underground mines. Two methods are typically used for DPM sampling: the personal sampling method or the direct exhaust sampling method, which takes a direct sample from the engine’s tailpipe. Many mines do not recommend using the direct exhaust sampling method since it involves complex measuring equipment and procedures, as well as it is not regulated in the United States or Canada. Thus, the personal sampling method is the preferred method in many mines when taking DPM samples. Even this method includes many variations, such as the Respirable Combustible Dust (RCD) method and the method devolved by the National Institute for Occupational Health and Safety NIOSH 5040. The NIOSH 5040 method is the preferred method overall because it gives more accurate measurements compared to the other methods. This method does not allow organic carbon sources other than those coming from diesel engine exhausts to interfere with the measurements, which otherwise would lead to overestimating the actual amount of the DPM in the mine environment. An impactor feature in the cassette, which holds the samples in the instrument, characterizes this method. Since the diesel particles are less than 0.9 micron, this impactor does not allow particles more than 0.9 microns to be collected in the cassette filter. The cassette is then analyzed in a lab and the concentrations of organic carbon (OC), elemental carbon (EC), and total carbon (TC) are determined. Lately, the National Institute for Occupational Safety and Health (NIOSH) has developed a new instrument that can use the same concept of NIOSH 5040, but with instant measurements of elemental carbon. It utilizes laser radiation with the cassette so it can give a real time measurement. The real time measurements give instant information about the underground environment that will allow the mining engineer to take immediate action and enact plans instead of waiting for results from the laboratories where NIOSH 5040 method may take several weeks to get the measurements."

Jan 1, 2016

By V. Duddempudi, B. Goertz, J. Brune, G. Bogin, F. S. Barreto

"INTRODUCTION In designing a new pneumatic Dust Sampling Device (DSD) for coal mines, it was essential to analyze the air and particle flow inside the device in detail using Computational Fluid Dynamics (CFD) modeling. Several CFD models were developed to simulate the air and dust flow and sample collecting process of the DSD. These CFD models were developed to assist in the design of the DSD instrument prototypes for laboratory testing. Nozzle and injection parameters such as geometry, air velocity and pressure, were varied across a wide range to obtain the optimal settings to accurately simulate the fluid dynamics of the multi-phase flow within the DSD. Accordingly, these parameters were used as a guide for the design of the DSD and to verify the dust scouring dynamics, which is designed to represent the dust entrainment during an actual methane or coal dust explosion. BACKGROUND The 2010 explosion at the Upper Big Branch mine has demonstrated the destructive violence of a coal dust explosion. A major contributing factor for this disaster was that the mine operators did not have a reliable, direct-reading method to collect mine dust and determine inert content and combustibility. This led to the development of a new prototype handheld, pneumatic mine dust sampling device (DSD), which blows a puff of air and entrains the mine dust by mimicking the entrainment process during a mine explosion. A computational Fluid Dynamics (CFD) model is used to analyze the air and dust flow inside the DSD. The objective of the CFD modeling effort is to find the optimum design of the DSD prototype, nozzle orientation, air pressure and pulse length by analyzing and varying these parameters so that the scouring action collects a valid, representative and repeatable mine dust sample. CFD MODEL DESIGN Figure 1 shows a wireframe image of the DSD which is utilized in the setup of the CFD model. The DSD has a triangular cross section and is 10 cm wide. Two nozzles with cross-sectional dimension of 2.8 cm by 0.25 cm act as inlets at the narrow end of the triangular cross section. The CFD model includes a reference plane 6 cm away from the nozzle to measure the quantity of dust collected. The geometry shown in Figure 1 was created for the model and it matches with the design of the actual device shown in the figure 2. Symmetry, along the plane X-Y through the center of the device, is used to reduce the number of computational cells in the CFD model. Figure 2 shows the prototype device used for experimental testing. CFD MODEL SETUP Figure 3 shows a hexahedral mesh with a cell size of 0.8 mm and the total number of cells is around 650,000. The ANSYS Fluent® pressure based solver with a transient case was used with a total duration of 40 ms. The 40 ms simulation time is based on experimental measurements to capture the injection of air and initial scouring of dust."

Jan 1, 2016

By Anthony Peach, Lok Home

Introduction Raise boring is the most accepted form of mechanized hard rock boring in the mining industry. It appeared logical to take this mechanization one step further by introducing computers. Atlas Copco Jarva has produced a series of raise boring models that use an integrated computer. The company decided to use electronics and computerization, not for marketing purposes, but to make its equipment more cost-effective. Basis of Cost-Effective Design From the manufacturer's standpoint, it is possible for the equipment owner to reduce the cost of putting in raises by: • Replacing existing components with less expensive components that produce the same results; • Replacing existing components with more expensive components that make the equipment more productive; • Mechanizing equipment to reduce associated labor costs; and • Combining the above. Analysis of a standard raise boring machine (RBM) system showed that little could be done with less expensive components. It appeared, however, that the RBM could be more productive by transmitting more horsepower through the expensive drill string, while being precisely controlled by computers. An RBM system includes a basic machine, drill pipe, accessories, reamer, and cutters. The approximate percentage cost of various components on a standard system capable of boring 300 m (985 ft) long and 3-m-diam (10-ft-diam) aises in medium to hard rock is shown in Table 1. Also shown is the increased cost above standard of the Jarva computerized machine, and the productivity of both. Increased Productivity Penetration is important during the reaming cycle for more productive raise boring. This is possible by increasing the cutter load with constant rpm or increasing the rpm with constant cutter load. To increase thrust and maintain rpm requires increased capacity in the cylinders, drive train, main thrust bearings, drill string, electrical motors, and power units. To increase rpm and maintain cutter load requires only increased capacity in the electrical motors and power units. This is possible because the torque requirement remains constant for a constant thrust load. Only the horsepower increases, proportional to rpm. Since cutter costs are a big factor in raise boring, changes in machine performance must be analyzed to assess the effect on cutter performance. With a standard or typical carbide cutter, as used on raise boring machines, the effects of increased thrust or rpm are shown in Table 2. The assumption is made that the base data is the current rpm and thrust range where the cutters are now operated. It is also assumed one variable is held constant while the other increases. The result of this comparison, approximately, is that a 50% penetration increase can be achieved with little or no increase in cutter cost if rpm is increased 50% and cutter load is maintained constant. A similar 50% penetration increase can be achieved with a 45% increase in cutter cost, if the cutter load is increased by 20% and maintained constant. From an equipment standpoint, it is significantly less expensive to increase rpm 50% than it is to in-

Jan 7, 1984

By Raimondo Ciccu, Francesco Satta, Marcello Ghiani, Piero Carbini

Nonpolar oils are utilized as collectors in low-rank coals flotation processes. The analysis of the mechanism of the hydrophobic film formation on coal particles permits the identification of the main characteristics that these reagents should exhibit in order to render the process technically and economically efficient. Such requirements - low repulsive energy developed in the interaction with coal particles; limited interfacial tension at the coal-oil boundary; relatively low viscosity and, at the sake time, poor ability to absorb into the coal pores - are found in some binary mixtures of oils having different volumic mass. The features of such mixtures as well as the advantages deriving from their use for the flotation of a Sulcis coal sample and experimentally proven, are described.

Jan 1, 1989

By F. Figge, T. Hahn

In this article we present Sustainable Value, a valuation methodology to assess sustainable value creation of companies. Sustainable Development posits that decisions must not only take into account economic capital but also natural and social capital. Sustainable Value, the methodology presented in this paper, borrows the idea from financial economics that the return on capital has to cover the cost of the capital. Capital costs are determined as opportunity costs, i.e. the forgone return that would have been created by an alternative investment. By expanding the well established logic of the valuation of economic capital in financial markets to also cover natural and social capital we provide a methodology that allows an assessment of the most efficient allocation of economic, natural, and social capital for sustainable value creation in companies. We demonstrate the practicability of the methodology by the valuation of the sustainability performance of British Petroleum (BP).

Jan 1, 2005

By Q. Xu, P. Somasundaran

Adsorption of nonionic/anionic surfactant mixtures on kaolinite has been studied, with •Sodium dodecylsulfate as the anionic surfactant, and •Octaethyleneglycol mono-n-dodecylether as the nonionic surfactant. Synergistic interaction between these surfactants was found to cause adsorption of the nonionic surfactant with its hydrophilic chains protruding into the bulk, leading to substantial changes in wettability and dispersion characteristics of kaolinite. Similarly, hydrophobicity changes are observed also for silica particles upon adsorption of nonionic ethoxylated alcohols owing to possible changes in the orientation of the adsorbed surfactant molecules at the interface.

Jan 1, 1993

By C. E. Jordan, B. J. Scheiner

The Bureau of Mines conducted research on the flotation hydrodynamics of fine particle flotation to improve the flotation efficiency in our domestic minerals industry. The turbulent fluid velocity profile was measured in various flotation cells at different levels of dissipation energy. The importance of dissipation energy and bubble size within the flotation cells for the flotation response of a chalcopyrite ore was evaluated. Both increased turbulent fluid flow and fine size bubbles improved the flotation rate of fine size chalcopyrite particles.

Jan 1, 1989

By D. Doepker

The dissolution of metals from various metal/ non-metal mine tailings has been studied through column leach tests at US Bureau of Mines laboratories. Metal mobilization in unsaturated columns was consistently greater than metal dissolution in water-saturated columns. Leachate pH was also frequently lower when a leachant was passed through columns but showed a mixed residence-time dependence. On the other hand, metal and sulfate ion concentrations in the leachate increased with dry-cycle residence time. Results suggest that acid formation through atmospheric oxidation of pyrite may compete with non-acid-forming oxidation of other metal sulfides. The two processes lead to decreased pH and increased metal mobilization, respectively. Leach tests using sodium lauryl sulfate indicated that microbial activity was not a factor in these studies.

Jan 1, 1991

By T. Vincze

Effective coal mine face ventilation, for remotely controlled and automated mining systems, is essential for the control of methane. The evolution of new mining equipment and methods has required changes and improvements in face ventilation methods. One emphasis today is on the use of remotely operated and automated mining systems that can be used to make continuous cuts of 6 m (20 ft) and deeper. U.S. Bureau of Mines research is studying ways to more effectively ventilate these extended cuts. Two face ventilation techniques that utilize either blowing brattice or a jet fan for deep cutting are examined in this paper. Bureau of Mines procedures for evaluating face ventilation systems are also discussed.

Jan 1, 1992

By Victor F. Hollister

This report summarizes data available on the Fort Knox gold deposit to the end of 1989. It is presented courtesy of Fairbanks Gold, operator of the Fort Knox mine. The ore body and the data base are being expanded in 1990, but this summary is pertinent for inclusion in a case history volume that, in part, stresses porphyry-type deposits. Fort Knox is a pluton-hosted gold deposit 22.5 km (14 miles) northeast of Fairbanks, AK. It is easily accessible from Fairbanks, and ultimately it will be the largest open pit gold mine in Alaska. The Fort Knox pluton has an interesting historical record, and it has been discovered at least twice. Fig. 1 shows the geology and location of major plutons in the Fairbanks mining district.

Jan 1, 1991

By J. N. Carras, N. W. Bainbridge

In order to further the understanding of spontaneous heating of longwall goafs a numerical model was developed, based on conservation principles applied to the transport of heat, water vapour and oxygen across the god Advective air flow into the goaf is caused by the differential air pressures across the god The air velocity field within the goaf area was computed using Darcy's law. The boundary and initial conditions concern air pressure, temperature and relative humidity. The oxidation rates and heat generation rates of the goaf materials required for the simulation were obtained from laboratory measurements. The main outputs of the model are temperature, oxygen and water contour maps, the rate of air leakage into the go4 velocity field and pressure distribution across the god. The model while still in its development stage, is able to simulate a heterogenous goafs constructed from different materials with different thermal and mass flow properties. Validation of the model by comparing its output with measurements from within goafs is required before the model can be used with confidence in a predictive sense.

Jan 1, 1995

Open pit optimization and mine design depend upon a realistic estimate of the grade-tonnage dis¬tribution. The estimate should reflect what can be reasonably recovered and processed. The McCoy/Cove operation in central Nevada is a gold and silver mine. Recoverable reserve estimations of gold and silver were made using indicator kriging and the indirect log normal variance correction to construct the grade- tonnage distribution. Optimal pits were generated using this distribution, and the results were compared to the pits generated by ordinary kriging and indicator kriging block mean methods. The results indicate that the proposed method for multimetal recoverable reserve estimation shows an improvement in terms of predicting the recoverable tons and grades. The optimal pits generated from the recoverable resource model are larger than those generated by the ordinary kriging and indicator kriging block mean methods. This model maximizes the overall recovery of the mineral resource.

Jan 1, 1999

By T. Janke

When Homestake Mining Company's Mclaughlin Gold Project was being evaluated for development, it was apparent that recovery of gold from mined ore would be difficult and relatively expensive. The ore was refractory, averaging less than 50% recovery in conventional direct cyanidation milling tests. Extensive testing narrowed the processing choices to either autoclave or roaster oxidation before cyanidation. Roasting was ruled out due to higher capital and operating costs --the Mclaughlin mill would be the first large-scale application of autoclave oxidation of a refractory gold ore.

Jan 1, 1989