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At present, discounted cash flow analysis is generally accepted as the preferred method of valuation of mine projects in surface coal mining. One of the major reasons for that is its ability to take into account the time effect of money over the life-of-mine. As a looking-forward method, it requires forecasts be made with regard to economic, technological, technical, geological, and environmental conditions that will prevail in the future. All forecasts are inherently uncertain as they are a function of the uncertainty of all variables of the discounted cash flows analysis. This indicates that the only alternative for modeling the uncertainty in the project evaluation is the development of adequate risk models to serve the decision-making process. The paper offers a model of project cash flows at risk in strip coal mining, which is an integrated corporate risk management solution. The model is based on a stochastic approach that provides the answer to the question about how large is the deviation between stochastic cash flows and the planned value (or that used in the budget) at each time step of the discounted cash flows analysis, that is due to the uncertainty in the model variables. A solution is worked out for the allowable range of the stochastic cash flows variation that determines the probability of achieving the planned value of a mine project. The Monte Carlo simulation technique is used to model the stochastic behavior of the project variables. A case study of an opencast coal mine project is provided to illustrate the applicability of the risk model. The results obtained provide a new understanding of the mine project risk as a component of the project discount rate.

Jan 1, 2006

By Robert B. Worthington

This investigation was undertaken to develop a more efficient copper smelting practice that would help meet the increasingly stringent antipollution standards. Continuous smelting to copper and a 0.8-to 5-percent copper slag using pure oxygen has been demonstrated for several hours at a time in a unique double furnace, which was devised to overcome the heat losses inherent in a laboratory furnace. The use of pure oxygen to effect the smelting and conversion of copper sulfide concentrate in a single unit to produce blister copper and a very high S02 concentration provides a much reduced gas volume for more economical and thorough sulfur recovery. Although the process was successfully demonstrated for several hours at a time, extended test work using longer runs will be required to balance the system and to obtain test data for adequately demonstrating its technical feasibility.

Jan 1, 1973

By Moorrees C, Everson P

A detailed examination of carbonic acid leaching of crude iron-containing magnesia derived from Savage River magnesite shows that the rate and extent of magnesium and iron dissolution are affected by the slake time, leaching temperature, carbon dioxide pressure, pulp density and rate of agitation. In order to produce high-purity magnesia from the leachate by precipitation and calcination, the optimum leaching conditions, which are those that yield maximum magnesium and minimum iron dissolution, have to be a compromise in terms of the above parameters. For example, iron dissolution can be limited by leaching at an elevated temperature (-45°C), but because the maximum concentration of magnesium biearbonate decreases rapidly with an increase in temperature, it is necessary to use a low pulp density (-2 per cent solids) in order to achieve an acceptable degree of magnesium dissolution.Evidence is obtained that iron dissolution involves the formation of a soluble ferric bicarbonate complex that decomposes at elevated temperatures. The extent of iron dissolution is much higher than might be expected and it is probably because the original magnesite contains siderite in solid solution with the magnesite; on calcination, the hematite whieh is formed is in a very finely divided condition and hence more reactive.

Jan 1, 1983

By G. Krogman, C. Walla, B. Wood

The Gebo Mining District (District) is located in the Bighorn Basin of Wyoming. Commercial underground coal mining began in 1906 with the arrival of the railroad in Thermopolis, which is located approximately 11 miles to the south. Mining in the District ceased by the early 1970’s. In Fall of 1999, Lidstone and Associates, Inc. (LA) and their subcontractors were retained by the Wyoming Abandoned Mine Land Division (WyAML) to perform an inventory of over 500 abandoned mine sites across Wyoming. During the summer of 2000 field inventory, a 30-foot deep headcut (Figure 1) and sink-hole were noted in the West Fork of Sand Draw (WFSD), immediately west of the Town of Gebo. The headcut and sink-hole were located at the culvert outfall associated with a stream crossing of a relatively well traveled county road. Upon further investigation, it appeared that underground mine workings had been exposed at this location. This resulted in a condition whereby water would be conveyed directly into the mine workings during a runoff event. The exposed mine workings as well as stream capture created a very hazardous condition. The WyAML implemented mitigation measures in the summer of 2000 by constructing a temporary stream crossing upstream of the existing failed crossing. To address this hazardous situation as well as a number of other hazards identified in the District during the field inventory, the WyAML retained PHC Reclamation, Inc. (PHC). PHC was directed to perform a field investigation and develop a Reclamation Plan to address all existing abandoned mine hazards in the District. Federal, state, and private parties own lands within the District. Hazards identified during the investigation included an underground mine fire, open adits, open shafts, subsidence, drainage problems, and coal slack. A Report of Investigation (ROI) was submitted to various regulatory agencies that documented the existing conditions and conceptual reclamation plans to remediate the hazardous conditions. After review of the ROI by the US Department of Interior - Bureau of Land Management (BLM) an on-site meeting was conducted. BLM Cultural Resource personnel declined to approve a District reclamation project until a historical overview of the entire District was prepared. Due to the hazardous situation associated with the WFSD stream crossing, Hot Springs County Road and Bridge Department convinced various state and federal regulatory agencies to allow reclamation of the stream crossing to occur. A decision was made to allow reclamation on privately owned lands within the WFSD drainage. This decision limited the amount of channel that could be subjected to reclamation upstream of the crossing to privately owned lands. PHC contracted LA to perform a geologic, geomorphic, hydrologic, and hydraulic investigation of the drainage to assist in the development of a WFSD reclamation plan. LA’s investigation consisted of four parts: Delineate the extent of mine workings in the area; Identify all drainage structures that required mitigation; Survey a series of channel cross-sections and a longitudinal profile of the impacted channel; and, Develop basin hydrology to assist in the design of a stable reclaimed stream channel.

Jan 1, 2006

By Steve Dillingham

Here in the United States, as well as around the world, pose a daily dilemma - to wash or not to wash. Let’s face it, all trucks, especially our industry work horses - bulk trucks - get dirty. We all know that these units can be very expensive and washing them keeps your business investment looking new, improves public relations, fuels company pride, and facilitates equipment safety and preventative maintenance inspections.

Jan 1, 2001

By Wilson G. L, Lord J. H

A detailed analysis of faulting indicatcs that blocks of "greenstone" have been thrust beneath the southern end of the Mt. Isa orebodies.This "greenstone" basement is considered to be a major structural control in the localization of these orebodies.INTRODUCTIONThis paper is based on exploration carried out by Mining Corporation (Aust.) N.L. from 1956 to 1960 in the area immediately south of Mt. Isa, Queensland. During this period over 20,000 ft of diamond drilling was completed together with costeaning and geochemical exploration.Early in 1959, it became apparent that diamond drill information could not be correlated with the current geological concepts of this area and a detailed geological appraisal became necessary. In all, sixty square miles were mapped at a scale of 1 in. to 500 ft, using enlarged aerial photographs. All drill core was logged and sections re-interpreted.Professor K. C. Dunham of the University of Durham consulted on this project and contributed through valuable discussion. Dr. A. Day of the University of Sydney carried out a gravity survey in February 1960 and Dr. H. Wilshire of the same University undertook microscopic examination of rocks from the area. Certain sections of the area were investigated geochemically by Mr. K. K. Hughes of New Consolidated Gold Fields (Asia) Pty. Limited in 1960.In outlining a theory of ore genesis in the area the writers have drawn heavily on the invaluable data published by many previous workers on the Mt. Isa field, in particular...

Jan 1, 1963

The relationship between neural network (NN) performance and the parameters that form the architecture of the neural network is complicated. This paper studies an issue that is still controversial—the effect of the number of neurons and number of hidden layers on NN performance. This paper tests if the above parameters affect network performance when the NN is trained according to the quick stop strategy. It was determined that the number of neurons did not have any effect on the NN performance for a single layer or a double layer network. It was also found that the training error and calibration error could be poor indicators of the prediction correlation coefficient.

Jan 1, 2003

By David C. Benson

This Bureau of Mines report is an update of IC 8725 and comprises tables listing the name, location, and other pertinent data concerning certain fuel-related projects. The tables include information on projects involving the proposed or planned development of fuel resources, as well as the development of storage, transportation, and conversion facilities; the report covers the 26 States east of the Mississippi River. Of the total 535 projects for which information is provided, 429 concern coal mines and electric generating plants (including Energy Supply and Environmental Coordination Act (ESECA) coal conversion notices).

Jan 1, 1978

By R. Karl Zipf, Kousick Biswas

The main objective of occupational health and safety research is to minimize or eliminate the events that may cause fatal or non-fatal injuries to human workers. A commonly used technique is to devise an “incident prevention plan”, which is more often the product of thorough investigations of past reported incident events. Incident documentation and methodical reporting and systematic and thorough data collection, often help identify the root cause of the incident – in other words, the etiology of the incident. These retrospective analyses of the incidents can efficiently identify the future steps to take to achieve the objective of minimizing occurrence of “events of interest”. This paper introduces a novel technique – “Taxonomic Analysis”, which identifies the root causes of an event (an incident in this case) and can provide future direction for corrective measures to reduce the probability of occurrence of the event. A taxonomic analysis involves systematic and organization of data based on observation, description, and classification. This paper utilizes the rock fall related incident narratives, available with the Mine Safety and Health Administration (MSHA) database (1984-1999), for a taxonomic analysis. The study found that 67.6% of groundfall incidents occurred in supported areas with the remainder (32.4%) in unsupported areas. Some form of rock mass failure appears to cause about 50% of groundfall incidents, although in 39.7% of the overall groundfall incidents or two-thirds of those involving rock mass failure, the exact nature of the rock mass failure could not be determined from the narratives. Human activities factors such as scaling or barring down, drilling or bolting, and setting timbers or cribbing accounted for another 34.5% of the groundfall incidents. Finally, support system failures made up the remaining 15.5%. Results from this taxonomic analysis may suggest focus areas toward which preventive measures and future research activities could concentrate.

By R. Dahlke, J. A. Finch

A campaign was undertaken during the greater part of 2001 at Noranda’s Brunswick mine concentrator to investigate the role of gas (air) superficial rate (Jg) distribution to the cells in the final Zn cleaning stage (bank of seven cells), i.e. the Jg profile. Three profiles were tested: “balanced” (each cell with same Jg), “increasing” (from cell 1 to 7 proportionally), and “decreasing,” along with an “as found” profile in a parallel control bank. The experimental design allowed for two confounding factors, changes in ore type and circulating load. The increasing profile consistently gave the best metallurgy (down-the-bank grade / recovery). The reason for improved performance was the response of the first cells in the bank where the increasing profile gave the highest selectivity of sphalerite against nonsulphide gangue (NSG). The other profiles gave lower selectivity and higher zinc recovery in the first cells, which combined to reduce overall bank performance. The higher selectivity with the Increasing profile is attributed to the low gas rate in the first cells reducing water recovery and hence limiting entrainment of NSG. The increasing profile was subsequently configured for all four stages in the zinc cleaner circuit.

Jan 1, 2004

Study on Pure Mineral Flotation Tests of Low-Grade Phosphate Ore in Zhijin, Guizhou Province, China

Sep 13, 2010

By Frederick C. Rhyner

Drilled shafts have become an economical foundation choice for bridges in the northeast United States, especially when they can be constructed over water without the use of cofferdams. For the Boscawen-Canterbury Bridge over the Merrimack River in New Hampshire, an unusual design was used to avoid the use of cofferdams and avoid the need for pier caps at the waterline. This design used a pair of integral drilled shaft ? columns to form a bent type of substructure for support. Drilled shafts were 8-foot diameter, about 90 feet deep, with 16-foot long rock sockets. These are integrally constructed with 6-foot diameter reinforced concrete columns extending 37 feet from the waterline to the superstructure. Design load cases focused on lateral loads from ice flows, stream flows, wind and seismic events. Alternative analyses using different methods were made to check the design results. This paper discusses the subsurface conditions, design of the drilled shafts and columns, rebar and joint detailing issues, and construction of the drilled shafts.

Jan 1, 2004

By Jan E. Nesset

It is just over 100 years since the practice of blowing small bubbles into a mixture of ground ore and water revolutionized the mining industry, resulting in uneconomic deposits becoming highlyprofitable mines, along with the inevitable lawsuits over this new technology called froth flotation. To this day, the viability of many mining projects rests largely with the ability of flotation to effectively capture the valuable minerals and reject wastes. Remarkably, bubble behaviour in flotation has not been well understood until very recently with the advent of new sensor technologies that can be brought directly into the operating plants. This presentation will review the importance to the mining industry of understanding bubbles, highlight these new technologies and illustrate, with examples, how paying attention to your bubbles will pay off.

Jan 1, 2009

By N J. Welham

This paper reports on an innovative professional development program for school science teachers run collaboratively between the Centre for Sustainable Resource Processing and Murdoch University. Ultimately the initiative aims at increasing the pool of school students with strong science and mathematics backgrounds while highlighting the challenging careers available in the mineral resource sector including the gold industry. The program is unique in that it seeks to develop a network of science teachers who may participate in a series of workshops, short courses and tours over several years. The objective is to raise secondary school studentsÆ awareness of potential careers within the minerals sector by exposing teachers to a real life, hands-on look into the mining and minerals resource industry. Though the program includes the breadth of the resource processing sector, the potential value to gold processing is in developing a greater pool of potential employees. The initiative allows teachers to develop a better insight into the practical applications of the theoretical sciences they are required to teach. The evolution of the program from the first trials with Western Australian teachers to the introduction of the initiative to Queensland teachers are reported on. Additionally, the results of a pilot study involving 40 participating teachers are described. This study used a questionnaire and follow-up interviews to gain quantitative and qualitative feedback from teachers. There is evidence that the professional development program has resulted in teachers acquiring a new found appreciation for the application of the fundamental chemistry and physics they teach within the school curriculum. Also reported are associations between teacher participation in this professional development program and changing attitudes towards the industry in a positive way. Finally, there is some indication that these positive teacher attitudes may result in their students developing a better understanding of the diversity and availability of career paths within this industry.

Jan 1, 2007

By Tom Treleaven

Several nonelectric blast initiation systems have been developed since the mid 1970's. Until that time, most blasts were initiated either electrically with electric blasting caps or nonelectrically with detonating cord. What the development of these new systems was attempting to accomplish was to provide a system that was nondisruptive to the stemming or explosive column, but still possessed the safety and flexibility inherent in nonelectric systems.

Jan 1, 1991

By Peter Claus

In the last years, supported gold catalysts with particle sizes smaller than 10 nm have attracted a lot of attention. While gold bulk metal is rather inert in chemical reactions and, thus, is of low interest for catalysis, highly dispersed gold particles supported on oxides as TiO2 or ZrO2 show surprisingly high activities in some reactions important for the chemical industry. The oxidation of carbon monoxide at low temperatures is mainly used as model reaction to study the unusual properties of gold catalysts [1]. On the other hand, to evaluate the catalytic potential of gold, other chemical reactions which allow to control also the selectivity have to be considered. The selective hydrogenation of ???-unsaturated aldehydes to allylic alcohols is of both commercial relevance (e.g. in fine chemical and pharmaceutical intermediate production) and specific scientific interest [2]. Note that thermodynamics favors hydrogenation of the C=C over the C=O group (stronger negative free reaction enthalpy of 35 kJ/mol), and for kinetic reasons the C=C bond is more reactive than the C=O group. Thus, in the presence of most of the conventional hydrogenation catalysts, based on Pt, Rh or Pd, -unsaturated aldehydes such as acrolein and crotonaldehyde are hydrogenated predominantly to the saturated aldehydes and only to a minor extent to unsaturated alcohols. Therefore, it is desirable to find catalysts which are able to control the intramolecular selectivity by hydrogenation preferentially the C=O group while keeping the olefinic double bond intact (Fig. 1).

Oct 1, 2003

By M. R. Geer

Information on the performance of coal-cleaning equipment is necessary to provide a basis for evaluating the performance of existing plants and projecting that of new plants. Performance data can contribute greatly to the wise selection and effective use of coal-washing equipment. The Bureau of Mines has published information on the performance of several commercial plants, as well as of some laboratory-scale equipment, 5 (2-9, 11, 12, 17-12, 21-25) from time to time for a number of years. A more intensive program to provide such information for all the principal types of cleaning equipment is underway. The present evaluation of table performance is part of this program.

Jan 1, 1962

By J. A. Organiscak

In the United States, respirable coal mine dust exposures are limited to a 2 mg/m3 time weighted average for a working shift. If the silica content of the sample exceeds 5 percent, the 2 mg/m3 standard is reduced according to 10- (% silica) to limit silica dust exposures to 100 µg/m3. Examinations of dust sampling data collected by the federal coal mine inspectorate showed that roof bolter occupations continue to be at risk for overexposure to respirable silica dust. Testing at the Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health assessed the effectiveness of a canopy air curtain for controlling occupational exposures to respirable silica and coal dusts. Initial testing found that zones of higher velocity airflow shrank as distance beneath the canopy increased. This suggested that protection from occupational dust exposures would likely decrease as distance beneath the canopy increased. Further testing revealed that coal dust reduction efficiencies were most affected by changes in interference air velocity and, to a lesser extent, changes in canopy air quantity. However, respirable silica dust percentages under the canopy were not affected by such changes and, in fact, were not significantly different from silica percentages measured outside the canopy. This implied that the air curtain was equally effective on both respirable coal and respirable silica dust particles.

By I. Stanculescu

The consolidation of thick and very compressible soil deposits by stone columns associated with cast-in-place plain concrete columns, has been performed for shallow foundations of some heavy industrial structures. The reduction of settlements and increase of soil bearing capacity were thus ensured as a result of soft soil interaction with stone and concrete columns. The results of model tests and in situ large scale applications are presented. A calculation procedure is also suggested for foundation bases improved by the proposed method.

Jan 1, 2010

By Mandius C. Lundal

This report describes the work done to develop a coal mining machine to increase productivity and recovery from thin seams beyond the highwall, in addition to decreasing the miner's susceptibility to to highwall hazards First, radar transducers were adapted to measure coal thinkness and detect rock and coal interfaces; Then, the radar was incorporated into a cutterhead with steering controls. Next, visual displays were designed to show cutter position in the coal seam, and anticipated change in coal seam inclination, Finally, development of a telemetry system made remote control of the cutterhead possible. Simultaneously, a high-performance extended depth (HPxD) auger machine was designed with an automatic system to handle 600 ft of 36-in, diameter dual spiral flight conveyor sections. A two man crew controls all operations from a weather conditioned cab outside the VDZ, either at night or day time. As a primary mining tool, working 4000 hr/yr (2 shifts/day) recovering 60% of the coal 600 ft beyond the highwall, productlon to 500,000 ton/yr can be achieved. Volume I provides an overview of machine, systems and productivity.

Jan 1, 1977