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By P. Otto, G. Borm, Th. Dickmann, F. Amberg, R. Giese

Based on many years experience, the well approved Tunnel Seismic Prediction System (TSP) has been substantially enhanced for online geological prognosis in underground construction. The method provides high resolution seismic images of the rock mass ahead of a tunnel face via an array of standard anchor rods. These contain3D-geophones and can routinely be installed during the excavation process. A further outstanding feature of the system is the newly developed high frequency repetitive seismic source which can easily be fixed at a tunnel boring machine. A user-friendly software package enables online data acquisition, processing, 3D-visualization, and interpretation.

Jan 1, 2001

By W. G. Pariseau

Recent advances in rock-mass mechanics and computational technology now allow for the stability analysis of excavations in "wet" mines where mining-induced changes in rock mass deformation and fluid flow are coupled and time dependent. In addition to water pressure and flow in jointed, possibly porous, rock masses, all of the usual dry-mine parameters, including the premining stress state and rock-mass properties, are taken into account. Finite-element analyses of shafts and tunnels, as circular, elliptical, rectangular and arched-rectangular hole shapes excavated in an initially stressed and pressurized rock mass, indicate that the usual guidelines for optimum shape and orientation of single openings apply. Here, optimum means maximizing the minimum wall safety factor or, equivalently, minimizing the peak stress concentration. The results also show that failure originates in elements at the wall and the minimum safety factor at the wall in the wet case is always less than the dry case, regardless of drainage time allowed.

Jan 1, 1997

By F. N. Kissell, C. D. Litton

This study ranks the factors impacting survival during a coal mine fire. It has already been established that reducing time delays is the most important factor in saving lives. Consequently, every event during afire is measured in terms of its duration, and the effectiveness of any action taken to improve survival is measured in terms of the time it saves. By ranking actions according to time saved, these authors found that a combination of actions was most effective. This combination was: •installing lifelines, •moderately decreasing air leakage and •decreasing the fire growth rate. Changing ventilation leakage alone was much less effective, as was altering the CO (carbon monoxide), sensor alarm threshold. These results confirm an earlier fault-tree study on escape from mine fires. The fault-tree study had shown that, with the exception of delays, single-factor changes have minimal impact. Significant reductions in fire fatalities only take place with multiple factor changes.

Jan 1, 1994

By Donald C. Moore

Asamera Minerals Cannan Mine has been producing a 170 g gold/tonne (5 oz gold/ton) siliciaus flotation concentrate since July 1985. Flotation concentrate is shipped to a smelter for gold recovery. Numerous processes have been investigated to economically produce bullion on site. This paper describes the laboratory and pilot plant test results of a bacterial assisted oxidation of the refractory minerals. Economic comparisons with autoclaving and roasting processes are included.

Jan 1, 1989

By Robert C. Freas, Donald D. Carr, Lawrence F. Rooney

Perhaps no other mineral commodities in this volume have as many uses as limestone and dolomite. These carbonate rocks are the basic building blocks of the construction industry, the material from which aggregate, cement, lime, and building stone are made. Carbonate rocks, and their derived products, are used as aggregates, fluxes, glass raw material, refractories, fillers, reactive agents in sulfur-oxide removal, abrasives, soil conditioners, ingredients in a host of chemical processes, and much more. Although the use of limestone and dolomite goes back before recorded history, new uses and products are continually being found. Carbonate rocks form about 15% of the earth's sedimentary crust and are widely available for exploitation. Found extensively on all continents, they are quarried and mined from formations that range in age from Precambrian to Holocene. Reserves of carbonate rock are large and will last indefinitely, although high-purity deposits may be absent or have limited availability in certain areas. Limestone and dolomite are so useful and so abundant that in 1989 about 798 Mt were produced in the United States. In fact, about 75% of all stone quarried or mined in the United States was carbonate rock. Sand and gravel was the only mineral commodity produced in greater quantity. In this chapter we have sought to provide the general reader an overview of carbonate rocks, their composition, distribution, production, and uses. The literature on the limestone and dolomite resources of the United States and Canada is so vast and diverse that one can easily become mired in print. We tried to list those references that are easily accessible and that provide the economic geologist with a starting point for more intensive study. The table listing selected references on limestone and dolomite resources in Canada and the United States reflects our attempt to be selective rather than exhaustive and to direct the reader to the best sources of detailed information.

Jan 1, 1994

By Ryne Goodnough

INTRODUCTION The Wyodak Mine is located in the northern Powder River Basin of Wyoming and is thought to be the oldest continuously operating coal mine in the United States, having recorded yearly production since 1923. The mine has expanded over its 80-plus-year history from an underground room and pillar operation to a modem surface snip mine. Currently, the mine feeds four on-site power plants using conveyors, has a filly automated truck load-out, and ships coal by rail to nearby Wyoming power plants. Annual production of 4.8 MTFT is accomplished on a single-shift basis with 53 fill-time production, maintenance and administrative personnel. In 1990 a decision was made to modernize the coal feed system to the power plant complex with modular conveying equipment. The project involved constructing coal storage silos, overland conveyors, feeder breakers and modular conveyors to follow the mining benches. Total project cost in excess of $25 million was used to construe or commission: A 2,150-TPH 48-inch overland conveyor with horizontal curve A 2,150-TPH 48-inch plant feed conveyor 13 shuttle conveyors, each 150 feet in length 2 front-end loaders equipped with large coal buckets 2 crawler-mounted feeder breakers with compatible discharge conveyor 1 high-lift shuttle conveyor with adjustable discharge height 1 high-angle conveyor 2 4,500-ton coal silos with automated truck load- out capabilities. Conceptually, the plan was to develop 33 MTONS of reserve adjacent to the plant complex and use front-end loaders to tram ROM coal to in-pit feeder breakers. The primary crushing would reduce coal to 6-inch minus and feed through a series of shuttle conveyors to an overland supply conveyor. The overland conveyor would feed the secondary crusher, and the crushed product would be moved to any of four storage silos using conveyors. The in-pit crushing and conveying system is a unique fit for the power plants and provided many interesting challenges for the coal mine to overcome. System integration, maintenance windows, equipment availability and the like had a major role in engineering the system to a power plant complex having no emergency coal stock- pile and limited plant storage. In crediting the designers and operators, the in-pit conveying system at the Wyodak Mine has delivered coal to the power generators since 1994 with little or no downtime. ENGINEERING CONSIDERATIONS Yearly production for the mine is based on 3.5 MTPY which requires about 1,550 TPH on an 8 hour, one-shift- per-day, 5-days-per-week basis. Considering efficiencies for starting and stopping, crew transport, loader trams, and operational delays, a nominal conveyor feed rate of 2,150 TPH or 72% system utilization was used in engineering design application. This ton-per-hour basis is used to size and commission the remaining components of the in-pit system. Coal quality requirements also played a role in equipment selection. The mine reserve grades vertically and coal from Upper and Lower benches needed to be mixed in any given proportion. This required equipment to be filly variable and capable of producing all or part of the 2,150-ton-per-hour requirement. Bisecting the 80-foot- high coal face for quality required construction of a high lift module capable of reaching a single overland conveyor 40 to 50 feet above the pit floor. Designers built a high-lift, adjustable and portable module specific for this application Having two bench systems capable of each producing the required feed for the power plants required computerized control processes to control on-line production. RSLinx, RSLogix, and RSView were chosen as the communication and control software, and a Data Highway Plus serves as the communication backbone. Each of the two in-pit benches are controlled with a data center equipped with Allen Bradley 5-40 processors. This

Jan 1, 2004

By E. I. Jurgens, K. E. Hanney, D. C. Comrie, R. H. Fletcher

Introduction The reclamation of mine/mill tailings areas is undertaken for a variety of objectives including safety, appearance, economical use of lands and forests and long term storage of a future resource. The establishing of criteria for these objectives at any site is a shared task of the government and mining company. Our attention in this paper is directed to uranium mine/ mill tailings as they are handled in the Canadian industry and in the unique Canadian climate. We focus our attention on the state of the art. Uranium is a ubiquitous mineral forming an average of 4 g per tonne of the Earth's crust. Ores are mined at about 500 g per tonne so that the residual content of uranium in tailings is comparable to average background levels. However, as in most mine/mill operations, the ore contains other minerals that become readily mobile after milling operations. Thus the main objective of tailings impoundment is the stability both physically and chemically of the mobile materials. Since the requirements for the operation and construction of tailings areas in Canada have changed considerably over the past decade, there exists a great many mine/mill tailings areas which while considered adequate in their day, would not meet modern criteria. However, most of these installations pose no concern or hazard to the public. The proximity of mine/mill development to inhabited land areas has necessitated more stringent modes of tailings operations and provisions for tailings site reclamation. The more important of these have been: 1) the prevention of dyke failure, with large liquid-solid outflows onto adjoining lands, and 2) the prevention of seepage from the tails of pollutants such as chlorides, sulphides, heavy metals and radionuclides. Uranium mill tailings are discharged as a slurry from the concentrator after the removal of generally only about 1000 g, or less, per tonne of uranium from the as-mined ore. As a consequence, a great volume of low level activity waste is generated. The amount of tailings is expected to grow in quantity in the future even faster than the increase in yellowcake production, as the demand for energy

Jan 1, 1980

By Richard D. Harvey

Petrographic properties of carbonate rocks are useful guides to the utilization of these rocks in SO2-scrubbing systems. High porosity and fineness of grain are thought to be the principal properties that contribute to high dissolution rates of the rocks in the scrubbing liquor. Lake marls and chalks are the major types of carbonate rocks that have these properties. Lake marls are composed mainly of equant grains of calcite (mean grain size generally less than 4 microns) weakly agglomerated in- to larger, porous particles. The marls commonly consist of 80 to 90 percent CaCo3 as calcite and aragonite. Impurities are, for the most part, quartz silt and organic matter. The average pore volume for samples of lake marls (1- to 1.2-mm particles) is about 0.50 cc/g, which corresponds to a porosity of about 57 percent. The mean size of pores in these marls is generally between 1 and 2 microns in diameter. Surface areas of lake marls range from 0.8 to 6.8 m2/g. Chalks have grain sizes and shapes similar to those of lake marls, but they generally have smaller amounts of quartz and organic matter and minor amounts of clay minerals. Pore volumes differ from one chalk formation to another; the 1- to 1. 2-mm particles average about 0.20 cc/g, which corresponds to a porosity of about 35 percent. The mean diameter of pores in chalks tested ranges from 0. 15 to 0.76 micron. Surface areas of chalks range from 3. 2 to 20. 1 m2/g. In the United States lake marls are restricted largely to Pleistocene- age sediments that occur in the states around the Great Lakes. Chalk and chalky limestones are restricted mainly to the Upper Cretaceous and Tertiary strata in the Kansas-Nebraska-Colorado area and in the south- eastern states, from Texas to Florida. Results of laboratory tests of the relative dissolution rates of samples at pH 6 and 44°C indicate that, in addition to many lake marls and chalks, oolitic aragonite, pelecypod shells, and carbonate waste sludges from certain industrial plants also have high dissolution rates.

Jan 1, 1974

By D. PATIL, B. K. Parekh

Water is the mainstay for the beneficiation of fine-size coal and minerals, but it is also the least desirable constituent of the final product. The basic concept of the novel process described in this paper is based on the differential surface heat absorption capacity of the individual particles. When a differentially heated solid mixture is placed on a moving belt that has been coated with low-temperature melting resin, the hotter component of the mixture will stick to the belt while the relatively cooler component will stay free on the belt and fall off at the end of the belt run. Experiments were conducted with pyrite, coal and quartz particles of 6 × 18 mesh size. The goal of the test program was to find the optimum conditions at which there exists a required temperature difference between minerals and coal particles by controlling the operating and system variables. Preliminary test results show that there is a potential for separating mineral matter from coal using the thermo-adhesive separation technique.

By FHATUWANI SENGANI

The understanding of yielding pillar behavior has been well documented in terms of pillar strength using numerical simulations and empirical formulas, but the understanding of how fracture propagates in a matured yielding pillar is not well established. A new empirical summation chart of fracture distribution along the matured yielding pillar is presented in this paper. The chart was developed using ground penetrating radar (GPR) supported by borescope observations, focusing on monitoring the distribution of extension fracture.

By F. W. Petersen

In the precious metal industry, activated carbon is used extensively for the recovery of gold and silver from cyanide solutions, particularly from slimy pulps and unclarified solutions. However, carbon can easily become fouled by inert particles in the pulp, thus decreasing the activity or gold loading of the carbon. This paper attempts to quantify the distribution of fine inert particles in activated carbon. Furthermore, a possible mechanism for the intrusion of fines will be postulated. Precipitated silica and ground silica sand were used to simulate pulp conditions and their loadings on activated carbon were determined by ashing. The kinetics of intrusion of fines into the pores of carbon were relatively fast, and were dependent on the concentration in the pulp. Results indicated that particle size of the solids and zeta potential of the fines influenced the loading of inert species on carbon. Scanning electron microscopy and secondary ion mass spectrometry showed a decrease in solids concentration to the centre of the carbon particle.

Jan 1, 1995

By S. J. Schatzel, V. Gangrade

A ventilation research study was conducted by the U.S. National Institute for Occupational Safety and Health (NIOSH) and a cooperating longwall trona mine in the Green River basin of Wyoming in the United States. The objective of the study was to evaluate the movement of longwall face air and exchanges between the face and worked-out areas to document the presence or absence of face airflow pathways between these locations. Tracer gas experiments using sulfur hexafluoride (SF6  ) were conducted to describe air movement on the face and in the mined portion of the active panel. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of gases emitted from the face and caved gob.

By Miguel Reyes, Chenming Zhou, MATTHEW GIRMAN

Electromagnetic energy emitted from electronic devices has been known to interfere with other electronic systems, hindering their ability to function properly. Mines have many electronic devices critical to the health and safety of mine workers that could be negatively affected by electromagnetic interference (EMI). To ensure that devices are electromagnetically compatible, tests must first be conducted to measure emissions and check for immunity. Standards are available across multiple industries that prescribe emission limits and test methods for electronic devices. A literature review was conducted in this study, and an overview of EMI standards in other industries is provided. Also, an example of how a standard can be applied to mining equipment is presented.

Nov 1, 2022

By Carl E. Williams

During the past two years a computer program called "COPOR," Computerized Open Pit Optimization Routine, has been developed and used for mine planning of several base metal deposits. This routine utilizes a three dimensional computerized block model of an orebody, some economic parameters and operating constraints to locate the mineable or economic limits of the deposit schedule the yearly production from the mine and produce bench by bench ore reserve summaries and maps of the yearly and ultimate pit configurations. The moving cone method is used to perform these functions with a conventional block model. This model is conventional in the sense that each block is assumed to be homogenous; i.e., either ore or waste but not a mixture of the two. Due to the nature of a seam type deposit this approach is not realistic; therefore, revisions have been made to form a new version of the COPOR program. This version has been named "COALOR," Coal Optimization Routine. COALOR contains all of the power of the COPOR program but is equipped to handle the intricacies of coal seam type deposits. The deposit can be composed of a single seam or multiple seams which are horizontal or dipping at any angle. The numerous coal quality values can be incorporated to aid the optimization of the economic pit limits and yearly scheduling.

Jan 1, 1978

By Turan Uysal, Thierno Saidou Barry, MURAT ERDEMOGLU, Mustafa Birinci

Nonbauxite ores such as aluminum silicate clays and coal fly ashes have been widely considered as potential resources of alumina (Al2O3). The interest focused on these ores is due to their high alumina content. Over the years, in countries where there are little or no bauxite reserves or where the recovery of existing bauxite ores to produce alumina with the Bayer process is not economical, alternative processes have been explored. Among these processes, acid leaching is seen as the most attractive process. In the acid leaching process, heat treatment for thermal activation to destruct the refractory structure of the minerals in the ores is generally recommended as a pretreatment method. Recently, the applicability of high energy ball mills, which are useful for mechanical activation as a pretreatment method before leaching, has attracted much attention. This is a short summary of our previous review [1], giving the details of alumina manufacturing from thermally and mechanically activated clays and coal fly ashes by acid leaching.

By D. X. Tang, G. Wilson, Y. Luo, S. S. Peng

Knowing the location of voids/fractures in roof rock will be greatly helpful for roof support design. The drilling parameters obtained during normal roof bolt installation cycle provide a fast and economic way for determining void location in roof rock. In this research, feed pressure and rotation torque are found to be good indicators for identifying the voids, based on the results of a series of laboratory experiments. A set of computational rules has been developed to locate voids in mine roof using the measured roof drilling parameters and implemented in MRGIS, a software package developed to allow mine engineers to make use of the large amount of roof drilling parameters for predicting roof geology properties automatically. Anew feature, 2D map+3D figure display, is also added to MRGIS.

Jan 1, 2004

Since first introduced, the coal mine roof rating (CMRR) has been widely accepted as a tool for geologic characterization and mine planning. This paper discusses the application of the CMRR to another practical ground-control problem: extended cuts. Extended cuts, i.e., cuts greater than 6 m (20 ft) in length, are commonly used with remote-control continuous miners. Extended cuts can greatly increase productivity, but they have been associated with a number of fatal roof-falls. When extended cuts are attempted in weak roof material, the roof may collapse before it can be bolted Until now, it has not been possible to predict where conditions may not be suitable for extended cuts. In this study, data on the CMRR and extended-cut experience were collected at 36 mines in seven of the United States. It was found that, when the CMRR was greater than 56, deep cuts were routine in nearly every case. When the CMRR was less than 37, extended cuts were almost never taken, and, when the CMRR was between 38 and 56, extended cuts were sometimes, but not always, feasible. The data also show that extended cuts are less likely to be stable if either the entry span or the depth of cover increases.

Jan 1, 2000

By Victor Rudenno

Cut-off grade is one of the most critical parameters affecting project cash flow. Its sensitivity is due to the number of other parameters that are correlated with any change in its value. Changes in cut-off grade, average grade and ore tonnage vary and they in turn can affect such parameters as capital and replacement costs, recovery, life of the project and operating costs. Perhaps one of the best definitions of cut-off grade is that of Taylor (1), "... any grade that, for any specific reason, is used to separate two courses of action, e.g. to mine or to leave, to mill or to dump ... . Obviously the most likely specific reason is one governed by economics, involving the return of investment and sufficient profit to motivate development and mining of the deposit. In this paper the cut-off grade is defined as that mining limit which will maximise the economic return for a projected mining venture. The following brief literature survey indicates that when computing the optimum cut-off grade there is a need to be able to directly compute the Discounted Cash Flow Rate of Return (DCFRR) or Net Present Value (NPV), as economically as possible, while allowing for parameter dependencies and variation in project structure.

Jan 1, 1979

By John T. Cantwell

INTRODUCTION The process engineer usually is responsible for the design operating philosophy and/or day-to-day operations of a process. Since instrumentation is an integral part of the operation, it is essential that engineers understand the general capabilities of the different types of control equipment available. Many "noncontrol" engineers have become involved with instrumentation for machinery monitoring and control as well as other plant applications. The advent of the microprocessor has led to significant changes in control, both in systems configurations and man-machine interfaces. Today's concept is called simply "distributed control." What is distributed control? Distributed control is exactly what the name implies; the control system is divided into several functional segments and spread out to cover a process. The systems are distributed for physical, functional, and risk reasons. Before delving further into the specifics of distributed control, let's look at the evolution of control systems to see how we got here. Instruments initially were located near measurement and control points in the field. Operators physically had to go to the instrument to change setpoints or take measurements. As processes became more complex, it became evident that a central control area was required. This allowed an operator to monitor and control many variables. The operator's effectiveness was increased dramatically, which resulted in greater efficiency, better quality control, and lower personnel requirements. At the same time, plants became much larger, control applications became more complex, energy became expensive, and the industry became more competitive. All of these factors placed pressure on process and production engineers to get the most for the money. The result was a continuing push to put more instrumentation into a central control room to maximize efficiency and productivity and minimize manpower. This chapter deals in some detail with devices for measuring physical and chemical properties of coal; devices for measuring the weight and weight-rate of flow of coal; devices for the monitoring and control of conveyor systems, solids inventory, fluid flow, liquid level, density, and specific gravity. These instruments have a multitude of uses throughout a coal preparation plant. The discussions cover advancements in "on-line analysis," nuclear control devices, and distributed control using microprocessors, mainframes, and soft-

Jan 1, 1991

By MEHMET ALI RECAI ONAL, MAHMUT CAMALAN

The key motivation of this study is to evaluate the potential of well-known hazardous gases—carbon dioxide (CO2), hydrogen (H2) and oxygen (O2)—as grinding aids for mineral liberation in ball milling. The results show that exposure of chromite ore particles to CO2 flow will promote chromite liberation at breakage and, therefore, using CO2 as a grinding aid may partially reduce the carbon footprint of the mining industry. For that purpose, the use of two-phase (gas–solid) or three-phase (gas–solid–water) moving-bed mixers are recommended for the pretreatment of mill feed before ball milling.