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By Steven Atkin, Rens Verburg, Bryony Hansen, David McWharter

The use of paste tailings as underground backfill and for surface disposal is rapidly expanding, and with it comes the requirement to understand and predict its long-term environmental stability. This paper presents the results from a kinetic testing study performed on cemented tailings paste mixtures under both subaqueous and subaerial conditions. In addition, the effects of grainsize reduction are investigated. It will be demonstrated that the long-term weathering behavior of tailings paste is controlled by its physical and chemical characteristics, as well as its placement conditions. The testing indicates that subaqueous disposal of paste inhibits acid generation, whereas the exposed samples produced acidic leachate despite the presence of cement added to meet geotechnical requirements.

Jan 1, 2000

By S. Atak, G. Bulut

The xanthate adsorption mechanism on pyrite was investigated with an emphasis on solubility studies. Additionally, adsorption studies, Eh and infrared spectrophotometer measurements were performed. Pyrite floats at pH levels between 3 and 6 using ethyl and amyl xanthates with a maximum at pH 4. The solubility of pyrite in the absence and presence of xanthate was investigated in detail with respect to pH and conditioning time. Experimental results showed that the solubility of pyrite increases from 60 to 120 ppm (10-3 to 2x10-3 mol/ L) in the presence of xanthate at pH 3. Fourier transform infrared (FTIR) spectra of ferric xanthate, dixanthogen and pyrite conditioned with xanthate indicated that dixanthogen is the only species that can be determined on the pyrite surface. Adsorption tests showed that the highest level of xanthate adsorption was in the acidic range; yet higher adsorption densities were detected in neutral solutions compared to alkaline conditions. Electrochemical data suggest that the doubling of the iron concentration is due to the reduction of ferric ion to ferrous by xanthate while xanthate is oxidized to dixanthogen. Dixanthogen formation together with the hydrophobic iron hydroxy-xanthate complex on the surface is proposed to be responsible for pyrite flotation. Key words: Flotation, Pyrite, Adsorption, Xanthate, Dixanthogen

Jan 1, 2003

By K. Morsy, S. S. Peng

A new method of pillar stability evaluation was proposed. The unique feature about the method is that it estimates two types of stability factors for the pillar. The first stability factor is to measure how much the applied stress at that point is smaller than its strength, and the second stability factor is to predict whether or not the pillar will fail violently. The strain-softening behavior of coal pillars was simulated by the Drucker-Prager yield criterion. A new algorithm that simulates the strain-hardening behavior of the gob was used. A numerical technique to estimate the local mine stiffness (LMS) was introduced and verified by both numerical and analytical methods. A case of massive pillar failure in a room-and-pillar mine was used to define the stability limits for the proposed method.

Jan 1, 2003

By Robert A. Jankowski, Natesa I. Jayaraman, Jay F. Colinet

The U.S. Bureau of Mines evaluated the dust control effectiveness of two-phase flow systems in a full-scale model mine using a mockup of a Joy 14CM continuous mining machine. In a two-phase flow system, air and water flow simultaneously through the nozzle. Air pressure varies from 10 to 60 psi, and water at 30 to 50 psi. Coal dust was introduced at the face, and dust concentrations were monitored at the operator locations and in the return. When compared with a conventional spray system, a symmetrical two-phase flow system reduced dust levels during the box cut by 43 pct at the operator location, and 30 pct in the face return. Dust levels, however, increased at the off-operator position during the slab cut. A directional two-phase flow system reduced dust levels at both operator locations by more than 90 pct in the box cut mode. While the use of two-phase flow systems will reduce respirable dust levels and water usage, it requires an air supply to the miner. Moreover, the ability of the two-phase flow system to redirect the dust cloud makes nozzle orientation a critical factor.

Jan 1, 1991

By M. A. Ackerson, R. E. Griffin, W. H. Pomroy

Two automated fire detection system configurations have been used successfully in underground mines: the pneumatic "tube bundle" approach and the electronic telemetry approach. The electronic telemetry approach is more widely used, owing to its greater speed, flexibility, and capacity to both monitor other underground conditions, and remotely control underground equipment. However, depending on specific mine conditions and layouts, pneumatic detection, or a combined pneumatic/telemetered system may offer significant advantages over the telemetered approach alone. This paper describes research by the U.S. Bureau of Mines to design and in- mine test a rapid response pneumatic fire detection system tailored to the unique requirements of multilevel metal mines. The relative merits of pneumatic detection are discussed in the context of typical multilevel mine layouts and environments. A Bureau developed proto- type system is described with emphasis on design features which counter commonly perceived and/or experienced pneumatic detection system operating problems. Finally, the results of a 3-yr in-mine performance evaluation of the prototype hardware are discussed. Included are descriptions of system layout and coverage, response time, tube leakage, sample dilution, elimination of accumulated water from sample lines, and system maintenance and reliability.

Jan 1, 1989

By Thomas H. Koenning, William E. Bruce

The importance and complexity of the ventilation systems in many underground coal mines necessitates the use of digital computers to model the ventilation networks. The modeling procedures used by the Mine Safety and Health Administration (MSHA) utilize the MSHA-modified Penn State computer program. The basic techniques used by MSHA have been described in detail in NESA (now MSHA) Informational Reports 1066 and 1183 (1. 2). Two basic methods are utilized for modeling underground mine ventilation systems. The first modeling method is the use of actual air-flow, pressure, and fan-performance data acquired during a full air-pressure, air-quantity ventilation survey to develop a mathematical model of the ventilation system. The second modeling method is the design of a ventilation system using data obtained from calculation, from past experience, or from technical literature. The latter method would typically be used to design a ventilation network prior to developing a new mine. Regardless of which method is used for modeling, there is a need to know, or to calculate, appropriate resistance values to be used for airways and for the various ventilation control structures. Such data is typically difficult to obtain and this report is an attempt to summarize typical resistance values which may be used in designing ventilation networks for new mines or in simulating proposed system changes in existing mines. Illustrations are presented to show where some of the resistances typically are located and how they are modeled in mine ventilation net- works.

Jan 1, 1987

By J. E. Gebhardt, S. Chander

Significant advances have occurred in the use of electrochemical techniques for sulfide mineral flotation research. The techniques have been used singly or jointly with other characterization methods. When used in combination with other methods, the electrochemical methods provide a means to control the state of oxidation of the surface. Various analytical methods are employed for characterization. The methods that have been used include wetting, x-ray photoelectron and fourier transform infrared spectroscopies. The electrochemical methods include voltammetry and transient electrochemical techniques of galvanostatic polarization and AC impedance spectroscopy. The challenge for the future lies in the utilization of this knowledge in plant operations so as to increase the overall efficiency of flotation separations.

Jan 1, 1989

By R. H. Grau

This Bureau of Mines report describes methane liberation trends from all U.S. coal mines liberating over 100 Mcfd (100,000 cfd) (2.8 Mm3/d). Detailed are results from the latest Bureau survey performed in 1985 and shown are mine and company name, location, coalbed and methane liberation quantity. The report shows that in 1985, there were 180 mines producing more than 100 Mcfd (2.8 Mm3/d) and the total quantity of methane liberated by these mines was 303,900 Mcfd (8,605 Mm3/d). This data is compared with previous studies performed in 1971 , 1973, 1975, and 1980. From 1971 to 1985, there was a 10% decrease in the number of mines liberating at least 100 Mcfd (2.8 Mm3/d) but there was a dramatic 34% increase of liberations from these mines. The increase seems to be caused by new mines being developed in deeper, gassier coalbeds, particularly in Alabama. Likewise, in comparing the ten highest liberating mines in 1975, 1980, and 1985, an increase in methane liberations each year was experienced. The report classifies mines by three levels of liberations: greater than 100 Mcfd but less than 500 Mcfd (2.8 to 14 Mm3/d); 500 Mcfd to 1 ,000 Mcfd (1 4 to 28 Mm3/d); and greater than 1,000 Mcfd (>28 Mm3/d). It was found that 87% of liberations were from mines producing over 1,000 Mcfd but these accounted for only 38% of all the mines in the study.

Jan 1, 1987

By Malcolm J. McPherson

Mine shafts that are used as primary ventilation routes are different in their airflow characteristics to other subsurface openings because of the aerodynamic effects of guide rails, buntons, pipes, cables, ropes, and shape, size and velocity of conveyances. As many shafts contribute heavily to the overall resistance of a mine ventilation circuit, it is important to be able to predict the resistance of a planned shaft with reasonable accuracy. This paper describes part of a study on the ventilation characteristics of hoisting shafts, conducted for the Basalt (Nuclear) Waste Isolation Program (BWIP). Methods of quantifying each of the four components of shaft resistance are developed; namely the shaft walls, fittings (buntons, pipes, etc.), the skips or conveyances, including the dynamic effects of their motion, and shaft stations. Practical guidance is given on ways of reducing the shaft resistance. The paper concludes by giving a step by step procedure for the ventilation aspects involved in the design of combined hoisting/ventilation shafts.

Jan 1, 1987

By K. S. Narayanan, Marcia L. Bartges, K. S. Venkataraman

The starting powders' physicochemical properties and consistency are essential for technical ceramic products to meet their performance specifications. The need for finer and more consistent powders has opened new technologies for synthesizing powders from atoms and molecules. However, submicron and near-micron powders obtained from conventional comminution and classification techniques are still competitive. This paper shows several examples from electronic ceramic applications of how we can use powder characteristics for micromanaging by design the ceramic properties such as the green and fired densities, slurry rheology, shrinkage during sintering, and the microstructure of the sintered bodies. The cross-disciplinary nature of the technology requires that the researcher not only should have a firm grip on the fundamentals of one or more disciplines, but also should be generally aware of the intricacies of other disciplines as well.

Jan 1, 1992

By Gemei Yang, Pierre Mousset-Jones, Felipe Calizaya, Malcolm J. McPherson

Laboratory tests on controlled airflow recirculation have shown the development of transient states in response to changes in system prevailing conditions such as those generated by a sudden start-up and stoppage of fans. Researchers in many European countries have developed various models to explain these phenomena. However, these models failed to consider some important factors such as diffusion and dispersion of gas in turbulent flows. For both in-line and cross-cut recirculation, tests have shown that after the start- up of a booster fan, the gas concentration in the system fluctuates, reaching high levels at the initial states and slowly dying out with time. These fluctuations cannot be represented adequately by simple step-wise functions but rather by smooth, albeit complex equations. In this paper, the phenomena are explained by the convection-dispersion theory, and represented by a mathematical model. Based on a few simplifications and applying Fourier's Transform Method to the differential equations of the flow recirculation model, an integral form of gas concentration function was derived. The Simpson Integration Method was used to compute numerical results for two laboratory tests. The paper also discusses the range of the dispersion coefficient to improve the accuracy of the model.

Jan 1, 1989

By V. Roze, M. E. A. Robertson, C. J. Sharland

Current Techniques - Fire Assay Fire assay of gold has been used for several thousand years and is a well known technique to the traditional assayer. Very few assayers wish to use the method but to date there has been no viable alternative. Fire assay is expensive in labour, time, capital and running costs. Workers can be exposed to hazards and uncomfortable working conditions such as lead fumes, heat stress, dust and eye strain. The high capital cost of putting up the building and equipping it, together with running costs which increase annually at a prohibitive rate makes the technique less attractive each year. The main requirement in most assay laboratories is to maximise throughput economically. This is difficult with fire assay as it is impossible to automate. Each sample for analysis is handled by at least 12 people and each person represents a potential source of error. Record keeping and report generation has to be done manually which is both slow and prone to errors. Replacement of staff requires a considerable training period and with a large turnover of personnel this presents yet another problem. The presence of silver and dross in the gold sample affects the accuracy at low gold values. X-ray fluorescent analysis Two methods of XRF instrumentation have been used with limited success. The first type is a laboratory instrument employing L X-rays. Small samples of a few grams, which are not representative,

Jan 1, 1988

By G. P. J. Schmitz, F. S. Gouws

In flotation processes the structure of the froth phase contains a wealth of information regarding the behaviour of the plant. Various structural features of the froth phase provide an indication of the froth viscosity, froth stability, mineral content, bubble size, etc., which can all in turn be related to the performance of the plant. In this paper the application of machine learning techniques to exploit information from digital images of the froth phase of industrial flotation plants is discussed. This includes both connectionist techniques to identify control decisions necessary to maintain optimal operation of the plant, as well as symbolic methods, such as induction techniques. Both approaches are used to classify froth structures based on statistical features derived from digitized images of the froth surfaces. It was found that backpropagation algorithms perform significantly better than either non-incremental or incremental induction. Backpropagation algorithms requires significant user input in order to optimally train the neural network as opposed to induction, which requires little user input. In contrast to back propagation, decision tree induction produces easily understandable decision trees which can be incorporated into a rule base or an expert system. Finally, incremental induction provides a simple means to smoothly and continuously adapt induced rules to follow changing process conditions.

Jan 1, 1996

By Y. C. Kim, W. L. Meyer, W. Cai

Although the first published optimum pit limit design algorithm by Lerchs-Grossmann dates back to 1965, the majority of the open-pit mines in the US has not as yet adopted such a rigorous optimization algorithm. Instead, the floating cone approach initially developed by Kennecott Copper in 1961 is still used today for various reasons. However, shortcomings with the floating cone algorithm, particularly for precious metal deposits with erratic mineral distributions, have provided a renewed interest in optimizing algorithms. This paper compares the performance of the floating cone algorithm with the rigorous optimization algorithm of the Lerchs-Grossman's graph theory and the newly developed maximum network flow algorithm by Hanson (1986). The maximum flow algorithm is a modified version of the logic as initially advocated by Johnson in 1968. Comparisons are made for three different deposits in terms of the total profits generated and the computation times involved. The results of the comparison show that both algorithms produced higher total profitability pits than the floating cone in all three deposits, although the increase in profits never exceeded 1 % of the base design obtained using the floating cone. Between the graph theory and maximum flow, graph theory produced consistently higher profits. The current version of maximum flow, however, cannot be modified to produce the optimum pit. Nevertheless, the authors prefer the maximum flow over the graph theory, simply because it is easy to program as well as to explain.

Jan 1, 1987

By A. Zorychta, T. Cyrul, Z. Kleczek

INTRODUCTION Underground mining causes disturbances of the primary state of stresses. Resulting from those disturbances a loss of stability of rocks that surround excavation may occur interrupting the production and creating life danger for the personnel. One of the manifestations of such an instability is a rock burst phenomenon which mainly occurs at great depths. From the mechanical mint of view the rock burst is a loss of stability /Filcek et a1.,1984; Pietuchow and Linkow, 1976/ due to : - quasi-static stress changes in the surrounding rocks; we will call it s seam burst , - dynamic stress changes in the surrounding rocks caused by rock shocks ; we will call it roof burst. Possibility of the rock burst occurrence Is uniquely determined by the state of stresses existing in the rock mass. In the following sections of the paper we will consider different aspects of this question. Moreover distributions of displacements and failure criteria for a coal seam at longwall mining will be defined. STATEMENT OF THE PROBLEM Determination of the vertical stresses and displacements resulting from longwail mining will be based on the Budryk’s idea of a stress wave /Salustowicz, 1955/. The idea originates from the analysis of a roof plate /beam/ resting on the deformable foundation /Sean/ and subjected to the cylindrical bending. Equation of the bending lice uniquely defines vertical stresses and displacements which are induced in the seam. The equation will account only the shear force effect. Elimination of the bending moment has been shown and discussed by Zorychta and Bcrecki /Zorychta, 1985; Borecki and

Jan 1, 1986

By Maurice C. Fuerstenau, Bruce R. Palmer, R. E. Johnson, B. R. Palmer, G. W. Warren

The environmentally sound processing of metal-bearing chloride solutions plays a key role in the extraction, plating, recycling, finishing and surface preparation of metals. Additionally, many chloride-bearing waste streams must be processed to obtain environmentally acceptable products. This paper reviews the technologies used for processing aqueous metal-chloride solutions and describes the challenges that have been overcome in application of these technologies.

Jan 1, 1993

By Clete Stephan, John Urosek, Ian Anderson

The Endeavour Colliery is operated by Powercoal Pty Ltd. It is located in the Central Coast of New South Wales, Australia. The mine has been in operation for about 30 years, producing around 600,000 tons of export coal annually from two production sections. On June 28. 1995, an explosion occurred underground in the 300 Panel at approximately 9:50 a.m.. There were thirty miners underground at the time of the explosion, all of whom were safely evacuated. From June 29 through July 10, personnel did not enter the mine. However, gas samples of the mine atmosphere were obtained from underground monitoring stations and analyzed. Samples were also obtained from boreholes that were drilled from an adjacent mine. On July 10, the atmosphere at the underground monitoring locations and at the boreholes appeared stable with minimal risk of combustion occurring underground. Plans were developed to begin the recovery of the underground workings. The recovery of the underground workings was completed on July 13. The underground investigation of the explosion began on July 14. The investigation was conducted by the New South Wales Department of Mineral Resources. Technical assistance was pro- vided by the United States Department of Labor's Mine Safety and Health Administration (MSHA).

Jan 1, 1997

By R. R. Klimpel

This paper is a summary of the author's industrial experiences on the selection and optimization of flotation reagent schemes for the recovery of gold species. The trends given are a composite of data and experiences gained on 24 different gold ores from around the globe. The primary emphasis is on the benefits of matching the associated gold mineralogy to a reagent scheme most appropriate for that mineralogy. Two general categories are discussed: the flotation of free or native gold species and the flotation of gold associated with a variety of sulfide minerals. Important plant operating factors influencing each of these two categories are presented with supporting examples. Carefully matching reagent chemistry and appropriate operating conditions to any given gold-bearing ore will not only lower the total reagent cost but, more importantly, can lead to measurable increases in gold recovery.

Jan 1, 2000

By W. J. Deutsch, W. J. Martin, R. J. Serne

At the termination of mining, the quality of ground water in the ore-zone aquifer must be returned to a condition predetermined by the permitting agency. To immobilize the redox-sensitive elements (e.g., uranium, arsenic, selenium, molybdenum), it has been suggested that a reducing agent be circulated through the leached ore zone. We have conducted laboratory experiments to test the ability of sodium sulfide as such a reducing agent. Sodium sulfide lowered the redox potential of the effluent such that insoluble minerals containing the redox-sensitive elements should be stable. The uranium concentration of the solution decreased by more than three orders of magnitude. In column experiments, by the time 10 pore volumes of the sulfide solution had flowed through, sulfide minerals were forming. The experimental results indicate that the addition of sodium sulfide should cause chemical reduction of the leached sediments, thereby producing long-term stability of the ground-water/sediment system.

Jan 1, 1988

By D. A. Curry

This paper describes a study of the influence of non-normal loading on the indentation behaviour of single bit-teeth. Indentation experiments have been performed on a soft, isotropic limestone using both sharp and blunt 60 degree wedge-shaped indentors constrained to penetrate the rock at 0, 15, and 30 degrees to the rock surface normal. For both sharp and blunt indentors, the normal force required to produce a given normal penetration decreased as the offset of the penetration direction from the rock surface normal increased. The crater volume produced by a given normal penetration with the sharp indentor was largely independent of the penetration direction. In contrast, the crater volume produced by the blunt indentor was increased markedly by non-normal penetration at small penetration depths, because the threshold penetration for chip formation decreased with non-normal loading. The crater volume produced by a given normal force was significantly increased by non-normal penetration, and this increase was particularly pronounced with the blunt indentor. The energy required to form unit crater volume was correspondingly reduced by non-normal indentor penetration. A simple method for predicting the reduction in the rock's resistance to chip formation is outlined, which is supported by the experimental data. The implications of these findings for rotary drilling are considered.

Jan 1, 1986