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By Malcolm J. McPherson

The highest recorded loss of life due to the collapse of mine workings occurred at the Coalbrook North Colliery in South Africa on 21st January, 1960. A total of 437 persons died when bord and pillar workings collapsed over an area exceeding one square mile The whole mass of strata from the 470 ft (143 m) deep seam to the surface being affected. Although the Coalbrook disaster was unique in its scale the problem of pillar failure, particularly in old workings, is by no means uncommon nor confined to recent history. Indeed, the collapse of large pillared areas was a regular feature of mining in the north of England in the early part of the nineteenth century. When a section of underground workings collapses, the air under the descending roof is compressed very rapidly. The pressurised air is dissipated subsequently at a rate governed by the leakage paths available. If the collapsing area is small, such as the case of a local fall of roof, then there will be little danger of an air blast. If, however, an extensive area collapses suddenly then the rapid compression of air will give rise to a pressure shock wave that will be transmitted through the remaining workings as an air blast. If worked out areas are connected to current workings via unstopped airways an air blast caused by pillar failure in the old workings will be extremely hazardous to personne1 and may cause extensive damage to equipment, perhaps even reaching to surface plant. At Coalbrook, the air blast blew out a wall in the surface fan house. Areas that are considered liable to sudden collapse may be isolated from current workings by the construction of stoppings. However, such stoppings must be capable of withstanding the 'hammerblow' effect of peak air pressures developed during the collapse. The work described in this paper was undertaken in order to determine the maximum air pressures that stoppings must withstand during a major pillar failure. The result has been a method of establishing peak air pressures that is quick and simple to use. Readers who are concerned primarily with the practical application of the method are advised to turn directly to the last main section of the paper.

Jan 1, 1980

By DeVerle P. Harris

The structure of an exploration model reflects a number of design considerations, one of which is the question or issue-to be investigated by the model. Thus, a model designed to evaluate the magnitude of risk and its economic implication to optimal decision making at each decision juncture of a multistage exploration architecture differs considerably from one designed to evaluate, say, the long run average cost of discovery, in which the architecture of exploration is suppressed and risk is simply an element of average cost. The perspective of the model examined in this paper is that exploration is investment in (purchase of) information and that the next stage of an exploration program is undertaken only when the expected value of information to be acquired in that stage exceeds its cost. The degree to which this perspective is honored influences considerably model design. Consider two design objectives:

Jan 1, 1989

By S. B. Bhagwat

Equipment capacities of a sample of Illinois surface coal mines representing about 60% of surface production in the state were studied. Available equipment capacity was compared with the required capacity, as indicated by coal production and stripping ratios reported. Most mines sampled showed surplus equipment capacity, which if avoided, would result in substantial cost savings. The surplus capacity results mostly from market fluctuations that result in underutilization of equipment. Study findings underline the importance of market assessment at the time of mine planning and of communication between marketing and engineering arms of a coal firm.

Jan 1, 1987

By Pierre Mousset-Jones, Felipe Calizaya

The design of an auxiliary ventilation system for long underground openings (drifts, ramps and shafts), often requires the installation of multiple fans. The fans are installed in series and separated from each other by rigid ducts of fixed or variable length. However, problems relating to excessive leakage often occur, with each project representing a unique problem requiring an efficient solution. In this study, a method to determine the design parameters of an auxiliary ventilation system is presented. The method is based on the principle of partitioning a long ductwork into segments of finite length and solving the resulting networks separately. Specifically, the method is developed to solve two types of problems: constant fan spacing, and constant fan size. In the former, the fan spacing is fixed, and the problem is solved for fan sizes. In the latter, the problem is to solve for fan spacing. An example is used to illustrate the method.

Jan 1, 1993

By Robert Cooke

This paper shows how technology developed to analyse stabilised slurries can be applied to paste flows. The rheological characterisation of paste mixtures using the generalised yield pseudoplastic rheological model is described. It is noted that the slump test does not provide a complete rheological characterisation of a paste. Methods for calculating pipeline pressure gradients for laminar and turbulent flow are presented. The minimum pressure gradient is an important consideration to ensure that solids do not settle on the pipe invert. Important points to be considered for a pipe loop test programme are noted. The usefulness of the pseudo shear diagram for scaling pipe loop test measurements is demonstrated. Issues to be considered for the design of paste reticulation systems are discussed.

Jan 1, 2001

By Laurel E. Burns

Alaska is in competition with the rest of the world for exploration dollars. Providing a "seed package" of airborne geophysical data for the state's numerous mining districts encourages companies to begin more detailed exploration in more areas than they could have afforded on their own. When data are already available, the initial risk decreases for people involved in exploration. Airborne magnetic and electromagnetic data help ge¬ologists and geophysicists determine what rocks and structures are present under overburden and vegetation. These data form a fundamental package that exploration companies want before intensively exploring most regions. Individual mining companies have conducted their own geophysical surveys during the past several decades. However, these data are not available to other companies. The companies able to afford geophysical surveys have less money for ground exploration after purchasing expensive, private geophysical data. Therefore, they are not able to explore as many places as they might. Additionally, since data are not shared with other exploration companies, the proprietary surveys do not foster intercompany competition to move projects forward. Individual prospectors and small companies can not afford their own geophysical surveys. "It is more often than not the grassroots exploration efforts of the smaller operator that leads to significant discoveries," said Klaus M. Zeitler, senior vice president for development and exploration at Teck Exploration. Acquiring and releasing the geophysical data to the public produces several benefits. The increased explo- [ ]

Jan 1, 1998

By Robert J. Ramsey, N. Finkelstein, Foster J. Witthauer

First mining operations in the Tyrone District, located just north of the Burro Mountains in Grant County, New Mexico, commenced in the 1870's. A major operation was undertaken by Phelps Dodge Corporation in the early 1900's when a 2,000 ton per day underground mine was developed and a gravity concentrator was built east of the mine and across the Continental Divide. It was during this time that the picturesque Tyrone townsite was built and occupied. In 1921, however, the underground operation was closed because of high operating costs and low demand for copper. The area was drilled extensively during the 1950's and in October 1966 Phelps Dodge announced the pending development of the new Tyrone with a large open-pit mine, a modern concentrator, suitable support facilities, and a new townsite to be located between the mine and Silver City. Stripping for the pit and construction of shop and milling facilities began in 1967. By the spring of 1969, ore was being stockpiled near the primary crusher. Operation of the concentrator on a 3-shift per day basis commenced on July 17, 1969. The concentrator as initially built had one primary, two secondary, and five tertiary cone crushers, two grinding sections of six ball mills each, two flotation sections, four filters, and four tailing thickeners. 'he capacity was about 30,000 tons per day. In 1971 and 1972, the capacity was increased to 48,000 tons per day by the addition of one secondary and two tertiary crushers, one section of eight ball mills, one flotation section, two filters, and four more tailing thickeners. Centralized automatic control was built into the original and expanded facilities to the greatest extent possible, considering the state of the art at that time. Installation of additional control

Jan 1, 1976

By H. Reginald Hardy, Maochen Ge

Data analysis is one of the most important steps required for the successful application of the acoustic emission/ microseismic (AE/MS) technique. A dedicated computer software package to analyze acoustic emission/ microseismic data associated with field applications in the geotechnical area has been developed recently at Penn State University. This paper addresses the major features and applications of this computer software package.

Jan 1, 1986

By L. Eros, R. H. King

The US Bureau of Mines has funded several research and development projects in computerized mine monitoring and control. Hardware and software components have been sufficiently developed so that mine operators have been provided with an efficient means to comply with federal regulations and increase mine safety. Several cost benefits have been realized as well, particularly with increased conveyor belt haulage availability. Western Fuels-Utah Inc. approached the Bureau to assist in planning, installing, and evaluating a computerized mine monitoring and control system because of the agency's research experience in this area. The installation was planned for Western Fuel's Deserado mine, located in Rangely, CO. Since a large, complex, underground mine producing about 2.4 Mt/a (2.7 million stpy) of coal was projected, the company anticipated significant benefits in safety and efficiency through a computerized monitoring and control system. A major part of the cooperative program was to document and evaluate the system design, installation, and operation. This will assist others to adequately design, specify, install, and operate future systems. Mine description The Deserado mine plan and layout have important impacts on the monitoring system requirements. Long range plans are to produce 2.4 Mt (2.7 million st) of clean coal annually from two longwall sections and four continuous sections. Presently, two continuous miner sections operate under 213 m (700 ft) of overburden in the 2.3 to 2.5 m (7.5 to 8.5 ft) thick D seam to develop main, submain, and panel entries have developed for a longwall. These began operation in December 1986. Belt conveyors haul the coal from the mining sections to a 1.4-m (54-in.) belt located in the upper compartment of the slope. The lower compartment contains a hoist for men and material transport. From the slope, the coal moves to two 9 kt (10,000 st) raw coal storage silos, then to a 680-t/h (750-stph) preparation plant. After cleaning, a 5.5-km (3.5-mile) overland conveyor carries the coal to a clean coal slot storage and rail load-out facility. An electric locomotive then transports the coal to the Bonanza Power Plant in Utah. Allen-Bradley monitoring and control hardware and software controls the preparation plant, with two PLC-3 programmable controllers and a Process Control Industries D-1200 color graphics interface. The system operator uses three "smart" color video display units and an alarm printer for hard copy records. Originally, it also monitored and controlled the conveyors from the bottom of the slope to the top of the raw coal silos, the preparation plant, the overland conveyors, the main mine ventilation fan, and the hoist. Some of these features, though, were later transferred to the mine system.

Jan 2, 1988

By M. Polat, S. Chander

Many models have been suggested in the past to obtain a satisfactory fit to flotation data. Of these, first-order kinetics models with a distribution of flotation rate constants are most common. A serious limitation of these models is that type of the distribution must be pre-supposed. Methods to overcome this limitation are discussed and a procedure is suggested for estimating the 'actual' distribution of flotation rate constants. It is demonstrated that the classical first-order model fits the data well when applied to coal flotation in narrow size-specific gravity intervals. When applied to material which is fractionated on the basis of size alone, the use of three parameter models, which were modified from their two parameter analogs such as rectangular, sinusoidal, and triangular, gave most reliable results.

Jan 1, 1995

By Wayne F. Crockett, Martin H. Col

Gold, as a precious metal, has been sought for several thousand years. During this time economics have generally determined whether or not a deposit is minable. Today, few would spend $500.00 or $1,000.00 to produce one ounce of gold, yet most gold deposits currently being mined would have such costs if they were mined using the methods of the 18th century. Innovation has been the key to success in the world of mining. We are constantly having to look for new ways to mine deposits of lower grade, at greater depths, or with higher stripping ratios. The mining of placer gold deposits has always been subject to the volatile swings of the world price and the constant rise in production costs. The rise in costs is compounded by the drop in overall ore grades. Occasionally, a major technological innovation will dramatically reduce the costs of placer mining to allow previously marginal or unminable deposits to be mined at a profit. The continuous bucketline dredge was the last such major innovation in the gold placer mining. The continuous bucketline dredge has allowed large volumes of placer deposits to be picked up and processed on a continuous basis. Unfortunately, as the overall grade of the deposit declines, it becomes impossible to process enough ore to pay for the operating costs. There are many gold deposits around the world waiting for the next technological innovation that will allow them to be mined. One such deposit has been the Grey River deposit near Greymouth in New Zealand. The deposit contains gold reserves of 8992 kg, yet the deposit has been sitting idle for many years because the average value

Jan 1, 1988

By L. Korkiala-Tanttu, M. Rinne, Z. Song

Disposal of mine tailings has been recognized as an unavoidable burden of mining companies and local authorities. Conventional methods dispose mine tailings in a passive manner which hardly generates any value from them. On the other hand, growing local communities close to mines need more infrastructures which require great amounts of raw materials. In view of the above mentioned situation, a novel utilization of mine tailings is explored as alternative material for asphalt pavement, in order to extract more value from mine tailings and solve the high cost of pavement material. Inherent physical properties of the mine tailings were first investigated to find out their availability as pavement material. Then test specimens were made as mixture of the mine tailings and other pavement material to be tested in laboratory. The mine tailing materials presented a considerable potential as asphalt filler for low-volume roads. Furthermore, the limitat

Jan 1, 2011

By P. R. A. Andrews, G. Heinrlch, V. I. Lakshmanan

The paper describes a simplified method to chemically modify the surface of industrial mineral fillers. Four industrial mineral samples were taken from feedstock of commercial fine grinding operations. These samples were ground in bench scale ball mills and in the presence of various organic solvents. The ground products were measured for particle size distribution, surface area, surface chemistry by oil absorption and degree of organicJminera1 bonding. Where appropriate, the ground products were compared to commercially available surface modified, industrial mineral fillers.

Jan 1, 1990

By H. Sis, S. Chander

The pressure filtration behaviors of dispersed and flocculated alumnae slurries at high percent solids were investigated with the objective of determining the effect of surfactant type and concentration on slurry properties. A high-purity alumina powder was used as a model solid. Dispersion of the alumina was controlled by pH and by surfactants that are known to act as electric and steric stabilizers. The effects of both ionic and nonionic sutfactants were investigated. Surface charge measurements of the slurries were carried out by an electrokinetic sonic amplitude (ESA) method to better understand the mechanisms. The effect of surfactant type and concentration on the kinetics of pressure filtration and cake properties are discussed.

Jan 1, 2000

By J. M. Mutmansky

The objective of this study was to produce coal dusts for laboratory research that are similar to mine airborne dusts in chemical, mineral, and physical characteristics. In this investigation, dusts produced in laboratory comminution equipment were compared with continuous-miner-generated dust for similarity in physical characteristics. Mining-generated dust (MGD) and bulk coal samples were first collected from an underground mining operation. The bulk samples were then processed in the laboratory for size reduction in various comminution devices. These laboratory-generated dust (LGD) samples were subjected to size and microscopic analyses. Physical properties of the dust particles were studied on a scanning electron microscope (SEM). A numerical shape coordinate system (SCS) was also developed and applied to 300 particles from each sample. Statistical analysis was then performed on the collected data and characteristics of the MGD and LGD samples were compared.

Jan 1, 1995

By D. R. Spears, D. A. Stanley

The US Bureau of Mines investigated the fundamental aspects of shear-flocculation using a rapid, in-situ particle size analyzer. Silica was stirred in the presence of an aliphatic amine to determine the effects of collector coverage, stirring speed and solids concentration on the kinetics of shear-flocculation. The results showed that shear flocculation is a two-stage process. In the first stage, which occurs during the first 1-2 min. of the reaction, the mean particle size increases rapidly, and in the second stage, an equilibrium is set up between the rates of floc growth and floc decay. Collector dosage affected the position of the equilibrium by altering the number of surface sites for particle-particle attachment. A minimum stirring speed was necessary for shear flocculation, which was dependent on solids concentration and collector dosage. This stirring speed was the minimum necessary for particles to overcome the electrostatic energy barrier, and that results in keeping the conditioned particles dispersed. Larger particles flocculated more rapidly. At very high stirring speeds, large flocs became unstable, resulting in a narrowed particle size distribution in the slurry.

Jan 1, 1995

By Jakub Nalaskowski, Robert Aranowski, Jan D. Miller, Jan Hupka

The polyolefins, mainly polyethylene and polypropylene particles, are used as an active filler material in polymer-polymer blends and are being used for the modification of asphalts to pro- vide for high-load, low-maintenance road construction. The stability of prepared blends depends on the interaction forces between polyolefinfiller and the matrix and/or between two polyolefin filler surfaces in the polymeric matrix. Various additives, especially surfactants, can be used to modify these interactions and improve the stability of polymer blends. In current research, direct force measurements between polyethylene (PE) surfaces in n-tetradecane, a nonaqueous solvent imitating the polymer matrix, were performed in the presence of lauric acid and dodecylamine using the AFM colloidal probe technique. Additionally, the zeta potential of polyethylene particles in the presence of surfactants in n-tetradecane was measured. The interac- tion forces between the polyethylene surfaces can be described as a combination of electrical double layer repulsion and steric repulsion between polymer chains extending into the n-tetradecane sol- vent. The addition of surfactant to the n-tetradecane was found to increase the repulsive force between the PE surfaces. The strongest repulsion was observed for dodecylamine. Additionally, the temperature efect on the interactions in n-tetradecane was studied. It was found that steric repulsion between the PE surfaces increases with an increase in temperature.

Jan 1, 2003

By Ellis G. Goree, George A. Simmons, Andrew B. Pervis

The pneumatic classifiers are widely used for fine dry powders separation These classifiers can be used for either the removal of fines from coarse feeds or the removal of coarse particles from ultrafine feed To optimize the operation of pneumatic classifiers, a thorough understanding of the impact of operational parameters on the efficiency of classification is essential This paper describes the design features and effects of operational parameters followed by illustrations of pneumatic classifiers usage in two case studies

Jan 1, 1983

By G. Bezuidenhout

The newly developed Bateman Flotation Machine has proven its versatility in roughing and cleaning flotation circuits. This mechanical flotation machine has the dual performance capability of suspending solids and dispersing air at relatively low power inputs without compromising these two important fundamentals. This new development has been successfully marketed to a wide cross section of concentrator mineral processes. The mechanical design of the flotation mechanism has been optimised to reduce operational costs and to lower manufacturing costs. Production process environments were utilised for verification of the scale-up of each cell volume size rated mechanism. These thorough investigations produced performance data which could be accurately quoted. This paper is a historical account of the Bateman Flotation Machine. Technical details of the development are covered with descriptions of the operational applications.

Jan 1, 1995

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

Eastern US oil shale contains approximately 10 to 12 gallons of oil per ton and 7 to 10% pyritic sulfur. Physical beneficiation of these low grade shales using froth flotation provides a high grade material that makes extraction of oil more economically attractive. The Alabama oil shale used in the present study contained 16.46% organic carbon and 14.5 gallons of oil per ton as determined by Fischer assay. Liberation size of the kerogen was estimated at 10 µm. `Ken-Flote' column flotation technology provided a high grade concentrate containing as much as 60% organic carbon. However, carbon recovery was about 60%. Carbon recovery was improved to 75-85% while maintaining concentrate grades in excess of 40% carbon by providing longer retention time in the column, which facilitated effective bubble-particle collision and attachment.

Jan 1, 1994