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By Weixing Wang, Zhenghe Xu

The paper applies the principles of the incompressible viscous fluid-flow to studying the movement of particles on shaking table and examines the separating process of tabling according to Bagnold's shearing theory. It is shown that, in addition to the periodic movement, the particles possess the uniform movement on the asymmetrical reciprocating table; the dilation of the particle layers on the table is periodically obtained; on the backward stroke, the particles in the bed are kept loose because the shearing dispersive pressure is of maximum: the differences between the light and heavy particles become greater when the length and frequency of the stroke are greater and the deck motion is more asymmetrical.

Jan 1, 1995

By Tan Xiang-Kun, Liu Ming-dong, Yao Dun-Pu

Since the 1980s, heap leaching of gold and silver ores has been developing rapidly and experienced widespread use in China because of its lower capital and operating costs, less time consumed in construction and specific applicability to small-to-medium scale mining operations and low grade ores. Ores treated include ordinary oxidized ores, refractory sulfide ores and even those containing deleterious elements (such as arsenic or antimony) and/or carbonaceous substances. In addition to chemical leaching agents, some micro-organisms (e.g. T-ferrooxidians and T-thiooxixians) and their biochemistry mechanism have been equally emphasized. To overcome the adverse effect caused by excessive content of fines and slimes, research and pilot experiments of agglomeration-heap leaching are currently underway at two gold mines in South China and their encouraging preliminary achievements will be briefly described as illustrations in this paper. It could be expected that heap leaching of gold and silver ores holds promise and will play an increasingly important role in China's gold industry.

Jan 1, 1998

By Nigel Fung, J. D. Humphrey, R. H. Oats, J. H. Ingle

Production dozing of cast material is a cost effective method of improving dragline or mobile equipment overburden removal. Yet dozer productivity is reduced during the part of the process that requires the dozers to cut material away from the highwall. One solution is to use a hydraulic excavator to remove this material and throw it into a windrow for the dozers. By freeing up the dozers for more productive work the overall system productivity increases 25% and cost per yard is reduced by up to 10%. Dozer fleet sizing can be determined to match a specific production schedule or can be sized to balance with an excavator’s production.

Jan 1, 2004

By William J. Gregg

Mechanical testing results on oriented Devonian gas shale core throughout the Appalachian basin show a preferred fracture direction perpendicular to bedding. The preferred direction is generally parallel to the Allegheny Front, but is only coincidentally parallel with in-situ stresses in some areas of the basin. The strength of the preferred orientation of induced fractures decreases with distance from the Front. It is suggested that strain related to Paleozoic deformation is responsible for this mechanical fabric and thus the direction of induced fractures in laboratory tests may not be of use as indicators of in-situ stress orientations as previously suggested.

Jan 1, 1986

By B. K. Mishra, Partha Chakroborty

Jigs are the most important equipment used in the separation process that exploits the stratification of particulate matter under the influence of hydrodynamic and gravitational forces. Very little is known about the determined mechanisms by which particles of varying density, size, and shape stratify in a moving bed. A model is developed by using the discrete element method to understand the behavior of jig bed. This model is utilized here to study the stratification behavior of the bed and its control. The control action is based on the understanding of the physics of the stratification process within the framework of fuzzy logic. The actions suggested by the fuzzy logic controller (FLC) depend on the current degree of stratification and the existing frequency of the jig cycle. The results show that the FLC achieves efficiency in stratification with minor variations to the jig cycle.

Jan 1, 1995

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 P. Mousset-Jones, F. Calizaya

Currently, a 4.3 km long drift is being developed on the 3440 level in the Lower Kalamazoo project at the San Manuel Mine, Magma Copper Company, AZ. The drift, located at 1050 m below surface, is being constructed using a 4.6 m diameter tunnel boring machine (TBM). The drift is ventilated by a forcing type auxiliary ventilation system. At the face, to mitigate the impact on the work environment of the TBM, the system is equipped with dust extraction and refrigeration systems. Recently, to evaluate the ventilation conditions in the drift, a continuous monitoring system has been installed. The system can be used to measure the air velocity, barometric pressure, relative humidity and air and rock temperatures. This study describes the capabilities and limitations of this system, and presents a summary of the results.

Jan 1, 1995

By H. Suharyono, R. Hogg, P. Bunnaul

The flocculation of fine-particle suspensions by polymers is a nonequilibrium process whose performance is strongly influenced by physical as well as chemical variables. A standardized test procedure has been developed that provides quantitatively reproducible measurements of process performance in terms of the floc settling rate, supernatant turbidity and sediment compressibility. The procedure provides information on the development of flocs in response to polymer addition and on their degradation behavior during subsequent handling. Extensive experimental observations using a variety of solids and flocculant types have been used to develop criteria for reagent selection and process design. It is shown that the appropriate choice of reagent(s) is determined primarily by chemical factors (solid type, solution chemistry, etc.). However, actual performance depends more on physical variables, such as agitation intensity and the rate of flocculant addition. Some general guidelines for flocculant selection and process design in industrial applications are suggested.

Jan 1, 1994

By Paul D. Kovscek, Charles D. Taylor, Edward D. Thimons

When blowing ventilation is used on a mining section, a machine-mounted scrubber is often required to maintain face dust levels below 2 mg/m3. Operation of the scrubber also affects airflow patterns at the face and the dilution of liberated methane. Reductions in scrubber flow can result in increased methane concentrations. During mining, loading of the scrubber filter with dust is likely to reduce airflow. Detecting changes in scrubber flow is difficult, especially with extended cutting, because the machine must be operated from a remote location. Tests were conducted to demonstrate how scrubber airflow could be continuously monitored at a remote location. Three variables, static pressure at the fan inlet, differential pressure across the scrubber filter, and scrubber fan motor current, were continuously monitored while the scrubber filter was incrementally loaded to reduce air flow. The results show that monitoring each variable provided a way for estimating scrubber flow.

Jan 1, 1995

By Thomas H. Koenning, William E. Bruce

Determination of the state of a mine fire is an important function during firefighting and during rescue and recovery operations. It is imperative that an accurate, up-to-date assessment of fire conditions be available for persons directing such activities in order to avoid unacceptable risk to mine rescue teas and/or fire fighters. Many indicators which consist of ratios of the concentrations of fire gases have been developed over the years for determining the state of a mine fire. Results from numerous gas sample analyses are necessary for determining the trend of the fire. Some indicators are preferred because the influence of sample dilution, a frequent problem, is said to be eliminated. Definitions and examples of indicator6 found to be useful in diagnosing recent western U. S. coal mine fires are presented. Mine gas explosibility is an important subject also requiring rapid assessment. Example explosibility calculations are presented applying one widely used method. Establishing limits for withdrawal of personnel are discussed.

Jan 1, 1987

By Dean Treweek, Anthony Harding

"Creating stable, safe, constructible and cost effective support to openings in segmental linings is often an important component of successful delivery of a tunnel project. The many constraints on successful implementation include operational, spatial, geotechnical, structural, and constructability. Failure to address these adequately can lead to significant impacts on cost, schedule, and safety. With reference to past project experiences, this paper provides a guide to the most commonly deployed solutions and their pros and cons to help designers quickly identify the most appropriate solutions for a particular project, or act as a starting point for developing new and/or project specific solutions. It highlights the challenges that designers and contractors must address together for successful support of tunnel openings, and the constraints that arise. It then describes the common structural forms of support, and how each form can mitigate the constraints, allowing an effective opening support system to be implemented. INTRODUCTION While only a small portion of the total excavated volume of a typical tunnel, cross passages are often one of the most complex elements of a bored tunnel to construct. Cross passages in soft ground typically involve ground improvement, groundwater control, and multiple temporary support measures to ensure safe construction in ground that has been overstressed due to the construction of the running tunnels. Permanent lining construction requires careful detailing of waterproofing and reinforcement to support both long term ground and water loads and support the broken out rings of the main lining. While there is not a great deal of literature specific to cross passage construction, the main issues are discussed in some detail by Lawrence and Taylor (2011). However, the temporary support of the running tunnel segmental linings during cross passage construction is not always given the attention it deserves. The authors have been unable to find much literature on the design of such systems, much less the considerations that have led to a particular solution. Lawrence and Taylor only mention two potential methods of support. It may be easy to dismiss the opening support as an inconsequential item, but selection of the wrong support type can have significant impacts on both cost and schedule."

Jan 1, 2016

By U. E. Paakkinen

Progress in computer control of flotation circuits has developed parallel with advances in reliability of on-stream X-ray analysis (Cooper, 1976). Attainment of acceptable results with X-ray fluorescence analysis over the past ten years has led to application of computer control in more than 30 concentrators. Gains in applying flotation control also have given incentive to improving measurement and control devices for other essential functions in control systems. At the same time, advancing technology has made available computer systems having characteristics practical and economical for the physical environments of concentrators and ore processing plants. Benefits from flotation control have centered on increased efficiency in mineral separations, derived by stabilizing circuit operation subject to changing ore characteristics. The gains have been most evident in processing complex ores for multiple concentrate products. In many cases, particularly when coupled with grinding control, the economic results from on-line control have been substantial compared to investments in monitoring and control equipment.

Jan 1, 1979

By R. R. Klimpel

The efficiencies of plant-scale comminution processes are often evaluated by various indices calculated and/or measured somewhat independently of the performance of any associated downstream froth flotation processes. To compare specific comminution factors, such as energy utilization, media consumption and equipment utilization time, comparisons of comminution efficiency independent of flotation behavior are appropriate. However, as increasingly detailed plant-level information is gathered on the joint and highly interactive nature of comminution and froth flotation, it is becoming even more obvious that knowing and using simple efficiency indices are not enough. What is needed are more performance-related measures of the efficiencies of the combined size reduction froth flotation system for effective plant-level economic optimization to occur. The purpose of this paper is to present examples of some of the important interactions that influence the joint efficiencies of size reduction and froth flotation processes.

Jan 1, 1999

By D. J. Shields

This paper describes a dynamic short-nun mineral supply model that incorporates secondary processing, transportation, mineral market structure, and direct mining and milling costs. The method employed is network flow programming. Empirical tests utilizing domestic phosphate industry data have been conducted by the Bureau of Mines, U.S. Department of the Interior. In the model, nodes represent physical locations such as a mine or port. Arcs represent either a process, such as mining, or movement, such as rail or barge transport. Each arc is described by lower or minims allowable flow bounds, upper or maximum possible flow bands, and variable cost. Mines and previous period inventories represent potential supply. The model is optimized via a cost minimizing algorithm, which attempts to fulfill stated total demand at the minimum possible system cost given the arc constraints. An optimal solution of the model will predict production patterns by mineral property for each prespecified level of demand. A mineral property is defined as a separate accounting entity such as a mine. The results of serial optimizations are used to construct the short-run supply curve. Dynamic policy analysis can be conducted by altering the arc constraints.

Jan 1, 1986

Acid mine drainage is still a common problem in the northern Appalachian high sulfur coal region despite mining and reclamation practices applied to control it. Mining companies must treat water with alkali to raise pH and precipitate metals in order to discharge the water into receiving streams. Common chemicals used to treat drainage are limestone, hydrated lime, soda ash briquettes, caustic soda, and ammonia. Each chemical has advantages or disadvantages under specific conditions. A simple spreadsheet program was developed to evaluate costs of treating acid mine drainage across several specified water quality parameters and time horizons. Caustic soda and soda ash were shown to be cost effective for treating low flows and low acidity over short time periods. However, as quantity of water increased, quality decreased, and time horizon increased, the ammonia and hydrated lime systems were found to be much cheaper than caustic soda.

Jan 1, 1991

By A. C. Kunkie, C. J. Marshall

Highly delaminated muscovite mica products (WG-1 and WG-2) have been developed by J.M. Huber Corp. The micas are characterized as a 325-mesh product having high brightness and very narrow particle size distribution. At 40% loading in polypropylene, WG-1 mica provides substantial improvement in tensile modulus and equal tensile strength to unfilled polymer; in high-density poly- ethylene (HDPE), WG-1 provides four times the tensile modulus and a 50% increase in tensile strength over unfilled polymer. Surface modification of the water-ground mica (SM ™) provides substantial improvement in tensile strength over untreated mica at greater than 20% loading in polypropylene; in HDPE, tensile strength is twice that of unfilled polymer.

Jan 1, 1988

By Nellie E. Guernsey

The Call for Papers described the session as "Top down applications; management tools for decisions, planning, investment/finance, and negotiations." In order to attract papers, and know which ones to include as well as those to reject, it was necessary to (1) define the executive suite, (2) review what had been done in previous APCOM symposia, and (3) find out what's happening now, what isn't being done, and what can be predicted. To accomplish this, especially the third task, senior managers throughout the mineral industry were generous with their time in telephone and personal interviews. Five papers were selected for presentation at the symposium and inclusion in the proceedings; the content is divided between the Executive suite in the mineral industry and those elements which apply to any Executive Suite. The Executive Suite is the top portion of the organizational tri- angle (I), those to whom the managers of functional areas such as exploration, production, finance, and marketing report. The make-up and specific activities within an executive suite reflect the organization and culture of its corporation. As there is no typical corporation, there is no typical executive suite; however, those who work within the executive suite typically do not have day to day operational responsibilities and either are, or report to, the Chief Executive Officer.

Jan 1, 1989

By Tommy B. Thompson

The Cripple Creek diatreme-intrusive complex is known primarily for its vein telluride-gold ores. It is also known for the great vertical range of its major veins - >990 m (>3250 ft). Not as well-documented, however, are the ores dispersed into the wallrocks adjacent to veins, the ores associated with hydrothermal and tectonic breccias, or mineralized zones within fluvial, lacustrine and volcaniclastic rocks de- posited within the diatreme complex. The ore-gangue minerals were precipitated from oxidized, alkaline fluids that yielded an abundance of carbonate, sulfate and oxide minerals along with minor base metal sulfides and precious metal tellurides. Wallrock alteration is limited adjacent to veins and is more extensive within hydrothermal and tectonic breccias. Cripple Creek background The Cripple Creek district has a spectacular production history. More than 653 t (21 million oz) of gold were recovered between 1891 and 1959. Early published accounts documented the principal production from narrow- sheeted vein systems (Cross and Penrose, 1895; Lindgren and Ransome, 1906; Loughlin, 1927; Loughlin and Koschmann, 1935). Production also came from spectacular open-space fillings within the Cresson diatreme, also known as the Cresson “blow-out” (Patton, 1917; Patton and Wolf, 1915). Beginning in the mid- l96Os, more modern studies were initiated by the US Geological Survey (USGS) (Gott et al. , 1967, 1969; Kleinkopf et al., 1970) and by universities (Lane, 1976: Dwelley, 1984; Trippel, 1985; Thompson et al., 1985; Saunders, 1986; Birmingham, 1987; Eriksson, 1987; Nelson, 1989; Wood, 1990; Seibel, 1991).

Jan 1, 1992

By Arthur E. Lord, W. Martin McCabe, Robert M. Koerner

Following the driving of each new section of tunnel, a prompt decision is required regarding the type and extent of primary support to control convergence and prevent ground failure. Sometime thereafter, the effectiveness of the in-place support must be evaluated over the entire length of excavation. It is therefore extremely desirable to have available a lightweight, portable, easy to install and interpret, cost effective monitoring system to assist with these ground control functions. Such a system can be assembled based on the acoustic emission (or microseismic) technique. This monitoring technique uses a piezoelectric transducer to detect subaudible noises associated with deformation of and/or crack propagation in the soil or rock being monitored. After detection, the signals are then amplified, filtered and electronically counted to provide a quantified assessment of the stability of the structure. In the simplest sense, the absence of emission, or counts, signifies no deformation and thus stability. Conversely, the occurrance of counts signifies instability to varying degrees. The higher the count rate, the greater the instability and the need for immediate or additional support. Described in this paper is an overview of the acoustic emission (microseismic) method, details of its use in a laboratory study measuring convergence and stand-up time in soil, and the behavior of rock samples under similar stress conditions. Field use of the method is recommended for ground control monitoring in tunnels, and some suggestions regarding monitoring procedure are presented.

Jan 1, 1979

By E. V. Bowman

This paper is intended to deal with the material handling aspects of fine coal cleaning as applied to a recently built plaint in: southern West Virginia. This plant is processing 160 tons per hour of 1/4" x.0 coal on a two shift basis. Past experience with this very friable low volatile metallurgical coal indicated that its plastometer readings, varied directly with the size and length of time elapsing between mining' and ultimate consumption. Due to the mines location with, respect to its consumers, little could be done to decrease the time element. Studies indicated that the plastometer readings are considerably less in the minus 60 mesh range than that experienced in the plus 60 mesh sizes. Therefore, handling the coal in such a manner as to have the least amount of degradation became extremely important.

Jan 1, 1961