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By H. J. Bogert

Shallow, gently dipping quartz veins at the Mineral Hill Mine are mined in room and pillar stopes. Ore zones are severely folded and fractured, thus actual pillar strength and physical properties of the rock mass deviate significantly from conventional laboratory tests and pillar theory. Laboratory specimens large enough to include pre-existing fractures proved to be representative of actual pillar strength. Further adjustment for specific pillars was based on RQD. Deformation and stress were measured in several pillars during pillar recovery. Stress data and finite element modeling were used to estimate absolute pillar stress at failure. The stress/strain relation provided an excellent indicator of pillar behavior. Good agreement between lab data and underground data was found.

Jan 1, 1995

By G. E. McClelland

Agglomeration techniques have been successfully applied to commerical heap leach cyanidation operations for the recovery of precious metals from low-grade ores, mine wastes, and tailings. The major parameters important for successful agglomeration pretreatment of these feed materials are discussed. Several commercial agglomeration-heap leaching operations are described. Two of the operations converted from conventional heap leaching to agglomeration-heap leaching after coventional heap leaching proved unsuccessful. Heap performance before and after agglomeration is discussed. A fairly recent operation that began production using agglomeration-heap leaching technology is also described. Two operations that processed milled tailings by agglomeration are discussed. The tailings feeds could not have been economically processed by means other than agglomeration-heap leaching.

Jan 1, 1986

By C. Haycocks

The Appalachian coal fields contain many mineable contiguously placed coal seams. Selection of the mining sequence for these seams, historically and currently, is based primarily on considerations of seam ownership, availability and economics. Mining any seam can seriously affect subsequent operations in coal seams both above and below the one being mined. The effect is often detrimental to recovery costs and safety of mining in the subsequent seams. The purpose of this paper is to examine the conditions that can develop in an underlying seam due to stress concentrations that can occur below pillars or abutment zones in an overlying seam, and suggest guidelines for avoiding them. This situation most commonly occurs when the overlying seam is mined first, although simultaneous and subsequent mining of the upper seam can also produce such effects. Other interaction phenomena resulting from subsidence or arching will not be considered here. The methodology used in this research utilized both computer and body loaded photoelastic models to study the interaction mechanisms. Field studies are used in both interpretation and analysis of the results. Numerous examples of load transfer from upper workings exist in all parts of the world and many of these have been incorporated into this work. Such interaction problems are quite common and likely to be an ever increasing occurrence as mining activities in old seams are completed and new seams opened up.

Jan 1, 1982

By Ernest F. Giovannitti

A couple of years ago, one of the major television networks produced a series on the environment. One episode in the series dealt with the nation's solid waste problem and some of the research being done to solve it. It was interesting to listen to one researcher who was attempting to develop a glass that when broken would dissolve in water. It was said that using this glass would eliminate over 100 million tons of solid wastes each year. At first glance, it would appear that this research-effort would make a significant contribution to environmental pollution control; however, if one pauses to consider the water, he can see that this solution to the solid waste problem may well contribute to a water pollution problem. The dissolved material must either end up in our surface streams or be removed in waste treatment systems. Either alternative may have a more adverse effect on the environment than the original problem. With today's emphasis on the environment, it is important that the effects of our activities be studied in depth. Then, by properly planning the activity, the adverse effects can be minimized. The coal mining industry 100 years ago was in the same boat, as our glass maker, is today. Unfortunately, it too failed to consider all the effects of its activities and as a result, in Pennsylvania, there are over 5000 miles of streams adversely affected by coal mine drainage. The situation is improving, however, because mine operators are beginning to recognize and accept the methods for controlling coal mine drainage. The purpose of this paper is to discuss the measures for the control of coal mine drainage and to set forth the factors that affect these controls.

Jan 1, 1972

By C. R. Fahnestock

One of the major problems for us in the earthmoving industry is the analysis of materials under the ground surface. Countless engineering and construction jobs would be simplified if there were an inexpensive and fast way to obtain information on problems such as: Depth and solidith of bedrock? Nature of the materials between bedrock and the surface? Adequate foundation for bridges and drainage structures? Location of supplies of materials to be used in construction? Investigation of tunnel sites? Characteristics of swampy areas and investigation of existing and potential slide areas? These questions are of paramount interest to highway contractors as they bid jobs and plan, equipment spreads to handle them at optimum efficiency. Such information also is invaluable to engineers in the design and construction of bridges, buildings, railroads, canals, and tunnels.

Jan 1, 1961

By Jack O?Hearn

A liquid and solid waste management plan for an operating uranium ore processing mill was developed to efficiently and effectively dispose of existing solid wastes and related, affected surface and ground water resources. The goal of this management plan was to achieve satisfactory clean up of these existing wastes ad their by-products as well as to prevent similar situations from occurring in the future. An existing, modern system of synthetically lined tailings ponds, constructed after many years of mill operations, now provides an approved site for the disposal and containment of waste streams currently generated by the mill. This system was thought to be readily adaptable to serve as a key element of the waste management plan. The potential presence of extra capacity in these ponds could eliminate or reduce expenditures for new facilities required solely for proper management of liquid and solid wastes generated by operations prior to construction of the modern tailings ponds as well as for a range of anticipated future operations.

Jan 1, 1984

By A. T. Visser

The expansion of surface mining has led to the development of very large off-highway trucks capable of hauling payloads in excess of 290 t (320 st). Mine haul roads have historically been designed empirically, relying heavily on local experience; the trend in increasing truck size will thus render the current pavement systems inadequate. Because truck haulage costs can account for 10% to 50% of the total costs incurred by a surface mine, not only would the maintenance costs of existing roads of inadequate design increase, but vehicle operating and maintenance costs would increase prohibitively. Thus, there is a need for improved design technologies encompassing the construction and management techniques of mine haul roads appropriate for the wheel loads of vehicles now in use. This paper presents the different components of a mine haul road design and management system and demonstrates the value of its application through case studies. The system has been applied at several South African surface mines, and distinct benefits have been derived. The improved structural design of a new road resulted in a 29% saving in construction costs and provided better service, while the optimal selection and management of wearing course materials provided better functionality at lower total transportation operating costs.

Jan 1, 2000

By G. Brien, O&apos

Selective in-plant breakage was investigated at a Central Queensland, Australia mine. Component seams and size fractions from in-plant samples were characterized petrographically and probability analysis of vitrinite reflectance data used to track the distribution of seam proportions through the plant. Results show that the 2 seams reported differentially to coarse and fine circuits, mainly as a function of coal type rather than rank. Seams were also preferentially concentrated in different size fractions of the coarse circuit. Breakage in the coarse coal centrifuge generated approximately 4% of -0.5 mm fines, but was not seam specific.

Jan 1, 1996

By N. P. Titkov

This paper presents the results of laboratory and pilot plant investigations for the development of efficient methods of beneficiating hematite ores from the Krivoi Rog, Kursk Magnetic Anomoly, Olenogorsk, and other localities. The tests included gravity, magnetic (in a high intensity field), flota¬tion, and magnetizing roasting methods. It was possible to develop efficient beneficiation methods depending on the mineral composition of the ore and degree of dissemination of ore and gangue minerals. The paper shows the relationship between the iron silicate and quartz content of the ore and the technologic indices of the various beneficiation methods. Some of the conclusions based on these investigations and the technical and economic computations related to the cost of one ton of pig iron produced from concentrates obtained by the various beneficiation methods are: 1. If the hematite ore is not disseminated uniformly, it is expedient to use a combined gravity and flotation process. Ore particles up to 50 am. in size are beneficiated by gravity (heavy suspension, jigging, and others) and yield a lump concentrate. The middlings from this process are recrushed and floated; 2. Finely disseminated hematite ores, containing small quantities (less than 5 percent) of iron silicates, are most effectively beneficiated by flotation. Anionic (sulphate soap, tall oil emulsion with various foam depressors) as well as cationic collectors may be used. Depending on the mineral and chemical composition of the ore, it is possible to obtain concentrates containing up to 65 percent iron with an extraction up to 94 percent; 3. Finely disseminated, mixed hematite-magnetite ores may be beneficiated by flotation or a magnetic separation-flotation process; 4. Finely disseminated hematite ores, containing large quantities of iron silicates and earthy hematite ores are most efficiently beneficiated by the magnetizing roasting method. This method will yield concentrates containing up to 68 percent iron with extractions up to 90 percent. Although beneficiation by the magnetizing roasting process is costly, it will nonetheless, when employed on this type of ore, yield the least expensive pig iron.

Jan 1, 1960

By P. I. James, M. R. Baker

This paper examines new copper production from waste-grade ore using Blue Planet Strategies’ DEMET™ (Dynamic Electrode Mining Effluent Treatment) technology, which aims to bridge the practical weak pregnant leach solution (PLS) processing gap in heap leach-solvent extraction/electrowinning (SX/EW) operations by electrochemically removing metals from weak streams and generating product streams strengthened in target metals in a functional analog to SX. Weak PLS treatment was studied and used to estimate the economic and production impacts for a representative hypothetical brownfield copper heap leaching and DEMET-augmented SX/ EW operation to utilize "waste ore." Copper removal at 86% plating efficiency to below 0.1 g/L copper with power consumption of 0.55 kWh/lb copper and product strengths of over 10 g/L copper are presented. Modeling yielded approximately $2/lb total copper production and = $1/lb treatment costs with an immediate operation gross margin increase of 12% for the augmented brownfield. Potential mine life extension with an average 38% gross margin on "waste ore" augmented production at copper values of $3.25/lb was also indicated.

Jan 1, 2014

By S. Ersayin, I. Iwasaki

The application of a magnetic field was shown to be effective in controlling iron losses in a pilot-scale cationic silica fIotation in the processing of magnetic taconite concentrates. The design of a magnetic field distribution device and batch flotation test results using a 1.42-m3 (50 cu ft) WEMCO flotation cell are reported. Major losses of iron units in froth products were in the -25-µm (-500-mesh) fraction, and the application of a magnetic field decreased the flotation of fine magnetite, thereby improving the selectivity of separation. The "as-received" sample was sufficiently magnetized, and no further benefit was gained by the magnetizing treatment. The selectivity was somewhat adversely affected by demagnetizing the sample, though its effect was minimal due to the magnetic field. The device is simple in construction, low cost and may be readily installed in existing equipment. Key words: Iron ore, Flotation, Taconite concentrates, Cationic silica flotation, Magnetic field, Flexible magnetic sheet, Magnetizing, Demagnetizing

Jan 1, 2003

By George H. K. Schenck

It seems appropriate to review the history of mechanization of our underground coal mines at this time when many favorable flags are flying for this industry. It is a reasonable hope that such a review may stimulate thinking as to the directions that new technological developments are apt to take and in which members of the Society of Mining Engineers are destined to play important roles. Discussion of the relative importance of the various changes that have taken place since the advent of electric power provides the starting point. It is in the economic factors utilized that we find conditions which permit more efficient utilization of the capital committed to the industry. Concepts rather than specific items are emphasized in the following discussion because once the value of a concept, such as mechanical conveyors, is established, it then spawns many variations which are not significantly different. The shift from animate to inanimate energy has been the most important change in the modern industrial scene, including coal mining. Although introduced into coal mines for some purposes early in the period of general electrification, the coal industry adopted mechanical power relatively slowly, and 1944 was the first year in which a majority of deep-mined coal was mechanically loaded.

Jan 1, 1968

By William P. Walsh

In December 1983 the author undertook an investigation in east Texas which was organized to learn the feasibility of applying geophysical techniques over shallow lignite deposits. The work embraced experimental high resolution seismic reflection and offset Wenner resisitivity sounds over three 4 to 4 mile test sections. This site also was sponsored by Woodward-Clyde Consultants (WCC) and a consortium headed by North American Coal Corporation. The principal objective of this investigation was to learn whether the aforementioned geophysical techniques could be applied over shallow lignite deposits (i.e. located at approximately 100' to 300' in depth) and consequently provide structural and stratigraphic information useful for resource and reserve characterization. A secondary objective was to determine if these same techniques could disclose the nature of the overburden and the distribution of ground water therein.

Jan 1, 1985

By Adam Bezuijen, Tiago Gerheim Souza Dias

"The construction of mechanized tunnels in soft ground has evolved significantly over the last 20 years, especially in the control of the face pressure and the closure of the soil-lining void to reduce the induced settlements. On the other hand, several mechanisms of the TBM excavation cycle are still not taken into account for routine design calculations, such as the increment of water pressures in front of the tunnel face, the flow of excavation fluids around the shield, the dynamic equilibrium between the grout pressures and the excavation convergence, among others. This paper discusses specifically the issue of face pressures and how several mechanisms, which are routinely not considered, can be easily verified and incorporated into the state-of-practice of design. INTRODUCTION The stability of underground excavations is traditionally assessed through analytical solutions based on the lower bound theorem of plasticity (Atkinson and Potts 1977; Mühlhaus 1985) or the limit equilibrium method (Anagnostou and Kovári 1994; Messerli et al. 2010). These methodologies depend on the tunnel geometry, certain ground parameters and the support pressure. When conventional construction methods are used, the internal support pressure is an abstract representation of the combined effects of partial excavation, ground reinforcement, and the different support elements. The use of closed-face tunnel boring machines (TBM) changed this perspective, as the magnitude of pressures acting on the excavation boundary could be controlled in a more direct way. In front of the TBM the ground is excavated as the cutterhead rotates and the cutting tools scrape the ground from the tunnel face while additives are injected to condition the material. Water, polymers, bentonite, and foam can be used as additives under different conditions (Thewes et al. 2012). The loosened ground with additives, herein referred to as the mixture, flows through the openings at the cutterhead and into the excavation chamber. This mixture is kept pressurized to support the face."

Jan 1, 2016

By D. M. Milne, H. H. Kanduth

INTRODUCTION The past few years has seen an increased interest in the determination of statistically valid properties of a rock mass. The increased use of computer modelling for the study of rock excavation behaviour has created a need for upper and lower statistical bounds for the properties of a rock mass being modelled. Obviously, to determine the statistical properties of a large volume of rock, many samples must be tested - an expensive proposition when using conventional testing facilities and procedures. As a result of high costs per sample, sufficient tests for statistically valid results are rarely done. In an effort to reduce both sample preparation and test facility costs, an instrument called the Bemek Advanced Rock Tester (BRT) was developed in Sweden. With a total weight of approx. 35 kg, the BRT is portable and sells at a small fraction of the cost of a conventional testing machine. It is comprised of a small 65 KN loading frame with attachments for a variety of tests (see Table 1) , a hand operated hydraulic pump, an electronic balancing unit and a programmable microprocessor. The microprocessor is capable of storing data, performing arithmetic operation on, and printing signals from, a transducer and two strain gauges. A detailed description of the apparatus is given by G. Swan et al. (1). The proposed test strategy involves first a 3-point flexure test on a notched core specimen, followed by a 4-point flexure test on the separated specimen halves. Finally, point load and Brazilian tests can be carried out on the quarter parts of the original specimen. Thus specimen preparation is kept to a minimum. These and other perceived advantages have prompted the purchase of this machine and an evaluation of its suitability to provide data on mechanical properties of intact rock for numerical modelling and rock mechanics design at Noranda's underground mines. Details of its performance evaluation and experiences with the unit are discussed in the following sections. [ ] INITIAL OPERATING EXPERIENCE During the commissioning stage the BRT had, or developed, a series of problems, some of which seriously affected its operation. Below are some examples. Poor documentation was the most serious problem encountered. Confusing instructions for the 4-point bend test installation and its microprocessor programing, as well as poor and ambiguous information on the calculation of gauge factors, are some of the difficulties which had to be overcome. Meehan~cal problems occurred, including failure of the hydraulic pump, as well as electronic difficulties with the microprocessor. Other problems with the printer, requiring its replaceqent, were fortunately covered under warranty.

Jan 1, 1986

By Britta Schoesser, Zdenek Zizka, Markus Thewes

"The support pressure of a slurry shield corresponds to the in situ earth and groundwater pressure to ensure the stability of the tunnel face. The support fluid (bentonite suspension) penetrates from the excavation chamber into the pore space and transfers the support pressure to the granular structure of the soil within this zone. At the same time, the cutting tools rotate periodically with the cutting wheel and remove the penetrated soil up to a certain cutting depth at the face. Shortly after the tool passing, the penetration process starts again. Both, the support pressure and the soil excavation, act in the same direction at the tunnel face, but they are subject to different cyclic intervals. This relationship between the time needed for the transient penetration process and the interval of the cyclic passage of the cutting tools at a local point at the face is examined and the impact onto the global face stability is discussed. INTRODUCTION Slurry shields are usually deployed for excavations in soft ground. The main application range is in non-cohesive soils (DAUB Recommendations 2010). In non-cohesive granular soils, the tunnel face stability is one of the key design issues. The slurry shields make use of pressurized bentonite suspension (slurry) to support the unstable tunnel face. To support the tunnel face effectively, the slurry pressure has not only to counter the groundwater pressure, but also has to be transferred into an effective stress to support the soil grains. In general, the pressure transfer can be achieved in two ways: (1) with a thin flexible membrane or (2) a penetration zone. The membrane (1), called filter cake, creates a thin impermeable layer from bentonite particles directly on the tunnel face, and enables a transformation of excess slurry pressure into effective stress. In case of penetration zone formation (2), the excess slurry pressure is transferred onto the soil skeleton along the entire penetration depth by shear stresses between slurry and soil grains. These theories, presently applied to assess the pressure transfer on the grains within slurry shield tunnelling, are originating from diaphragm wall technology, e.g. Müller-Kirchenbauer (1977), Kilchert and Karstedt (1984). They assume that the support pressure transfer mechanism is built-up instantaneously on the whole tunnel face and is not damaged or influenced by the interaction with excavation tools. These assumptions are valid for conditions during the excavation of diaphragm wall trenches whose bottom is excavated and the walls of the trench are supported. At the tunnel face of a slurry shield, the support suspension acts on the same area as the soil excavation. Hence, the conditions on the tunnel face are transient (time dependent) due to the time period needed for the penetration process of the slurry and the periodical damage of the pressure transfer mechanism by excavation tools (Fig. 1a)."

Jan 1, 2016

By James J. Scott

Introduction Friction Rock Stabilizers, trade name Split Sets, are presently under research and development by Ingersoll-Rand Company and Dr. James J. Scott, inventor. Conceived in 1953, the system is a patented process undergoing extensive field and laboratory testing. The author has published papers on the Split Set System earlier (References 4, 5, 6) The Split Set System holds promise to be a revolutionary development in the field of ground control. The system produces an interior reinforcement to a rock mass which: 1. Is simple in its concept. 2. Adjusts to the degree of restraint needed to match rock properties. 3. Provides a yieldable support and, later, a more rigid support as it is needed. 4. Pre-loads the rock in compression to increase stability. 5. Is a full-contact, fully tensioned device to resist rock loads. 6. Minimizes the stress concentration effects inherent in many interior support devices. 7. Improves safety for the miner. 8. Is cheaper than a grouted system. 9. Offers the rock mechanics engineer an opportunity to design in a fashion not before possible.

Jan 1, 1977

By William E. Spence

Gold was discovered at the Haile mine in Lancaster County, South Carolina in 1827 or 1828, and since that time the mine has been worked intermittently by both open pit and underground methods until its forced closure in 1942 by World War II. Production figures are incomplete, especially for the early years, but the total gold produced is estimated to have been greater than 200,000 ounces. Thus, the Haile mine has been the most productive gold mine in the eastern United States. The upper, residually enriched ores were relatively rich, but the bulk of the production has come from the mining of lower grade ores.

Jan 1, 1978

By Marion A. Goudie

The Devonian salt basin, which contains the Saskatchewan Potash deposits, extends from just east of the foothills in Alberta, north as far as the Peace River area, across Saskatchewan and into Manitoba as far east as Range 10 west of the First Meridian and south into Montana and North Dakota. The basin is closed everywhere except to the northwest. The known potash deposits are confined almost entirely to the Province of Saskatchewan, with the exception of a small area in western Manitoba bordering the Saskatchewan boundary. The following discussion will concern only the Saskatchewan part of the basin. The evaporite series in the basin is defined as the Prairie Evaporite Formation of the Elk Point Group, of Middle Devonian age. Recent work done by potassium-argon dating methods has indicated an Upper Middle Devonian (Givetian) age of from 265 to 347 million years for the potash. The Elk Point Group consists in ascending order of the Ashern, Winnipegosis and Prairie Evaporite Formations. The Ashern formation, sometimes called the Third Red Bed, consists of dolomitic shales or shaly dolomites. The Winnipegosis is a reef type dolomite, usually with good porosity, and in many cases oil-staining, although to date no production has been obtained. The Prairie Evaporite formation consists of anhydrite overlain by halite and finally, in Saskatchewan, by the potash beds. In almost all wells which have been cored for potash the lowest potash bed is underlain by one or two bands of anhydrtte, which are used as marker horizons. Cores from a few wells which cored to the bottom of the salt series have shown flecks of potash throughout the halite.

Jan 1, 1959

By D. Pappas

Over the past decade, the number of contractors working in underground coal mines has nearly doubled; however, the effect this has had on the industry's injury rates has been the subject of much speculation. The confusion exists because the U.S. Mine Safety and Health Administration (MSHA) database does not assign contractor hours to the individual mining operations where they worked. To better understand the safety record of the contractor segment of the industry, the National Institute for Occupational Safety and Health (NIOSH) undertook a comprehensive analysis of the data contained in the MSHA database. The first part of the study compared overall contractor and operator trends from 1983 to 2009 related to employment, hours worked and injury rate. One unexpected finding was that the larger contractors tended to have higher injury rates than the smaller ones. The second part of the study directly addressed the role of contractors on the safety record of 10 large underground coal mines. A detailed analysis provided both injuries and estimated contractor hours worked at these mines for the period 1992-2007. Comparison between the estimated contractor injury rates and the reported operator injury rates at these mines indicated that the contractor injury rates were significantly higher at most of the operations studied. However, the industry-wide data indicates that contractor and operator injury rates have converged since 2005 and are now equivalent. Mining Engineering, 2011, Vol. 63, No. 11, pp. 73-79. Official publication of the Society for Mining, Metallurgy and Exploration, Inc.

Jan 1, 2011