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By J. W. Merks

At mineral processing plants the accuracy and precision characteristics of assays in mill feed, tailings and concentrate largely determine the reliability of the metallurgical balance. The accuracy of measurements is ensured by selecting effective sampling methods and efficient sample preparation procedures, and by effecting each phase without introducing a systematic error while the precision of measurements is determined by the sampling regime. Sampling systems and components, sampling methods and regimes, and sample preparation procedures will be reviewed. Different techniques to determine variance components for sampling, preparation and analysis, and to detect systematic errors in assays at mineral processing plants, will be discussed.

Jan 1, 1986

By K. V. Viswanathan, P. Sornasundaran, S. E. El-Mofty

Dolomite is found to undergo preferential dissolution in aqueous solutions and this is found to be strongly dependent on the solid to liquid ratio (SIL). Electrokinetic studies done under the sump conditions revealed that the mineral surface charge is also affected markedly by the solid content in the suspension. Conditioning of the dolomite at low SIL ratios for short time intervals showed preferential dissolution of calcium leading to a magnesium-enriched dolomite surface. At higher SIL ratios and longer conditioning times, calcium depletion from the solution and a calcium-enriched dolomite surface resulted. The results are discussed in terms of surface precipitation and/or bulk precipitation and surface conversion of dolomite to the calcium-enriched phase (calcium carbonate and/or magnesian calcites).

Jan 1, 1990

By Robert G. Bottge, Paul C. Hyndman, Don J. Barnes, Clark A. Roberts

The effect of Federal restrictions on Federal mineral estate in Alaska and the Western States is being addressed by systematic, State-by- State studies. The Bureau of Mines has inventoried and classified 3.5 million sq km (876 million acres) of land, section-by-section, according to 1) mineral ownership, 2) availability for mineral exploration and development as affected by Federal restrictions, and 31, areas containing mines and mineral resources. The availability of Federal land for exploration and development is spatially compared to areas containing mines and mineral resources. The methodology and overall results of the studies are presented.

Jan 1, 1991

By Joseph Cervik, Fred Garcia

Gob holes are routinely used by the mining industry to vent methane from gobs and to prevent it from entering the mine ventilation system. In some cases, flows from gob holes are measured by centering an anemometer on the end of the discharge pipe. These measurements are erroneous and tend to be high by as much as 30%. The Bureau of Mines determined correction factors (method factors) for anemometer measurements taken in this manner. Method factors for 10.2, 15.2, and 20.3 cm (4, 6, and 8 in) ID pipe are 0.68, 0.71, and 0.78, respectively. Comparisons between horizontal and vertical flows indicated no significant change in method factors. Consequently, the method factors for horizontal pipe flows can be applied to vertical upward flows.

Jan 1, 1987

By Gösta W. Diehl

During the past five years the use of all-hydraulic drilling equipment has increased rapidly, and we have now reached a point where the hydraulic drill has become an alternative to be seriously considered for every drilling operation. The hydraulic drills have many advantages over pneumatic drills, but they also have certain characteristics, which makes a potential user hesitate before making the switch. And when the decision to use hydraulic drills has been made, the user then faces another choice of equal difficulty: the choice between different hydraulic systems. This paper discusses some of the factors to be taken into account when considering hydraulic drilling equipment for rapid tunneling in hard to medium hard rock. THE CHOICE BETWEEN HYDRAULIC AND PNEUMATIC EQUIPMENT The choice between a hydraulic and a pneumatic drill is much more than just that: It is a choice between two different systems. The choice is usually based on the productivity, economy or ergonomy of the system. However, also other factors should be considered, such as service capabilities and training requirements. And finally the choice will be influenced by the need to acquire know-how in the new technology. Productivity If the prime consideration is to achieve the highest possible tunneling speed, then the high penetration rates of the hydraulic

Jan 1, 1979

By Z. D. Hora, W. N. Hamilton

Evaporite units of the Western Canadian Sedimentary Basin are known to host native sulfur. In British Columbia, a large number of oil and gas exploration drilling holes reported intersections with native sulfur. The most important ones include 6 meters (20 feet) and 27 meters (90 feet) of native sulfur among 23 occurrences in Devonian Muskeg evaporite or adjacent Slave Point reef facies carbonates. A small Frasch sulfur deposit is known from Devonian Wabamun Group sediments near Camrose in South Central Alberta. Occurrences of native sulfur are common also in association with presently mined gypsum of Devonian Burnais Formation in southeastern British Columbia. Triassic sediments with evaporite members in British Columbia are also known to contain native sulfur showings. A widespread presence of anhydrite in many sedimentary units of Alberta and British Columbia together with oil and gas fields in the same areas and associated native sulfur occurrences point to a possibility for Frasch sulfur deposits in this part of western Canada.

Jan 1, 1992

By Priscilla P. Nelson, Francis L. C. Fong

Introduction Fracture mechanics is the study of the behavior of cracks and their modes of propagation. During cracking, energy is consumed in creating new surface area. The more energy a material absorbs, the higher is its fracture resistance. This fracture energy is provided either by work done externally, by the release of elastic strain energy within the cracked body, or by a combination of these two effects. Fracture resistance is measured in terms of either the stress intensity factor, K, or the energy release rate (also referred to as crack driving force), G. For linearly elastic materials, these two quantities are related by the following equation: [ ] where [u] is Poisson's ratio and E is the modulus of elasticity. Both K and G are direct functions of the applied force and the crack length. The process of rock cutting with full-face tunnel boring machines (TBMs) involves the indentation of a rock surface by rolling disc tools. Excavation occurs as fractures, extending from the locus of chip indentation, propagate between concentric disc grooves and liberate rock chips from the intact rock face. Since disc cutting is achieved by a fracture process, it is logical to anticipate that differences in cuttability of a variety of rocks should be related to the variation of fracture material properties among the rocks. Such a relation has been demonstrated between the performance of full-face TBMs and the critical crack driving force for excavation in relatively high strength, brittle, low porosity, isotropic rock (Nelson et al., 1985). The objective of this paper is to report on the results of a continued investigation of the relationship between fracture material properties and the effectiveness of disc cutting. Additional reliable data on full-face TBM performance is difficult to obtain, so that the results of disc linear cutter tests performed by the Transport and Road Research Laboratory (TRRL) (U.K.) are utilized in this study. Fracture Material Property Evaluation If a crack tip is subjected to a perfectly plain strain condition, many materials will behave in a brittle manner, and the material resistance to fracture is constant during crack growth. This resistance is referred to as the plain strain fracture toughness, believed to be a material property. The standard testing procedure for this parameter is given in the American Society for Testing and Materials (ASTM) test designation E399. To ensure plain strain conditions, acceptable specimen geometries are specified. Unless these geometric specifications are adhered to, the measured fracture resistance is regarded as the apparent fracture toughness, and a subscript Q is used, as [ ]. The methodology adopted by ASTM E399 is within the framework of Linear Elastic Fracture Mechanics (LEFM). This approach assumes that material resistance against cracking is developed instantaneously, without initial stable or subcritical crack extension. Prior to crack advancement in rock, however, much of the crack driving energy is absorbed in a localized volume in front of the crack tip, referred to as the plasticity or microcracking zone. This capability for energy absorption substantially increases material resistance, and a crack may be arrested unless an increased crack driving force is applied. The LEFM or plain strain assumptions would underestimate the actual fracture resistance of such a material. Such a conservative approximation may be desirable in the design of structures against fatigue or brittle failure. In mining or tunneling, however, an underestimation of crack resistance can lead to the selection of underrated excavation equipment and a decrease in production efficiency. The development of fracture resistance in rock is best described by the material resistance curve, or R-curve, which is a plot of fracture resistance as a function of crack extension. Typically, peak resistance is only reached after a finite amount of subcritical crack growth. The

Jan 1, 1986

By Rudolf E. Greuer

Modeling a mine ventilation system is a formidable mathematical problem requiring the solution of twice as many equations as there are airways with half of these being quadratic equations. The addition of a mine fire to the problem adds many more complexities. The U.S. Bureau of Mines and Michigan Technological University attacked this problem in stages. During the 1970's and 80's, a series of computer simulation programs were developed which offered progressively increasing levels of modeling capability and accuracy. The current version of this software, MFIRE 2.0, was released in 1993. This programs provides for full dynamic state mass flow-based modeling of a mine ventilation system, and includes natural ventilation, mechanical ventilation, air reversals and recirculation, methane and fire contaminant spread, and moisture condensation and evaporation in the mass flow and heat exchange calculations. This program is a useful tool for routine ventilation planning and can significantly improve mine safety by enabling detailed quantitative analysis for mine emergency preplanning. This paper reviews the evolution of the MFIRE program from its infancy as a simple digital network simulator replacing analog computers to the present version.

Jan 1, 1994

By E. J. Rorem

Rockfall and unstable rock slopes can be effectively controlled by utilizing steel wire rope net systems, either as barriers or as slope draping. The chief advantage of such systems over rigid type barriers is the flexibility of wire rope netting, permitting kinetic energy dissipation, yet providing high strength and consequently low maintenance. A review of the design considerations involved with these systems, as well as a review of several mine and non-mine installations is presented with the hope that the information may contribute to the safety against the dangers of rockfall and other mine hazards in active and abandoned mines.

Jan 1, 1996

By J. H. Bassarear, P. F. Thomas

Large-scale equipment can reduce both capital and operating costs for concentrators. Large semiautogemus (SAG) mills can be effectively utilized in big mills but they must be kept fully loaded to tab advantage of their great potential. With varying hardness ores, controlling throughput is difficult and careful design must take this into consideration. A variable speed drive on large primary semiautogemus mills can overcome this problem to a considerable degree. This paper provides a base case using standard accepted technology of two wound rotor single speed 4476 kW (6000 hp) motors to drive the primary SAG mills of a hypothetical 36,364 t/d (40,000 stpd) typical porphyry copper mill. One other fixed speed drive will be described and jive variable speed drive configurations will be reviewed. Capital costs for the entire grinding circuit, from crusher product to flotation feed, were developed for the base case and each of the alternatives. A technical evaluation comparing the advantages and disadvantages of each drive is presented.

Jan 1, 1987

By W. A. Cincilla, S. C. Tadolini

INTRODUCTION Resin bolting systems continue to gain popularity in underground coal mines in the United States, and their general success under a wide range of geological and operational conditions is well documented. In 1984, 36% of all bolts used were resin-grouted systems. However, many questions dealing with basic support mechanisms and the influence of various factors on bolt effectiveness in situ remain only partially answered. The Bureau of Mines' Denver Research Center conducted a major research project to investigate the influence of installation procedures on the effectiveness of resin-grouted roof bolts. The project consisted of two main studies: the first dealing with the contribution of bearing plates to the load-carrying capability of the bolt; the second examining the relationship between installed grout column and the anchorage capacity as measured by the standard pull-out test. Additionally, a finite-element computer model and other analytical and empirical techniques were applied to aid in the basic understanding of the test procedures and to examine the load transfer mechanism in resin-grouted bolts, which to date has not been comprehensively assessed. The plate study includes field test results from two mines (Fig. 1). At these test sites two behavioral parameters were measured: the actual loads that bearing plates were subjected to when installed in conjunction with full-column resin grouted bolts, and the roof movements generated by the applied loads. Results indicate that bearing plates are subjected to varying degrees of loading, which range from conventional installation pressures of 2.2 kN (500 lb), up to a measured load of 142.4 kN (32,000 lb) when the immediate roof is shifting and deforming. These measured loads indicate that the bearing plate is an integral part of the support system. Differential sag stations, installed to monitor roof displacements in the test sites, show the highest degrees of loading occur in conjunction with the largest amounts of movement. The column-length study addresses possible reductions in anchorage capacity of "full column" bolts. These reductions could result from such factors as the loss of grout to surrounding strata, or improper mixing of catalyst and resin. Field test sites were established at eleven mines located in major coal mining districts throughout the United States (Fig. 1). Four major roof-rock types were represented in the study: shale,

Jan 1, 1986

By S. S. Peng

Since the introduction of shield supports in 1975, safety and production in U.S. longwall faces have improved considerably. Many faces had a daily production of up to 8,000-10,000 tons and productivity reached 600 tons per man-shift. But a longwall face requires expensive equipment which slows down the growth rate of the percentage of longwall production. Among the equipment cost the shield support accounts for 50-60%, a very large proportion. Therefore, it will have a large impact on the growth of longwall mining in the U.S. to reduce the support cost (1).

Jan 1, 1988

By J. Tavares

It is no mystery why the mining industry has such lofty safety standards. In dealing with Mother Nature and gravity, the combination of the two can create significant hazards from high wall and tunnel collapses to huge landslides. The loss of production from a major disruption could be enormous. The price tag on the loss of human life is immeasurable. The evolution of geotechnical instruments and software has been ongoing for years. But the biggest innovations have occurred during the era of cell modems, internet, and wireless networks, allowing for real time data and alarms to be delivered globally anywhere and anytime to one?s computer, laptop and smartphone. Yet in some ways you can thank the urban construction projects for developing much of the technology in use by today?s mines. Due to the density of population and the billions in dollars of structures and infrastructure in cities throughout the US and the world, urban projects have faced intense scrutiny for years. Out of this scrutiny was born the necessity of real time automated monitoring of instrumentation and sensors, a defence against catastrophic failures, and real time early warning systems through alarms that can and do saves lives. It is also possible to identify areas of concern with subsequent remediation prior to failure.

Feb 23, 2014

By J. Duran

Mining at Phoenix is currently done by surface operation in the Fortitude and Bonanza Pits, at a combined rate of approximately 110,000 tons per day. A portion of the ore bodies targeted by these pits was mined previously by underground mining methods, dating back to the mid to late 1800?s. Most of the underground workings (voids) are located in the west central area of the Bonanza Pit. The surface operation requires excavation through voids, and there is a risk of pit floor subsidence that has to be addressed. This paper presents a review of the risk mitigation measures that were implemented to reduce risks to people and equipment working in the area.

Feb 23, 2014

By J. A. Baicker

A 2 1/2 inch diameter probe containing a high resolution gamma ray spectrometer was developed for downhole ore grade assays to depths of 6,000 feet. Tests have been conducted on the characteristics of this tool for in-situ determinations of uranium by means of natural gamma ray counting, and of copper, silver, gold, iron and coal quality by means of neutron-induced gamma rays. Application of the technique for improved carbon-oxygen logging in oil fields is promising. The probe contains a cryogenically cooled high purity germanium detector and a 4,000 channel spectrum analyzer. Gamma ray spectra are digitally transmitted up the cable to the truck-mounted data processing system. We found that uranium can be assayed directly in different types of formations independently of the degree of geochemical disequilibrium by counting the relatively weak 1.001 MeV gamma ray of protactinium-234m. Neutron activation work shows that in-situ determinations of copper, silver, iron and coal quality are technically feasible. In carbon-oxygen oil well logging the technique allows an accurate determination of carbon, oxygen, hydrogen, chlorine, silicon, calcium and iron, and shows promise of providing an improved oil/water differentiator.

Jan 1, 1982

By D. R. Kelland

A program has been carried out over the last two years to apply the technology of High Gradient Magnetic Separation (HGMS) to the problem of mineral beneficiation and specifically oxidized taconite iron ores. This program, supported by the RANN division of the National Science Foundation, has consisted of a laboratory program at the Francis Bitter National Magnet Lab- oratory at MIT and a pilot investigation at the Hanna Mining Company Research Laboratory. 1 The laboratory tests were conducted using several batch type high gradient separators and a continuous separator with a rotating matrix which was constructed at the beginning of the program. The high field magnets available at F.B.N.M.L. were used for investigations above 10 kG but most of the test work was performed in the range of this field value. Ore samples were contributed by several iron ore companies and consisted of oxidized taconites having goethite and hematite as their principal components.

Jan 1, 1975

By S. Koro

The current economic climate of low commodity prices and increasing costs has put a lot of pressure on mining companies to ensure their operations will survive through the current economic downturn. While history tells us that the cycle will turn around and prices will go back up again, how many mining companies will be left to take advantage of the next upturn? On average in Australia, the maintenance of mining equipment accounts for up to 50% of operating costs; which equates to nearly $15bn per year. In addition to trying to boost productivity, mining companies are also putting a lot of pressure on reducing costs; all with the intention of maintaining/increasing profit margins and thereby keeping shareholders ?happy?. The whole premise of our economy is based on ?growth? and ?profits?. Movements in the market place force mine owners to ?react? to short term fluctuations. And if that movement is downward; operations people at the sites are forced to start reducing costs. Is this cost reduction done in a logical, systematic way where all risks (short-, medium- and long term) are considered? Invariably, the answer is no! Short term ?fixes? are normally implemented with little, or no, regard for medium- and long-term impact. And the reason for this is that management is not fully focused on the long term; focus is mainly on survival. Decision making is driven by shareholder sentiment and history tells us that this is largely short-term. So given these paramteres to work within, what role can ?Asset Management? play in assisting management to meet shareholder and market requirements whilst still maintaining long-term viability of their operations (to the long-term benefit of shareholders dare I say). As maintenance costs account for nearly half the operating costs of mining companies; the ?smart? management of assets is not only crucial; it is essential for survival in today?s economic climate. What is asset management? Asset Management, according to the UK-based Institute of Asset Management (IAM) is ?the systematic and coordinated activities and practices through which an organization optimally and sustainably manages its assets and asset systems, their associated performance, risks and expenditures over their life cycles for the purpose of achieving its organizational strategic plan.? How important is asset management in today?s mining companies? IAM goes on to say: ?This definition of asset management represents a significantly greater scope than just the maintenance or care of physical assets, and is closer to the central purpose of an organization. Good asset management considers and optimizes the conflicting priorities of asset utilization and asset care, of short-term performance opportunities and long-term sustainability, and between capital investments and subsequent operating costs, risks and performance. ?Life cycle? asset management is also more than simply the consideration of capital costs and operating costs over pre-determined asset ?life? assumptions. Truly optimized, whole life asset management includes risk exposures and performance attributes, and considers the asset?s economic life as the result of an optimization process (depending upon the design, utilization, maintenance, obsolescence and other factors).?

Feb 23, 2014

By S. L. Bessinger

In the design and specification of a ventilation system for an underground mine, it is necessary to make reasonably accurate estimates of the pressure losses in the various airways of the mine. These estimates can be made with little difficulty for open airways with simple geometric cross-sections, such as those cut by continuous miners or tunnel-boring machines. The situation is much different on a longwall face, where the airway's complex geometric cross-section and the presence in the airway of obstructing equipment having a variety of shapes make it difficult, if not impossible, to estimate pressure loss using traditional methods of calculation. Headlosses in mine entries are calculated using Atkinson's Equation (1). [H = (English) H = (SI) (1)] where H = pressure ,loss, in. of H20 (Pa) K = friction factor, lbf min2/ft"4(Kg/m3) P = perimeter, ft. (m) L = airway length, ft (m) Q = airflow quantity, ft3/min (m3/sec) A = flow cross sectional area, ft2 (m2)

Jan 1, 1987

By R. L. Taylor, S. D. Abbott

"INTRODUCTION Mines are filled with a mixture of gases, some of which are toxic, flammable, explosive. Others can be early reporters of potential problems. It has previously been shown that analysis by gas chromatograph can the most accurate conventional analytical tool for common mine gas mixtures when used correctly. There are some other detection methods (e.g hand held sensors), but they do not detect many situations which are immediately dangerous to life or health (IDLH). Examples include explosive hydrogen mixtures, toxic carbon dioxide levels, and some explosive mixtures of methane with oxygen. (Reference our previous paper). There are several reasons for mines to consider onsite GC analysis. (1) Timeliness of results. Samples can be taken and analyzed immediately. Samples do not have to be shipped to a lab and wait for results. (2) Ability to run greater number of samples a lower for the same cost. This allows mine to increase the number of samples taken to be more informed about the gases/conditions of the mine without the worry of financial constraints. (3) Fewer sample media needed, and there is no wear and tear or cost from shipping them offsite. When samples are shipped offsite, those sample media cannot be used to take until the lab returns them when the analysis is done onsite, the sample media can be used again almost immediately. However there are several challenges associated with using GC to analyze mine gas samples onsite. To date there has been a clash of the requirements for a successful analysis, the capabilities of the technology, and the practicalities of implementation. The purpose of this paper is to discuss some of the difficulties in getting accurate reliable data and doing so in an economic way. This whole measurement activity is a cost center for a mine, so there are economic concerns for the mine to address. These concerns are mainly staffing costs, capital costs, maintenance, and consumables costs. A properly staffed and equipped analysis lab, including burdened overhead, costs about $500K per year. At a sampling rate of 10 per day, this is about $140 per measurement for a proper onsite lab."

Jan 1, 2016

By Erik Vlot

"The mining industry has recognized the advantages of high density backfill or ‘paste’, which is typically pumped with a hydraulically driven piston pump. Due to the discontinuous flow of this type of pump, pressure pulsations can occur in the discharge line. Pressure pulsations are an undesired phenomenon in pumping installations for a number of reasons that include: damage to the pumping system; piping and supports; disturbing noise levels; and even safety risks for operators and maintenance personnel.This paper describes an advanced system on the GEHO® piston pumps, which will prevent virtually no pressure pulsations from occurring, rather than merely reducing the already existing pulsations.INTRODUCTIONThe first GEHO® hydraulically driven piston pump was developed in the mid-1970s. It was an industrial design pump designed to operate in the high-standard industrial environment with regards to operating hours per day, duties, maintenance and lifetime of the pump and spare parts. This type of pump has a proven track record and has been further developed for the type of applications that we are describing today. The special feature of this pump type is its ability to pump extremely viscous slurry with solids content of up to 90% by weight, at high pressures. Typically, in the mining industry, this pump is used for tailings transportation, with a focus on mine backfill and is often referred to as a paste pump.In the 1980’s the hydraulically driven piston pump made its entry into the application of mine backfill, thanks to the high discharge pressure capabilities enabling the mines to pump higher density (i.e. higher solids concentration) slurries and pastes over longer distances.Part of the ongoing development was (and still is) the increase in discharge pressure and flow capacity to comply with the ever growing demands for high power piston pumps. In line with the technological developments and increase in performance duties, the popularity of this pump type increased significantly and many other industrial applications have discovered the benefits of this pump type.Together with the increase in pump discharge pressures and flow capacities the effect of an undesired phenomenon also increased: the phenomenon of pressure pulsations. Before we explore this subject in more detail it is important to first understand the design and the characteristics of a hydraulically driven piston pump."

Jan 1, 2017