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By J. C. Yingling, R. J. Sweigard, S. T. Mickleborough

The geostatistical technique of conditional simulation is applied to measure the uncertainty inherent in the factor-of-safety (FS) predictions for soil slopes in which there is an incomplete knowledge of the spatial distribution of soil properties. A case study that considers a natural clay slope in Canada is presented. The sequential-indicator simulation technique was used as a means of generating a series of spatial maps of the soil properties at the site. These maps approximate random draws from the conditional probability density function that characterizes existing uncertainty in the spatial distribution. FS determinations were made for each simulated map using the simplified-Janbu approach. In using this approach, computations are performed using a new computer program that can operate on irregular spatial profiles of soil properties specified on a discrete grid. A unique capability of this approach is the ability to generate the FS distribution conditional to the type, position and value of existing site-characterization measurements. This capability should reduce uncertainty in FS predictions.

Jan 1, 1996

By Anthony G. Fonseca

About 45% to 50% of the coal mined in the United States passes through coal preparation plants. East of the Mississippi River, this number increases to about 75% to 80%. Although the cost for coal preparation is worthwhile to some, the coal industry faces the challenges of continuing downward pressure on the price of coal and the impact of new environmental regulations. Coal preparation is an effective process that achieves 75% to 80% ash reduction, 15% to 80% trace element reduction and 85% to 90% Btu recovery. It is less effective for pyrite reduction (35% to 70%) and on-line operating time (40% to 60%). It also suffers from obsolete control systems. In coal preparation, raw coal is modified to a more preferred form to enable its use. The methods used to achieve this modification must be cost-effective and appropriate to the raw coal, the scale of production and the end-user requirements.

Jan 1, 1995

By Alex Harrison, Steve Kasper

Various countries around the world have testing and manufacturing standards in place for steel cord belting. These standards are very comprehensive in what they allow the end user to specify, however, their practical significance in terms of belt life is more difficult to quantify. Such testing standards will be briefly reviewed in this paper in relation to the implication for end user expectancy. Since there is no US standard of manufacture, the end user is left with writing their own specifications. In addition, such standards do not address the effect on belt life of manufacturing faults, such as cord plane buckles, or lateral cord movement. Some new technology used to test steel cord belting will be described as an aid to both manufacturer and end user. Specific end user related issues addressed on this paper are: Tracking and belt quality Cord plane irregularities and performance Cord size and belt life Cord fatigue and testing

Jan 1, 1993

By Joe D. Mitzel

The Indian Head fine has been in existence since 1922. For over 56 years there have been North Dakota people mining coal at this same location. The area affected will fit inside a circle 5 km in diameter, and the coal is lignite. The seam thickness has varied from 2.4 m to 3.65m, and the overburden from 6 m to 30 m in depth. me Lignite coal which is being mined at the Indian Head Mine is from 15.8 x l0 6 to 16.7 x 10 6 J per kg; it has a moisture content of 33 to 38%; an ash content of 5 to 10%; and a sulfur content of from 0.5 to 0.7%. The moisture content and the fact that we crush the coal co a top size of 14 cm x 0, are two of the characteristics or the product which cause it to freeze and remain inside of the railroad cars on the slope sheets. The market for the coal initially was almost entirely local coal sales. That is, coal was sold to people in the area who used the lignite to heat their homes, stores, offices, schools, and churches. Back in the early 1920's, there were no stoker-fed boilers, or pulverized fuel boilers, as we have in today?s marketplace. Basically, all of the coal was sold as lump coal, pieces about 30 to 35 cm square, to be used in furnaces: and nut coal with a top size of about 7.5 cm to 10 cm to be used in the old kitchen cookstove. All of the coal fines, less than 5 cm, were screened out and layed onto a pile. There was no market for the smaller sizes of the lignite coal. It has been our experience that when the coal is in lumps or chunks larger than 7.5 cm to 10 cm, there is a very slight possibility of freezing. That is the chunks themselves freeze, but by their nature, they do not cling to one another or form large masses of frozen material which are difficult to remove from the slope sheers of the railroad cars.

Jan 1, 1980

By Chen Bingchen, Ma Shaojian

A new magnetic liner, with unique magnetic circuit and novel structure designs, was developed. It was characterized by light weight, low noise, as well as corrosive and abrasive resistance. The wear rate of the magnetic liner was one twentieth and one ninth those of the manganese-alloy steel and rubber ones respectively. The forming mechanism of the protective layer and that of influencing factors on magnetic liners were also investigated. The research results could not only instruct using magnetic liner, but also widen their application.

Jan 1, 1995

By T. Leftwich, G. Faison, K. Pavlich, R. Borden, S. Pavlou

Recent regulatory and policy initiatives under the Resource Conservation and Recovery Act (RCRA), and the Comprehensive Environmental Response Compensation and Liability Act (CERCLA), will have a significant effect in risk reduction requirements for the mining and minerals processing industry. For example, Congress is considering regulating 20 special wastes from the processing of ore and minerals through RCRA Subtitle D and TSCA. The performance of risk analyses and environmental planning at mining projects is often driven by Federal and state regulatory standards. Recent regulatory and policy initiatives by the Environmental Protection Agency under the Resource Conservation and Recovery Act (RCRA), and the Comprehensive Environmental Response Compensation and Liability Act (CERCLA), will have a significant effect on environmental planning and risk reduction programs for mining and minerals processing. Regulatory programs implemented under other Federal laws including the Safe Drinking Water Act, Clean Water Act, and Clean Air Act will also impact industry practices. This paper provides: 1) a brief overview of mining waste and mining waste management, and 2) a description of these regulatory initiatives and a discussion on the impacts of new requirements on environmental and risk reduction programs in the mining industry.

Jan 1, 1992

By D. R. Spears, C. E. Jordan

The U.S. Bureau of Mines examined the influence of turbulence on the fine bubble flotation of fine-sized (minus 40 micron) galena in order to improve flotation efficiency. Fine bubble flotation was carried out in a spinning-disk flotation cell and was compared to results obtained from flotation in a conventional cell at equivalent agitation levels. An automated electrochemical technique was used to monitor the turbulent velocity distributions of the fluid within the cell as a function of time and position. The velocity profiles were used to increase the precision of the fine particle, turbulent flotation model. While improved flotation response was obtained with intense agitation, the effect of bubble size was small. These results matched the model's predicted response for fine particle flotation.

Jan 1, 1989

By Walter C. Labys

There has been considerable growth in public enterprise institutions involved in mineral commodity markets. These institutions typically consist of trading organizations (STO1s), regulatory agencies, and mixed agencies. The particular character of these institutions varies according to whether they reside in developing countries, in Eastern Europe (COMECON Countries), in industrialized countries, or in the form of international agencies. The purpose of this paper is to explain recent attempts to assess the growth of public enterprises as well as their impacts on mineral markets and trade. Some earlier analyses of market impact made by the author have been up- dated for four major mineral markets: copper, tin, bauxite and iron ore. Conclusions are drawn regarding the dynamics of market structure changes and their impacts.

Jan 1, 1986

By G. Balletto

Increasing environmental awareness leads to a reflection on the consequences of a non-appropriate use of mining resources. In this sense the determination of the mining requirements for the building industry is the necessary prerequisite to activate planning in mining according to the principles of environmental sustainability. Experience shows that there is a relationship between the production of buildings in relation to the shape of the city and the resulting demand for minerals. The increasingly urgent demand for maintenance and restructuring by existing buildings will stretch further the demand for minerals with an excessive, no longer sustainable withdrawal, which will lead to focussing greater attention on environmental policies oriented to the use of alternative materials including materials from recycling. It is pointed out moreover that the joint action of land use planning and mining planning leads to interesting applications that have significant repercussions on the environment.

Jan 1, 2005

By J. Alvarez, S. H. Castro

The feasibility of chalcopyrite-pyrite separation in the flotation of a chalcopyritic copper ore, at reduced surface tensions regulated by methanol, was investigated. It was found that with methanol dosages from 0.5% to 1.5% v/ v, the chalcopyrite might be effectively separated from the pyrite, without use of other flotation reagents and pH regulators. However, under this simple condition, the chalcopyrite recovery was only around 50%, recommending the use of other reagents to reinforce the collector action. Low dosages of different collectors were tested, including SF-323 (Shell Float), S-6588 and S-7251 (Cytec), and S-701 (Molycop). Very promising results were obtained with low dosages of the collector S-701 and 1% v/v of methanol in the pulp, which evaluated against a reference test, gave similar copper recovery, higher Mo recovery and higher depression of pyrite. Consequently, this is an alternative process which does not require the use of lime to depress pyrite.

Jan 1, 1995

By A. B. Phillips

The Randfontein Estates Gold Mining Company (Witwatersrand) Limited (REGM) operates three metallurgical complexes for the recovery of gold from the Witwatersrand Gold Reefs at the town of Randfontein, 40 kilometers west of Johannesburg. Mining operations in the. area commenced in March 1889 and ceased temporarily in 1965 when the viable ore reserves had been depleted. Exploratory drilling in the 1960's indicated viable deposits of gold in the Elsburg reefs, south of the Witpoortjie Horst Block, _which formed the Southern limit of the previously exploited areas. Three shaft complexes have been established to exploit this area, known as the Cooke secti'on. In 1983 the Doornkop shaft was sunk to the north of the Cooke section to mine Kimberley reef and the South reef.

Jan 1, 1992

By D. R. Nagaraj

Literally thousands of new flotation agents, both collectors and modifiers, have been proposed for sulfide and non-sulfide flotation over the past six decades since the beginning of the use of soluble surfactants in flotation. In stark contrast, the number of flotation agents used in practice is small. Xanthates and fatly acids, along with a few well-recognized modifiers, dominate the industry. Three major questions will then arise: a) are there truly specific needs in the industry that call for chemistries that are different from those used currently ? b) if yes, given the track record in the industry, what is the likelihood that such different chemistries will ever be used and to what extent ? and c) is more research into developing new chemistries necessary ? A critical assessment of flotation agents in general is made in this paper to provide answers to these questions and to identify the major factors that are responsible for the large disparity that exists between flotation reagent research and commercial usage.

Jan 1, 1994

By Robert A. Jankowski, J. Drew Potts

By implementing various mining practices, mine operators can reduce the respirable dust exposure levels of the roof bolter and the continuous miner operators. The Bureau of Mines has developed a computer program, entitled AMP (Alternative Mining Practices), that gives a quantitative comparison of these reductions. The alternative mining practices and their corresponding reductions in dust exposure levels that are evaluated by the program include a remote control continuous miner, a half-curtain ventilation system, two auxiliary fan-tubing bypass ventilation systems, a modified cutting sequence, a comparison between single-split and double-split ventilation networks, and a comparison between exhausting brattice and exhausting tubing. Descriptions of each of these mining practices are included in the report. The report also includes a hypothetical case study to show how AMP enables mine operators to select the technique(s) that is best suited to their particular needs. AMP is a compiled basic program that has been designed to run on computers with a DOS version 2.0 or later operating system. It includes high resolution graphics (640 X 200 dot positions) designed to run with video boards that are functionally compatible with the IBM Monochrome/ Printer Adapter. Graphic screens are selected from menus, and can be bypassed if the computer is not equipped to handle high resolution mode. Their primary function is to show proper implementation of the mining practices evaluated by the program. This package requires a minimum of 256K bytes of RAM. (Reference to specific products does not imply endorsement by the Bureau of Mines.)

Jan 1, 1987

By Mark Gershon

This paper describes an application of a new approach to mine planning and production scheduling in a gold mine. The technique, limited to use in open pit mines (but not limited to gold), has been described previously (Gershon, 1987). The-computer program used is the HOPS software, which has been described previously as well (Gershon, 1988). The mine is scheduled for the production of 8,000 blocks out of a mine having 25,000 blocks (50 x 50 x 10). The technique is based on the concept of inverted cones (Gershon, 1987). While it does not provide a true optimization of results, it does approximate the optimal situation. As opposed to most scheduling software that only serves as a computerized notepad for the scheduler, the use of this approach allows for a scheduling intelligence to be built into the software.

Jan 1, 1989

By Norbert Patzelt, Hans Knecht, Wolfgang Baum

Future ore reserves of major gold producers in North America and elsewhere will consist of refractory gold ores. About 60 % of the current U.S. gold production is mined in Nevada. Several of the large gold operations in this state indicate that 40 to 90 % of their future ore feeds will contain refractory gold. To compound problems, average head grades for refractory U.S. gold ores have fallen from 8 - 9 g/mt to about 4 g/mt by 1991. In Latin America, 52 % of the gold operations will require milling for optimal recovery. Deeper reserves are, like in North America, refractory. Particularly in hard, (semi)refractory sulfide ores, many operations may experience substantial decreases of gold recov­ery. For example, Martins et al. (1991) report that at an Austra­lian mine, sulfide ore treatment led to 4 - 10 % lower gold reco­veries as the work index increased from 8 kWh/t to 14 kWh/t and the grind coarsened. Many refractory ores should actually be classified as semirefractory since a fine sulfide fracturing and liberation would make 80 - 90 % of the gold cyanide leachable. However, conventional comminution is often prohibitively expensive for these ore types.

Jan 1, 1995

By D. L. Schenk

The Navajo Mine is exclusively a multiple-seam surface coal mine located in the northwest comer of New Mexico. The property is situated entirely on the Navajo Indian Reservation. It is owned and operated by the Broken Hill Propriety Co. Ltd., of Melbourne, Australia. The mine began production in January 1963 with a long-term fuel supply agreement with the Four Corners power plant. The 2175 MW nominal generating capacity of the Four Corners powerplant consumes 7.2 Mt to 7.7 Mt/a (8 million to 8.5 million stpy) of coal. The Navajo Mine has estimated reserves totaling 1 Gt (1. I billion st) of strip minable coal. Only about one-third of that total is presently committed to the generating station. As development continued over the years, mining operations advanced into more complex geologic areas to satisfy the utility's demand for coal. To optimize the committed reserve and provide competitively priced coal to the customer, the Navajo Mine began developing a new pit in June 1986. The Dixon Pit boxcut development was completed in April 1987. About 6 hm3 (7.9 million cu yd) were stripped, uncovering 929 kt (1 million st) of coal. Strip ratio was 7.74:1 including 36.8% rehandle of prime yardage. This case study of the fourth production cut highlights a variety of dragline stripping techniques including highwall bench (overburden) side cast, intermediate highwall bench (parting-interburden) side cast and spoilside bench (partings-interburden) stripping methods. The Dixon Pit offers considerable challenges in the surface recovery of up to seven seams of coal within the 1432 m (4700 ft) of total pit length.

Jan 1, 1990

By Liuming Wu, Willis Forsling

The complexation of Alizarin Red S (ARS) at the surface of hydrous fluorapatite particles has been investigated at 25.0 C by means of potentiometric titrations, adsorption experiments in 0.1 M NaCI ionic medium, and Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT) studies. A chemical model describing the reaction at the aqueous mineral surface has been established under equilibrium conditions according to the reaction [== -CaOH2 + HA2 - « _ =PO CaA2 - z + H30&apos;; to (int.) = -5.61 ± 0.02 3 a =PO- logBs-1110(int.) ( ) within the range 8.40 <_ -log[H ] <_ 9.80.] Experimental data were evaluated using the computer program FITEQL on the basis of a constant capacitance model for the electric double layer. The surface complex structure, has been proposed to involve the quinoid and alpha phenolic oxygens of ARS coordinated to the calcium sites on the fluorapatite surface.

Jan 1, 1993

By C. O. Brawner, A. Bellamy, D. S. Cavers

Pit slope designs at Nickel Plate Mine have used relatively steep interim and final wall slopes of 60 degrees overall. The rock is unusually strong and tough with most discontinuity sets being steeply dipping. An integrated program of monitoring and drainage has been used. Stopes of large extent which are generally unsupported occur on the property. For the most part, no deterioration of the stability of the stopes has occurred over the last 30 or more years. Mining methods through these areas have used a combination of fill s placed via VCR drop raises and crater blasting of the backs. One of the major challenges in mining through the stope areas is to maintain slope stability conditions and to reduce dilution of the higher value ore zones occurring immediately around the stope areas. The paper discusses geology, slope stability and mining methods at Nickel Plate Mine.

Jan 1, 1988

By Lok W. Home

INTRODUCTION Today, raise drilling (boring) has become the stan¬dard method of raising throughout the Western world. It is estimated that the majority of raise footage com¬pleted in 1977 was accomplished by the raise drilling method. Extensive replacement of the drill and shoot system by mechanized raise drilling has occurred be¬cause users have recognized one or more of the follow¬ing advantages. In a direct cost per meter comparison, mechanized raise drilling is economically more attractive than drilling and shooting. Mechanized raise drilling offers improved personnel safety over the drilling and shooting method. Mechanized raise drilling is a faster and more predictable method for excavation than is drilling and shooting. The raise cost per unit of length becomes less as the raise length increases, offering greater flexibility in the overall design of mines. Mechanized raise drilling provides a substantial reduction in labor requirements. 6) Mechanized raise drilling improves the working environment. 7) Mechanized raise drilling improves the rock in¬tegrity of round, unblasted raises. Increasing acceptance of the raise drilling technique is enhanced by continuing equipment development. Today, a wide range of machines and capabilities is available, machine drive systems have been improved, reliability has been increased, and cutter technology is being improved quite rapidly. Table 1 lists the four major manufacturers of raise drilling machines, cutters, and reamers, together with the approximate number of machines that each company had in operation at the end of 1977. Although Reed and Smith are major suppliers of reamers and cutters, they do not manufacture the drilling machines. Four or five other relatively minor suppliers have built machines, reamers, and cutters for raise drilling, but they did not have a substantial num¬ber of machines in the field at the end of 1977. MACHINES FOR MECHANIZED RAISE DRILLING There are three principal arrangements for making machine-bored raises. They include the use of standard raise drills, reversible raise drills, and blind-hole or box¬hole raise drills. Standard Raise Drills The standard raise drilling machine is set up on one mine level or on the surface, and a pilot hole is drilled from that level or surface to a level below. When the pilot hole has been drilled, the raise then is reamed back from the lower level to the upper level or the surface. This arrangement is illustrated in Fig. 1. Reversible Raise Drills The reversible raise drilling machine is set up on a lower level of the mine, and a pilot hole is drilled up¬ward to a higher level. The raise then is reamed back from the upper level to the lower level. This arrange¬ment is illustrated in Fig. 2. The machines used for this type of raise drilling normally are capable of being used as standard raise drills. Blind-Hole or Boxhole Raise Drills The blind-hole or boxhole raise drilling machine is set up on a lower level of the mine, and a full diameter raise is bored to a higher level without the use of a pilot hole. This type of machine is illustrated in Fig. 3. Drill Recommendations If access to upper and lower mine levels is equal, the standard raise drill should be used. The complexity of the equipment and associated handling procedures for boxhole drilling far outweigh any mechanical advantage or reduction in the number of operations, provided that access to an upper level is available. If there is good access to a lower level but only limited access to an upper level, the use of a reversible raise drill should be considered. If there is no access to an upper level, a blind-hole or boxhole raise drill is the only practical mechanized system. MACHINE SELECTION There are six major considerations in selecting a machine for raise drilling. These include operating range, cutter loading, machine structure and main¬tenance, drill string configuration, drive system, and automated controls. Operating Range As shown in Table 2 and Figs. 4 through 6, raise drilling machines are available for a wide range of hole sizes. Standard raise drill ratings range from raises of 0.9 m (3 ft) diam and 120 m (400 ft) length up to raises of 3.5 m (12 ft) diam and 900 m (3000 ft) length. Boxhole raise drilling machines are available for raises ranging from 0.9 m (3 ft) to 2 m (6 ft) diam with lengths up to 90 m (300 ft). Table 2 lists, among other criteria, the torque and thrust of typical machines; torque and thrust are the main criteria for analyzing the capacity of a machine. The raise sizes shown in Table 2 assume a condition of medium hard to hard rock formations and optimum cutter loading. The recommended raise size for a given machine can be exceeded when raising softer rock formations or when the operator is willing to accept a lower level of performance; the performance is related directly to the 1093

Jan 1, 1982

By M. E. Rossi, V. Camacho

Reconciliation of production information is critical to evaluating the effectiveness of predictive models that would allow for the optimization of mining operations. Whether mining open pit or underground, mine-to-mill reconciliations can be one of management&apos;s better tools for the performance of proper accounting. Such reconciliations can also be a very useful tool in evaluation and optimization. This paper proposes a set of criteria and objectives for a typical reconciliation program. This paper also presents a stepwise, logical approach to performing reconciliations and discusses the benefits associated maintaining good information. It also highlights some of the potential pitfalls involved and the methods used to avoid collecting misleading information. These issues are illustrated with an example of a model-to-mine-to-mill reconciliation program that is being implemented at an operating mine. The program involves multiple predictive models (long-term and short-term block models), feed from three open pits and one underground mine, in addition to intermediate stockpiling, for a total of 23 mill streams. This paper presents a summarized version of this reconciliation program and its initial results as implemented at Minera Michilla S.A.

Jan 1, 2000