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By Steve Kral

Competition in the gold mining industry throughout the world has become fierce in recent years. The challenge facing operations personnel is to produce more gold for less money. Likewise, the explorationist's charge is to find more gold in a more cost-efficient manner. That means using new technology to find new gold deposits and expand present ones. More accurate mapping instruments are available to geologists in the search for new deposits. Advanced geophysical and geochemical methods enable explo¬ration teams to review previously mined districts in their search for minable reserves. Four technical sessions on the geology, exploration, and development of gold deposits were part of the program at `world Gold '89,' a Gold Forum on Technology and Practices," held by SME and The Australasian Institute of Mining and Metallurgy in Reno, NV, Nov. 5-8, 1989.

Jan 1, 1990

By Douglas D. Donald

The financial analyst's job is to make an objective appraisal of the investment opportunities which exist within the various industries under his supervision within the context of the economic model provided by his firm and the a climate of investor sentiments. Industry analysis is critical. When a major investment trend develops, usually the stock of all companies within the specific industry react in the same direction. I should emphasize here, however, that an investment trend is influenced by the economic outlook, but economics is not the only determinant - investor psychology and arbitrary political factors may be of equal or greater importance. Part of our job is to recognize trends early and determine whether they are valid. Following industry analysis, the analyst must examine the specific companies within that industry since some companies usually react more violently than others to industry trends, whether they be favorable or adverse. To simplify the process of evaluating an investment opportunity, it is convenient to isolate three types of factors which have a bearing on every sort of business although the degree of influence of each factor may vary from industry to industry. These categories are, 1) independent or external factors insofar as they are beyond the control of corporate management, 2) interdependent factors insofar as influence may be exerted by industry-wide action, and 3) dependent factors covering the area of internal decisions which are basically under the control of the individual corporate managers. Although the title of this paper, "The Corporate Use of Cash Flow," is only one segment of the third category, it may be useful to continent on the first two categories as well. The independent factors may be either economic or governmental. The economic factors include cyclicality which may be very high in the case of the basic commodity industries or relatively low as in the case of utilities. Underlying growth rates, another independent factor, may range from the business equipment industry with an annual growth rate of 14% through the electric utility industry with a growth rate of about 7% per year to the

Jan 1, 1970

By C. Timothy Shaw

Traditionally, only the large mining companies have maintained specialist departments in such areas as Rock Mechanics, Ventilation and Safety. To the small companies this has been a luxury that they could ill afford. Any work required by such companies in these areas, more complex than could be handled by the existing staff, was done by consultants. This situation is changing though and there is a need arising for many specialist departments. These changes are partly being brought about by the effects of inflation as the ever increasing costs are causing more and more operators to increase the size of their operations in search of economies of scale. In addition though the plethora of new laws and regulations are creating a need for many more specialists in all areas of mining in order to ensure compliance. The abovementioned factors, added to the existing Pattern of mines endeavoring to improve the working environment for their labor force, both for reasons of practical labor relations and also due to further legislative pressures, have thus created a climate where, in the near future, departments such as Rock Mechanics, Safety, Ventilation, Environmental Engineering and Subsidence Control will be commonplace in mining companies. It will no longer be practical to function without such services. Many mining companies already maintain such departments and this has particularly been true of the big mining groups of South Africa. From the experience gained by many of these large companies with specialist departments, it is clear that the maintenance of a cadre of experienced, competent professionals in such a department has not always been easy. It would seem from the experience gained that one can generalise and state that graduate mining engineers tend not to view specilisation as an optimum direction for their career development. It is of course true that many professionals, especially those with higher than a bachelors degree, do view these areas as valid career options, but even here experience shows that wastage is high. The time therefore seems to be ripe to take a look at this area in some detail to see whether reasons for the problems can be isolated. Working from that some suggestions can be made as to directions in which improvements might be made. If the challenge of the demands of the new regulations are to be met then such improvements must be made.

Jan 1, 1980

By D. R. Tweeton, L. W. Lake

A modified push-pull field test and a computer model of cation exchange were developed to aid in evaluating cation exchange parameters prior to in situ mining. Reliable determination of these parameters is essential when modeling restoration of ground-water quality. The field test involves a much larger volume and much less disturbance to the ore sample than is feasible with laboratory measurements. This test can be per¬formed in two or three weeks. It is relatively inexpensive, requiring one injection-production well and two or more wells for collecting samples of leach solution. The use of the model in interpreting test results is illustrated with field data from an in situ uranium mine. Much of the research was performed by the University of Texas at Austin and was partially funded by the US Bureau of Mines.

Jan 1, 1987

By P. D. Lafleur

A concerted effort to determine the quantities and effects of trace elements in the environment requires the application of a number of different analytical techniques in the same or in different laboratories. The interpretation of analytical data is often difficult because of differing results between analysts or even by the same analyst at different times. Standard Reference Materials (SRM), which are certified for their trace element content and are in a matrix similar to the one of interest, can greatly increase the accuracy of analysis and the reproducibility between laboratories. The United States National Bureau of Standards (NBS) has developed a number of SRMs applicable to the determination of trace elements in environmental materials. Two of these, SRM-1571, Orchard Leaves, and SRM-1577. Bovine Liver, are excellent for biological tissue analyses. Several new standards are of value for fossil-fuel analyses. These are: SRM-1632. Trace Elements in Coal; SM-1633, Trace Elements in Fly Ash; SM-1634, Trace Elements in Residual Fuel Oil: and SRM-1635, Trace Elements in Gasoline. In cooperation with the US Environmental Protection Agency, the NBS has recently concluded an interlaboratory comparison involving analyses by more than 60 laboratories on these fossil-fuel materials. The resulu of this intercomparison and the broad range experience with the biological materials will be presented showing both intratechnique and intertechnique variations, and the sensitivities and comparisons with the values certified by NBS.

Jan 1, 1975

By G. Y. Li, D. Farahmand

The dilemma of a numerical analyst not only concerns the problem of modelling the non-linear behaviour of intact rock, but also the non- linearity contributed by structural discontinuities. In this light, it is the intention of this paper to examine some aspects of the non-homogenity and structural discontinuities of rock and incorporate this behaviour into boundary element numerical solution. Non-homogeneous material is considered piecewise, thus homogeneous and is modelled by using sub-regions. The Mohr- Coulomb failure criterion is employed to model the non-linear behaviour of the major discontinuities. A computer program is developed based on the procedure for combining the direct boundary element method and the displacement discontinuity method. A linear element type is employed in the formulation of numerical solution. The computer program is used to study the stress distribution in a gold mine.

Jan 1, 1986

By J. Harrison Daniel

Increasing mechanization of underground mining operations throughout the years has reduced the dependency on large, concentrated working forces. Fewer workers in scattered locations, coupled with the versatility of diesel equipment to load and haul personnel, supplies, and mineral ore, has made diesel equipment attractive in mine feasibility and design studies. The use of the mobile equipment along with higher production or "bulk" mining methods provides for more efficient mineral extraction systems. These systems are expected to become more widespread until long-term research provides a further evolution to more complete automation of underground mining. The U.S. Department of the Interior, Bureau of Mines, has been conducting research to reduce the health and safety hazards posed by increasing use of diesel equipment and the higher power ratings being proposed. The goal is to provide for safe and efficient use of the equipment. The National Institute for Occupational Safety and Health has recommended that diesel exhaust be regarded as a potential occupational carcinogen adding importance to the Bureau's research program. The paper describes advances in engine design, the use of diesels in mining operations, and significant health and safety research accomplishments of the Bureau of Mines. These accomplishments will help assure that diesel equipment remains an option for determining the most efficient system to mine an ore body.

Jan 1, 1989

By R. K. Young

Producing a sound plant design for a major project requires hundreds of engineers and many drawings. Economical accomplishment of this task is based upon careful and orderly organization of the design team so that at all times there is a complete and workable staff but at no time a surplus of costly talent. This paper will describe the various stages in the development of plant design which normally follow the laboratory and pilot plant investigations discussed in other papers today. An outline of the procedures used in the assembling of a project design group, within an established engineering organization will be presented. Actual procedures may vary according to the size and character of the plant, the special requirements of the owner, and the make-up of the engineering organization performing the design, but most of the points covered will be found to be basic to any plant design project.

Jan 1, 1960

By Norbert Patzelt, Johann Knecht, Wolfgang Baum

High pressure roll grinding (HPGR) is a mature but still expanding comminution technology. In the metals mining industry, HPGR is slowly gaining acceptance as a cost-efficient, high-throughput alternative for plant optimization. The increasing need to treat ores with progressively lower grades, complex mineralogies, refractory metal occurrence and variable rock types requires an energy-efficient comminution technology that reduces metallurgical problems inherent in conventional crushing and grinding, while stabilizing leach and flotation circuits and increasing metals extraction. This paper will summarize our latest HPGR pilot test results for gold and copper projects in the United States and South America and their confirmation through the first HPGR operation in copper mining. This paper will also stress the use of the high pressure grinding roll as a metallurgical tool. The application of HPGR for the treatment of heap leach SX-EW ores, semi-refractory gold ores, waste rock material and concentrator feeds will be illustrated.

Jan 1, 1998

By Gary S. Brierley, Ronald E. Romley, Alan L. Howard

The Price Road Drain Tunnel in Tempe, Arizona is part of the drainage system constructed in conjunction with the Outer Loop Highway in metropolitan Phoenix. The Outer Loop Project is a part of a much larger expressway system that includes other large drainage tunnels such as the Papago Freeway Drain Tunnels. Large diameter downhole inspection borings were utilized to obtain subsurface data for the design of these tunnels. Subsurface data obtained from the large diameter borings resulted in the development of empirical parameters that were successfully incorporated into the Geotechnical Design Summary Report and which satisfactorily predicted ground behavior, formed the basis for improved geotechnical design criteria, and facilitated the cost effective assessment of third party risk. The purpose of this paper is to describe the subsurface exploration program performed for this project and to explain the methods used to evaluate underground construction procedures.

Jan 1, 1991

By J. F. Able, F. Djahanguiri

The US Bureau of Mines conducted research on underground stope leaching of metalliferous ores. Leaching underground would minimize the environmental impact of ore processing on the surface and would maximize minable reserves. An important aspect of this process is the minimization of pregnant solution losses and groundwater contamination by leach solutions. Bulkhead design and construction are important issues for solution control and stope-leaching economics. A reinforced-concrete bulkhead was designed, constructed and tested for solution control in an underground mine near Idaho Springs, CO. This paper presents the bulkhead-design methodology and construction procedure.

Jan 1, 1998

By O. Fernandez, M. Vesely

Abrasive grinding, leading to ultrafine product and "critical size" material buildup inside the mill, is proposed as the cause of high power consumption and low capacity in many fully autogenous grinding processes. Addition of steel balls (hence, semiautogenous grinding) or pebble removal and separate crushing have been used, with different efficiencies, to overcome the problem. Information and data for the conceptual analysis, basic design, and operation of a pebble crusher at the Los Bronces semiautogenous grinding plant is presented along with data showing a production increase of 1000 t/d (1100 stpd) and significant operating costs savings.

Jan 1, 1987

By Pierre Mousset-Jones, Felipe Calizaya

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

Jan 1, 1993

By Jeong-Heum Kim, Jan M. Mutmansky

A number of solution methods for solving the nonlinear equations derived from mine ventilation networks use meshes selected from the network as the basis of the solution techniques. Mathematicians working in network theory have outlined several methods for speeding up the computations through mesh selection and ordering procedures. In the mine ventilation area, a fair amount of attention has been paid by ventilation specialists to procedures for choosing the meshes so that the computational effort is eased. However, little attention has been paid to mesh ordering methods. This paper outlines research into random mesh ordering procedures plus two non-random mesh ordering procedures and compares some results using these procedures within four solution algorithms.

Jan 1, 1993

By Ingo Ossenbühl, Wolfgang Dolsak, Vojtech Gall, Axel G. Nitschke

"Yielding support systems for application in underground construction have a long history, primarily in mining. Typical examples are tunnels subject to loading conditions that lead to overstressing of the newly installed support or existing tunnel structures in active fault zones. Recent applications for tunnel rehabilitation projects unveiled the capabilities and flexibility of combined yielding support systems presented in this paper. Frequently, the main requirements for tunnel rehabilitation applications are a fast, safe, and simple installation along with the need for flexibility with regards to existing tunnel geometries. A combined support system consisting of steel sets with yielding connections and special groutable hoses has proven to be an efficient support measure providing a multitude of advantages compared to conventional rehabilitation approaches. The presented yielding support system provides an immediate and active support, while it allows for controlled yielding upon experiencing loads beyond its support capacity. INTRODUCTION The excavation of underground spaces leads to redistribution in the existing stress regime. This load redistribution goes along with deformations in the surrounding rock mass. Magnitude and duration of these deformations depend on the tunnel’s depth and geological conditions, but also on the installed support system. Modern civil tunneling infrastructure has generally an envisioned service life of about 120 years. Conventional tunneling provides typically a dual support system, split into the initial (or primary) and final (or secondary) lining. A typical design principle in civil tunneling is to let the vast majority of deformations acting on the initial lining cease, before the final lining is installed. Based on this approach, the loading on the final lining is significantly reduced and signs of overstressing, such as cracking of the lining, are typically limited to the initial lining. However, special cases in swelling and squeezing ground require different approaches, including yielding support systems."

Jan 1, 2016

By James D. Bliss

Evaluation of data for three engineering variables-absorption, bulk specific gravity, and freeze-thaw durability (350 cycles)-was made for quarries in carbon- ate rocks in Oklahoma that supply aggregate. It was found that lower Paleozoic carbonate rocks (Cambrian through Devonian) are likely to make a better quality aggregate than upper Paleozoic (Mississippian to Permian) carbonate rocks. In addition, freeze-thaw durability can be forecast from absorption and is exemplary for lower Paleozoic carbonate rocks.

Jan 1, 1999

By F. Djahanguiri

The US Bureau of Mines con¬ducted research on underground stope leaching of metalliferous ores. Leaching underground would minimize the environmental impact of ore processing on the surface and would maximize minable reserves. An important aspect of this process is the minimization of pregnant solution losses and groundwater contamination by leach solutions. Bulkhead design and construction are important issues for solution control and stope-leaching economics. A reinforced-concrete bulkhead was designed, constructed and tested for solution control in an underground mine near Idaho Springs, CO. This paper presents the bulkhead-design methodology and construction procedure.

Jan 1, 1997

By I. Shah, L. G. Austin

A method for quantitative investigation of the phenomena involved in fine grinding of materials that follows the changes in the breakage rates of fine particles has been presented. For relatively hard, brittle, non-coating material like quartz, the slowing down effect of breakage rates starts to be significant at relatively coarse sizes, which goes often undetected in closed circuit grinding systems, producing relatively coarse product, say P80=75µm However, for fine grinding systems, as the -10µm fractions begin to build-up, and classification becomes more difficult, the build-up of fine sizes causes a slowing down effect Compounding this problem is the difficulty of obtaining accurate cumulative weight size distributions in the fine size region.

Jan 1, 1983

By E. Topuz, Xing Wu

INTRODUCTION The air flow in the mine ventilation network can be categorized in three ways: natural splitting, controlled splitting, and semi-controlled splitting. In natural splitting, the air flow in branches of a ventilation network apportions itself according to the aerodynamic resistance of the branches. In controlled splitting, a prescribed quantity of air is circulated through each branch. In semi-controlled splitting, flow in some branches is fixed to a desired quantity while in other branches it is split naturally. In practice, the mine ventilation networks present the latter two situations. Usually, the resistance of each branch in the network is known and the quantity of air in the working place is predetermined by safety considerations. If the number of branches whose airflow quantities are known is equal to or larger than the number of the fundamental meshes in the network, then the network becomes a controlled splitting network (Wang, 1982 a). Otherwise, it is a semi-controlled splitting network. If no booster fans are used in the network, the problem can be solved as either controlled or semi-controlled splitting networks in order to determine the main fan pressure and regulator size and location. All techniques are based on Kirchoff's flow and energy conservation laws and Atkinson's Equation. Booster fans can be used in controlled and semi-controlled splitting networks. It has been proven both theoretically and practically that using booster fans in these ventilation systems can improve flow distribution and reduce consumption of power (McPherson et al., 1985). The current techniques used in determination of booster fan location and size include simulation, linear programming, CPM and cutset operation, out-of-kilter, and critical-path crashing. These techniques can be classified into two groups. The first group, including linear programming, CPM and cutset operation, out-of-kilter, and critical-path crashing techniques, deals with controlled flow networks. The second, simulation, can be applied to the handling of semi-controlled flow networks. Mathematically, the problem of controlled splitting networks can be solved more easily than that of semi-controlled splitting networks. This is because the controlled flow network can be formulated as a linear programming problem, for the solution of which there are several sophisticated algorithms. Moreover, the semi-controlled flow network is usually modeled through nonlinear programming, for which there are no universally applicable solutions. The procedure described by Wu and Topuz, 1986, can be used to convert a semi-controlled network to a controlled flow network, and the problem can then be easily solved by the techniques used for solution of a controlled flow network problem. In practice, a mine ventilation network may change from controlled splitting to semicontrolled splitting with advancement of mining. This dynamic nature of mine ventilation makes the problem more complicated and necessitates development of new solution procedures which will consider the overall economics of the system. CONTROLLED SPLITTING NETWORK The problem in controlled splitting networks with booster fans is to determine the operational characteristic of the main fans, and the location and size of booster fans and regulators. The objective is to satisfy the air flow rate requirement for each branch while minimizing consumption of energy. The techniques used for the controlled splitting network problem include linear programming, CPM and cutset operation, out-of-kilter, and critical-path crashing. The objective function and constraints can be expressed as follows (Wang and Pana, 1971): [ ]

Jan 1, 1989

By Zhang Youdi

According to general guidelines, deposits suitable for surface mining can be divided into two basic categories: horizontal or flat-bedded deposits and inclined or dip-buried deposits. A series of mathematical models for surface mine long-term planning (SMLTP) has been developed and can be used for any kind of deposit. The basic theory and methodology of the models are oriented- graph simulation which combines graph and network theory with a systems simulation technique to form a new approach. From the viewpoint of surface mining and long-term plan modeling, the main differences between the two categories of deposits are analyzed, an important algorithm is put forward, and the structure of the models and some results of applications are introduced. Dynamic and comprehensive optimizations have been completed by the SMLTP model series. Combining different OR branches, the new approach has been proved to be a powerful tool to solve the strategic problems of surface mine planning.

Jan 1, 1989