Search Documents

By John Wiebmer

Several industry trends are putting new demands on surface mining equipment. This is true both on the “hard” side of the equipment business - the research and product development programs, and on the “soft” side - the business processes, human resources and competitive strategies. This article describes seven key industry trends and the impact each is having on surface mining equipment suppliers. 1. Globalization Earth-spanning technologies are shrinking the world into an economic village, causing corporations to think and plan on a global scale. This “globalization” is one of the great buzzwords of the 1990s, meaning precisely whatever the user says it means. In this case, let us take it to mean that political boundaries arc less restrictive than in the past, permitting mining companies new freedom to roam the globe for ore bodies. Evolving out of this are global mining houses that have ownership and management interests in labyrinthian webs of mines spanning the world. There are several impacts on surface mining equipment suppliers.

Jan 1, 1994

Mining has traditionally been seen as a relatively risky business. Exploration is expensive and the failure rate is high, while start-up costs commonly run to many hundreds of million dollars. To justify the risk and expense, the returns from successful projects must also be high. Accurate estimation of mineral resources and reserves is fundamental to the processes of optimising returns and managing risk in mining developments. Systematic development from initial exploration through a series of development stages enables expenditure and risk to be balanced. As a consequence, large scale modern mine are more akin to manufacturing businesses. This paper examines the life history of a mineral reserve estimate from the perspective of a large mining company against a background of modern estimation and reporting requirements. It will also touch on what constitutes, in the author's opinion, `best' practice in reserve estimation, and how this concept can be spread more widely. [Abstract to be re-written and reduced to 100 words]

Jan 1, 2003

By P. M. Sandgren, H. Al-Dabbagh

Saudi Company for Precious Metals (SCPM) is jointly owned by the Saudi Arabian state organization Petromin (The General Petroleium & Mineral Organization) and Boliden of Sweden. The company operates the Sukhaybarat gold mine in the Saudi Arabian desert and produces some 80,000 ounces of gold per year by agitation and heap leaching. The discovery, development, and operation of this mine is a success story. After the first drill hole intercepted a gold mineralization in 1983, it took the partners only 8 years to delineate the ore reserve, locate water sources, prepare pre-and final feasibility studies, obtain permits, design, and construct the facilities. Sukhaybarat, which is an open pit mine, started off with a carbon-in-leach agitation plant only, but a heap leach facility was added in the beginning of 1995. Since start of operation in the middle of 1991, a total of 300,000 ounces of gold has been produced in the first four years of operation at a very competitive cost.

Jan 1, 1996

By Maynard O. Serbousek, Melvin E. Poad

Shotcrete, a useful support material in underground openings, is a sprayed concrete, and, when used with fast-setting agents, is immediately self-supporting. Although shotcrete has been used extensively for tunnel support, the technique has not been readily accepted by the mining industry because of the lack of essential information on such basic items as material properties and rock interaction. The Spokane Mining Research Center (SMRC) of the Bureau of Mines has been active in the field for the past 2 years, including research on fibrous reinforced shotcrete. IIT Research Institute, Chicago, under Bureau of Mines contract, is investigating physical properties of shotcrete as affected by (1) type of process (wet or dry) and (2) fast-set agents and controlle-dset cements. Already the contractor has shown the advantage of a regulated-set cement over normal cement and fast-set additives for the dry process. The regulated-set cements can produce high early strengths with no decrease in ultimate strength.

Jan 1, 1997

By Justus B. Deen

Given that the majority of mine ventilation operating costs are imposed by shafts, the need to predict the resistance of a planned shaft with reasonable accuracy is important. During conceptual design, shaft resistances are usually predicted by use of published friction factors, k, based upon lining and fitting configurations. More often than not, published friction factors do not directly coincide with "real" shafts, so their use is somewhat limited. For more accurate shaft resistance determination, equations both theoretical and empirical may be employed if there is detailed knowledge of the shaft. These equations treat the shaft resistance as discrete components, with their sum being the overall shaft resistance. This paper describes the basic shaft resistance equations and verifies these equations by comparison to field measured shaft resistances. Several shafts were examined which varied in depth, shape and fitting arrangements. Results are presented and conclusions drawn to show that the shaft resistance equations are accurate.

Jan 1, 1991

By J. Donald Rimstidt, Jeanette K. Jerz

Acid mine drainage is a major environmental problem worldwide. A key to remediating this problem is understanding the rate and mechanisms of the complex, multistep pyrite oxidation reaction under geologically relevant conditions. Because many waste piles are not submerged, a large amount of pyrite oxidation actually occurs in air. We have designed a Barcroft-manometer reactor to measure the rate of pyrite oxidation in air as a function of relative humidity and oxygen partial pressure. The reactor consists of two chambers joined by a manometer. Each experiment occurs at constant temperature, initial oxygen partial pressure, and relative humidity, although these variable can be changed between runs. Oxygen consumption was measured and pyrite oxidation rates were calculated from those data. Initial data indicate that rate of pyrite oxidation by oxygen in humid air is much faster than the rate of oxidation by oxygen in solution. The rates determined by this study can be used to develop better remediation techniques for acidic mine waters.

Jan 1, 2000

By S. K. Kawatra, T. C. Eisle

In froth flotation of phosphate, it is important that the flotation be as selective as possible in order to maximize grade and recovery without adding additional stages of flotation. Flotation columns provide a means for improving the selectivity compared to conventional flotation machines and are of considerable interest for phosphate processing. The selectivity of a flotation column is largely limited by the degree of back mixing of tailings into the froth zone, and its recovery is limited by the degree of short-circuiting of feed to the tailings. The horizontally baffled flotation column was therefore developed to minimize back mixing and short-circuiting without introducing problems with plugging or reduced capacity. The introduction of horizontal baffles to a column reduces both entrainment of feed water into the froth and short-circuiting of feed to the tailings, which improves the column selectivity. The results of horizontally baffled column flotation of phosphate are presented for fatty acid flotation of phosphate, with comparison to conventional flotation using the same reagents.

Jan 1, 1999

By R. J. Sweigard, T. Beckman, C. T. Justice, E. D. Thompson, T. C. Hopkins

As a means of permanent disposal, fine coal refuse is often pumped as a slurry into surface impoundments. As the available volume is filled, the embankment heights are frequently increased. The additional embankment material is often placed upon consolidated fine coal refuse. There has been concern about the long-term effect of consolidation of this material at or above the liquid limit on its shear strength. A laboratory investigation was performed using three different types of fine coal slurry taken from central Appalachian coal-preparation plants. The refuse was consolidated in 3-m (10 ft) Plexiglas columns under incremental amounts of surcharge loading. The incremental loads were designed to simulate the effect of increasing the height of a refuse embankment on top of the consolidating coal slurry. After the refuse in the columns had consolidated for several months, the columns were cut apart, and triaxial tests were performed on both the consolidated and unconsolidated material for comparison of their shear-strength parameters.

Jan 1, 1998

By B. C. Cornilsen, X. Shan, D. H. Carlson, J. H. Johnson

Airborne respirable Diesel Particulate (DP) presents an additional health hazard in that it has been shown to be mutagenic. This problem is of increasing concern as more coal mines introduce diesel vehicles. If the DP present in coal mine air is to be controlled it must first be measured. This paper describes development of the laser Raman spectroscopic measurement of the amount of DP in DP/coal mixtures collected on filters in the laboratory and in coal mines. The Raman technique provides a chemical measure of the carbonaceous material in each component, and is not dependent upon particle size. When this work was begun there were no known analytical methods for this measurement. Side-by-side in-mine comparisons of the results obtained from Raman, neutron activation analysis, and size selective analyses (MOUDI and personal samplers) are presented. The neutron activation and size selective analyses were obtained by the USBM Twin Cities Research Center and University of Minnesota. Good agreement has been found among these three methods.

Jan 1, 1991

By Gemei Yang, Yihui Zhao

In caved goaf, the friction loss of fluid head is: [h = (R'+ R/Q/ )] Q (for one-dimensional transition flow). The R' and R, which are the functions of two dimensional spaces, are calculated through an empirical formula. Then, the bulking factor and permeability are determined. It is supposed that the airflow in porous media are similar to those in tiny tubes crossing each other. Therefore, the network calculation technique can be used to tackle the field transition flow problem. A lot of case studies showed that the emission of methane in mines mainly depends on the air velocity and has little relation to air pressure. Summing up our experience and experiments, we provide an empirical formula to calculate the gas emission rate per unit area. By means of mass conservation and network calculation, the methane content distribution in steady-state is worked out. Then the dynamic change in airflows and gas content can be analyzed by the characteristic-difference method.

Jan 1, 1987

By Hiroyuki Kawata, Toshiyuki Ueno, Mikio Yamazaki

INTRODUCTION For the construction of several kinds of structures which pass through under railways, we have recently developed an effective and new tunnel construction method, aiming at more secure train operation during the construction as well as the rationalization in the construction works for such structures. Most important in carrying out the construction works for the structures under railways is how to maintain the safe operation of trains. For such construction works, temporary supporting structures and supplemental works have been often applied, for which high cost and long period for the construction have been required. While, this new tunnel construction method has the feature that it is capable of constructing definitive structures for various purposes, which, at the same time, acts as the temporary supporting members for protection of railways. Therefore, this method is now drawing much attention in that higher safety of train operation, low construction cost, and shorter construction period are accomplished, minimizing the period required for slackening the train speed during the construction works.

Jan 1, 1979

By E. F. Divers

Adequate ventilation of coal mine working faces is the most important technique for controlling respirable dust and methane. Choosing the right technique presents some tough questions. US Bureau of Mines research has shown that to control respirable dust, you must contain the dust near the face, keeping rollback (turbulence) to a minimum. For methane, the most effective approach has been to use a blowing brattice, or tubing, and to create turbulence and disperse the face methane, allowing it to pass over the machine and into the return. It is immediately apparent that the two approaches may counteract one another, thus complicating the decision as to which system may be best for a given situation. At present. Bureau research has developed two successful machine-mounted face ventilation systems to meet these different needs and allow deeper cutting. The fan- powered dust scrubber is designed to control dust primarily associated with blowing face ventilation systems. The spray- fan controls methane on exhaust-ventilated sections.

Jan 1, 1987

By Harry Sutcliffe

INTRODUCTION The need for discussion of Owner-Engineer-Contractor relationships in tunneling arises from the increase in costly and time-consuming litigation. The paper examines the objectives, motivations and responsibilities of each party, discusses some common causes of claims in underground work, and makes some suggestions for improvements. The viewpoint and bias are those of an engineer. If a subtitle were required for the session, "Sharing the Risk" would be appropriate. Sharing the risk is an important aspect of Owner-Engineer-Contractor relationships because when a risk is shared, all parties have an incentive to minimize it. The System It would be shortsighted not to recognize that the system is wider than the Owner, the Engineer and the Contractor. There are many outside influences which affect the day-to-day behavior of each party: Financing agencies Insurance agencies Bonding agencies OSHA and other safety legislation The Federal Power Commission The Public Utilities Commission The General Accounting Office

Jan 1, 1997

By Bruce T. Stanley

Though most porphyry-molybdenum deposits lend themselves to various reserve estimating techniques, still there must exist the constant effort to not merely obtain an estimate but rather to obtain the best estimate. To answer the challenge of a complete ore reserve estimation, one must attack the problem with the purpose of obtaining the results closest to reality. What we wish to determine is simple: metric tons (short tons), grade, and kilograms (pounds) of molybdenum contained. In order to effectively accomplish this task, further consideration must be given to the ease of using the information obtained and its inherent reliability. The only known method for ore reserve estimation that supplies the needed results along with its distribution and a measure of confidence provided by sound mathematical backup is geostatistics. The following review is an example of geostatistical application of an ore reserve estimate at the AMAX Henderson mine demonstrating technique, viability, and usefulness of results.

Jan 1, 1979

By Y. L. Su

This paper describes a case study where solutions were sought to the truck queuing that occurred at a central processing plant. Ore from three production shafts at Falconbridge Limited's Sudbury Opera¬tions is hauled by three trucking contractors to Strathcona Mill. On return trips, the classified mill tailing is carried back to the mines for backfilling. The ore feeder at the mill handles three times the tonnage designed for and the situation is not expected to improve. Excessive truck queuing and consequent mine production interruptions are therefore of great concern. During the study, stochastic models were formulated and programmed for the IBM/AT personal computer. Basic information sought from the models were truck waiting time and ore production interruptions. The existing system was tested, not only to verify the validity of the models, but also to understand the causes of the problem. Several alternatives were simulated and a simple solution selected for implementation.

Jan 1, 1986

By E. Topuz, J. Mastoris

The problem of defining the optimum final limits of an open-pit mine has challenged the mining industry for the last three decades. The difficulty results mainly from the great number of variables involved and from the sheer computational effort required in real-life applications. An actual lignite deposit is used in this study to introduce and apply a new methodology that can be used as a basis for surface-mine design optimization. A geologic-reserves model of the deposit is first developed with the use of an integrated geostatistical-modeling package. The model is transformed into an economic one through the use of flexible objective function formulation(s). The final open-pit limits are then optimized using a competent commercial optimizer, and comparative-sensitivity analyses are performed to study the effect of some basic mining and economic parameters on the optimal pit design. The conclusions drawn can develop useful guidelines for decision making by the mine operator.

Jan 1, 1996

By J. Alton Burks, Robert R. Stein

This paper focuses on the noise exposure levels of miners employed on longwall production faces. Along with the increased production from longwall units has come the potential for greater noise exposures. Typical noise levels are given for the various noise sources that are present on modern longwall faces. Exposure times have typically increased since the introduction of longwall technology in this country. Representative exposure times and patterns are analyzed. Possible solutions are presented for generalized cases. Engineering controls developed by the Bureau of Mines are explained and their potential effectiveness is calculated for the cases presented. The role of hearing protectors in an overall hearing conservation program is also investigated. Recent research performed by the Bureau suggests that the actual performance level of muff -type protectors may be less than the manufacturers ratings under certain circumstances. The use of muff- type protectors is discussed and analyzed with respect to their use on longwall operations.

Jan 1, 1992

By Nick J. Miles, Gareth J. Brown

The degree of fragmentation of dispersed systems of brittle materials such as pulverised rock has been described by a fractal dimension i.e. the fragmentation fractal. This fractal dimension represents a power law size-frequency distribution, where, in this case, the size is defined as the square root of the projected area. The existence of a fractal dimension for the number-size distribution, of the progeny of failure event, is direct evidence for scale invariance of the fragmentation process. Since a fractal dimension infers that failure mechanisms operate on all scales it has been suggested that the fractal dimension is a measure of the fracture resistance properties of materials during fragmentation. In order to investigate this a range of rocks of varying fracture toughness were broken under similar levels of impact velocity in the dynamic tensile failure of single particles. The fragmentation fractals determined from the resultant particle populations, of the breakage experiments, were monitored and are discussed.

Jan 1, 1995

By Donald E. Hulse

Selection of a block size for a computerized 3 dimensional ore body model is an exercise in compromises. Larger blocks decrease the use of computer resources and decrease the variance of the block estimates. Smaller blocks increase the resolution of the model and the selectivity which can be used in the planning, but increase the variance of estimates in the individual blocks. A common rule is that blocks can be as small as one fourth the average sample spacing, however this ignores the interrelationship between the block size, the sample spacing, and the variogram model. This paper will explore this relationship Kriging estimation variance will be used as a comparative measure of estimate quality. Graphical techniques will be used to show that there is a point where smaller block sizes cease to contribute to the resolution of the model. A method of evaluating the consequences of block size decisions will be examined.

Jan 1, 1992

By R. A. Lohnes, S. M. Levorson

As part of research to develop a coal handleability index that predicts the ease with which coal will flow through a handling system, comparative tests were conducted with a Johanson Indicizer and a low-stress triaxial apparatus on 12 coals at a variety of gradations and moisture contents. The lndicizer test provides a rapid method for generating data associated with coal handling characteristics. The arching index measured with the Indicizer is a function of the geometry of the apparatus as well as the properties of the coal. The handleability index determined from triaxial data is a more direct measure of coal characteristics. The handleability index shows a wider range of values than the arching index and, therefore, appears to be more sensitive to coal variations. Neither the arching index nor the ratholing index, as measured with the Indicizer, agreed well with the handleability index. This is attributed to differences in sample preparation as well as to the tests themselves.

Jan 1, 1993