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During the past decade, international mining companies have descended on South America. Countries like Chile, Brazil and Peru have seen billions of dollars in exploration and development funding turn their once meager mineral industries into mining giants that have become the envy of the world. Part of this outpouring of foreign investment in those countries has been because each has privatized its state-owned mining companies and has liberalized its foreign investment laws. In addition, they have rewritten their mining codes to encourage minerals development and passed new tax laws that have made natural resource development more attractive. Now these same international mining companies are turning their attention to Argentina. This a country that, like Chile, Brazil and Peru, has a wealth of largely un- tapped mineral resources. And Argentina wants its share of the foreign investment that its neighbors have enjoyed. With that in mind, ministers of Argentina's natural resource agencies came to Denver, CO to meet with mining executives and pitch their country's mining industry. The meeting, attended by about 200 people, was sponsored by the US Trade and Development Agency and organized by the World Trade Center Denver. Others involved were the Colorado Mining Association, the Colorado International Trade Office and the Secretariat of Industry, Commerce and Mining of Argentina. The following is a summary of a report on Argentina's mining industry. It was prepared by Anderson & Schwab Management Consultants and distributed to attendees as part of the meeting's program.

Jan 1, 1998

By John Brouwer

Through the use of good preventive maintenance procedures in which the work of both production and maintenance personnel is well-coordinated, production downtime can be drastically minimized, and costly repairs and interruptions in planned maintenance and production schedules can be eliminated. There had been some conflict in the past between production and maintenance people over the proper method of achieving maximum machine performance. The usual practice was to operate production equipment at maximum capacity for the longest possible time until breakdown occurred, and then make hurried repairs to get back into production. In most cases, these repairs involved unscheduled work and were thus performed inefficiently. Both production and maintenance have the same objective: to produce a quality product at maximum efficiency and at minimum cost. Preventive maintenance is a common tool available for both production and maintenance personnel to achieve this objective. Actually, one of the main objectives of preventive maintenance is to find any abnormal machine condition that may cause machine failure before a breakdown occurs. This makes it possible to plan and schedule maintenance work with the least amount of interruption and plan production volume with a higher rate of accuracy. Maintenance people prefer to perform this work on a scheduled basis and get away from the "crash" situation that accompanies breakdowns. They thereby increase the utilization of available manpower and machine time, prolong equipment life, and improve maintenance costs.

Jan 1, 1979

By Richard H. Gates

INTRODUCTION The U. S. Army Corps of Engineers is developing chemical explosive excavation as a construction technique for use on Civil Works projects. Large chemical charges are being used in multiple charge arrays in a variety of media and topographic situations to achieve actual construction projects. The target is the development of chemical and nuclear explosive excavation as an accepted cost-competitive construction technique. Military research using explosive excavation is also being conducted to apply this technique to military engineering for combat purposes and to military construction. The information gained from both the civil and military research is integrated into the overall development of explosive excavation. This research and development work is being conducted under the auspices of the U. S. Army Engineer Waterways Experiment Station Explosive Excavation Research Laboratory (EERL) located at Livermore, California. This organization was formed in 1962 as the Nuclear Cratering Group (NCG) to carry out the Corps of Engineers (OCE) portion of a joint agreement with the Atomic Energy Commission (AEC) to develop nuclear explosives for construction purposes. The AEC, through the Plowshare Division of the Lawrence Livermore Laboratory at Livermore, California, has been responsible for developing nuclear explosives, conducting nuclear cratering experiments, developing nuclear safety information, and developing methods for predicting the shape of the craters. The Army part of the program includes corollary chemical high-explosive cratering experiments, participation in the AEC's nuclear cratering experiments, and development of

Jan 1, 1997

By K. P. Unrug, E. Thompson, S. Nandy

The method of coal pillar design involves primarily two aspects: the geometry of the pillar and the strength of the coal. However, the strength of the coal has to be emphasized with respect to the entire pillar dimension rather than isolated strength values of coal samples taken and measured from different locations. As of now, the presently applied pillar design systems do not specify clearly what the coal sample strength really represents. The intention of this paper is to introduce the concept of seam strength as opposed to the current practice of using coal strength as a prime design criteria in the formulation of pillar calculations. Seams are most often composed of multiple layers of coal, partings, and bone in various configurations, changing within the vertical section of the seam even in relatively close locations. The difference in strength between the weakest and strongest component of the coal seam could be as much as five times or more. An experimental approach based on multiple uniaxial compressive strength tests performed on coal samples from the Coalburg and Warfield seams from eastern Kentucky was undertaken. Analysis of the results led to the conclusion that for pillar dimension calculations, both the weighted mean of the seam strength and the strength of the weakest stratum should be considered, rather than the relatively vague aspect of coal strength. The design of pillar dimensions based on the aforemen¬tioned criteria should assure a more realistic design performance.

Jan 1, 1987

By R. S. Ondrey, R. A. Haney, T Tomb, R. T. Stoltz, Novakowski D. L. Chiz, E. J. Gerbec, D. J. Atchinson

Although the number of operating longwalls in the United States (approximately 100) has remained relatively constant over the last five years, longwall production levels have significantly increased and in some cases more than doubled. As a result of this production increase, control of respirable dust continues to be a problem. Therefore, the Mine Safety and Health Administration (MSHA), Pittsburgh Health Technology Center, Dust Division, initiated a study to investigate the availability and adequacy of technology for controlling dust on longwall mining operations. The study involved 23 longwall mining operations in three different Coal Mine Safety and Health Districts. Each operation was visited for a full shift. Respirable dust samples were collected on face personnel and at fixed locations along the face. Methods being used to control dust were noted, with special emphasis placed on obtaining quantitative data relative to ventilation, headgate dust controls, cutting drum sprays, external machine sprays and cutting sequence. Attempts were made to correlate dust control practices in place at the time of the visit to dust concentrations measured at the tail and on the tail shearer operator and to the average of all the dust concentration measurements from the occupations sampled. The methods used to control dust were also compared to the gamut of methods known to be available. This paper presents a discussion on the effectiveness of the methods being used to control dust and on the availability of technology for the control of dust on longwall mining operations.

Jan 1, 1991

By Louis W. Riggs

The primary concern in dealing with contractual arrangements for construction is getting the work completed satisfactorily, in the shortest time, and for the least expense for the owner--while assuring that all other parties associated with the contract make a reasonable profit for their effort. In our complex construction climate of today, achieving all of these is usually not possible. Somewhere between the beginning of design and the completion of the work, disagreements and delays arise which can destroy the best of intentions. Assuming that all parties associated with the contract are acting honorably and professionally, the disagreements generally arise through inappropriate contract types or through flawed contract documents. These flaws can be either sins of omission or commission, but we must find a way to lessen, if not completely eliminate, their impact. Disagreements and delays are directly related to the extra cost which the owner and the other involved parties must suffer. Usually the attorneys are the only ones who come out on the positive side. Inappropriate or defective contract documents can be the result of inadequate time for preparation and review, laziness in not searching out the proper terms and language, insufficient recognition of the proper assignment of risks, or just ignorance as to what is right and what is wrong for the particular project. They can also result from a client, particularly a public agency, providing rigid general conditions and format requirements with which the engineer is not allowed to tamper. Arguments

Jan 1, 1979

By Mike Horn, Keith Meade, Marvin L. Smallwood

Technological changes in programmable logic controllers (PLC)'s and the need to improve the architecture of Mine Wide Monitoring Systems (MWMS) has resulted in the design of a PLC based system at the Virginia Division of Island Creek Coal Company. The system which is presently in the installation phase, is a joint effort of Island Creek Coal Company, Westinghouse Electric Supply Company and Mining Controls Incorporated. The system uses an ethernet based network for graphic display of system data operating under the Genesis software package. Telemetry for the system utilizes the Seimens/Westinghouse L1 network operating over two twisted pairs. Remote telemetry uses fiber optic links and modems operating over standard telephone lines. 500 and 2000 series PLC's provide distributed data processing for the system with hierarchial processing operating under the Genesis software on the ethernet network for individual mine site monitoring along with the remotely located division office monitoring. System control and data acquisition is provided for underground MWMS operations and on the surface for a vast methane gathering system that is used for degasification of the mines and collection of pure methane for sale to the Columbia Gas Company as natural gas. The inability of industrial MWMS companies to keep up with the vast changes in technology, along with economic considerations associated with expanding the existing MWMS created the need for the development of the PLC based system to replace the older industrial monitoring systems.

Jan 1, 1993

By Todor P. Stefanov

The thermal draught within ventilation networks of underground mines depends to a great extent on the shafts depths and degree of change of ventilating air density. When the topology and space orientation of a ventilation network are constant, the dynamics of thermal draught is determined mainly by the variations of the heat- and mass-transfer processes in the openings. This conclusion follows from the well known basic theoretical notions about the thermal draught-aerostatics and thermodynamics [1]. Quantitative evaluation about the influence of heat- and mass-transfer processes on dynamics of thermal draught could be made through: direct mine measurements, special experiments and with the aid of mathematical models. The first two methods produce sufficiently accurative results, however it is very difficult to perform such studies, particularly when these processes are evaluated within a large scope and multifactor aspects. Mathematical models of thermal draught allow to overcome easily these difficulties. The degree of accuracy of results, obtained by this method, depends to a great extent on the degree of approximation achieved by the model to the real heat- and mass-transfer processes. In this paper, with the aid of Bulgarian developed method, algorithm and computer program V WT-4 - for complex evaluation of ventilation parameters in active mine ventilation networks [2], the authors investigate some changes in the thermal draught. Basically, the method is an iterating evaluation of an open set of equations, which represents relationships between the following basic parameters of a mine ventilation network: [ ]

Jan 1, 1980

By R. W. Mossman, George E. Heim

Seismic exploration techniques offer the engineer and geologist a way of obtaining detailed information on the physical parameters and geometry of the rocks where extensive underground excavation or tunneling is proposed. Use of the seismic method can provide a greater amount of detailed information at relatively less cost than can be obtained by any other known subsurface exploration method. Boreholes are still required for calibration of the seismic data but at a much wider geographic spacing than otherwise would be needed for subsurface mapping. The seismic data can define with precision the actual location of zones of flexure or fracture of the rocks and reveal the configuration of the surface of the rock layers. ENGINEERING PROBLEMS One of the major requirements in the planning of subsurface installations is that of locating tunnels and other underground openings in favorable rock units. Such rock units should exhibit uniformity of composition, both vertically and horizontally, to minimize variation in excavation techniques. The depth and thickness of the unit must be known: a 30-foot diameter tunnel cannot be contained in a 25-foot thick limestone. The rock unit needs to be as free as possible from structural defects and should be suited to efficient excavation procedures. If liquid conduits are planned, the slope of the rock unit needs to be known so that maximum advantage can be taken of gravity flow with the tunnels wholly contained within the unit.

Jan 1, 1997

By Robert S. Setren, Jeffrey L. Ambs

The disposable diesel exhaust filter (DDEF) system developed by the U.S. Bureau of Mines and Industry cooperators for heavy-duty permissible, diesel-powered haulage vehicles, effectively reduces in-mine diesel particulate matter concentrations up to 95%. However, there are concerns about the hazards that exist when the filter is used in situations for which it was not designed. This work investigates the exhaust gas temperature limits to which the filter elements can be exposed without posing a safety or health hazard, such as 6re or off-gassing toxic compounds. A filter approved by the Mine Safety and Health administration and after-market filters were evaluated under varying engine exhaust conditions to determine if after-market filters pose an unacceptable hazard when used in a DDEF system. Filters were laboratory tested at engine exhaust temperatures ranging from 77°C to 290°C. Of the seven filter types tested, six appeared suitable for use on water scrubber-based cooling systems and two appeared suitable for use on dry heat exchanger type exhaust cooling systems with exhaust temperatures up to 150°C. Any filter elements used as exhaust filters on permissible diesel machines must be approved by MSHA for that application. Mine operators who wish to use an after-market filter element should request an MSHA field modification. MSHA will work with the mine and filter manufacturer to ensure its use in this exhaust system application does not pose a health or safety hazard.

Jan 1, 1995

By J. F. T. Agapito, C. E. Brechtel, C. J. Gilbert, T. R. Kelly, R. C. Karlson

A multi-lift benching cut-and-fill mining method was adopted at Asamera Minerals (U. S.), Inc.'s Cannon Mine to balance the goals of high productivity and near 100 percent recovery with the need to minimize subsidence. High strength backfill was required to provide effective long-term overburden support and safe working conditions during the pillar recovery operations. Operational designs were evaluated using numerical modeling to predict global mine stability and backfill strength requirements. These models incorporated sequential mining of primary stopes, backfilling of primary stopes and recovery of pillars, and have been transferred to the mine operations group for use in evaluating different production sequences. The modeling has provided a better understanding of the structural response of the mine to excavation of the primary stopes and removal of the pillars. Predictions about the transfer of overburden weight to the abutments, pillars and cemented fill pillars have provided a criterion to evaluate mining plans and production sequence. Comparison of these predictions with actual mine structural performance has developed confidence in the design of the mining method and in the geomechanical design methods being employed. Primary mining of the B-North zone is nearly complete, and the stopes have been generally stable, as projected in the original design. Some exceptions have occurred where locally stope pillars have failed due to the presence of adversely oriented sheared beds. Recovery of the pillars between the

Jan 1, 1987

By R. A. Jankowski, R. Gong, R. Bhaskar

The control of respirable coal dust in continuous mining sections involves careful analyses of the generation and transport of the dust, including airflow pattern analyses. Potential dust control devices must be evaluated based on their effect on both local dust transport and potential dust exposure of face personnel. The development of larger and more productive continuous miners increases the need for research on dust control and improvement of visibility in the face area. Two studies relating to underboom dust control are discussed. The first study involved the valuation of potential underboom dust control techniques to reduce operator exposure to dust and determining the relationship between the positioning of exhaust ventilation and the exposure of face personnel as a function of face and operating variables. The study involved full-scale laboratory experiments using a state- of-the-art data acquisition system. The second study related to the use of foam under a continuous miner boom and its effect on silica concentration and respirable dust. The foam study was performed in a coal mine. The laboratory studies involved the fabrication of a full-scale test facility and development of a computer based data acquisition system. This was followed by baseline data collection, smoke trace tests, detailed performance testing of various underboom dust control measures and data analyses. The underground foam test involved the design and installation of the foam generation and delivery system, testing, and data evaluation. The results of the studies are summarized in this paper.

Jan 1, 1991

By D. R. Lowe

Silicic volcanic ash and its alteration product, bentonite (montmorillonite and cristobalite), occur widely within sedimentary phosphate deposits. The genetic link, if any, between volcanism and phosphate deposition has yet to be satisfactorily established The phosphatic member of the Santa Margarita Formation (upper Miocene) in northwestern Ventura County, California, consists of approximately 15 per cent volcanic ash and bentonite. Ash and bentonite units greater than one foot thick can be subdivided into a lower zone of airfall origin and an upper zone of mixed ash and terrigenous detritus washed in from surrounding land areas. This upper zone also contains up to 20 percent phosphate pellets. These thick volcaniclastic units are typically overlain sharply by thin beds (less than 6 inches thick) of relatively pure, silica-cemented pelletal phosphorite. The shelf basin in which the phosphatic sediments accumulated was characterized by quiet, reducing but not euxenic bottom waters; Abundant decaying organic debris, mainly diatoms, served as a reservoir of readily available phosphate. The sudden influx of a large volume of silicic volcanic ash into this basin and its subsequent alteration to montmorillonite had two profound effects on thechemistry of the interstitial and bottom waters: (1) during alteration magnesium was removed from these waters and incorporated into the montmorillonite lattice, and (2) the pH of these waters increased as alteration progressed Both of these effects led to the crystallization in the bottom waters of carbonate fluorapatite. This accumulated as thin phosphorite beds immediately above the volcaniclastic units.

Jan 1, 1972

By F. N. Kissell

The US Bureau of Mines undertook a study of those factors influencing worker escape from an outby coal mine fire. The results of this investigation were two-fold. First, those factors affecting escape from a mine fire were defined, and second, the relationships between these factors were identified. Although the individual components had been studied before, little information was available on their interdependence. Fault tree analysis was used to evaluate the miner escape scenario. After constructing the fault tree, a two-phase analysis of the tree was conducted. During the first phase, the minimal cutsets of the fault tree were identified and ranked. These sets were the smallest sequence of events leading to fatalities during the fire. This ranking revealed that reduced evacuation delays, improved self-rescuer training, and improved stopping construction were important in controlling fatalities during escape from the mine fire. The second phase involved additional analyses of the fault tree. These evaluations were started by first determining occurrence probabilities for each event in the fault tree. Two types of sensitivity analyses were then conducted. The first analysis dealt with changes in event probabilities and their impact on the likelihood of fatalities. The final sensitivity analysis considered dramatic reductions in the probability of fire fatalities. This revealed what event probability values were necessary to reach this level. These results have revealed various remedial actions that could be used to improve the survivability of an outby mine fire.

Jan 1, 1990

By Jean-Michel M. Rendu

According to statistical theory, the geostatistical methods of ore reserves estimation are greatly superior to any other method. However acceptance of geostatistics by the mining industry has been slow and not as wide spread as one would expect. One of the reasons for this cautious approach is that it is often questioned whether the geo- statistical assumptions are satisfied in real world situations. When blocks of ore are estimated in a mineral deposit, geostatistical theory can be used to determine which method of estimation should give the best results. Using this theory, the relationship between estimated value and true block value can be quantified. There is a need to verify that this theoretical relationship is actually observed in practice, and that the block estimates ' obtained using the theoretical ly best method of estimation, are actually most similar to the true block values. In this paper the results expected according to the theory are compared with the results actually obtained. Sample values from a large bedded gold deposit have been used. Blocks of ore have been estimated by a number of methods, including the polygone, inverse power of the distance, kriging, logarithmic kriging and other geostatistical methods. The block estimates have been calculated from samples on a large grid, and compared with the true block values obtained from additional samples on a much smaller grid. The results of this comparison show extremely good agreement between theory and actual results.

Jan 1, 1979

By Allan E. Hall, Stephen G. Hardcastle, Lucien D. Nel, Jean-Paul Saindon

A description is given of the investigation conducted at Sherritt Gordon's Ruttan Operation in Manitoba during 1986. Gas and dust concentrations were measured in the exhaust air of the major working sections to assess the potential for recirculating exhaust air into the intake air in winter to reduce heating costs. The results indicate that there is excellent potential to significantly reduce winter heating costs by controlled recirculation of exhaust air. Gas and dust concentrations vary significantly during the working shifts but have consistent trends from shift to shift and day to day. The variations in gas concentrations have similar trends but no single gas could be reliably used to predict the variation of the other gas or the dust concentrations. Dilution and the other effects which reduce pollutant levels as the exhaust air returns to surface indicate that recirculation should take place as close to surface as possible, subject to the economic constraints of the airway construction required and the extra fan energy required for the longer recirculation path. Recommendations are made for the choice and positioning of air and dust monitoring sensors and the logic of a control system. Economic analysis of the results indicates that controlled recirculation is viable at an existing mine with a pay back period of approximately two years. Incorporation of a system into a new mine at the planning stage would significantly shorten the pay back period.

Jan 1, 1987

By K Martin, C. J. Nelsen, J. L. Schutz, S. R. Maynard

Investigations in the Ortiz Mountains have revealed the relationship of igneous activity and gold mineralization to the Tijeras-Canoncito Fault System (TCFS). The northeast-trending TCFS passes through the southeastern part of the Ortiz Mountains where its principal structure is the asymmetric Ortiz Graben. Several fault blocks, containing up to 305 m (1000 ft ) of Eocene Galisteo Formation, comprise the graben that has up to 1220 and 610 m (4000 and 2000 ft) of stratigraphic separation on its southeast and northwest sides, respectively. Intrusions in the Ortiz Mountains can be subdivided into two petrochemical types: an older calcalkaline suite and a younger alkaline suite. The calc-alkaline rocks are characterized by extensive sill, dike, and laccolithic bodies of latite-andesite intrusives and at least one younger (?) granodiorite stock at Candelaria Mountain. The alkaline rocks consist of a large nepheline-bearing augite-monzonite stock, a latite-porphyry hypabyssal plug, the Ortiz diatreme (vent breccia), and trachytic-latite dikes radial to the diatreme. K-Ar age determinations suggest the older suite to be 34 +/-2.2 million years while the younger alkaline rocks range from about 30 to 26 million years. Gold mineralization in the Ortiz Mountains occurs in five distinct environments: brecciapipes, skarns, veins, porphyry-like stockworks, and placers. Lode mineralization is associated with the alkaline suite of intrusive rocks postdating the Ortiz diatreme and predating most of the trachytic-latite radial dikes.

Jan 1, 1991

By George Aul, Richard Ray

Short-hole horizontal degasification systems have been utilized in Island Creek's Virginia Division mines since 1986. These systems remove methane from the coal seam in advance of longwall mining. Without an in-seam methane drainage program, methane liberation rates from the longwall faces may exceed 0.47 cu m/s (1,000 cfrn), requiring 47 cu m/s (100,000 cfm) of air for adequate dilution capability. Optimization of the degas systems has enabled methane liberation levels and the associated ventilation requirements on the longwall faces to be reduced by 50 to 80 percent. Since the inception of the first degas system at the Virginia Pocahontas No. 6 Mine, Island Creek has developed an overall methane drainage program designed to maximize gas production and minimize ventilation requirements for methane dilution. Gas production from the degas systems is affected by four main design criteria: (1) hole location, (2) hole length and spacing, (3) collection system capacity, and (4) time available for drainage. Drilling equipment and materials for the gas collection system are selected to meet the necessary criteria while minimizing manpower requirements. Benefits gained from reducing methane liberation rates from the longwall faces are fourfold: (1) improved safety due to lower methane concentrations in the face area, (2) fewer production delays caused by excessive methane concentrations, (3) lower fan operating costs resulting from reduced air requirements, and (4) enhanced worker comfort resulting from lower air velocities and less dust generation.

Jan 1, 1991

By C. Douglas Lee

This case study describes the work done at the University of Arizona on the development of a computer mine model for an irregularly shaped and spotty ore deposit. The purpose of the work was to develop techniques for modeling any highly irregular deposit, for which the regular 3D fixed block model is not well suited. The deposit contained complex geology consisting of sedimentary beds that had been faulted, thrusted, and intruded by igneous rocks (see Fig. 1). The physical dimensions of the modeled ore body were 1067 m (3500 ft) along the N-S direction and 914 m (3000 ft) along the E-W direction. Topographic relief in the modeled area was approximately 274 m (900 ft). The highest grade of ore was found near the surface with mineralization extending down to approximately 152 m (500 ft) below. Using a fixed bench height of 12 m (40 ft), the model required 25 levels with the highest elevation being at 1286 m (4220 ft). Fig. 2 shows a cross section of the developed computer model of the ore deposit. The particular modeling approach selected for this deposit was the 3D irregular block model.* This meant that only the dimension of bench height was fixed at 12 m (40 ft). Irregular size blocks in the form of polygons were adopted in the model to describe the ore zones and geologic contacts. The following sections of this chapter describe some of the techniques used in modeling.

Jan 1, 1979

By Isobel Clark

The problem of the estimation of ore reserves is essentially a simple one to describe. Given a set of sample data, at specified locations within a deposit, how can we estimate the value (or quantity) of ore in unsampled areas. The question may be posed of a whole deposit (global) or it may be more desirable to estimate smaller volumes within the planned mine area, e.g. stopes or blocks (local). Many methods have been evolved to tackle this problem, from hand-contouring of values by the mine geologist to extremely sophisticated geomathematical analysis. The main difficulty with any estimation method in this context is that it is almost impossible to check whether the "predicted" value bears a close relationship with the "actual" value. The only reliable way to decide if an estimation method has "worked" is to test the eventual value of ore against the predicted value. This is, more often than not, impossible - even allowing for the time factor involved. To know the "actual" value of a mined block it has to be sampled intensely, and these values with their positions recorded accurately. Alternatively, blocks may be passed through the concentration process individually and these results recorded. In most producing mines neither of these alternatives are practicable or seen to be-important. Another problem with comparing in-situ (so-called) mineable reserves with production figures is the introduction of many variables into the concentration process -- dilution, wastage, possible stockpiling, mill recoveries and so on.

Jan 1, 1979