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By Thomas de Lange

Extensive test work performed on the Coalscan 3500 ash analyzer at the Grootegeluk Coal Mine has led to the successful implementation of on-line ash monitoring to control the quality of coking coal and power station coal. Test work results are given and the advantages of on-line bias compensation discussed. Some details of the quality control systems subsequently implemented are also highlighted. Finally, the economic benefit of on-line ash monitoring based on the Mayer curve is demonstrated.

Jan 1, 1992

By Robert J. Timko, Lincoln Derick

This work is a follow-up to previous research that attempted to predict the location of spontaneous heating episodes in underground coal mine pillars. The objective of the original work was to see if the data obtained by commonly used detection methods could accurately predict spontaneous combustion episodes in coal pillars. Data accumulation during the study was enhanced when a spontaneously generated fire occurred within one of the pillars being examined. The fire provided researchers with realistic data that could be used to determine if fire prediction was possible. Results from the initial study found that the atmospheric status equations that were used provided little advance notice that combustion would occur where it did. This study reevaluated the accumulated data by applying it to recently developed equations and compared these results with previously obtained information to determine if a combination of these techniques could more effectively predict impending combustion.

Jan 1, 1995

By Patrick M. James

Many in mining believe that the industry is slipping behind in public image, in public mineral education and, particularly, in mining's basic right to do business. It is critical to turn things around - to change the rules of the game soon - before mining loses any chance of recovery. In the industry's experience, there is a technique of project development and operation that can help gain ground on public opinion. Only recently has this technique had a name, and that is sustainable development. What is sustainable development? Sustainable development is broadly accepted and supported by the international business community. And significant thought and work has been devoted to the subject. Research into the topic was initially confusing because the definitions of sustainable development are written in terms the writer, and his or her constituency understands. To some, it refers to environmental protection. To others, it is about social responsibility. And to the developer, it is about economic benefit. Slowly a theme emerged from the research that seemed to be part of all the definitions. That theme has three parts. First, the development, whatever or wherever it is, must contribute economic value to the developer and the stakeholders of the development. Stakeholders in this context include employees, neighbors, residents of the surrounding area, citizens of the country, suppliers and all others affected by the development. Next, sustainable development must contribute environmental value. This means that at a very minimum it must be neutral and not cause irreparable damage. And last, and what is new for miners and most other businessmen, it must contribute real social value to the stakeholders. How to use the concept? With that three-part theme as a working definition, the mining industry must find ways to use that “the challenge is for an individual company to translate what sustainable development means for them. There is no one model..." Donald W. Gentry is president and chief executive officer of Polymet Mining and former professor emeritus of mining engineering at Colorado School of Mines. He added: "While simple to state, the concept is anything but simple to implement. Present trends indicate ... one wins the sustainable development argument by staking out the high ground early..." In other words, start using sustainable development principles at the beginning of the project. New ways of doing business The mining industry's challenge is to implement sus¬tainable development universally around the world. Paternalism as a way of doing business is dead and a new model of doing business is emerging. All types of businesses are learning to deal with the stakeholders of new developments. Mining cannot be an exception to these trends. To understand how the international mining business came to sustainable development, it is useful to look back a few years. For many North American mining engineers, there were few opportunities for foreign assignments from the 1960s to the 1980s. American companies had been asked to leave many of the Latin American countries. Africa was going through a continent-wide upheaval. The Soviet Union and China had Eastern Eu-

Jan 1, 2000

By Y. C. Kim

Three rock fracture parameters define three points along empirical cumulative size (of rock fragments) distribution curves at Inspiration copper mine. These parameters are: rock quality designation (RQD), longest piece of intact rock and % of +1 inch. The RQD and the longest piece are actually measured on drill hole cores whereas % of +1 inch is visually estimated on the same cores. These size distribution curves are then utilized in a variety of engineering applications such as; slope instability analysis, blast design, copper recovery prediction from heap leaching, etc. The three rock fracture parameters for two dominant rock types (porphyry and schist) in the pit had to be estimated separately due to different rock fracture characteristics.' Both ordinary kriging (OK) with measured hard data only and soft kriging (SFTK) with hard and soft data were used to estimate each parameter. The cross validation of 100 measured sample values served as the-basis for evaluating the potential benefits of SFTK over OK. Use of subjective information during SFTK required obtaining (prior) probability distributions for all three rock fracture parameters. These distributions were obtained from the typical rock fracture parameters observed in drill hole cores falling inside the geologically interpreted structural domains with varying degrees. of fracture intensity and also through direct mapping along the exposed bench faces. Two different types of soft information were developed for this study; namely, Type "A" and Type "K". The former is based on sample distribution of fracture parameters whereas the latter is based on two step estimation designed to narrow the range of variation observed in data Type "A". The results of the cross validation were analyzed using a linear regression of actual values versus estimated values. The results confirm an improvement on the estimates made by SFTK with hard and. both types of soft data over those produced by OK with hard data only.

Jan 1, 1989

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 M. Polat, S. Chander

Many models have been suggested in the past to obtain a satisfactory fit to flotation data. Of these, first-order kinetics models with a distribution of flotation rate constants are most common. A serious limitation of these models is that type of the distribution must be pre-supposed. Methods to overcome this limitation are discussed and a procedure is suggested for estimating the 'actual' distribution of flotation rate constants. It is demonstrated that the classical first-order model fits the data well when applied to coal flotation in narrow size-specific gravity intervals. When applied to material which is fractionated on the basis of size alone, the use of three parameter models, which were modified from their two parameter analogs such as rectangular, sinusoidal, and triangular, gave most reliable results.

Jan 1, 1995

By Kenneth L. Schellie

In preplanning the reclamation of a pit or quarry the geology of the site is the name of the game! The planner must know the parameters of the deposit, the quantity and kind of earth materials to be removed, and the amount and nature of the materials to be left behind or wasted as the result of processing the marketable product. With many states and most local jurisdictions requiring reclamation plans prior to the issuance of mining permits, the need for accurate and complete data concerning the geology of the site becomes increasingly important. The producer need only know that marketable materials are available in sufficient quantity to make the mining operation economically feasible-the planner, in order that the land may be reshaped for a useful purpose, must have reasonably precise information as to the dimensions and configurations of the pit or quarry following extraction and the amount and type of materials available on the site (or in some cases offsite as well). Therefore the geology of the site is of major significance in determining the land forms and use capabilities of the property upon completion of the mining process.

Jan 1, 1974

By Joseph W. Kupfner

It is a recognized fact that a good maintenance program is a pre-requisite for minimum delay costs and maximum availability of equipment. To develop such a program and to make it effective, one must establish detailed instructions pertaining to inspections, lubrication, servicing, and/or replacing of various parts. A schedule must also be established for these maintenance checks, whether they be weekly, monthly, or whatever period is essential for the equipment. The number of tasks to be performed becomes monumental, and the administration is beyond error-free human capacity. It is for this reason that the computer must be an essential element in any efficient and economical preventive maintenance program. The evolution of a computerized maintenance program began some 18 years ago in the Mining Division of USSteel. It started with a manual system of preparing cards containing preventive maintenance instructions that had to be performed on some regular basis. We were very quickly overtaken by the massive task of administration and distribution of instruction cards to the users. The task became insurmountable as more mines were added to the system, mines that were spread over a large geographic area. It also became evident that the ability to make changes in equipment assignments and in the "what to do" instructions would require more time than had been anticipated.

Jan 1, 1986

By L. W. Stanger, Erich U. Petersen, William J. Tafuri, Donald M. Hausen, Douglas N. Halbe

Gold mineralization at the Mercur Mine was controlled primarily by structure and secondarily by lithology in Mississippian-age sedimentary rocks. Gold was localized where Sevier-age high angle northeast-striking faults are intersected by younger northwest-striking fault zones. The Lulu Graben is a northeast- striking fault zone composed of a south-dipping master fault coupled with subsidiary or antithetic faults. The Twist Fault zone, a sinuous, low-displacement , north-striking zone of fracturing, bisects the graben. Large- tonnage disseminated ore bodies formed east of the Twist Fault zone within silty, thin-bedded, bioclastic carbonates. West of the Twist Fault zone, gold was restricted to rock near peripheral faults surrounding a subvertical collapsed pipe developed within the graben. An overlying thick carbonaceous shale capped the ore zone. Presence of abundant limited- displacement faulting and of hydrothermal jasperoid is associated with cartonate-hosted disseminated gold. Conversely, increased fault displacement and widespread brecciation are associated with reduced dissemination of gold into normally receptive carbonates.

Jan 1, 1990

By C. J. Pritchard, R. D. Jacksha, K. V. Raj, C. B. Sunderman

In underground metal/nonmetal mines, repeated localized short-term exposure to high levels of airborne contaminants can become a serious health issue. Currently, there are no common mechanisms to control or mitigate these short-term high exposures to contaminants. To improve miners’ health and safety, the U.S. National Institute for Occupational Safety and Health’s Spokane Mining Research Division (SMRD) is developing a smart monitoring and control (SMAC) system for the real-time monitoring of mine air quality, with integrated countermeasures to reduce high concentrations of airborne contaminants in localized sections of mines. To develop and test a SMAC system capable of being implemented in an underground mine, SMRD researchers built a test apparatus incorporating a fan, louver, ducting and sensors combined with atmospheric monitoring and control software. This system will institute effective countermeasures to reduce contaminant levels, improving miner safety and health.

Jan 1, 2018

By G. A. Goller, Y. C. Lo

Microscale studies involving an ultrafast load cell have been shown to provide direct and accurate measurements of particle strength, particle fracture energy and particle breakage functions under different loading geometry conditions. The effect of grinding media size, shape, density and surface properties on the energy efficiency can be quantitatively determined for different materials to be ground. The applications of microscale comminution studies have been demonstrated to provide good predictions of grinding mill performance with different grinding media.

Jan 1, 1995

By A. S. Dremukha

The problems of geological exploration are discussed on the basis of computerized modeling of, complex orebodies, as well as the task of data authenticity evaluation. The theoretical baseof modeling is solving the problem of determining the parametres of orebodies sizes distribution along random intersections by exploratory workings. The relationship is established between univariate distribution moments in the intersections and the moments of the orebodies sizes distribution in three dimentions. It is suggested to use the obtained results for compyter modeling of the orebodies accumulations and for imitation modeling of their exploration. The computer experiments with the models make it possible to establish the optimum parametres of exploration networls.

Jan 1, 1989

By J. C. Stankus, S. Guo, S. S. Peng

In this paper, a model is developed for a resin anchor bolt system in which the smooth bar is modeled by using one-dimensional truss elements, and the resin annulus is modeled by using axisymmetric elements. These two submodels are combined and then incorporated into an existing computer code called Roofbolt. After this development, all of the components in the resin anchor bolt system, including smooth bar, bearing plate and resin annulus, can be correctly modeled.

Jan 1, 1997

By Young C. Kim

Because of the high cost of obtaining coal washability samples, it has been difficult to obtain washability variograms in the past. As a result. It could not be determined if geostatistical prediction tool known as kriging can be applied to predict in-situ coal washability characteristics.

Jan 1, 1988

By Gustavo G. Pilger, Jair C. Koppe, João Felipe C. L. Costa

Information for mine planning requires to be close spaced, if compared to the grid used for exploration and resource assessment. The additional samples collected during quasi-mining are frequently located in the same pattern of the original diamond drill holes net but closer spaced. This procedure is not the best in mathematical sense for selecting a location. The impact of an additional information to reduce the uncertainty about the parameter been modelled is not the same everywhere within the deposit. Some locations are more sensitive in reducing the local and global uncertainty than others. This study introduces a methodology to select additional sample locations based on stochastic simulation. The procedure takes into account data variability and their spatial location. Multiple equally probable models representing a geological attribute are generated via geostatistical simulation. These models share basically the same histogram and the same variogram obtained from the original dataset. At each block belonging to the model a value is obtained from the n simulations and their combination allows one to access local variability. Variability is measured using an uncertainty index proposed. This index was used to map zones of high variability. A value extracted from a given simulation is added to the original dataset from a zone identified as erratic in the previous maps. The process of adding samples and simulation is repeated and the benefit of the additional sample is evaluated. The contribution of an extra sample was evaluated locally, globally and in terms of variation in total measured resources. The procedure showed to be robust and theoretically sound, mapping zones where the additional information is most beneficial. A case study using coal seam thickness illustrates the method.

Jan 1, 2002

By Armando Z. Remacre

The purpose of this paper is to attest the effectiveness of conditional simulation technique's for determining the principal pre-mining control parameters during mine planning. These parameters include: determining the selective mining unit size, the optimum pre-mining grid spacing and the number of mining faces to be used. The research work was developed in an iron ore deposit located in the Minas Gerais State, Brazil. Phosphorus was considered the master control variable for the research work. This paper provides the structural analysis (variography) , a description of the steps the were taken for setting up the numerical model, the kriging studies which were applied to the numerical model and the final optimum grid spacing, block size and number of mining faces.

Jan 1, 1992

By G. R. Struble, J. R. Marks, A. B. Brown

The center of mining at the Homestake gold mine in Lead, SD, is moving deeper every year. As a result, it has become necessary to upgrade the ventilation system. This paper describes the first phase of a scheduled two-phase upgrade - installation of a 2.2-MW (3000-hp) centrifugal fan. The higher pressure fan is required to route larger airflows into the deeper production levels. Selection of the fan began by specifying the necessary operating point to provide these larger airflows. Special site work had to be done on the surface to accommodate the new fan structure as well as underground to reroute airflows.

Jan 1, 1987

By L. J. Nicks

The current U.S. Bureau of Mines research program is addressing the recovery of flake graphite from kish, a steelmaking waste product, and the use of zeolites from abundant domestic natural deposits for efficiently cleaning up mining industry wastewater. The United States is almost totally dependent on imports for its graphite needs, but this may change depending upon the results from a pilot plant being constructed by industry using Bureau technology. Standard mineral processing techniques were applied by the Bureau to recover high-quality flake graphite from kish. It was considered innovative enough to receive an R&D 100 Award in 1992, and its commercialization has the potential to supply the total U.S. demands for graphite many times over. Zeolites have ion exchange properties similar to ion exchange resins, but are less expensive and available in large quantities. Samples of naturally occurring zeolites were tested for their efficiency in removing metal ions from synthetic and industrial waste solutions. The tests focused on defining their selecting, loading, eluting, and regenerating characteristics, and on developing a method for recovering the metal ions as added value products. The results showed that the removal of metal ions with zeolites from acid rock drainage (ARD) solutions is technically feasible and that this technique has the potential for being used in an integrated chemical treatment systems approach either as a primary or secondary cleaning step.

Jan 1, 1995

By Pierre J. Wauters, Eddy J. Jacques

Starting up a fan or modifying its setting point either by rotational speed variations or blade angle changes, obviously results in new ventilation conditions in the network, which is, of course, the object of the operation. However, since transient phenomena may then occur, particularly in complex networks, there may be a need to simulate these situations prior to any action. This is all the more true, if we are dealing with a multiple interactive fan sys- tem. Simulations with a transient model have shown that the flow in certain airways could be temporarily reversed due to the pres- sure variations that reach both its ends with a different time lag. This phenomenon may cause dangerous situations to occur in cases of fire or outburst of methane. It is also true that the air flow could be reversed in secondary and less powerful fans, while still rotating in the normal direction. The study and the experimental investigation of the extension of the reverse flow characteristic is therefore justified from two points of view : • a numerical simulation model for transient flow conditions must be capable of handling temporary reversed flows, and thus have appropriate fan characteristic curves available over the entire operating domain; • while operating fans, reversed flows should be avoided or at least reduced. Therefore, the design of start-up procedures or real time control algorithms should take these phenomena into account. A particular interesting application is the operating of two fans in parallel. In order to investigate experimentally the characteristic curves of a fan under reversed flow conditions a small scale model was built. This facility was designed in such a manner that it was possible to carry out experiments concerning flow reversions and to try out sequential start-up procedures for two fans in parallel.

Jan 1, 1997

By J. A. Ryder

Compressed air is a relatively inefficient yet very convenient vehicle for transmitting mechanical energy. It is inefficient when compared to, say, hydraulic or electric energy systems since compressor and pneumatic machine efficiencies are quite low (in the range 20-65%) and reticulation losses can be quite high unless adequate pipe diameters are used to minimize friction drops. It is convenient in that capital and maintenance costs of pipes and machines are exceptionally low, the equipment is flexible and lightweight, the technological level is simple, the form of the energy supply is intrinsic- ally safe, and as an additional minor but psychologically important benefit, it provides a ready source of cooling and air supply for emergency use in deep hot mines. It is for these reasons that compressed air is a premier source of energy for many forms of underground equipment, in particular hand or rig-mounted rockdrills, some forms of rock- handling equipment, and a host of minor applications including agitators, small-lift pumps and temporary f am installations. In a typical S. African deep-level gold or platinum mine, compressed air generation accounts for 15% of the total mine electrical energy bill - more than is used for hoisting. In these mines it is not uncommon for over 100 km of underground compressed air piping to be installed, primarily to supply handheld rockdrills.

Jan 1, 1979