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By D. L. Passmore

The development of microcomputer software that provides an analysis of pit-specific accident and production data for the mining industry is seen as a vital component in a total loss-control system. The Mine Injury Reporting System (MIRS) allows users to access accident and production data prepared by the Health and Safety Technology Center of the Mine Safety and Health Administration of the United States Department of Labor for any particular state and to generate a simple, yet informative, report.

Jan 1, 1988

By P. Huttagosol

The use of computer models to design ultimate pit limits during feasibility study and long range mine planning is becoming a significant practice in open pit mining. One of the problems in determining optimal ultimate pit limits using true optimization techniques has been they require a great deal of computer memory and execution time. In this paper, the maximum closure of a graph, which is a true optimizing model developed by Lerchs and Grossmann, is modified for solving ultimate pit limit problems. By using some properties of the original L&G graph algorithm, the tree configuration can be reduced to only connections between positive ore nodes. The modified algorithm is shown to require less memory and processing time while still yielding an optimal solution.

Jan 1, 1989

By A. Johnson

When are SMART transmitters the smartest choice? To answer this question requires a closer look at SMART transmitter technology. It is necessary to understand this technology in order to recognize how it can best be utilized to give the greatest value for the application. And, once the decision to buy transmitters has been made, it becomes a question of whose SMART transmitter to buy. For, although the under-lying technology is similar, the differences that exist in how the technology has been implemented can make a dramatic difference in the end result. What prudent users of SMART technology do is to analyze their needs by application before making their buying decision.

Jan 1, 1988

By William R. Bond

The pressure/vacuum lysimeter is being used as an effective vadose zone monitoring device for mining heap leach facilities, tailing disposal ponds and tailing waste sites. Their use has proven reliable for baseline data collection, early warning leakage detection and analyzing geochemical variations in the vadose zone. The lysimeter structure utilizes a closed cylindrical chamber made of PVC or inert material. The soil water intake portion of the cylinder is made of a porous material of low permeability. The application of vacuum or pressure to the unit is via two access tubes from the ground surface. Available soil moisture is drawn by vacuum through porous material into the lysimeter chamber and then collected from the access tubes. Case studies show their usefulness for monitoring around a uranium tailing pond constructed in glacial till material, under heap leach pads and pregnant, barren, and overflow ponds, and investigating the movement of contaminant moisture through old tailing deposits. Relatively easy to install and sample, regulatory agencies and facility operators are accepting and negotiating for their application as a site integrity monitoring device and unsaturated zone research tool. Their use at heap leach facilities lends credibility to solution balance calculations when considering a leachate loss of 5 or 10 percent can make or break a mine's profitability.

Jan 1, 1984

By Thomas R. Yanske, Jonathan E. Carmack, Lyndon M. Clark

In order to maximize the extraction of high grade pillars at The Doe Run Company, artificial pillars are created using cemented rock fill (CRF). CRF pillars aid extraction of pillars in two ways. One is to offer back support for the immediate area where pillars are being extracted. The second is to increase the post failure residual strength of pillars surrounded by backfill. The CRF is produced using a combination of minus 1.0 m run of mine (ROM) rock and minus 5 cm crushed rock. Depending on the operation the CRF slurry is either produced in an underground or a surface batch plant. The slurry and rock are transported to the fill area by truck where they are mixed and placed in 1 m lifts. To reduce the amount of CRF needed, fill fences are constructed around the perimeter of the CRF pillar. Within these fences ROM CRF is placed in lifts until within 0.6 m of the back after which minus five centimeter CRF is slung tight to the back utilizing slinger trucks. In constructing these artificial pillars a number of set procedures have been established to ensure that the work is done both properly and safely.

Jan 1, 2001

By Matthew Spedding

The complex nature of the carboniferous measures prevailing in the U.K. has dictated the types of mining required to exploit the coal seams. Most mines in Britain are referred to as deep mines in the sense that they operate at depths of 1800 - 3000 feet. The main system of coal transport to the surface is by vertical shafts which intersect the workable seams which at times number between 4 and 5. As mining has been practiced in most of the major coalfields in the U.K. for well over 100 years, with the initial extraction of the shallower and more profitable seams, the present management have been left a legacy of indiscriminate extraction which severely hampers their efforts to maximise the mine layouts. There is no single standard design of mining layout capable of meeting the wide variety of conditions which exist in the British coalfields. Mining layouts are subject to fixed and variable parameters. In discussing multi-seam working, the main parameter must be the effect of old workings above and below the seam to be extracted. There is a distinct lack of reliable information which would enable layouts to be designed to completely avoid or control these destructive forces. The guidelines are, therefore, mostly empirical.

Jan 1, 1977

By Dennis P. Bryan

Natural lightweight aggregate may be defined as inherently low density natural mineral materials. In most all instances they are relatively young volcanic rocks which, because of their geologic environment, are limited to the Western U.S. These Tertiary and Quaternary volcanics are low-density glass and vesicular material including, but not limited to, pumice and volcanic cinder. The distribution is widespread throughout the West with the principal producers being New Mexico, California, Oregon, Idaho and Arizona. The primary user is the construction industry where weight reduction equates to cost savings. Principal products in which natural lightweight aggregate is utilized because of its lower density include lightweight portland cement concrete and lightweight concrete masonry units. In addition, due to location, some natural lightweights compete with normal weight constructions aggregates for uses such as road base and common backfill material.

Jan 1, 1989

By C. H. Lee, F. Concha, L. G. Austin, P. T. Luckie

The Concha-Almendra batch-settling treatment for concentrated suspensions of single-diameter spheres has been modified. This modified version is used in the differential equations of simple batch settling of a particle size range of different density materials. The equations have been programmed for a finite difference solution, and a number of test cases have been analyzed. By cutting the settling column at a fixed fractional height, the material below this height can be treated as underflow and the material above as overflow. The predicted partition curves obtained from treating the settling in this way have Sharpness Indices in the range of 0.5 to 0.6, in the absence of dispersion effects. The Sharpness Indices decrease as dispersion increases. When the feed size distributions are of the Rosin-Rammler form, the partition curves (corrected for the bypass fraction) fit the Rosin-Rammler equation with reasonable accuracy. The predicted Sharpness Index of a component of a mixture of two materials of different densities was unchanged from that of the same materials settled alone. However, for the same, feed size distribution and volume fraction of solids in the feed, the heavier material settled faster, and the lighter settled slower, than when settled alone.

Jan 1, 1993

By M. R. Fletcher

Slags generated by the ferrous-metals industry can be used to produce high-tech ceramic materials. The properties of these ceramics can be controlled by judicious choices of composition, additives, and processing parameters. Standard methods of materials handling, such as comminution and mixing, are as applicable to slag as to any other mineralogic raw material. In this study, foundry slag was ground, homogenized, melted and formed to produce a glass, and then heat treated to crystallize it into a high-strength glass-ceramic. The product shows promise as a low-cost wear-resistant tile material which can be custom cast. This and similar materials, made from slags and natural rocks, are candidates for use as construction materials, acid-resistant piping, shock-resistant sheathing, rot-proof pilings, and, when foamed, even as pontoons.

Jan 1, 1988

By Marek Niec

Native sulfur deposits in Poland occur in Upper Miocene strata on the northern (platform) border of the Carpathian foredeep. Systematic exploration since 1953 has resulted in the discovery of seven stratifom-stratibound sulfur-bearing limestone deposits that together contain about 0.6 billion tons of demonstrated sulfur reserves and about 0.5 billion tons of inferred and hypothetical resources. One open pit and three Frasch mines are currently in operation; another is under construction and one has been abandoned. Total production is about five million tons per year from ore containing on the average about 25% sulfur. Field, isotope, and micropaleontological data indicate that the sulfur-bearing limestone was formed through the bacterial reduction of gypsum in the presence of methane discharged from source beds and traps in the Carpathian foredeep. Subsequent recrystallization of the sulfur-bearing limestone, tectonic activity, jointing, karstification, and partial leaching of the sulfur has transformed the sulfur deposits and has altered the thickness and content of the sulfur-bearing strata, and their porosity and permeability, affecting the productivity and water consumption of the sulfur wells. Caputerized borehole logging techniques and geostatistical reserve estimates are used in mine planning. Great environmental impact constrains the development of sulfur mines.

Jan 1, 1992

By F. C. Schwerer, C. R. McKee, J. C. Seccombe

Production of methane from coal seams requires hydrofracturing, and the length of a hydraulic fracture determines we11 spacing. Since the volume of fluid injected is known, the fracture length is the volume divided by average width and height. If the fracture is contained in the known height of the seam, then fracture width becomes the major factor con- trolling length. Width is proportional to coal compressibility; bulk compressibility is known to be larger than intrinsic compressibility. A method is given here to measure in-situ compressibility (a) from transient pressure testing. Theory linking flow in porous media with rock mechanical properties is reviewed. A consistent derivation of the porous flow equation is given incorporating 3-D deformation and the effective stress parameter "st' linking changes in effective stress and pore pressure. The relations for "st' in terms of a and intrinsic compressibility (ai) are substituted into the field measured porosity-compressibility product (net) and solved for a, the constrained matrix compressibility. In a field example, using 4 wells with an anisotropic analysis, the ratio of major to minor permeability was 17 for the Pratt A seam. a was found to be 6x10-5/psi as opposed to the laboratory value of 1.4x10-6/psi.

Jan 1, 1986

By William M. PhD. Schafer

The net acid generation (NAG) pH method is an important analytical tool that supplements static and kinetic tests for assessment of the acid generation risk of rock samples. This method is useful because it is simple, rapid and cost-effective; it combines features of the static and kinetic tests; and it can be conducted at mine assay labs. The NAG pH test is particularly effective for operational testing programs used to classify, selectively handle, and route potentially acid-generating waste rock. The NAG pH procedure is based on a 24 hour oxidation of a pulverized rock sample with hydrogen peroxide and subsequent measurement of the sample's pH. If the NAG pH is below a critical value, determined empirically, then the sample has the potential to generate acid in the field. The critical NAG pH value is typically within the range of 3 to 4.5, but the exact relationship between NAG pH and potential acid generation should be determined individually for each mine site, based on comparison with results of acid base accounting, humidity cell tests, and mineralogical analyses. Calibration and use of the NAG test for predicting ARD risk at several mines are described in this paper.

Jan 1, 2000

By G. R. Tostengard

Gold plant performance during the start-up period, which extends until capacity production is sustained, has a major impact on the internal rate of return and the net present value of gold projects regardless of mining and processing configurations. The start-up period experiences substandard production, extra expenses, and sometimes reduced recovery. This results in lost profits, a portion of which are recouped at the end of the life of the mine. Poor start-up performance can put projects into financial jeopardy. The gold mining industry regularly experiences start-ups ranging from good to poor. Problem areas, which affect start-up performance, include shortcomings in ore reserve sampling and testing, equipment design and installation, untrained plant operators, inability to cope with problems which arise, and organization of the maintenance program. An investment, equal to 0.5% to 1.0% of plant capital cost, in programs to prepare for start-up, in advance, is recommended. Investment in such a program will make a good start-up possible. Without it the best result which can normally be expected is a fair start-up. Developers of new gold mines are urged to compare the cost of this investment with the anticipated increase in project net present value. Funds for this investment should be included in feasibility studies.

Jan 1, 1988

By Dinah O. Shumway

California's annual production of >11 million tons of cement, at a value of over $640 million, comes from eight companies, which operate 11 plants. Cement is California's second most important mineral commodity, representing 25% of its total annual mineral production. Although most of the cement produced is consumed within the state, current export locales include the Pacific Northwest, Nevada, Arizona, Utah, and New Mexico. An enumeration of the components required to produce cement is deceptively simple: calcium oxide (65%), silica (20%), alumina (4-5%), iron (3-4%), and calcium sulfate (4%) as a retardant admixture. The last, and most expensive, ingredient in cement manufacture is energy. Detrimental materials in cement mixes include excess .magnesium, alkalis, heavy metals, sulfur, and other volatiles. Each of the 11 cement plants in California requires a unique chemical solution of combined raw materials to produce a uniform product: portland cement. The geologist proposing solutions for the additive raw materials in cement manufacture must have a thorough knowledge of a particular cement plant's needs. In the California cement market, keeping the costs of additive raw materials down is one way to also stay competitive, and using a combination of natural and waste materials as additive raw materials allows cement producers to stay competitive.

Jan 1, 1999

By G. Hargrave, K. W. Moloney, M. R. Stokes

In recent years drivage advance rates in the UK have in- creased from 35m per week in the 1980's to 100/150m per week possible today. These extended rates of advance have resulted in an increase in the potential methane, dust and heat generation at the drivage face. In order to disperse this additional pollutant load requires an increase of fresh air at the face. Although advance rates have changed, current auxiliary ventilation practice has not. UK mining law requires that the fresh air must be delivered to within 5m of the face. This has lead to the wide spread use of overlap auxiliary systems, since a pure forcing system set at this distance would lead to excessive airborne dust. UK mining law does not at present consider on-board mounted exhaust scrubber fans to constitute an effective overlap fan within mechanised drivages. In an attempt to determine whether working conditions could be safely and economically improved within mechanised drivages, a series of preliminary full scale gallery trials were con- ducted. A summary of the principal findings of these trials are presented together with an outline of a series of representative CFD simulations, scale model experiments.

Jan 1, 1997

By Keith G. Wallace, Gary K. Rogers

As a supplement to an analysis involving methodologies for the estimation of airflow resistance in shafts used for both ventilation and hoisting, a detailed shaft characterization survey was distributed worldwide. The survey provided detailed information which enabled verification of recommended velocities and established limitations on fill factors and relative velocities. This paper evaluates the information obtained for 37 shafts and presents a statistical evaluation of the results. Apart from airflow rates, conveyance rates, and physical characteristics, qualitative information regarding means of conveyance stability and velocity control techniques at unloading and loading points are also presented. Calculations of fill coefficient, free area velocity, and most importantly, relative velocity between the airflow and hoist, are conducted. These results are presented by frequency diagrams which illustrate the trends, as well as provide limitations for these parameters. The data illustrates that, commonly, the fill coefficient for two or more conveyances, does not exceed 30 %. A limit of 50% is suggested for a single conveyance shaft. A recommended free area velocity of 10 m/s (1,970 ft/min) for combined ventilation and hoisting shafts, is sup- ported by these results. Relative velocities of 30 m/s (5,905 ft/min) are most frequent and 50 m/s (9,840 ft/min) being a practical maximum.

Jan 1, 1987

By Thomas O’Neil

Part 2 of this article continues with a discussion of features that distinguish contemporary investment analysis in mining from earlier methods. Part 1 traced the evolution of evaluation methodology from the traditional and discounted cash flow methods to the present. Quantitative investment models of the past 20 years played an important role in mine evaluation, but a new integrated approach to mine investment decision-making is now developing because of growing economic, technical, and political uncertainties. One of those uncertainties -inflation-was discussed in Part 1. Increased Risk At a time when mineral production technology and analytical evaluation tools have never been more sophisticated, it may seem anomalous to claim that mining ventures are riskier. Whereas technical risk has, indeed, been notably reduced, business risk the chance of a major loss due to market factors-has increased. This has been caused by two factors: the rapidly rising capital requirements of new projects and increasingly unpredictable future economic conditions. These difficulties are compounded by the long lead times of large, new mining projects. Rising Capital Requirements A $100 million investment is no longer considered to be a large mining project in most cases. For a large metal mining project, the total cost of the concentrator alone can exceed $100 million. Amoco Minerals' Thompson Creek molybdenum mine being developed in Idaho will cost over $350 million, for a relatively modest sized (23-kt/d or 25,000-stpd) ore operation with no extraordinary features. For a major grass roots copper operation producing blis¬ter or refined copper, the capital requirements are billions of dollars, not millions. Project costs are higher for two reasons. One, the projects themselves are larger; and two, the capital cost per unit of production is rising rapidly. Projects are larger because lower grade ores, yielding smaller margins, must be mined in greater volume-particularly in view of the high fixed costs of modern technology. When analysts contemplate any capital project, an important consideration is the minimum economic size of the facility. This is the smallest size that can be built and still be competitive on a total unit production cost basis. In the conventional copper smelting business, for example, a production rate of at least 91 kt/a (100,000 stpy) of blister copper is about the absolute minimum for reducing unit fixed costs to competitive levels. Clearly, many variables affect the minimum economic size of a mining facility, but with few exceptions that size continues to grow. Unit capital costs of new mining projects also are continuing to rise. The accompanying table shows that the capital costs in primary copper production have risen faster than the cost of living. Of particular note is the capital charge of over $1.70/kg (77411b) required for a new, fully integrated facility in 1981. Thus, the mid-1982 copper price would not even cover the cost of capital for a new copper producing complex without considering the direct operating costs for such a facility. The breath-taking costs of new mining projects are caused by factors such as increasingly complex technology, the rising social costs of creating attractive living and working conditions for employ¬ees, and the expenditures re¬quired for environmental protec¬tion. For whatever reasons, how¬ever, unit capital costs in mining continue to exhibit staggering growth rates. Future Economic Conditions Risk is not only a function of the size of the potential loss-an im¬portant measure of which is the capital intensity of mining dis¬cussed above-but also of the like¬lihood of incurring the loss. It is here that the ever increasing lead times of mining projects and the glaring limitations of economic forecasting are so important. In comparison to nearly all other in¬vestments, mining has more capi¬tal at stake for a longer period of time before commercial uncer¬tainty is resolved by distant eco¬nomic conditions that are subject to high forecasting errors. A sobering example of the pre¬ceding points occurred with the Lakeshore copper mine in south¬ern Arizona that Hecla Mining Co. undertook to finance and manage in 1969. The project was a joint venture of Hecla and the El Paso Natural Gas Co. and included two mines-one producing oxide ore and a second in the sulfide zone¬and a complex processing facility producing both electrowon cop¬per cathodes and copper precipi¬tates. The project originally was

Jan 12, 1982

By P. Walshe

A common belief among Itlnl.ng operators today is that computer based truck m:mitoring and dispatching systems are only applicable to, or affordable by, very large scale open pit mines. Before the advent of microcomputer technology this belief was generally a valid one. Microcomputer technology as it currently exists has reached a high level of sophistication and capability, rapidly approaching that of the minicomputer standard. When coupled with reliable software and data communications packages, it now provides the means to make truck monitoring and dispatching a viable and attractive management aid to mines of all sizes. This paper briefly addresses the evolution and current state of computer truck dispatching and examines a microcomputer based system in this context. To demonstrate the effectiveness of this approach to truck dispatching a recent installation in a medium sized mine is presented. Preliminary field data from the case mine are presented to illustrate the methodology.

Jan 1, 1989

By R. J. Sawyer

*An earlier version of this paper was presented at the IMM meeting, "Use of Cultivated Carbon in Extraction of Gold and Other Metals," held in London in January, 1983, and was subsequently published in Trans. IMM (Sect. C: Mineral Process. Extr. Metall.) in December, 1983. Reprinted with permission of The Institution of Mining and Metallurgy, London. INTRODUCTION This paper describes the development of the processing route for the Alligator Ridge Mine which commenced operation in 1980. It also reviews the modifications which have been made to improve operating efficiency during the three years that the mine has been in production. Alligator Ridge is located 70 miles Northwest of Ely, Nevada. The mine is a joint venture between Amselco and Nerco with Amselco acting as operator. The deposit consists of micron sized disseminated gold imbedded in siltstone. Although definitive conclusions have yet to be drawn as to the age and origin of the deposit, it is probable that it is young by geological standards, perhaps only 5 million years old. It is likely that the gold was brought to the surface by hot springs. As the superheated solutions rose through the porous siltstone, they redeposited minerals in the rock, forming the present ore bodies.

Jan 1, 1984

By K. Nielsen

This paper is based on two recently (2002) published reports: - "Breaking New Ground". Final report on the Mining, Minerals, and Sustainable Development Project (MMSD). - "2002 Sustainability Reporting Guidelines". Published by the Global Reporting Initiative (GRI). The GRI guidelines can be applied in all kinds of industries and other organizations, whereas the MMSD project report is sector specific. However, both reports center on the three pillars of sustainability. The performance indicators as they are presented in the GRI guidelines have been assessed and compared with the sector specific arguments in the MMSD report. Based on this evaluation, the paper points at some indicators that may be useful in the start-up phase of sustainability reporting, seen from the perspective of the aggregate industry in an industrialized North European country with increasing environmental awareness and pressure on natural resources.

Jan 1, 2003