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By P. N. Psarropoulos

During many strong earthquakes in the past, a significant number of tailings dams failures has been recorded, leading in some cases to human life losses. However, over the last decades, seismic design of tailings dams has drawn much attention mainly due to the high environmental hazard. Although the stability of such geostructures under dynamic loading is mainly related to their liquefaction potential, there exist several technical issues that have not been adequately investigated. One of these issues is the impact of local site conditions on the dynamic earthquake stresses developed, and therefore on the inertial instability of these dams. Based on the models examined in the first part of the present study (Stability of Tailings Dams ? Part I: Static Loading), two-dimensional numerical simulations are performed in order to examine the effects of local site conditions in the dynamic response of tailings dams. Imposing dynamic loading via characteristic pulses and real earthquake records, the most commonly used types of construction methods are studied at their final stage. Emphasis is given on the special characteristics of the ground motion, while the material nonlinearity of both soil and tailings is taken into account by an equivalent-linear procedure. The results obtained indicate that local site conditions may have a significant impact on the seismic response of a tailings dam.

Jan 1, 2005

By R. Hogg, M. Polat, S. Chander

A fresh dust generator was designed and built in order to study the agglomeration behavior and other characteristics of freshly generated airborne dust. The size distribution of the freshly generated quartz airborne dust produced by the generator was measured both directly in air and after dispersion in water. It was observed that same dust particles had an apparently coarser size distribution in air than in water, suggesting possible agglomeration of the dust particles. It was also observed that the size distribution obtained by a cascade impactor was very similar to the liquid dispersed size distribution, implying deagglomeration by the impactor. The agglomeration was confirmed by microscopic observations of particles in air and those collected on a microscope slide. The extent of agglomeration played a decisive role on the fraction of the dust actually becoming airborne. It was also found that contamination of the airborne dust by the rolls of the crusher was almost twice as much as that of the product.

Jan 1, 1991

By I. Tsolas

Sustainable development is becoming increasingly more important for the mining industry and therefore mining companies should be able to measure their progress towards sustainability. Greek Public Power Corporation (PPC) S.A. is a company which produces lignite in open cast mines in Western Macedonia and in Peloponnesos. The present paper uses operational data kindly offered by PPC S.A. to derive sustainability indicators by means of Data Envelopment Analysis for three large scale lignite open cast mines of PPC (i.e. Main Field, Kardia Field and South Field mines). It also examines three environmental parameters related to the contribution of these mines to sustainable development; namely, the annually produced volume of waste masses, the annually produced quantity of ash from the lignite combustion and the annual volume of pumped water. The calculated sustainability indicators were keeping constantly better during the last years of the different periods for each one of mines studied here, showing that the mines met their goals from both economic and environmental aspects during the last years of their operational periods studied. The contribution of open cast lignite mines studied here to sustainable development can be monitored by the derived indicators analyzing annual mine operational data. The derived indicators can serve as tools to detect where improvements can be made, though another potential use of these indicators can also be during the preparation of feasibility studies or environmental impact studies using necessary benchmarking data.

Jan 1, 2007

By Ernest Peters, Fiona M. Doyle

The leaching and bulk decomposition of sulfide minerals is of enormous commercial importance in several areas of the minerals industry. These include: direct leaching of ores or concentrates for the recovery of the contained metal values; decomposition of sulfides to recover associated values such as encapsulated gold; and the potentially hazardous oxidation of sulfides in waste disposal facilities. A significant challenge to successful future developments in these areas is to improve our fundamental understanding of the mechanisms of the chemical, electrochemical, and bacterially-mediated interactions between sulfides and aqueous solutions. The paper summarizes current understanding of these mechanisms, and discusses promising new directions for research.

Jan 1, 1989

By Mahesh C. Jha, Frank J. Smit

Column flotation and selective agglomeration are promising advanced physical cleaning processes that can be developed for preparing premium quality coal-water slurry fuel from coal fines. Such a fuel could either replace oil or natural gas in certain industrial and utility boilers or else could be burned in advanced combustors currently under development. These applications require coal cleaned to sulfur and ash contents below 258 g/GJ and 430 - 860 g/GJ (0.6 lb/million Btu and 1 - 2 lb/million Btu), respectively, to meet clean air emission requirements. A highly loaded slurry must be produced in order to avoid derating the boilers, and the total cost of the fuel must be below $2.37/GJ ($2.50/million Btu) in order to penetrate the market by the turn of the century. Achieving these technical and economic goals depend critically on the selection of suitable feed coals. This paper describes the identification and evaluation of 18 coals and final selection of six coals from different regions of the United States as potential feedstock for preparation of premium fuel. The work is being performed under a cost-shared DOE project.

Jan 1, 1995

By Douglas J. Piper

On reflection of certain overall circumstances which have pervaded the gold mining industry, it appears useful to point out some specifics which the writer hopes will improve the potential for success in the application of hydraulic dredges to gold mining activity. I will, prior to entering into that discussion, comment briefly on rule of thumb for the application of the three types of equipment. The three are bucket line, bucket wheel and drag line dredges. From a standpoint of high volume movement over a short distance, between 50 and 300 feet, the drag line dredge is historically the most cost effective type of machine to be utilized if bulk excavation is the single driving consideration. It is typical for this sort of equipment to operate in the 10 to 30 cents per cubic yard range, however, cost of operation is not the sole consideration. Typically the drag line mixes and remixes the material which it excavates. In the event that gold recovery is the object of the exercise, a strong potential for loss of the valued mineral exists. Additionally, drag lines do a poor job of bottom cleaning, particularly if there is a ridged or creviced bottom which must be cleaned and in some cases partially removed to assure recovery of the highest percent of valuable ore. The bucket line dredge has, until recently, been considered an extremely cost effective device. However, the high cost of manufacture of this type of equipment has mitigated against its use in the majority of

Jan 1, 1992

By B. L. Gibbs

Computers have been used in the minerals industry for about 30 years and, in a few cases, longer. With the explosion of microcomputing during the past 10 years, computers have changed how many minerals producers go about their work. What computer usage trends are active in the minerals industry today, and what can we expect in the future? In general, computer usage is accelerating. Engineers and geologists are becoming increasingly "application literate." Soft¬ware is increasingly oriented to how people work. User interfaces have improved, so most users need to know only a mini¬mum of system commands and structure to work with a computer. Most industry professionals know how to use word processing and spreadsheet pro¬grams. AutoCAD appears to be the drawing program of choice. One reason is availability of training and add-on programs for earthwork, mapping, contouring, etc. Another frequently cited reason for using CAD is the ability to quickly make changes to a map or design, as compared to hand methods. Management is moving toward greater acceptance of computer usage. Computers do not need workman's compensation ... even though they may get sick and take a few days off! Computer hardware used in most minerals-producing companies is strongly personal-computer based and likely to remain so. The 486 personal computers are inexpensive as compared to workstations and provide the power and speed to run most applications in minerals industry engineering offices.

Jan 1, 1994

By J. E. House

Creative ideas and endeavors require imaginative and positive responses, if they are to be reduced to practices. This lecture will define the plurastic roles of various technical disciplines which were important in the development of the LIX reagents. Specific personalities, facts, and events will be used to trace the development from an idea, to the exciting acceptance and practice of the technology. An objective analysis of the entire LIX reagent development, spanning twenty-five years experience of the author, will be given, these will be used as a basis for critical examination of how the various technical disciplines could improve their effectiveness in advancing future technologies.

Jan 1, 1990

By B. J. Arnold, F. F. Aplan

Prior laboratory work has demonstrated that much of the fine ash forming minerals entering a flotation froth are there as a result of water carryover- from the bulk contents of the flotation cell (Arnold and Aplan, 1986a). Using a bank of four 8.5 m3 (300 cu ft) Wemco flotation cells cleaning a well-liberated Lower Kittanning seam coal, test results show that the sulfur and ash content of the froth is directly related to the water content of the froth (or inversely related to the percent solids in the froth). Reagent changes that result in a watery froth produce a higher ash content in the froth. A direct comparison of laboratory and plant results show that the standard laboratory flotation test produces a product higher in sulfur and ash than that produced in the plant. Caution should be exercised when extrapolating laboratory test results to the plant situation. A method of estimating coal flotation product quality in the plant based on laboratory tests is given.

Jan 1, 1991

By Meliton M. Garcia, Satya Harpalani

The volume of gases produced in major and trace amounts as a result of detonation of explosives in an underground mine was determined. The volumes of major gases (CO, CO2, NO and N02) were measured immediately following detonation, during the mucking operation, and following the removal of muck. Tests to identify and quantify the gases produced in trace amounts were performed following the detonation only. The composition of the gases produced varied significantly depending on the composition of the explosive/blasting agent. An average of 95% of the gases produced were found in the test chamber immediately following the detonation, while 2% was found in the chamber following the removal of the muck. Several compounds were identified in trace amounts. Of particular interest was the detection of benzene, toluene, butenes, ethyl benzene and naphthalene since exposure to some of these compounds, even in trace amounts, could present a serious health hazard.

Jan 1, 1987

By Solomon S. Katz

As more and more computer software is written for geological mapping applications, the users of the software are discovering the problems of transferring data between the programs, maintaining correct data and integrating maps produced last week with those produced today. One way to deal with these situations is by using a geographic information system (GIs). Last September the USGS and National Academy of Science held a 5-day GIs symposium on integrating technology and geoscience applications (USGS, 1988). It was followed in October by GEOTECH '88 (Peters and Krajewski 1989) which had a session exclusively for GIs applications in the Geo-Sciences. Editorials in Geobyte (Leonard, 1986, 1988) suggested that geographic information systems will be the next major computer programs to be adopted by the mineral industries. As far- back is 1985, the Computer Oriented Geological Society (COGS) printed An Introduction to GIs in their newsletter (Katz, 1985). About 20 years ago, a revolutionary idea occurred in the world of business data processing. It was the idea that all related data be stored in a standard format, in a single place and that all related computer application programs would use the same data.

Jan 1, 1989

By Th. Petropulos

The Zn-Ag-Pb mineralization zone near Molai (Greece) was explored by more, than 60 drillholes. Promising results led to the decision of additional drillholes in order to confirm the expected spatial extension of the deposit. A multiobjective approach is described which optimizes the location of a set of 5 additional drillholes. The decision is based on estimation errors for grade, thickness and depth of the main ore bearing layer, with respect to cut-off values for grade and thickness. The linear combination of these variables defines a favorability index which is used for mapping optimal drillhole locations. The map shows several clusters of favorable cells. A declustrering algorithm is used to select a representative cell for drilling in each cluster.

Jan 1, 1989

By A. S. C. Owili-eger

An efficient state-of-the-art dynamic model to simulate and predict the rate of water production in longwall coal mining operations was developed as a tool for mine planning purposes. The model can also provide an estimate of any potential resultant hydrogeological impacts of an operation via an array of element-specific single-valued parameters referred to as the field rating indices. The computational procedure was designed to fully exploit the benefits of hydrogeotechnology and use a combination of conceptual, physical, empirical, and numerical approaches to define, characterize, analyze, and evaluate flow controlling properties of fractured rock systems. The model presented here provides a dynamic prediction method for highly fractured flow; a practical tool in mine and water control planning; and a cost-effective means of assessing, based on the best available technology, the impacts of mining on the water resources within a mining environment to satisfy local and federal regulatory requirements. Unique features include consideration of laminar and non-darcian flow domains in double-porosity-pressure hydrogeological media.

Jan 1, 1990

By K. Burke, G. Zhan, A. Mayer

A cover with capi1lary barrier effects (CCBE) is being constructed an the AA leach pad at the Barrick Goldstrike mine near Carlin, Nevada. The purpose of the cover is to eliminate/minimize infiltration of meteoric waters into the leach pad. Laboratory and numerical analyses indicate that Carlin Formation siltstone (TCS), a locally available material, has the necessary hydrologic characteristics when placed on the leach pad to act as a CCBE. A pilot study was conducted on a mall-scale test cover placed on the AA leach pad to examine the cover performance under irrigated conditions. The preliminary test results demonstrate that the designed cover is capable of preventing meteoric water infiltration.

Jan 1, 2002

By R. I. Pennington, J. L. Vanderbeek

Investigations have been conducted at Chino Mines Co. into the effect that SAG mill recycle material (critical size) exerts on SAG mill throughput and specific energy requirements. Tests were conducted on laboratory, pilot, and plant scales to evaluate the merits of alternative treatment options. Removing critical size material from the SAG mill circuit has been shown to improve new feed rates by 84% with a reduction in specific energy (kWh./t) of 88%. Test results obtained to date are presented.

Jan 1, 1987

By R. J. Sweigard, G. T. Lineberry, B. K. Slone, F. A. James III, D. S. Maggard

The depth at which it becomes more economical to use slope access instead of box-cut access for nearsurface coal reserves is termed the "transition depth." The transition depth can be established for a given coal property by considering cost estimates for those parameters that determine respective access methods. Fourteen parameters that influence access cost were identified, and ranges for these parameters were determined. A transitiondepth formula was developed to permit the determination of which is the better method of accessing a reserve, given information such as high wall slope, road width, total bench width, pit dimensions, road grade, belt component costs, pumping costs and the cost of overburden removal and reclamation. In most cases in Appalachia, especially in eastern Kentucky, the observed transition depth ranges from 20 to 30 m (66 to l00 ft). This indicates that actual practice is consistent with the analytical approach used.

Jan 1, 2002

By R. A. Kirkland

The oxygen consumption method utilises an oxygen sensor to monitor the gas-phase oxygen concentrations in sealed chambers filled with reactive waste rock with subsequent confirmation of the oxygen content by gas chromatography. Results of experiments utilising low sulphide (<0.5w1%) waste rock yielded reproducible oxygen consumption rates on the order of 10-10 mol O2.kg-1. s-1. Petrographic analysis of the waste rock material indicated that the dominant sulphide mineral is pyrite (FeS2). Assuming a stoichiometry of 1.75 moles of O2 per mole of SO4 sulphate release rates were inferred to be between 6 and 18 mg SO4 kg-1 wk-1 Typically these results are 2 to 3 times greater than measured sulphate release rates from humidity cells. Our findings suggest that this techniques offers a rapid. cost efficient method for determining sulphate release rates in waste rock piles, even at low sulphide concentrations.

Jan 1, 2000

By Jack Parker

Pillar design ought to be a matter of matching pillar strength against pillar loading conditions to come up with dimensions that will cause the pillar to behave as required - to stand forever, or for a limited time, or to fail in a controlled manner. But something has gone wrong in recent years, seriously wrong. Pillar design practices have departed from reality. The laboratory and computer have taken the place of the mind. If the mind is put to work and such pillar design practices are examined critically, it becomes obvious that they deal with conditions that do not exist in a real mine. Time, effort and money are wasted, and the end results are incorrect and misleading. These questionable pillar design practices have been passed on from generation to generation over the past 30 or 40 years. The hope here is that we can return to reality as soon as the questionable practices are generally recognized. We could then go back into the mines and define how pillars really work, and mining safety, efficiencies and costs should improve. Let us take a close look at current textbook design practices and compare them to real-life conditions. Common sense might then prevail. (At this time, we will consider only mine pillar design, but similar scrutiny should be applied to design criteria for width of openings, floor conditions and roof support systems.)

Jan 1, 1993

By J. J. Moore, I. Iwasaki, L. A. Lindeke

Correlation of scale-up from small-scale batch laboratory mills to large-diameter industrial mills was established by performing two series of laboratory and pilot plant grinding tests using a magnetic taconite ore and a siliceous sulfide ore. In one series, controlled batch grinding tests in 203-, 508-, and 914-mm (8-, 20-, and 36-in.) diameter mills were carried out followed by a second series involving continuous grinding tests using 305-mm (12-in.) and then 1067-mm (42-in.) diameter pilot plant ball mills in open circuits. The effects of ball diameter on wear and of mill diameter on grinding power and ball wear are illustrated.

Jan 1, 1988

By Robert Mullen, Patrick K. Sollars

In 1994, Cyprus Twentymile Coal Company and Scandura formed a joint task force charged with the purpose of developing the highest rated fabric belt for underground longwall coal mining. This paper details the development efforts and concepts utilized by Cyprus and Scandura to meet the challenging demands of Twentymile Coal&apos;s East Mine District (EMD). The finished panel consisted of a 5,500 meter (18,000 feet) conveyor with 245 meter (800 feet) of drop over the first 3,660 meters (12,000 feet) and 245 meters (800 feet) of lift out-by over 1,830 meters (6,000 feet). The panel was designed with an operating capacity of 4,500 tph (5,000 stph) and 4.1 m/s (800 fpm) belt speed.

Jan 1, 1998