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By R. Dorey

The Kennecott Ridgeway Mine in South Carolina is scheduled to complete mining and ore processing in the last quarter of 1999. Tailings are disposed in a 300 acre, lined tailings impoundment. To facilitate closure and reclamation, modification of the tailings impoundment operation has been adopted. Mining involved the sequenced development of two open pits. In 1996 mining of the South Pit was completed and backfilling of the pit with waste rock from the North Pit was initiated and will continue until mining ceases. Both pits will be reclaimed as fresh water lakes. This paper presents the physical, geochemical and hydrogeochemical evaluation of the operational and post operational management of the project. Comparison of the operational monitoring data against predicted performance is reviewed.

Jan 1, 1999

By S. Dubnewych, S. Kieffer, M. T. McRae, R. R. Redd

The seismic vulnerability of the existing outlet tower at Lake Mathews reservoir, located in Riverside County, California, necessitated the design of a new outlet facility to assure serviceability of the facility following a major earthquake. The components of the proposed facility include: a new outlet tower; a shaft; a new outlet tunnel; an approach channel that will be excavated underwater; and two short tunnels that will connect the new outlet tunnel to the existing outlet tunnel via the shaft. As the new facilities will be constructed while the reservoir is in operation, a cofferdam will be constructed around the site of the new outlet tower. The design for the underground facilities used a combination of empirical methods; limit equilibrium analyses, including displacement-based pseudo-static analyses for dynamic loading conditions; and numerical analyses. This paper outlines the design methodology used to develop an innovative design for the facilities which can be constructed within the time frame required by the operational schedule of the reservoir and existing outlet facility.

Jan 1, 1999

By John C. Nichols

The Ouachita, Ozark-St. Francis, and Mark Twain National Forests are located within the Ozark and the Ouachita Mountains regions of southern Missouri, central and northern Arkansas, and eastern Oklahoma- an area generally referred to as the Ozark-Ouachita or Interior Highlands. These national forests share many similarities in geography, biotic resources, and areas of shared public, market, and user interests. The three national forests have joined together to evaluate the natural resources within the Highlands and to study the impacts of the forests on local and regional economies and on the people who use these national forests and their resources. Other federal, state, and local government agencies and universities have joined with the Forest Service in this project, broadening the assessment area beyond the national forest boundaries to include 107 counties in Arkansas, Missouri, and Oklahoma. The diverse, resource-related data for the as- sessment area address social, economic, terrestrial, and aquatic issues and conditions throughout the Highlands. The assessment report currently is being developed by the Forest Service and will include an accoMpanying CD-ROM. The Ozark-Ouachita Highlands assessment has provided a forum for minerals- and geology-related resources, industries, social significance, and potential to be profiled and discussed along with other critical assessment resources. The state geological agencies in Arkansas, Missouri, and Oklahoma were active contributors to this effort. Their reports and other key data bases developed and used for the minerals sections of the published assessment report will be available either as a supplemental CD-ROM or on the Internet. Updated information on the progress of the assessment report can be found at the Ouachita National Forest Website, at <http://www.fs.fed.us/oonf/ouachita.htm>. This will also include a matrix displaying the minerals in the assessment area, their occurrence by assessment-area counties, and a potential ranking, as well as information on interesting geologic features. The state and federal reports, resources, and data bases, have helped answer key questions concerning mineral resources and related issues in the Highlands:

Jan 1, 1999

By C. Strachan

This paper presents an evaluation of tailings dam incidents from the 1994 USCOLD Tailings Dam Committee report. Comparisons are also made with water storage dam incidents from USCOLD reports and recent tailings dam incidents. The evaluation results show that tailings dam incidents are due to a number of factors including overtopping, static and seismic instability, seepage and internal erosion, and foundation conditions, and that no particular type of tailings dam or operational condition is more susceptible to incidents. In addition, the results confirm that tailings dams should be located, designed, operated, and reclaimed with a thorough knowledge of site conditions, mill operation, site monitoring, and tailings characteristics.

Jan 1, 1999

By Bruce Gellar

In March, the Prospectors and Developers Association of Canada (PDAC) held its annual conference in Toronto, Ontario. This is the third PDAC meeting the author has attended. The following are some impressions of the meeting. And the author looks forward to the joint meeting of the PDAC and the Canadian Institute of Mining, Metallurgy and Petroleum to be held March 5-10, 2000, entitled Mining Millennium 2000. One of the features of next year’s gathering is a proposed forum of world mining ministers, the first ever to be held anywhere.

Jan 1, 1999

By Larry Taylor, Thomas Zdeb, Brian Jacobs, Dennis Jensen

Subway tunnels proposed for the Los Angeles County Metropolitan Transportation Authority (LAMTA) East Side Extension are to be excavated below the groundwater through an area of Los Angeles, California with dissolved hydrogen sulfide concentrations in excess of 200 mg/L. To address unique construction and worker safety issues, bench scale and field pilot test studies were conducted to evaluate various mitigation alternatives including in-situ oxidation by chemical injection, slurry pH adjustment to suppress H2S evolution, and chemical treatment to remove the H2S from the slurry and muck material. The results provided the basis for detailed hydrogen sulfide control specifications for the contractor.

Jan 1, 1999

By K. A. Dudley

Basic solvent extraction theory indicates that pH initiates the basis of an oxime&apos;s metal complex formation and therefore its selectivity toward certain metal species. The recommended optimum pH for some of the commercial copper reagents is in a range that should maximise copper loading of the oxime. However, this pH range also tends to maximise iron(III) loading under certain operational conditions resulting in low selectivity values. Recent operational parameters at Girilambone Copper Company have highlighted some of these conditions that have a major influence on the oxime&apos;s selectivity for copper over iron(III) in the leach solutions. The result is that the pH for maximum copper extraction is no longer within the optimum range to maximise oxime selectivity. Therefore, specific copper and iron(III) pH isotherms have been determined on-site for the changing leach solutions that are fed to the solvent extraction plant in order to optimise oxime selectivity. The influences of solvent extraction plant configurations are also discussed as a controlling parameter.

Jan 1, 1999

By D. W. Park

Geologic condition is one of the most important factors for longwall mining operations, especially, the existence of faults limits the mineable area, or cause stress variations at the longwall face. Recently, a longwall panel passed through a fault at the Shoal Creek Mine of Drummond Company, Inc. The fault was situated diagonally along the longwall face and the coal seam was displaced up to 2.4 m (8.0 ft) in a mode of a normal fault. LoSCoMS (Longwall Strata Control and Maintenance System) was used for monitoring shield pressure every minute and interpreting data in terms of setting, developing and final pressures. The results of the analysis regarding the influence of the fault on the shield pressure are presented.

Jan 1, 1999

By Alex Cormode, Carlos Perucca

"Sylvinite ore from the Saskatoon area typically contains about 5% insolubles, occurring as clays and carbonates. These insoluble slimes must be removed sufficiently well to permit an efficient subsequent potassium chloride flotation, due to their high adsorptive capacity for amines used as potash collectors. The insolubles are liberated from sylvinite by high attrition scrubbing in a slurry. The liberated slimes are separated by multistage cycloning or by a selective flocculation-flotation process.An outline of the potash processing operations at Agrium Vanscoy Potash Operations is given, emphasizing the insoluble slimes froth flotation separation process. This process was originally implemented at the Agrium plant in the mid- 1970's and replaced a hydrocyclone system.IntroductionAgrium Vanscoy Potash Operations is located 40 Km southwest of Saskatoon, almost midway between the communities of Vanscoy and Delisle. Processing operations started in 1969, and the annual production capability was subsequently increased to the current 1.8 MM tonnes per year of muriate of potash.The mining operation at Agrium Potash which was described in a paper by Jones and Pruggerl , is done underground using four large continuous double rotor boring machines for the main production with development done by heliminers. Annual ore production is 5.5 MM tonnedannum. Ore is hoisted 1,100 m to surface for processing."

Jan 1, 1999

By Hingant Pierre

The Hurtières Tunnel was built in 1995 with drill and blast method, in metamorphic schist. It is located between Lyon and Torino on the A 43 motorway in the French Alps. During the construction, a geological hazard was encountered, which caused a massive ground collapse. The tunnel was filled up with 3,000 m3of glacial materials. Geological investigations realized after the accident showed that a narrow glacial valley was present at this location the water table was 40 m above the tunnel level. The paper will describe the collapse and the remedial methods which were implemented to proceed through the failure area. These included drainage works,2,000 m3 grouting and 6,200 ml jet grouting columns.

Jan 1, 1999

By Helga Larravide

A new on-line database of literature about copper has been created through a joint undertaking by the Copper Development Association Inc. and PROCOBRE-Chile, with funding provided in part through the International Copper Association, Ltd. The new database will permit Spanish-speaking technologists to access publications maintained by PROCOBRE-Chile by means of standard keyword searches. In addition, a new Spanish- English thesaurus has been written to enable Spanish-speaking individuals to search d access the Technology and Environmental databases of the Copper Data Center, which together comprise more than 80,000 publications dealing with the production, properties, uses and environmental effects of copper. Planned expansion of the new Spanish literature database is described.

Jan 1, 1999

By Bryan J. Lane, Paul N. Worsey

The recommended maximum explosive weight for boulder blasting using internal charges is 0.1 O-kg/m” (3.5 oz./yd) (Olofsson, 1988). Normally this charge results in excessive scattering and flyrock, creating increased liability for the operator, especially in congested areas. An alternative technique using smaller explosive charges is being developed at the University of Missouri - Rolla. It is designed to reduce boulder scatter, flyrock and fumes and allows shooting in close proximity, using common blasting products.

Jan 1, 1999

By Denghong Wang

Abstract- The Ashele Cu-Zn deposit is a recently discovered volcanogenic massive sulfide deposit in Xinjiang, China, hosted by Lower to Middle Devonian submarine bimodal volcanic rocks. The primary ores of this polygenetic deposit are represented by massive syn-depositional pyrite, chalcopyrite, and sphalerite, and were formed by submarine exhalation. Hydrothermal alteration consists of strong sericitization, chloritization, silicification, and carbonatization of the metavolcanic rocks beneath the massive orebodies. Depletion of Na2O is an obvious chemical change in the hydrothermal halo. Geological and geochemical evidence suggest that the Ashele Cu-Zn massive sulfide deposit was formed by submarine exhalation related to bimodal volcanic rocks, trapped in a rifting basin, then deformed by shearing, and thermally metamorphosed by the intrusion of dacitic porphyry. Sulfur and lead isotopic studies indicate that metals such as copper and zinc may have originated from spilites, but that volatile components, especially sulfur, were derived directly from submarine volcanic magmas.

Jan 1, 1999

The Khanong supergene-enriched copper resource, (~23 Mt at 3.0 per cent Cu), is one of several resources recently discovered in the intrusive-centred, sediment-hosted Au-Cu Sepon mineral field located in southern Lao PDR. The unusual style of hypogene mineralisation and unique set of conditions have resulted in the development and preservation of a supergene-enriched profile in this subtropical climate. Hypogene sulphide-rich mineralisation replaced calcareous cataclastite (fault rock) developed in the flat-lying, extensional, Khanong Fault. Spatially, the hypogene mineralisation was immediately out board of the skarn û hornfels Cu-Bi front and in board of sediment hosted Au-(As-Sb) mineralisation in a zoned intrusive-centred hydrothermal system. In situ supergene enrichment of the sulphide protore has resulted in a high-grade chalcocite-clay zone (~10.3 Mt at 4.6 per cent Cu) overlain by leached limonite-clay. A very high-grade in situ to exotic limonite-clay Cu-oxide-mineral zone is locally developed above impermeable dolomite at the base of chalcocite-clay zone. Exotic Cu-Mn-wad mineralisation developed for up to 1 km down the hydraulic gradient from the chalcocite-clay zone. Unique supergene enrichment conditions have resulted in the high-grade Khanong Cu resource in a subtropical weathering environment. The base of the currently active supergene profile coincides with the base of a flat-lying, pyrite-rich fault rock, dipping parallel to the hill slope, maximising Cu enrichment. Meteoric water has been channelled along subvertical faults and narrow horizontal subsurface zones. Low permeability of the fault host rock and footwall rocks has controlled the low volume and slow movement of groundwater required for supergene enrichment. Erosion has been slowed by the resistive ironstone and limonite-clay layer at surface, which assists in preserving the gentle slope over the chalcocite-clay zone.

Jan 1, 1999

Geophysical surveys are currently being carried out over mineral prospects all around the Pacific Rim. Many of these surveys are successful in locating mineralisation in porphyry intrusives, mesothermal environments, and epithermal vein systems. A number of examples of surveys in Indonesia and Papua New Guinea are presented, which show the successful application of various geophysical techniques to the discovery of mineral deposits on the Pacific Rim.

Jan 1, 1999

By Sibley C. Burnett

Early attempts to apply superconductivity to the beneficiation of kaolin required very large refrigerators to remove the heat generated during rapid charging and discharging of the magnet. In the early 1990&apos;s, Advanced Cryo Magnetics, Inc. developed and patented methods to reduce this pulsed heating by a factor of fifteen. Small, helium refrigerators and cryo-coolers are now used. Along with savings in electric power, superconductivity allows operation at higher magnetic fields and greatly improves separation process efficiency. New designs offer enormous reductions in weight, size and capital cost as compared to older copper magnets. Application of this technology to minerals other than kaolin is emerging.

Jan 1, 1999

The history of mining is rightly proud of its achievements in improving productivity and cost improvements over the years. No matter what measure is used, tonnes per manhour, cost per tonne, etc vast improvements have been made over the last hundred years. In fact over the last ten years in Australian coal mines raw coal output per employee has increased by 60 per cent. When one examines why these improvements have taken place the principal reasons have been technological advancement in mining equipment, excavator and dump truck capacity increases, longwall and continuous miners continually improving in reliability and size. Of course all these improvements are correlated to an increase in capital cost. Even with the above-mentioned advances the pressure for increased performance is as strong as ever. The international mining and mineral-processing sector is currently operating in a recessive market with some traditional commodities, eg gold trading at 20 year lows. During recessive times senior management will demand greater returns on capital employed: the obvious choices being reducing costs or increasing throughput. In addition, head office environments will often place a capital freeze on operational management so the opportunity to take advantage of technological change is not available. The challenge is, therefore, to increase throughput and cut costs without the need for capital. The answer is to optimise the existing labour and plant. If done systematically a result in productivity improvement, in our experience, as high as 45 per cent can be achieved with the average across South East Asia and Australasia being 21 - 23 per cent. The intention of this paper is to present a systematic approach to labour and machine utilisation thereby gaining the greatest possible return on the existing capital base.

Jan 1, 1999

By R. Filippone, Donald Leroux, Colin Hardie, G. Leichtle, Cesar Gomez, Jim A. Finch

"Bubble surface area flux (Sb) is the surface area of bubbles per unit time per unit cross-sectional area of flotation machine. The units are: (m2 bubble surface/s)/(m2 cell) or s -1. For bubbles of mean size db (m), s b = 6-Qg/A db where Qg is the gas rate (m3/s), and A the cell cross-section (m'). This parameter is now receiving wide attention as the possible key machine variable in flotation diagnosis and modelling. The concept is described and the potential use of sb is illustrated by work on flotation columns and mechanical cells. In column flotation of recycled paper, the dependence of ink recovery on s b was the same regardless of size of column or type of sparger. In mechanical cells, it has been established that the rate constant is related to Sb independent of impeller type.The use of s b is limited by the problem of measurement, primarily that of estimating db. A prototype probe designed to estimate db (and hence sb) based on conductivity measurements is described. Exploratory work with the probe in a mechanical cell suggests the promise of making estimation of s b routine.INTRODUCTIONFlotation is the result of interaction among variables associated with the feed particles, chemistry and the machine (flotation cell). Trying to isolate the effects of each aids in process diagnosis and is at the centre of attempts to model flotation. The machine variables that have been investigated include the air flow number, the power number and specific power (Harris, 1976). None have survived as the basis for predicting flotation response perhaps because they did not include directly the properties of the bubble swarm (or dispersion). Recently, Gorain (1 997) explored the relationship between the flotation rate constant and various ""gas dispersion"" parameters notably: superficial air rate (Jg = Qg/A, where Qg is the volumetric gas rate and A is cross-sectional area of cell), bubble size (db), gas holdup (Eg, i.e., the volumetric fraction of a cell occupied by gas) and bubble surface area flux (sb = 6.Jg/db). Of them all, Gorain et al. (1997) conclude that the latter, the surface area flux, correlated best with the flotation rate constant. This concept was adopted from column flotation where it was used to estimate, among other factors, the maximum amount of gas that could be injected (Finch and Dobby), 1990). Let's start by reviewing the concept. Following that some examples of where the concept has been applied will be described to illustrate the current interest and finally we will consider how to measure the surface area flux."

Jan 1, 1999

By S. A. Beeson, C. Poole

This paper describes the development of a novel selective flocculation technique for recovering phosphate values from ores containing silicate or carbonate gangue minerals. Data from initial flocculation response and reagent adsorption studies on component mineral suspensions and synthetic mixtures were used to assess the influence of various process parameters (e.g., reagent dosages, particle size, solids concentration, and conditioning regimes) on single-stage selective flocculation tests involving natural silicate and carbonate ores. In these tests a high degree of selectivity was achieved using low dosages of a low-molecular-weight cationic dispersant and a mid-range molecular weight cationic flocculant. Testwork was then extended to the evaluation of several floc recovery systems (sedimentation, hydrocyclones, and floc flotation) in a multi-stage process involving redispersion and reflocculation. Results from these tests clearly demonstrated the feasibility of producing marketable phosphate concentrates from both ore types.

Jan 1, 1999

By J. E. Friant

The Mini-Disc TM cutter drill bit is a radical design departure from the traditional tri-cone rock drill bit. Miniature disc type cutting tools as small as 3.25 inches (82.5 mm) diameter are fitted to a bit body to cut individual concentric kerfs. The action is the same as that commonly used on large tunnel boring machines but miniaturized. The high performance rate and efficiency of a disc cutter are the result of producing a large proportion rock chips rather than sand or powder. The Mini-Disc TM drill bit, referred to as the "Disc Bit" has other unique features as well. It can be re-greased between runs. It can be rebuilt in the field in about 15 minutes, cutters can be replaced and the Disc-Bit appears to require less down hole hydraulic power than conventional bits. Thoroughly tested in the laboratory, the bit has recently been undergoing field trials in well drilling, blast hole drilling and shaft drilling. As any engineer knows, the laboratory cannot shake out all the problems but it eliminates the more glaring weaknesses. Performance results have been exhilarating, and a few mechanical problems were discovered and largely overcome. This paper is a progress report.

Jan 1, 1999