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By M. Ghoreychi, X. Daupley

ABSTRACT: The paper is devoted to two major aspects related to the abandonment of salt mines: 1)- Long-term risk associated with the mechanical instability of surface and its consequences for public security and properties. 2)- Long term dissolution and transport of salt resulting from its communication with groundwater. Basic characteristic features of salt deposits and mining methods are presented through the studies already undertaken on French mines. This analysis allows to identify major hazards encountered in different traditional salt mines and solution-mining cavities. In particular, the role of overburden (presence and thickness of salt layer in exploitation roof, presence of clayey rocks or hard rocks e.g. dolomite or anhydrite), presence of water-bearing strata and possibly natural brine levels, discontinuities, etc. are discussed. In the second part, the main features of mechanical behaviour of salt (creep, damage) as well as transfer processes of this material are presented. The influence of these aspects on the long term evolution of abandoned salt mines is then analysed. KEY WORDS: exploitation, abandonment, salt, mechanical, stability, transport, solution, brine. ZUSAMMENFASSUNG: Der Artikel bezieht sich auf zwei bedeutende Aspekte beim Salzabbau: 1)-Das langsfristige Risiko zur Bodenoberflächeunbeständigkeit und sein Einfluss über Mensch= und Gütersicherheit. 2)-Die langsfristige Auflösung und Beförderung des Salz beruhen sich auf Studien über französiche Bergbauen. Diese Analyse emöglicht es, die bedeutendesten Risiken in verschiedenen Salzgruben zu identifizieren, bzw. Traditionellen oder durch Auflösung abgebauten. Insbesondere wird die Rolle des Deckgebirges (Vorhandensein und Dicke von Salzschicht am Dach des Grube, Beisein von Tanlager oder hartem Gestein wie Bitterkalk oder Anhydrid), Beisein von wasserhaltigem Boden und/oder gesalzenen Wasserflächen, Trennflächen, usw… erötert. Im zweiten Teil werden die haupsächlichen Eigenschaften des Salzverhaltens (Kriechen und Beschädigung) beschrieben. Ihr Einfluss über das Verhalten von stillgelegten Bergwerken lässt sich analysieren. SCHLÜSSELWÖRTER: Bergwerksbetrieb, Stilllegung, Mechanik, Beständigkeit, Ausbreitung, Aussolung, Solewasser. RESUME: L’article est consacré à deux aspects majeurs liés à l’abandon d’exploitations de sel : 1)- Le risque d’une instabilité à long terme de la surface du sol et son incidence sur la sécurité des personnes et des biens. 2)- La dissolution à long terme et le transport de sel sous l’effet d’une communication avec des eaux souterraines. Les principales caractéristiques de gisements et d’exploitations de sel sont présentées en s’appuyant sur les études antérieures réalisées sur les exploitations en France. Cette analyse permet d’identifier les risques majeurs rencontrés dans différentes mines de sel traditionnelles ou exploitées par dissolution. En particulier, le rôle du recouvrement (présence et épaisseur d’un banc de sel au toit de l’exploitation, présence de terrains argileux ou de roches dures telles que la dolomie ou de l’anhydrite), présence de terrains aquifères ou de nappes salées éventuelles, discontinuités, etc. sont discutées. Dans la deuxième partie, les principaux traits du comportement mécanique du sel (fluage, endommagement) ainsi que les processus de transport de ce matériau sont présentés. L’influence de ces aspects sur le comportement à long terme d’exploitations abandonnées de sel est ensuite analysée. MOTS CLES: exploitation, abandon, mécanique, sel, stabilité, transport, dissolution, saumure.

Jan 1, 2003

By Paul Eger

The use of wetlands to treat mine drainage has become increasingly common, particularly as more information is available on their operation and construction. However, the lifetime of each system is still, at best, an estimate. Treatment lifetime depends on the types of processes that provide the majority of the metal removal. Anaerobic systems (vertical flow systems) rely primarily on sulfate reducing bacteria, which reduce sulfate to sulfide and generate alkalinity. Metals can be precipitated as sulfides, and acidity is neutralized. These systems can remove over 90% of the metals and increase pH from around 4 to over 7. The bacteria will remain active as long as the system remains anaerobic and contains an adequate supply of sulfate and small chain organics. Although estimates of lifetime made on the total carbon in the system suggest that lifetime should exceed 20 years, data from field and laboratory studies show that the rate of sulfate reaction decreases with time, and that after several years rates decreased substantially. To maintain acceptable treatment, either additional organic material must be added or the total metal and acid load to the system would need to be reduced substantially. Aerobic systems (overland flow wetlands) can effectively remove metals from neutral mine drainage by reactions with organic material in the substrate. Over 90% of the copper and nickel have been removed in aerobic systems treating mine drainage in Minnesota. The primary removal processes in these systems include adsorption, ion exchange and complexation, which are finite; removal will cease unless new removal sites are generated. Two wetlands built in Minnesota have been successfully treating mine drainage for 12 years. At one of the wetlands, the annual production of new removal sites has been estimated to be equal to the annual metal input, and, as a result, metal removal should theoretically continue indefinitely.

Jan 1, 2005

By Malcolm Ross

Asbestos crystallizes within rock formations undergoing intense deformation characterized by folding, faulting, shearing, and dilation. Some of these conditions have prevailed during formation of the taconite iron ore deposits in the eastern Mesabi Iron Range of Minnesota. This range includes the Peter Mitchell Taconite Mine at Babbitt, Minnesota. The mine pit is over 8 miles long, up to 1 mile wide. Fifty three samples were collected from 30 sites within areas of the pit where faulting, shearing and folding occur and where fibrous minerals might occur. Eight samples from seven collecting sites contain significant amounts of ferroactinolite amphibole that is partially to completely altered to fibrous ferroactinolite. Two samples from two other sites contain ferroactinolite degraded to ropy masses of fibers consisting mostly of ferrian sepiolite as defined by X-ray diffraction and TEM and SEM X-ray spectral analysis. Samples from five other sites contain unaltered amphiboles, however some of these samples also contain a very small number of fiber bundles composed of mixtures of grunerite, ferroactinolite, and ferrian sepiolite. It is proposed that the alteration of the amphiboles was caused by reaction with water-rich acidic fluids that moved through the mine faults and shear zones. The fibrous amphiboles and ferrian sepiolite collected at the Peter Mitchell Mine composes a tiny fraction of one percent of the total rock mass of this taconite deposit; an even a smaller amount of these mineral fragments enter the ambient air during mining and milling. These fibrous minerals thus do not present a significant health hazard to the miners nor to those non-occupationally exposed. No asbestos of any type was found in the mine pit. © 2007 Elsevier Inc. All rights reserved. Keywords: Taconite; Asbestos; Amphibole; Reserve mining; Tailings; Mesabi iron range; Mineral fibers

Jan 1, 2007

The material presented in this paper describes experimental work to determine the effect of variations in suction nozzle design upon inlet flow conditions. Four entrance profile shapes were examined under controlled conditions of slurry flow and it was found that the straight ended nozzles had consistently higher entrance losses than the straight taper or the ellipse, and that the circular arc profile nozzles were the most efficient. Subordinate considerations were the measurement of the quantities and the forces involved.As the work progressed, three distinct phases in the pattern of flow were apparent and the static pressures in each were carefully examined. An inlet zone was found to be unstable in changing boundary conditions, a transition zone was largely independent of slurry density and in a zone of stability the pressures were found to be directly related to the characteristics of the flowing pulp. In this zone pressure measurements were reproducible within ± 2 per cent regardless of changing boundary conditions.The effect of varying the "1" parameter of nozzles with a part circular entrance profile was examined and it was found that flow conditions approaching the ideal were obtained when the radius of curvature was between 0·40 and 0·550.

Jan 1, 1966

By Syd Peng

"As the International Conference on Ground Control in Mining (ICGCM) enters its 35th year in 2015, it is time to look back and identify the areas that need to be emphasized and to look forward to see what areas need to be researched in the future. In the past three decades, ground control has made a tremendous advancement, and many case studies published in the 36 volumes of proceedings have demonstrated its important role in the daily mining operations. However, there is still plenty of room for improvements. This paper discusses the research needs in 12 subject areas, including mine geology, rock property, zones of disturbance in overburden, computer modeling, underground stress measurements, research method, roof bolting, coal pillars, failures, subsidence, shield supports, and coal bumps.INTRODUCTIONThe International Conference on Ground Control in Mining (ICGCM) was founded in 1981. Since then, 1,546 papers have been published in the 36 conference proceedings, including the three surface subsidence workshops held in the 1981, 1986, and 1992. All types of topical areas regarding mining, from geotechnical core loggings in the exploration phase through backfilling after mining to finally spoil piles stability on the surface, have been addressed. A review of these papers, and other related literature as well, indicate that ground control has developed to become an inseparable part of mine design and a problem-solving tool for safe production.After 34 years, it is time to look back and identify the areas that need to be emphasized and to look forward to see what areas need to be researched in the future. There is no doubt that the conference series has achieved the goal for which it was originally designed: to provide an annual forum for the exchange of information among the researchers, government regulators, equipment manufacturers, consultants, service providers, and—above all—mine operators. There have been many papers addressing the application of ground control techniques for successful mine design and safe production, and, without these papers, many projects would have failed. In fact, the conference emphasis on application types of papers may have steered too far toward the application side. A review of the conference papers shows that papers have been leaning mostly toward the applied side, leaving most, if not all, fundamental issues behind in nearly every topical area. This paper addresses research needs in 12 topical areas: mine geology, rock property, zones of disturbance in overburden, computer modeling, underground stress measurements, research method, roof bolting, coal pillars, failures, subsidence, shield supports, and coal bumps."

Jan 1, 2015

By Tristan Worsey, Nathan Rouse, Kyle Hall

Drilling accuracy is the foundation to any successful blast operation. Even the best blasting practices cannot overcome poor drilling and still obtain desired results. Inaccuracies in boreholes can result in flyrock, increased vibration, uneven floor, and other undesired effects. As depth increases, variation in actual burden and spacing is expected even if collars are located precisely. Problems arise when this deviation reaches a point where it adversely affects the function of the blast design. Not only can unsafe conditions such as insufficient burden at the face develop, but poor fragmentation can compound adverse effects. As with any troubleshooting, problems cannot truly be fixed if they cannot be measured. As a result, significant work has been done in the past on this subject. Currently, there are both cheap and expensive methods used to quantify deviation for a given borehole. However, implementation of these techniques is limited. In general production blasts, little is known about the variance in designed versus true borehole geometry. This is especially true if the blaster does not see telltale signs of drilling deviation. However, losses in blast performance may exist and provide an opportunity to obtain better fragmentation and reduce fines. As drill and blast operations strive for better optimization, greater focus is being placed on drilling accuracy and solutions to this problem. The following paper details the use of several current methods for deviation measurement in order to help prevent compromises of safety and improve overall blast performance.

Jan 1, 2018

By J. Trckova, P. Prochazka

Physical models from equivalent materials satisfying geometrical and physical similarity have been constructed. A special technology of simulating the excavation of an opening at the front part of a tunnel and of measuring the deformation at the tunnel face was applied. The results yielded by the physical models were used to formulate constitution relations in the numerical solution. This coupled modelling enables us to predict the behaviour of tunnel structures more accurately. On a construit des modèles physiques, réalisés en matériaux équivalents et répondant aux conditions de ressemblance géométrique et physique. Sur ces modèles, on a utilisé une technologie intéressante de simulation du forage du tunnel et de la mesure de déformation du front de taille pendant le forage en progression. Les résultats donnés par les modèles physiques ont été utilisés pour formuler les relations de constitution dans la solution numérique. Une telle construction de modèles combinés permet de prévoir plus précisément le comportement de la structure du tunnel. Es wurden physikalische Simulierungsmodelle aus äquivalenten Werkstoffen konstruiert, welche die Bedingungen der geometrischen und physikalischen Ähnlichkeiten erfüllen. Bei diesen Modellen hat man die interessante Simulationstechnologie des Tunnelvortriebs sowie die Verformungsmessung beim Tunnelabbaustoß während des Vortriebsvorgangs eingesetzt. Die Ergebnisse der physikalischen Simulation wurden zur Formulierung von Konstitutionsrelationen in der numerischen Lösung genützt. So eine kombinierte Simulation erlaubt eine genauere Prognose des Benehmens der Tunnelstruktur.

Jan 1, 2003

By R J. Goldfarb

Reduced intrusion-related gold deposits have become a new, low-grade, large-tonnage exploration target during the last decade. The best recognized examples of such deposits are recognized throughout the Tintina Gold Province of the northern North American Cordillera. Because such examples may have many features in common with orogenic gold deposits, such as anomalous Bi, W and Te, low salinity and CO2-rich ore fluids, and a spatial/temporal association with igneous rocks, confusion and controversy have now become commonplace in classification of many gold deposits formed along convergent margins. The best discriminators of IRGS are likely to be their: +        regional location in deformed shelf sequences on the inboard side of a series of accreted terranes and within terranes that also contain important tin and (or) tungsten deposits; +        local spatial association of gold ores with cupolas and contact aureoles of relatively reduced, alkaline-leaning, and volatile-rich plutons; +        post-deformational timing of gold deposition; +        extremely low sulfide content (commonly <1 vol %) of ores within igneous bodies and the outward zoning, through proximal skarns and to distal base metal-rich veins, from the causative pluton; and +        low grades (<1 g/t Au) of auriferous sheeted vein systems in pluton cupolas.

Jan 1, 2005

By David A. Hill, James R. Wait

This report contains a summary of analytical research on electromagnetic methods of nondestructive testing of cylindrical conductors. The principal objective is to provide theoretical insight to the operation of electromagnetic sensing of the internal properties of wire ropes that are used extensively in mine hoists. An overall review of past work is also included.

By Davy A. T, Hansen J. O

The causes of ferrosilicon loss from Dense Media Separation (DMS) plants, and the related properties of ferrosilicon, are identified. Two characteristics, corrosion resistance and saturation magnetisation, are examined in detail. The chemistry of the corrosion mechanism is described and its relationship to plant parameters discussed. Methods of reducing corrosion losses are proposed. Lack of particle homogeneity, and its influence on corrosion and abrasion is noted. The relationship between low magnetic susceptibility-and increased magnetic separator losses is demonstrated experimentally.

Jan 1, 1986

By S. D. Viljoen

The use of ceramics to protect equipment subjected to wear in abrasive and corrosive applications has been accepted by most plants as the industry norm. Little is, however, known about alternative special ceramic based products which are available for the protection of plant assets. With careful engineering, impact resistant ceramics can be used in high impact zones using modern ceramic technology. Properly selected and properly installed, ceramics will provide a tough wear resistant lining for protection against abrasion and impact. Basalt, on the other hand, is widely used in coal washing plant process pipes with varying degrees of success. Basalt is normally not used for the lining of bends, ?T? pieces or reducers due to the reduced wear resistance compared to alumina ceramic. The advantage is a much reduced initial capital cost. A patented ceramic composite non-return valve solved an old problem encountered in the operation of medium sumps. The design approach overcomes the lack of functionality of alternative designs and reduces valve wear while preventing medium settlement during plant shutdown periods. Direct bonded ceramic pulley lagging is becoming the industry norm, eliminating most of the problems encountered with conventional pulley lagging systems.

Jan 1, 2010

By Orlando E. Romig

As metals and alloys are composed of an aggregate of allotriomorphic crystals or grains, each possessing an individual orientation, the physical characteristics of a metal or an alloy are closely related to the properties of the individual crystals. The preparation and study of single metallic crystals are, therefore, matters of considerable importance. The advent of the X-ray spectrograph as a valuable metallurgical tool has magnified the importance of this subject, because the interpretation of some X-ray spectrographs is difficult unless single crystals are used in these studies. Previous Work The first paper, as far as the writer knows, on the behavior or preparation of single crystals of metals is by Baker.' He describes the behavior of extruded wires of sodium and potassium. These wires, when pulled in tension, instead of showing the usual conical fracture common to most metals, had a chisel-shaped fracture when they were broken. I and 11, Fig. 1, have a similar fracture. Baker checked his results by preparing single crystal wires from molten sodium and potassium and observing their properties. He pre- pared the wires by filling glass tubes, under oil, with the molten metal. The surfaces of the strained wires showed slip bands of remarkable clearness of which photographs are shown in his paper. He concluded that these wires were single crystals and "that the portions of the metal brought into play are cubes. Such cubes, when placed so that a plane through two opposite edges was parallel to the axis of the wire, would allow of lateral contraction by faces gliding over one another in one direction only and not in the direction at right angles."

Jan 1, 1927

By A B. Christie, S C. Cox

Effective land-use planning requires accurate knowledge of mineral resource potential. Mineral companies during reconnaissance exploration, feasibility investigations and mine development also use this type of analysis. The Institute of Geological and Nuclear Sciences is undertaking a two-year project reviewing the resource potential of the West Coast of the South Island of New Zealand. Spatial prospectivity models have been developed as part of this resource assessment process, using computer based statistical pattern recognition techniques to delineate areas that are prospective for mineral deposits and to test deposit genesis models. Digital GIS data-sets of mineral occurrence were correlated against geology and exploration information. The distribution of mesotherrnal shear zone gold deposits in the Reefton Goldfield, were examined against geological data-sets from both the regional (QMAP) and local prospect-scale mapping. Weights of evidence analysis generated a correlation matrix that highlights relationships and degrees of association that might otherwise not normally be recognised.   Mesothermal shear zone gold deposits have strong positive spatial correlations with Greenland Group host rocks and areas with moderate to high quartz vein densities; moderate-strong positive correlation with regions <500 m from folds, with regions <600 m from faults and five to eight kilometres from granite contacts; moderate correlations with Ntrending fault and fold segments; and no/weak/poor correlations with fault intersections, fold-fault intersections, bends in regional structures and magnetic and radiometric data. The regional and prospect scale data sets give different results, with the more detailed prospect scale mapping giving generally better correlations. This emphasises the value of detailed geological mapping in the exploration process.   Maps generated by prospectivity modelling consistently highlighted areas of known mineralisation and generate targets where follow-up investigation is warranted. The prospectivity per unit area provides a measurable value that should change as new information comes to hand and, in addition to highlighting targets, can be used to measure the impact of increased exploration expenditure and assess the effectiveness of exploration investment.

Jan 1, 2001

By J. Shang, P. Howarth, B. Morris

Tailings from the nickel refinery in Copper Cliff, Ontario, consist of fine silicates mixed with a variable amount of conductive and magnetic minerals mainly associated with sulphides and iron oxides. Subsequent oxidation of sulphide- rich phases within the tailings results in the formation of an acidic leachate that may contain significant concentrations of trace metals. Mapping the spatial distribution of regions of higher sulphide concentration therefore provides insight into the distribution of the acidgenerating potential within the tailings. Electrical conductivity is constrained by two parameters — the concentration of metallic sulphides and the ionic concentration of acid in groundwater. Magnetic susceptibility is directly related to the pyrrhotite and magnetite content. It is proposed that combining information derived from airborne electromagnetic and magnetic surveys can provide an indication of metallic sulphide distribution. Preliminary investigations of airborne electromagnetic and magnetic data acquired concurrently over the sulphide-rich Copper Cliff tailings site reveal that these parameters can provide information on mine tailing extent and permit separation of tailings with varying compositional and alteration levels. Airborne geophysical data provide information about the subsurface while a digital elevation model (DEM) and hyperspectral imagery record surface conditions. Integration of the two data sets can reduce ambiguity when interpreting mine tailing distributions and their subsequent alterations.

Jan 1, 2001

By Donald J. Hallbom

"While pipeline hydrotransport is often the most economical way to transport large volumes of mineral concentrate, tailings, or fine ore slurry over long distances, it is in mountainous terrain that pipelining becomes particularly attractive. These areas are often remote, with limited existing infrastructure and few potential users willing to share in the cost of new infrastructure. The rugged terrain makes the construction of railways or roads suitable for haul trucks difficult and expensive. The elevation difference between the mine and the terminal means that the empty trains or haul trucks need to return up-hill, resulting in high fuel costs. With pipelines, this elevation difference may reduce or even eliminate the need for pumping. As a result, numerous pipelines have been built, or are being considered, in mountainous regions around the world including: Tasmania, New Guinea, China, Madagascar, the Rockies of North America, and the Andes of South America. However, there are technical difficulties that need to be overcome in the design and operation of mountain pipelines that do not affect pipelines on more level terrain. This presentation reviews some of these difficulties and methods used to overcome them.INTRODUCTIONPipeline transport of solid-liquid slurry (“hydrotransport”) is an important and cost-effective means of transporting large volumes of solids over long distances, especially from a single supplier to a single user (e.g., a concentrator to a port, a concentrator to a tailings dam, or a coal mine to a power plant). Pipelines are generally found to be more economically attractive than alternate transportation methods (e.g. trucking, rail, conveyors, shipping, or some combination) over the life of a project (Aude et al. 1974).Hydrotransport systems have been built in a variety of terrains, but it is in mountainous regions that pipelining becomes particularly attractive. These regions are often remote and generally do not have existing transportation infrastructure (roads, railways, navigable rivers). There are few potential users (e.g., farmers, other mines, forestry companies, etc.) who may be willing to share in the cost of new infrastructure. The rugged terrain makes the construction and maintenance of railways or all weather roads suitable for large haul trucks difficult and expensive. Mines tend to be higher than the receiving terminal (e.g. a port). This means that the empty trains or haul trucks need to return up-hill, resulting in high fuel costs. With pipelines, this elevation difference may reduce or even eliminate the need for pumping. Pipelines are easier to construct than roads and railroads in these areas for several reasons, including:"

Jan 1, 2006

By Greg Sheppard, Eduardo Nebot

Australian researchers have developed new technologies aimed at improving safety and productivity at openpit mines. A data acquisition and feedback system for electric rope shovels has been shown to substantially reduce cycle times and decrease excessive machine duty caused by stalls. This data acquisition system was developed by the Cooperative Research Center for Mining Technology and Equipment (CMTE). It has been tested on a P&H 4100A shovel at Coal & Allied’s Hunter Valley operations and a P&H 4100XPB at BHP Billiton Mitsubishi Alliance’s Goonyella Riverside Mine in Central Queensland. In addition, CMTE member P&H Mine Pro Services has used the technology to acquire field data from a P&H 4100XPBrope shovel at RAG’s Belle Ayr Mine in Wyoming’s Powder River Basin.

Jan 1, 2002

By G. B. Shea

"In 1928, there were 47 fatal accidents in the California petroleum industry, 14.6 per cent more than occurred in 1927 when 41 men lost their lives in the drilling, producing, manufacturing, and marketing divisions of the industry. This increase in the number of fatal accidents for 1928 has caused the first upward trend in the fatality curve of the California petroleum industry since 1923. In no other year during the 6-year period have the fatalities in any one year been greater than those for the preceding year. This fact should be given serious consideration and study by the petroleum industry, and an endeavor should be made to cause the number of fatalities again to decrease and conform to the previous gradual declining trend of the fatality curve.The following chart shows the trend of fatal accidents during the past six years:Of the 47 fatalities in 1928, 30 occurred in the drilling and producing division, 1 in the pipe line and transportation division, 14 in the refining division, and 2 in the sales and marketing division. A comparison of the number of fatalities in each division for 1927, and 1928, is given in the following table:3"

Sep 1, 1929

Uranium exploration over a wide area of the Southern Frame Embayment, South Australia, has defined a number of Lower Tertiary fluvial palaeochannels incised in older rocks. The buried channels contain similar stratigraphicsequences of interbedded sand, silt, and clay, probably derived from the adjacent uranium-rich Olarv Provinee. Uranium mineralization is pervasive within two major palaeochannels, and four small uranium deposits have been found in the basal sands of these channel sequences, at the margins of extensive tongues of limonitic sand.One of the channels is examined in detail with respect to channel morphology, stratigraphy, and rock alteration and the geology and ore controls of the contained uranium deposits are described.A geochemical zonation reflected by variation in limonite, pyrite, carbon, and humic malleI' is defined across one of the deposits. A genetic model is proposed suggesting formation by a uraniferous geochemical cell which migrated down the stream gradient and concentrated uranium on its lateral margins adjacent to the channel bank.

Jan 1, 1978

By Madgwick J. C

Leaching column techniques and microbiological methods have been described in detail in Madgwick and Ralph (1980) and Madgwick, Ralph and Sadler (1981).Sixty-nine kilograms of copper porphyry ore (0.4 per cent Cu, 2.7 per cent Fe) (particle size 2.4-11.2 mm; 60 The effect of sodium chloride (O.6M) irrigation on bacterial leaching of Bougainville copper porphyry ore was studied.Viability of suspended Thiobacillus ferrooxidants was reduced to less than 10 cells/ml in NaCI (O.6M) compared with 10' eells/ml in dilute II,SO, (0.01 M, pll 2). Salt irrigation had no significant effect on heterotrophic and sulphur oxidizing bacteria. Increascd short term recovery of copper (145 g/tonne/ 15 days) was followed by a marked decrease in tenors to less than 20 mg/litre/day compared with an acid leach, steady release, of 110 mg/litre/day. Resumption of acid leaching restored average solution copper to 46 mg/litre/day and the viability of suspended T Ierrooxidates to 10 cells/ml.Quantitative removal of sodium ehloride from ore particles was difficult and t races of NaCI remained for more than 200 days.

Jan 1, 1982

By Christopher Mark

"Many problems in rock mechanics are limited by our imperfect knowledge of the material properties and failure mechanics of rock masses. Mining problems are somewhat unique, however, in that plenty of real world experience is generally available and can be turned into valuable experimental data. Every pillar that is developed, or stope that is mined, represents a full-scale test of a rock mechanics design. By harvesting these data, and then using the appropriate statistical techniques to interpret them, mining engineers have developed powerful design techniques that are widely used around the world. Successful empirical methods are readily accepted because they are simple, transparent, practical, and firmly tethered to reality.The author has been intimately associated with empirical design for his entire career. But where his past papers have described the application of individual techniques to specific problems, the focus of this paper is the process used to develop a successful empirical method. A six-stage process is described:1. Identification of the problem, and of the end users of the final product2. Development of a conceptual rock mechanics model, and identification of the key parameters in that model3. Identification of measures for each of the key parameters, and the development of new measures (such as rating scales) where necessary4. Data sources and data collection5. Statistical analysis6. Packaging of the final productEach of these stages has its own potential rewards and pitfalls, which will be illustrated by incidents from the author’s own experience. The ultimate goal of this paper is to provide a new and deeper appreciation for empirical techniques, as well as some guidelines and opportunities for future developers."

Jan 1, 2015