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By J J. Jiang, M Reimnitz

The Kalgoorlie Consolidated Gold Mines (KCGM) Fimiston Open Pit is mining through a dense network of disused level workings and open stopes of greatly varying sizes. The condition of the stope crowns and remnants is often unknown, and ultimately these structures become a significant proportion of the production floor and pit walls. Significant seismic events and occasionally rock bursts often occur in the underground workings. Seismicity is becoming an issue to the viability of the KCGM Fimiston operations. KCGM needs to take a leading role in understanding mine-induced and regional seismicity. The seismic system trials were initiated in the Fimiston Open Pit in 1996 using the ISS system. The initial system included two triaxial geophone arrays and two triaxial accelerometer arrays installed into two boreholes. The main objectives of the trial were to investigate the suitability of the two types of sensors and the detectability of seismicity in the pit. The trial was regarded as a success and the system has been expanded and improved. The current system consists of 12 triaxial geophone and accelerometer arrays and nine uniaxial geophones. The 12 triaxial arrays are installed in nine boreholes drilled from the pit and the nine uniaxial geophones are installed from underground level workings about 660 m below the original surface elevation. The system is designed to provide seismicity coverage for the entire pit area that is about 2.7 kilometres long, 1.5 kilometres wide and about 300 metres deep. The accuracy of the source location has always been a challenge due to the existence of the dense concentration of stopes and lack of the sensors. It is uncommon to have direct ray path for the seismic waves to propagate to the sensors across the strike, hence sensors have been located along strike and under the old workings. This paper discusses some of the challenges associated with seismic monitoring near mine remnants and seismically active faults. The results of the seismic monitoring are presented, and contrasted to results of three dimensional boundary element numerical modelling. The impact of the seismicity upon pit slope stability is briefly discussed.

Jan 1, 2003

By C. P. Manning

This paper reports recent progress in the development of a unique metal extraction technology utilizing zirconia-based inert anodes for the electrolytic reduction of metals from their oxides. In this process, the target metal oxide is dissolved in an ionically conducting liquid solvent phase. An extended anode consisting of an oxygen-ion-conducting stabilized zirconia membrane in intimate contact with a catalytically active electronic phase and an inert electronically conducting cathode are inserted into the molten flux containing the oxide. When the appropriate electric potential is applied between the electrodes the target metal is reduced at the cathode and oxygen ions are selectively transported across the stabilized zirconia membrane and oxidized at the anode. When the process is conducted at temperatures between 1200-1400°C, the ohmic resistance drop across the stabilized zirconia membrane is low, and high current densities on the order of I A/cm2 or greater can be obtained. In addition, the process efficiency can be increased further by directly reforming hydrocarbon fuel over the anode. Laboratory experiments at Boston University have demonstrated the technical viability of employing zirconia-based inert anodes for environmentally sound production of metals such as magnesium, tantalum, aluminum, etc., directly from their oxides. Significant progress has been made in the application of this concept to the electrolytic reduction of magnesium at 1300°C. The research topics covered include stability of the zirconia membrane in the selected molten solvent (flux), volatility of the flux, electrochemical characterization of the electrolytic cell, and analysis of the metals produced.

Jan 1, 2003

By Michael Zinigrad

The quality of metallic materials depends on their composition and structure and these are determined by various physico-chemical and technological factors. To effectively prepare materials with required composition, structure and properties it is necessary to carry out a research in two parallel directions: Comprehensive analysis of thennodynamics, kineties and mechanisms of the processes taking place at the solid-liquid-gaseous phase interface during welding processes and development of mathematical models of the specific welding technologies. We have developed unique method of mathematical modeling of phase interaction at high temperatures. This method allows us to build models taking into account the thennodynamic characteristics of the processes, the influence of the initial composition and temperature on the equilibrium state of the reactions, the kinetics of heterogeneous processes, the influence of the temperature, composition, hydrodynamic and thennal factors on the velocity of the chemical and diffusion processes. The model can be implemented in the optimization of various technological processes in welding, surfacing, casting as well as in manufacturing of steels and non-ferrous alloys, materials refining, alloying with special additives, removing of non-metallic inclusions.

Jan 1, 2003

By M. H. Pelkki, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

Research has shown that excessive soil compaction is detrimental to the establishment of trees in reclaimed soils. Dry bulk density and penetration resistance are two soil parameters that can be used to indicate the level of compaction in reclaimed soils. It is believed that reclamation practices that minimize soil compaction will produce better results when forestland is the intended postmining use. The University of Kentucky has developed reforestation test cells on reclaimed soils at a surface mine in eastern Kentucky to test this hypothesis. Each test cell has been planted with various species of trees. Since 1997, data have been collected at these test cells for soil average dry bulk density, average penetration resistance, average depth to refusal and average survival rate of trees. These data have been correlated to determine the relationship between soil compaction and tree-survival rate. It is believed that these two soil-compaction parameters may ultimately be used to predict tree-survival rates on reclaimed surface mined lands.

Jan 1, 2003

By M. Cambridge

During the latter part of the twentieth century exploitation of mineral resources, and gold mining in particular, experienced a resurgence in Europe, with major mining houses and many junior companies involved in exploration and subsequent mine development. Gold projects in particular were actively encouraged and exploration programmes and permitting studies initiated in more than 15 countries, both within the European Union (EU) and the former eastern bloc. During the initial period, governments in many countries provided active support. Following a series of negative environmental mining incidents in the latter part of the century public opinion, often ill-informed, led to political pressure to withdraw governmental assistance. This in turn resulted in the revocation of exploration licenses, and ultimately to the failure to develop a number of potentially world-class mines within the region. Despite these setbacks, gold production in Europe continues, and is probably higher now than 20 years ago. The mining industry is currently coming to terms with both changing attitudes of governments, and the increase in scope and prescriptive nature of legislation. Recent experiences, particularly in Greece and Turkey, exemplify the problems faced by the industry in the region, which are causing major mining companies to reconsider future activities in Europe. The paper presents an overview of European gold mining and its environmental performance in the context of international practice, new legislation, and public perception of mining generally. The rationale of governments in withdrawing support for the industry is questioned, and the feasibility of achieving sustainability where there is no level playing field globally is reviewed. The question is posed to governments, regulators and mining companies alike as to whether there is a future, not only for gold mining, but for the minerals industry in general, within the EU.

Jan 1, 2003

By M. C. Bétournay

Strainbursts are common in overstressed brittle rock around deep mine openings. Such failures are characterized by a biaxial state of stress in the plane of the opening boundary. A zone of compressive stresses imposes initial failures near or at the surface of the opening that results in spalling of thin slabs of rock roughly parallel to the free face. While the failure of rock under biaxial loading conditions is increasingly common in deep underground mines, only a few representative laboratory studies have been reported in the literature, without emphasis on rockbursting aspects, and none in the last decade. This paper presents the results of a testing program on a granite rock type. Biaxial testing, conducted on 100 mm cubic samples, was carried out to examine the influence of lateral confinement and loading rate on the rock’s ultimate strength. The paper reports the test results in terms of normalized biaxial failure envelope s1/sc-s2/sc. A discussion of the failure mechanisms observed is presented. Les coups de toits de déformations sont choses communes dans le rock cassant surcontraint en place autour des ouvertures minières profondes. De telles ruptures sont caractérisées par un état de contraintes biaxiales dans le plan de la périphérie de l’ouverture. Une zone de contraintes compressives impose des ruptures initiales à ou près de la surface de l’ouverture, qui produit des relâchements de minces plaques de roc plus ou moins parallel à la surface. Bien que les ruptures de roc sous des conditions biaxiales sont de plus en plus communes dans les mines à grandes profondeurs, il n’y a eu que quelques études représentatives en laboratoire de publiées, sans emphase sur des aspects de coups de terrains, et aucunes publiées depuis la dernière décennie. L’article présente les résultats d’une campagne d’essais appliquée à un type de granit. La campagne d’essais biaxiaux, sur des échantillons cubiques de 100 mm, avait pour objectif d’examiner l’influence du confinement latéral et le taux de chargement sur la résistance ultime du roc. Cet article fait part des résultats en terme de l’enveloppe de rupture biaxiale normalisée s1/sc-s2/sc. Une discussion sur les mécanismes de ruptures observés est présentée. Dehnungsbrüche findet man häufig in übergespannten spröden Felsen um die Öffnung von tiefen Minen. Solche Brüche sind von einer zweiachsigen Spannung in der Ebene der Grenze der Öffnung charakterisiert. Eine Zone von Druckspannungen verursacht initiale Brüche, entweder an der Öberflache der Öffnung oder in der Nähe. Davon scheiden sich dünne Felsplatten mehr oder weniger parallele mit der freien Wand. Obwohl Felsbrüche unter zweiachsiger Beanspruchung immer mehr häufig in tiefen Minen beobachtet sind, hat man über nur einige repräsentative Laborversuche in der Literatur berichtet. Diese Studien diskutieren das Thema ohne Betonung auf Felsbrüchen, und keine sind in den letzten zehn Jahren erschienen. Die vorliegene Arbeit gibt die Ergebnisse eines Testprogramms auf einem Typ von Granitfels. Durch zweiachsige Prüfungen von kubischen Proben mit Seitenlangen von 100 mm sollte man den Einfluss von seitlicher Ermittlung und der Beanspruchungsrate auf die Bruchfestigkeit des Felsen studieren. Man findet auch die Prüfergebnisse in bezug auf das normalisierte, zweiachsige Bruchkriterium s1/sc-s2/sc. Die beobachteten Bruchmechanismen sind auch diskutiert.

Jan 1, 2003

By J. Broadhurst

"A number of metal supplying industries have in recent years seen the compilation of life cycle inventories (LCIs) and life cycle assessments (LCAs). The activity has largely been driven by the interest of ultimate metal users, such as the automotive industry, in the interest of designing more sustainable products. Often, the compilation of such inventories has been little more than an auditing exercise. However, the process of conducting an LCA can have more value, guiding designers and operators to points within the technology train where significant emissions and impacts originate. The LCA product can thus be used to inform on-site environmental management, and, where process data is used to construct dynamic operational models, to support strategic decision making in the realm of project planning and technology selection. LCA thus serves as a valuable tool to support the industry’s drive to support the sustainable development of the societies in which it operates.This paper reviews and compares the priorities of environmental and closure planning in the design phase, with environmental management and auditing during operation, and with green procurement of minerals and metals products. It shows how life cycle assessments of various complexities can be used to reconcile these various objectives, ensuring that the latter, critical to business success, can be addressed from the outset in a new project. The paper then reviews a case study of the use of LCA in the base & precious metals industry, where the complexity of the operation disallowed the simpler auditing process so that a detailed process understanding had to be built up in order to compile a meaningful life cycle inventory."

Jan 1, 2003

By J Mar·n, R Anderson, S Strohma, R Harvey

Xstrata is the operator of both Minera Alumbrera Ltd (50 per cent Xstrata, 50 per cent Wheaton River) and Ernest Henry Mining Pty Ltd, (99.99 per cent Xstrata), both copper-gold deposits, using conventional SAG/ball milling at current capacities of 36 Mt/yr and 10.3 Mt/yr respectively. Alumbrera is located in Catamarca Province, in the north west of Argentina. Ernest Henry is located in Cloncurry, north west Queensland, Australia. Both operations started in late 1997, with commercial production achieved in early 1998. Different designs and equipment are in use for both operations, however the evolution of SAG milling performance, although logically related to their specific features, reflect similar trends of consistent increases in throughput. This paper will discuss the main changes to the SAG mill liners in both operations and the results achieved to date. A summary of the operating strategies will be included.

Jan 1, 2003

By Jerome P. Downey

Technologies developed within the field of extractive metallurgy to recover, concentrate, and purify metals and industrial minerals from ores, have served as the foundation for all of the subsequent environmental remediation, materials recycling, and waste management technologies. This paper discusses the application of classical extractive engineering principles to the development of a thermal process for the recovery of mercury from solid wastes. Process development is presented as a series of logical stages, which begin with a thorough characterization of the site-specific waste, move on to bench and pilot scale testing of the process options, and end with a functional process flowsheet. This paper also presents thermodynamic data on many mercury species of interest to the minerals, power, and chemical industries. These data can be used to model the speciation and recovery of the mercury as a function of various process parameters.

Jan 1, 2003

By I Gipps

The mining industry has come through a period of major change in community expectations regarding safety and environmental impact and these changes can be expected to continue in the future. These changes are ultimately reflected in Government regulations and industry safety standards and form the basis of the ælicense to operateÆ. Equally, advances in technology have made possible new equipment and processes either available now, or close to completion, that will allow mines to meet these more stringent expectations if properly introduced. Changes in technology provide opportunities for mine management to introduce new systems that will remove people from hazardous areas and lead to improvements in the ætriple bottom lineÆ. In a longer time frame of five to ten years, novel and advanced technologies that are currently being developed will deliver new mining methods and conversion of presently uneconomic resources to ore. This is consistent with the time frame required to develop a new mine from discovery. Strategic decisions can be taken now by mine designers to enable the introduction of these major technology changes. Examples of both practical and strategic opportunities are drawn from the integration of rock cutting/blasting, automation, electronic communications and new mining methods. This paper discusses emerging industry trends, changes to legislative framework and some practical choices for existing and imminent technology.

Jan 1, 2003

The process of mine planning at AnacondaÆs nickel and cobalt laterite operation located at Murrin-Murrin in the Northern Goldfields of Western Australia is carried out in a number of stages in an endeavour to determine the optimum mining sequence in order to maintain supply to the 4 Mtpa plant subject to operational constraints. The 296 Mt @ 0.99 per cent Ni and 0.064 per cent Co ore reserve (based on a cut-off grade of 0.8 per cent Nickel) is spread geographically widely over three regions comprising Murrin North (15 km + 15 km), Murrin South (7 km + 16 km) and Murrin East (5 km + 13 km) (refer Figure 2). The nickel mineralisation has been broken up further within each region into 18 separate manageable block models representing the 32 different deposits. The models are based initially on the 50 m + 50 m resource drilling for long term planning and updated with 12.5 m + 12.5 m grade control drilling prior to mining. Each of the individual block models are optimised using Whittle 4X software to provide the shells used as the basis for each of the 126 pit designs. The pits are generally nested with starter pits targeting the higher value shells with subsequent pits incrementally cutting back ultimately to the life of mine shells. A series of steps including: the coding of the individual pits into the block model; data export; TCL scripting (to calculate additional economic and tracking information); importing; and re-blocking; completes the transfer of the data into a MineMax (mixed integer linear programming schedule optimising software) model. Using MineMax and the application of operational and production constraints allows the optimisation, assessment and economic evaluation of alternative scenarios in order to determine the optimum life of mine plan and schedule.

Jan 1, 2003

By K. Hambrice, E. Fauveau

"When it comes to measuring the level of bulk solids, liquids, and everything in between, guided-wave radar technology now offers more level-detection capabilities than ever before. For an ever-widening range of previously hard-tomeasure products such as molten sulphur, liquid ammonia and petrochemicals, guided-wave radar transmitters provide accurate level measurements even under harsh chemical environments, wide variations in operating temperatures and pressures, and low dielectric constants.Great strides have been achieved in making these units easier to configure to a variety of process applications coupled with the simplicity of integrating these devices with most digital communication protocols. These improvements come as welcome relief to process engineers within an expanded range of level applications across several different industries that seek solutions to measuring the contents of tanks, silos, hoppers, bins, mixing basins, and vessels.Because radar transmitters have no moving parts, radar has already established a dominant niche in level measuring that quickly distances itself from mechanical means, which do not hold up as well in dirty service. Radar achieves its nonmechanical level detection capability by measuring the time of flight of the transmitted signal.Known more accurately as time domain reflectometry (TDR), the process involves sending microwave energy down into a vessel. When the pulse of radar energy reaches the product (indicated by a change in impedance), part of the pulse is reflected back toward the transmitter.A receiver measures the exact duration of time between the transmitted and reflected signal — the “time of flight.” The device analyzes this time and ultimately displays the level of the product as a distance in feet, metres, or other engineering units."

Jan 1, 2003

By William E. Roscoe

"Non-producing mineral properties include those at various stages of exploration, properties at the pre-feasibility or feasibility stage, properties with currently uneconomic mineral resources, and past-producers. The market approach is applicable to all these types of non-producing mineral properties. Income approach methods such as discounted cash flow and option pricing are generally not applicable to properties at the exploration stage, but may be applicable to non-producing mineral properties with defined mineral reserves or mineral resources.The value of a non-producing mineral property depends on its perceived potential for the existence and discovery of an economic mineral deposit. The potential, in turn, depends on a number of factors which must be considered when choosing market comparables. These comparability factors include such items as geology, mineralization, stage of exploration and results, mineral resources, location and geography, and political jurisdiction. The date of the market comparables must be within a reasonable time period of the valuation date of the subject property. Although it is difficult to find good market comparables because of the unique nature of mineral properties and the small number of transactions, these difficulties are compensated for by analyzing a number of transactions on similar properties to develop a range of values for the subject property.For valuation purposes, market comparables can be expressed in terms of total property value, value per unit area (e.g., $ per hectare), or value per unit of metal contained in mineral resources (e.g., $ per ounce of gold, or $ per pound of copper). The market comparable value can be used to estimate the value of the subject property by using the total property value, unit area value or contained metal value."

Jan 1, 2003

By Larry B. Smith

"Feasibility studies are the means by which mineral reserves are established prior to financing a project. However, guidelines are generally lacking for the content, data quality and accuracy of these studies. Regulators take a principle-based rather than prescriptive approach to the content of studies and look to the industry to define study content. Professional organizations, engineering firms and mining companies must eventually establish guidelines and best practices for this work. Most likely these will draw on standards or “stage gates” that have been developed by major mining houses and engineering firms. Engineering studies must: 1.,Define optimal mining and processing methods, production rates, infrastructure, product sales, environmental management and risk mitigation. 2.,Increase confidence in resources, reserves, production plans, processing performance, infrastructure design, environmental management, permitting, capital and operating costs, and financial performance to support financing. 3.,Provide engineering designs suitable for accurate cost estimates. 4.,Develop project execution plans with sufficient confidence that project delays and cost overruns will not occur. Conceptual (scoping, preliminary assessment) Establish the principal characteristics of the project from the geology, resources, metallurgy and development constraints. Assess different approaches to mining and processing. Identify project execution requirements. Test project viability with economic analyses. Recommend additional work to increase the confidence in geology, resources, metallurgical performance, infrastructure, operating and capital costs, environmental conditions and permitting to allow selection of the best development options."

Jan 1, 2003

By Greg Gosson, Larry B. Smith

"These are heady times for the mining industry, with strong metal prices, investor enthusiasm for the junior explorer and ready access to finance for mineral projects. Many projects were shelved in the past because of technical deficiencies — insufficient tonnes or grade, metallurgical problems, the deposit was too deep or too narrow, or the project was physically or economically under water. With the possibility of sustained metal prices, now is the time for those previously “challenged” projects to be re-evaluated and financing sought for continued development. The question is, do these deposits have reasonable prospects for economic extraction, as required by all mineral resource reporting codes? NI 43-101 defines a mineral resource as that portion of the mineral inventory that has reasonable prospects for economic extraction. However, a mineral resource is not simply an inventory of all blocks above a given cut-off grade. The spatial distribution and geological and grade continuity must also be considered. The qualified person (QP) must consider factors significant to project economics at the mineral resource estimation stage, and not just when qualifying mineral reserves. CIM Best Practice Guidelines for estimating mineral resources require the factors significant to project economics be current, reasonably developed and based on generally accepted industry practice and experience. In establishing the cut-off grade, it must realistically reflect the location, deposit scale, continuity, assumed mining method, metallurgical processes, costs and reasonable long-term metal prices appropriate for the deposit. Variations within the resource model (rock characteristics, metallurgy, mining methods, etc.) may necessitate more than one cut-off grade or economic limit in different parts of the deposit model. There must be sufficient knowledge of the metallurgical characteristics of the deposit, which should be supported by preliminary metallurgical test results."

Jan 1, 2003

By J Jeffrey, G W. Wilson, L Gilbert, C

Prior to the commencement of mining, the acid rock drainage (ARD) potential of the waste rock to be produced by an open cut mining operation is assessed by a variety of techniques carried out on drill-hole samples. These include, among others, acid base accounting (ABA), net acid generation (NAG) testing, and kinetic testing. Based on the results obtained, a strategy for the identification, separation and selective placement of waste rock having different potentials to form ARD is developed. During the course of mining, the waste rock classification scheme will be re-assessed periodically to confirm that it is appropriate. This re-evaluation may result in a change in classification scheme, and waste rock dump samples may be obtained for ARD assay purposes to confirm the appropriateness of the revised scheme. The paper describes the evolution over time of the scheme used to classify waste rock at a major open pit gold operation in New South Wales, Australia, including the development of a hydrological model. To confirm the appropriateness of the revised scheme, ARD assay testing was carried out on drill-hole samples collected from dumps having different ARD potential designations, including Non-Acid Forming (NAF), Potentially Acid Forming (PAF), and Low Grade Ore stockpiles. The results of the ARD assay testing and water quality monitoring confirmed the appropriateness of the ARD potential designations and the revised classification scheme, which has been adopted.

Jan 1, 2003

By R L. Verburg, R Johnstone

DeBeers Canada Mining Inc (DeBeers) recently submitted an Environmental Assessment (EA) for its proposed Snap Lake Diamond Mine located in Northwest Territories, Canada. As part of the EA process, a site water quality management plan must be developed. Plan development requires an integrated approach such that the key factors influencing water quality can be identified and managed to minimise potential impact. A system model was therefore developed to simulate the site-wide water quality conditions and mass loadings to the principal environmental receptor of concern, Snap Lake, during operations and post-closure. Requirements of the simulation included integrating hydrology, geochemistry, hydrogeology and site management practices in a dynamic way. A unique feature of the site was the need to accommodate a complex flow system that included a feedback loop between lake water and mine water. A system model was constructed using the GoldSim software package that integrated on-site water quality and flow measurements, as well as results from independent groundwater flow and geochemical modelling efforts. The GoldSim model simulated concurrently the movement of 39 solutes through the subsurface mine and surface facilities. Solute sources considered included four different waste rock and tailings types, explosives use in the mine, treatment plant discharge, and recycled process water for dust suppression. Separate solubility constraints were identified for different regions of the flow system (eg underground mine; treatment facility; surface water bodies). Kinetic test data were used to derive temperature-dependent rate constants for use in calculating mass inputs from surface sources such as waste rock piles. The model generated water quality estimates over time for a variety of management scenarios at several potential discharge locations. The integrated approach used by the model was effective in identifying the significance of key factors influencing overall water quality such as explosives use, mine water inflow rates, waste rock reaction rates, site/mine management options, and effectiveness of treatment. The model provides an example of an effective tool for comprehensive, integrated system evaluation and management.

Jan 1, 2003

Dilution in underground coal operations can be underestimated by up to five times during feasibility studies, with disastrous economic consequences. Every one per cent of stone waste introduced can reduce an in situ specific energy of 25 MJ/kg by some 0.25 MJ/kg and increases the abrasiveness of the run-of-mine coal. Where a wash plant is not in place, penalties imposed for not meeting contractual specifications alone can amount to some $A 1 million per year. This paper presents a method for monitoring, reporting and ultimately controlling dilution in an underground coal mining operation and presents the dilution trends from a continuous miner/longwall mine over an eight year period. The overall dilution level for the mine can be back-calculated by comparing the run-of-mine coal quality to the predicted in situ, undiluted quality. However, this will not identify the actual contaminant types, areas of the mine responsible for the dilution and the reasons for the dilution. This additional information is essential for controlling dilution to acceptable levels. Quality and horizon control using existing sampling information is generally only adequate for longer-term control purposes, and is not suitable for monitoring mining-induced dilution. The cost of close-spaced surface drilling to collect the information necessary for short-term control is prohibitive, particularly for deeper mines. However, much of this data can be collected through underground channel sampling and horizon control measurements taken during continuous miner development and longwall extraction. The mine runs the risk of not meeting contractual quality specifications and of increased equipment wear if this additional information is not available and the sources of dilution cannot be controlled. The information can also be used to plan longwall extraction heights on a short-term scale with resulting improvements in productivity.

Jan 1, 2003

By A. K. Singh, R. Singh, P. K. Mandal

On the basis of in situ study of pillar loading at different sites, an attempt is made in this paper to visualize the development of mining induced stress under varying geo-mining conditions. Field study demonstrated interesting interaction between size of pillar and nature of roof rock mass under the influence of increasing dimension of the excavation. Stiffness of pillars/overburden, extraction ratio and depth cover are observed to be the important parameters for the estimation of mining induced stress over the pillar. These parameters influence, both, the value of ultimate induced stress (vertical) and its range of influence ahead of the face line. Further, it is observed that the change in width/height (w/h) ratio of a pillar has got considerable influence over the nature of mining induced stress over it. Impact of highly dynamic nature of mining induced stress over the natural supports is observed to be the most serious factor for the safety of working under a hard and massive roof rock mass. On the basis of these observations, a conceptual model of interaction between the natural support and overlying strata is discussed in the paper. ZUSAMMENFASSUNG: Aufgrund ist in situ Studium von Säule Beladung an verschiedenen Stellen, ein Versuch in diesem Papier gemacht, die Entwicklung des Bergbaus vostellen sich, Spannung unter Änderung von Geo Bergbau von Bedingungen hat veranlaßt. Feld Studium hat interessante Wechselwirkung zwischen Größe von Säule und Natur von Dach Felsen Masse unter dem Einfluß von Vermehrung Dimension des excavation vorgeführt. Steifheit des Säulen Overburden, Herausziehung Verhältnisses und Tiefe sind beobachtet bedeckt, die wichtigen Parameter für die Schätzung des Bergbaus zu sein, Spannung über der Säule hat veranlaßt. Diese Parameter beeinflussen, beide, der Wert allerletzter veranlaßter Spannung (senkrecht) und sein Bereich des Einflusses voraus von der Gesicht Linie. Weiter ist, es beobachtet, daß die Änderung in Breite Höhe (W H) Verhältnis einer Säule beträchtlichen Einfluß über der Natur des Bergbaus erhalten hat, Spannung hat darüber veranlaßt. Schlag sehr dynamischer Natur des Bergbaus ist Spannung über den natürlichen Stützen beobachtet hat veranlaßt, der ernsteste Faktor für die Sicherheit des Arbeitens unter einer harten und massiven Dach Felsen Masse zu sein. Aufgrund dieser Beobachtungen, ein begriffliches Modell der Wechselwirkung zwischen der natürlichen Stütze und der überlagernde strata ist im Papier diskutiert. RESUME: En se basant sur dans l'étude de situ de chargement de pilier aux sites différents, une tentative est faite dans ce papier pour envisager le développement de creuse la tension persuadée sous varier de conditions de geo creuse. L'étude de champs a démontré l'interaction intéressante entre la taille de pilier et la nature de masse de rocher de toit sous l'influence d'augmenter de dimension de l'excavation. La raideur de piliers overburden, la proportion d'extraction et la couverture de profondeur est observée pour être les paramètres importants pour le jugement de creuse la tension persuadée par-dessus le pilier. Ces paramètres influencent, les deux, la valeur de tension persuadée ultime (vertical) et sa gamme d'influence en avant de la ligne de face. Plus, il est observé que le changement dans la largeur hauteur (le w h) la proportion d'un pilier a reçu l'influence considérable par-dessus la nature de creuse la tension persuadée par-dessus il. L'impact de nature extrêmement dynamique de creuse la tension persuadée par-dessus les soutiens naturels est observé pour être le facteur le plus sérieux pour la sûreté de fonctionnement sous une masse de rocher de toit dure et massive. En se basant sur ces observations, un modèle conceptuel d'interaction entre le soutien naturel et les couches recouvrant est discuté dans le papier.

Jan 1, 2003

By Lenny Winkel

With the aim to develop a solar-driven process for the extraction of copper from sulfide concentrates research on the decomposition of copper sulfides under inert atmospheres has been initiated. Thermogravimetric measurements on chalcocite,(Cu2S) revealed that copper is formed already at 1823 K. Chalcopyrite (CuFeS2) also disintegrates at this temperature, although at a lower rate. Copper and iron have been identified in the solid residue. The results confirm the feasibility of copper extraction by direct decomposition of sulfides under atmospheric pressure. The decomposition under inert atmosphere prevents generation of SO2, it also alters the behavior of volatile impurities during decomposition of copper sulfide concentrates. Chemical equilibrium calculations for chalcopyrite contaminated with enargite (Cu3AsS4) have shown that the absence of an oxidic slag allows for a complete evaporation of arsenic and subsequent separation from intermediate sulfides. The need to better assess the potential of direct sulfide decomposition has prompted the development of an experimental setup for studying the decomposition reactions. The experiment has been devised such that data on the decomposition kinetics and on impurity removal can be obtained at temperatures up to 2500 K.

Jan 1, 2003