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By Robert F. Randolph, Arnold C. Love

This study describes the positioning strategies used by operators of radio controlled underground mining machines. The observations have implications for task design to insure adequate visibility and task performance. Radio controlled continuous coal mining machines have allowed many mines to increase safety and production by placing human operators away from the hazards of an unsupported mine roof. The operator is no longer confined to an operators component and visibility can be enhanced with proper positioning. Also, the operator is no longer subjected to the shocks and vibrations of the mining machine. The operator's ability to move freely about the worksite requires a careful analysis of several competing safety and production considerations. Thirty-five operators of remotely controlled continuous mining machines were observed using work sampling followed by interviews to determine where the operator was positioned and what he or she was watching. These observations were separated according to the task being performed by the continuous mining machine and summarized as position density plots. The specific task of tramming in reverse through a crosscut is analyzed along with more general summaries of the time miners spend outside of the policy-defined operating positions while performing other production tasks. The operators were: observed to frequently vary from company standard operating procedures (SOP). Many of the variations from company SOPS were based on task demands. Interview responses indicated that portions of the mining task place visibility demands on the operators that are difficult to accommodate within existing procedures. An improved task design process would include these visibility requirements. Also, the operator's vision can be augmented thorough video cameras in future teleoperated mining systems, and the operator can be increasingly isolated from environmental hazards.

Jan 1, 1992

By L. M. Klimov

In recent gears in the coal industry a great deal of attention is attached to the questions of elaborating and introducing the problems of planning and management and, first of all, in the sphere of mine production. The basis for planning of mi- ne production is complexes (sets) of problems for planning the development of mining operations based on different time periods, ensuring the follow-up of changes of mine productive capacities. Complexes of problems for planning, the development of mining operations at existing underground and surface mines within the OASUugol system (Coal Industry-wide Automatic System of Management) are aimed at ma- king decisions close to optimum, i.e. general lay-out of panels, blocks and pillars; transport and ventilation networks; schedules for working out parts of mine take; coordinated mining operations with limited labour and material resources; control of mining operations and ultimately maintaining productive capacities of existing mines at the required level.

Jan 1, 1979

By Ann M. Hagni

One of the most costly factors in the production of aluminum is the consumption of energy in the form of electricity. Energy consumption is increased as refractories in the Hall-Heroult reduction cells are corroded by penetration of the fluxes cryolite (Na3AlF6) and villiaumite (NaF). To decrease thermal conductivity and refractory waste, protective barrier linings are installed. Dry powder barrier linings form stable reaction products at cell operating temperatures. Four dry powders composed of vermiculite, corundum, wollastonite, and anorthite are characterized mineralogically by X-ray diffraction, reflected light microscopy, scanning electron microscopy, and cathodoluminescence microscopy in this research project.

Jan 1, 1998

By Nick J. Miles, Gareth J. Brown

The degree of fragmentation of dispersed systems of brittle materials such as pulverised rock has been described by a fractal dimension i.e. the fragmentation fractal. This fractal dimension represents a power law size-frequency distribution, where, in this case, the size is defined as the square root of the projected area. The existence of a fractal dimension for the number-size distribution, of the progeny of failure event, is direct evidence for scale invariance of the fragmentation process. Since a fractal dimension infers that failure mechanisms operate on all scales it has been suggested that the fractal dimension is a measure of the fracture resistance properties of materials during fragmentation. In order to investigate this a range of rocks of varying fracture toughness were broken under similar levels of impact velocity in the dynamic tensile failure of single particles. The fragmentation fractals determined from the resultant particle populations, of the breakage experiments, were monitored and are discussed.

Jan 1, 1995

By C. K. Blair, V. J. Hucka, E. P. Kimball

In central Utah, a coal mining operation is taking place under an 0.5-m (20-in.) pressurized natural gas pipeline. The room-and-pillar method with pillar extraction is being used to extract the coal from the seams. The pillars beneath the pipeline will not be extracted; however, there is a possibility that some subsidence may occur due to pillar failure. To assess possible damages on the pipeline, an attempt has been made to predict subsidence in the area where pillars may collapse. The resultant values of subsidence strain and slope have been used to determine the magnitude of strain, stress, and shear induced in the pipeline. Also, a network of survey points has been installed along the pipeline to detect ground move¬ment that would indicate excessive subsidence.

Jan 1, 1987

By C. Flores, L. G. Twidwell, T. S. Jordan

It is well known that manguniferous silver ores containing manganese intimate) associated with silver are not amenable to conventional extraction methods. The segregation process has been applied primarily to the recovery of copper from oxidized and oxide-sulfide ores. A new alternative process, consisting of segregation roasting followed by flotation to recover the silver from refractory manganiferous silver ores, was studied using a 23-factorial experimental design. Laboratory investigations were conducted on a manganiferous silver ore analyzing 0.02% copper, 0.09% lead, 0.33% zinc, 12.55% manganese and 187 g/t silver. The investigation was designed to study the effects of the addition of salts, coke and copper (11) oxide on silver recovery. The results indicated that 79.3% of the silver can be recovered in the absence of copper oxide and 88.4% of the silver can be recovered with a copper oxide content of 1.5% at 750°C, 2% salt (NaCI). 1 % coke and 30 min of roasting. It was concluded that the addition of copper oxide improves silver recovery.

Jan 1, 1996

By Ian McFeat-Smith, Robert J. Fowell

Roadheader machines have a specific place in modern tunnelling, not simply as a compromise between drill and blast techniques and full face machines, but as an economic and versatile form of mechanised tunnelling where the method of excavation is easily integrated with tunnelling operations. In the past, roadheaders have been subjected to misuses by engineers who failed to realise that, as in all mechanised tunnelling, a planned and systematic approach is essential if the full potential of these machines is to be gained. An increasing awareness of this, together with the introduction of the more powerful roadheader carrying their cutting potential into the hard range of rock is changing this situation and now makes the prospect of using roadheaders particularly attractive (1). The advantages gained by employing these machines can be considerable and Table 1 lists some of them. This table illustrates that from both cost, and installation points of view, the roadheader has considerable benefits over the full face machine. However, the principal advantage gained is in broken ground where heavy supports can be installed immediately at the tunnel face. In addition, access for planned maintenance and repairs to most working parts of the machine is at a premium and average machine utilisations of 40 - 60% can be expected. In comparison to drill and blast methods, up to 40% better progress can be regularly achieved, and the subsequent savings in overbreak costs alone would more than pay for the cost of a roadheader used to drive a 3km long tunnel. As with full face machines, ground disturbance is minimal and for short tunnels in urban areas a road-

Jan 1, 1979

By Finn Ouchterlony

INTRODUCTION Much of present fracture toughness testing con¬cerns chevron notched specimens (Newman Jr., 1984) since these, in principle, require neither fatigue precracking nor more registration than failure load to determine fracture toughness. Two such specimens which can be made from diamond drilled rock cores with minimal machining are the Short Rod (Barker, 1977) and the Chevron Edge Notch Round Bar in Bend¬ing or CENRBB Specimen (Ouchterlony, 1980). Even if the precracking property is especially valuable for a material like rock, practice has made the relative advantages of these chevron notched specimens much less apparent (Ouchterlony, 1982; Ouchterlony and Sun, 1983). Enough remains, however, to have the Commission on Testing Methods of the International Society for Rock Mechanics (ISRM) focus on them as standard configurations in a "Suggested Method for Determining Fracture Tough¬ness of Rock Material", which is in preparation. This paper presents material which supports the ISRM effort: 1. An experimental compliance calibration of the Chevron Bend (CENRBB or CB for short) and re¬sulting formulas. 2. Specimen tolerances, evaluation formulas, and loading rate requirements relating to both Short Rod and Chevron Bend Specimens of suggest¬ed standard proportions. 3. Some fracture toughness values obtained with the Chevron Bend Specimen. This material is mainly based on two reports (Ouchterlony, 1984 and 1985). CALIBRATION OF THE CHEVRON BEND SPECIMEN Preliminaries The specimen and basic notation is shown in Figure 1 together with a straight notched variety (SECRBB). Subscripts c and s are sometimes used below to distinguish between them. Assuming linearly elastic conditions the load point compliance [ ]

Jan 1, 1986

By Valcana Stoyanova

The distribution pattern, abundance variations and types of polymetallic nodules and associated megabenthic communities in area covers more than 60 000 km2 laid out in the eastern Clarion-Clipperton Zone (CCZ) is presented. Our observations are based on data from 158 boxcore stations collected during the cruise of the Interoceanmetal (IOM) in 2004 on board of RV Yuzhmorgeologiya. Although those polymetallic nodules for two decades been subject to prospecting and exploration studies carried out by IOM, the knowledge of megabenthic communities and their distribution pattern within nodule field was extremely limited. With purpose to evaluate the relationship between polymetallic nodules and associated benthic megafauna, an comparison analyze was carried out in respect to their composition, types, abundance across the studied area owing into account the local particular feature of bottom topography. It is suggested that the nodule-bearing seafloor supported more diverse fauna (higher number of morphotypes) than the nodule-free areas. Moreover, based on correlation between types of nodules and associated faunal morphotypes frequency the apparent relationship is considered. The most abundant megafaunal taxa (between 68 ? 92%) is essentially associated with the occurrence of the diagenetically growth nodules type (D-type and its D1-subtype); the role of the H and HD nodule-types was variable. In respect to the bottom topography, the highest diversity in the structure of megafaunal communities was recorded in the gently undulating plains and on the horst slopes, thus the highest nodule abundance occur on the topographic slopes.

Jan 1, 2008

By Gustavo G. Pilger, Jair C. Koppe, João Felipe C. L. Costa

Information for mine planning requires to be close spaced, if compared to the grid used for exploration and resource assessment. The additional samples collected during quasi-mining are frequently located in the same pattern of the original diamond drill holes net but closer spaced. This procedure is not the best in mathematical sense for selecting a location. The impact of an additional information to reduce the uncertainty about the parameter been modelled is not the same everywhere within the deposit. Some locations are more sensitive in reducing the local and global uncertainty than others. This study introduces a methodology to select additional sample locations based on stochastic simulation. The procedure takes into account data variability and their spatial location. Multiple equally probable models representing a geological attribute are generated via geostatistical simulation. These models share basically the same histogram and the same variogram obtained from the original dataset. At each block belonging to the model a value is obtained from the n simulations and their combination allows one to access local variability. Variability is measured using an uncertainty index proposed. This index was used to map zones of high variability. A value extracted from a given simulation is added to the original dataset from a zone identified as erratic in the previous maps. The process of adding samples and simulation is repeated and the benefit of the additional sample is evaluated. The contribution of an extra sample was evaluated locally, globally and in terms of variation in total measured resources. The procedure showed to be robust and theoretically sound, mapping zones where the additional information is most beneficial. A case study using coal seam thickness illustrates the method.

Jan 1, 2002

By K. Vaxevanidou

A combined chemical and biological treatment for the removal of heavy metals and arsenic from a contaminated soil was studied as a potential method for soil remediation. Small scale and column tests were conducted in order to ex-amine the effect of plant-compost and Na2CaEDTA addition on a calcareous soil highly contaminated with heavy metals and arsenic. EDTA is known to be an efficient leaching agent of heavy metals from contaminated soils but has no effect on arsenic. Compost tea on the other hand contains humics that can leach several iron compounds including Fe(III)-oxides and thus can extract arsenic bound to these oxides. The action of Fe(III)-respiring bacteria D.palmitatis was also evaluated for the reduction of iron oxides and compared to simple chemical treatment in the presence of compost in small scale tests. Results indicated that the addition of compost and EDTA into soil pulp lead to the predominance of reductive conditions and the simultaneous dissolution of both heavy metals and arsenic at high percentages. The presence of D.palmitatis did not further enhance the reductive dissolution of Fe(III)-oxides by compost and EDTA as it was observed in the inoculated samples. Column tests using soil as received revealed that, although the extraction of metals seems to be a slow process, compost is an effective oxygen barrier that promotes the reductive dissolution of iron oxides and the subsequent arsenic release together with the dissolution of heavy metals by EDTA.

Jan 1, 2005

By Winfield G. Wright, Philip L. Verplanck, Douglas B. Yager, Dana J. Bove, M. Alisa Mast

The upper Animas River watershed is affected by metal-rich drainage from abandoned mines and by natural weathering of mineralized bedrock. To investigate the importance of natural metal sources, surface waters were sampled in a minimally mined but intensely altered area of the watershed. Water chemistry was strongly controlled by the degree of bedrock alteration. Propylitically altered rocks, which contain calcite, produced neutral waters with low metal concentrations, whereas quartz-sericite-pyrite alteration was characterized by acid-sulfate type waters with high metal concentrations. A mass-balance approach was used to estimate natural metal sources, which accounted for 56-905 of the dissolved metal load discharging from the study area

Jan 1, 2000

By G. R. Rao, K. A. Natarajan, P. Devasia

The role of growth conditions and adhesion of Thiobacillus ferrooxidans on the leaching of chalcopyrite was investigated. Thiobacillus ferrooxidans grown on sulfur, thiosulfate and ferrous ion substrates was used in this comparative study. Growth on sulfur, a solid substrate, requires bacterial adhesion unlike that required in the presence of soluble thiosulfate and ferrous ion in a mineral-salts medium. Solid substrate-grown cells showed higher rates of leaching than those grown in liquid media. An initial lag period noticed during leaching by solution-grown cells was absent when solid substrate-grown cells were used. Such a behavior is attributed to the presence of an inducible proteinaceous cell-surface appendage on the sulfur-grown cells. This appendage aids in bacterial adhesion onto the mineral surfaces. Such an appendage is absent in solution-grown cells, as substantiated by electrophoretic measurements. The importance of bacterial adhesion and the direct mechanism in leaching by Thiobacillus ferrooxidans are demonstrated.

Jan 1, 1997

By T. M. Barton, M. Gauna, A. A. Campoli

Coal mine bumps, the violent failures of overstressed coal, present a safety hazard to miners when longwall mining is conducted in deep, bump-prone coal mines. Two different longwall gate entry systems were evaluated in a southern Appalachian coal mine located in the Pocahontas No. 3 coalbed under approximately 610 m (2000 ft) of overburden that included a massive sandstone member. Both gate entry systems employed a center abutment pillar flanked by yield pillars. The original design used a 24.4-m (80 ft) square abutment pillar, while the new design employed a 36.6-m x 54.9-m (120 ft x 180 ft) abutment pillar. Rock mechanics instrumentation data analysis and in-mine observations indicated that this increase in abutment pillar size significantly decreased bump potential. The new design in worst-case conditions increased effective bearing area 62%, with only a 9% increase in gate entry system width, and eliminated face bumps that were experienced with the original gate entry design.

Jan 1, 1993

By M. G. Bakker, D. D. Murphy, D. R. Spears

The US Bureau of Mines studied the mechanism of shear flocculation of silica with stearic acid. At pH 6 and 12, shear flocculation of silica was not observed with the addition of up to 4.5 x 10-4 M (5 lb/st) stearic acid. However, in the presence of 0.1 M NaCl at pH 6, shear-flocculation was observed at stearic acid concentrations = 10-4 M (22.5 lb/st). Adsorption of stearic acid on silica was studied using stearic acids spin-labeled with a doxyl group. The presence of the spin-labeling group did not greatly affect the shear flocculation properties of stearic acid. Adsorption of labeled stearic acid on silica was measured as a function of surfactant concentration with electron paramagnetic resonance (EPR) spectroscopy and gas chromatography (GC). The GC results indicated that the stearic acid was predominately adsorbed on the surface at concentrations above 10-4 M. From the EPR spectra, the formation of aggregates of stearic acid was apparent at concentrations of approximately 10-5 M (22.5 lb/st). The results are discussed in terms of a possible mechanism for shear flocculation.

Jan 1, 1995

By Keith G. Wallace, Robert Wise, Ian J. Duckworth

This paper describes a case study for the ventilation planning at Utah Fuel Company's Skyline Mines which are located outside Price. Utah. The Skyline Mines are currently comprised of two longwall coal mining blocks located in two different mines. A third replacement longwall block is currently being developed. Future ventilation systems for the mines were determined by establishing ventilation models developed from data collected during a detailed ventilation survey. The paper discusses the challenge to coordinate immediate ventilation requirements with long-term demands. The continuous movement of the longwall, which frequently represented the only open split in the ventilation network, resulted in cyclic ventilation demands dependent upon the length of the tailgate. A series of system configuration changes were recommended based on the results of the network modeling exercise and an economic evaluation of the various options. The scope and cost of the configuration changes, and the mead improvement resulting from these changes is discussed.

Jan 1, 1995

By Thomas Oberndorfer

Recent publications indicate that there is a rising interest in the field of mining method selection, and increasing efforts are being undertaken to develop satisfying solutions. Yet, computer assistance for mining method selection (MMS), or in other, terms assistance in the (pre-)feasibility state of a project, still lags behind the computer application in other mining activities. This is true for research as well as for application. This paper is intended as a contribution to the development in computer-assisted mining method selection, and focuses especially on underground hard-rock mining. It is structured in four main parts. The first deals with general aspects of mining method. selection within the process of mine planning, and with problems and requirements which derive from this specific situation. In the second part some numerical MMS-approaches hitherto published are briefly introduced, and investigations on these approaches are discussed. Based on .these experiences, in the third part an analysis of the complex system MMS is presented. It focuses on heuristics, influencing factors, objectives, assessment-routines and mining methods, and emphasizes the essential necessity of a profound mining method description (MMD) specially developed for the requirements of MMS and numerical processing. Accordingly the fourth part of this paper presents a mining method description model developed at the Department of Mining Engineering, Montan-University Leoben (MUL), Austria. It describes the consequences of the investigation, in particular the new mining method description model, on 'the design of a MMS-system. The paper closes with a outlook on the possibilities of an successful MMS-system being realised.

Jan 1, 1992

By A. W. Easton

INTRODUCTION This presentation will address changing trade patterns in lead and zinc from the mid 1980's to the early 1990's. Lead and zinc deposits are developed where they are found in many parts of the world. As many are not in major consuming areas, there is significant international trade in both lead and zinc concentrates and in refined metal. Forecasts of mine production have been analyzed, primary and secondary refining capacity and future consumption levels have been estimated, to arrive at the changes in trade patterns expected during the next half decade. This paper will first address concentrate and metal trade patterns for lead, then for zinc, and finally some remarks will be made on captive mine/smelter agreements, on regional trade agreements, and on barriers to trade. I would like to note that. there is only a small international trade in semi-fabricated products such as zinc die-cast alloy, zinc oxide, lead oxide or rolled lead and zinc. Most of the world's zinc and lead trade is in concentrates or refined metal. LEAD TRADE PATTERNS Lead Concentrates Six countries are exporters of lead concentrates. Three countries are in the Americas - Canada, Mexico and Peru, with two in Africa - Morocco and South Africa (including Namibia), and Australia. Due to the limited growth in lead consumption and consequent minimum investment in new production facilities expected, mine and metal production levels and future consumption levels are not forecast to change much between now and 1990. Accordingly, the tonnage of lead concentrates exported will remain essentially unchanged from these six countries. In total they have exports of 480,000 metric tonnes (metal content)* and by 1990 this figure is forecast to rise only slightly with the only increase taking place in Mexico. The concentrates are exported mainly to Western Europe & Japan. Apart from these six main lead concentrate exporting nations, a significant change is expected in the United States. In the mid * All concentrate trade figures are based on metal content

Jan 1, 1986

By Jacques Villeneuve, Stéphane Brochot, Jean-Claude Guillaneau, Marie-Véronique Durance

Since 1986, BRGM has been developing a powerful process simulation software package, USIM PAC. These last years have seen significant developments in mineral processing technologies, particularly in hydrometallurgy, bio-hydrometallurgy and mineral liberation. The new version of the simulator, USIM PAC 3.0, incorporates these modem-processing fields. Its structure and tools allow the user to take into account, at the same time, a wide range of technological, economical and environmental aspects. The improvement of the existing features and the introduction of new unit operation mathematical models and tools such as the supervisor, global optimization, workshop model or chemical reactions contribute to a global approach in mineral processing design.

Jan 1, 2002

The minerals industry contributes to the economic growth, prosperity and quality of life of nations, particularly in areas where there might be limited opportunities for employment in other sectors. However, notwithstanding their economic importance, the minerals extraction and processing industries are considered to have significant impacts on the surrounding environment. In recent years many mines have implemented modern monitoring technology and modelling of the monitored environmental parameters to provide scientifically proven indicators about the state of the environment. The flexibility required by the minerals industry to respond dynamically to a changing natural, social and economic environment has become a major consideration. Whilst the notion of continuous improvement is embodied within most environmental management systems, what is now required is a structured audit trail which tracks the flow of resources through the production process to the ultimate environmental impact associated with their consumption, transformation and disposal. Imperial College is coordinating an EC funded project, which is developing a methodology to minimise the ?full life-cycle? impact of metalliferous mining projects, adopting an integrated approach to production and process design, and the costs involved. In order to develop a life cycle assessment (LCA) system that will incorporate different types of data related to the minerals extraction operations, a data inventory was designed and coded in an object-relational database model. The calculation procedures accounting for the input/output balance of the alternative scenarios for mining production, processing, waste disposal, monitoring, and their financial implications are being programmed into a software system. This paper presents the rational and innovative aspects of this work. The methodology developed for the life cycle database is illustrated for the mining production and gaseous emissions components of the system.

Jan 1, 2003