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By Robert Boyd

The Diamond Markets ? Supply has continuously increased over the past 25 years ? However, global supply is expected to drop by 1 to 2% by 2015 ? Demand Driven Market ?Demand is expected to grow 3% annually through to 2015 ? Supply Squeeze Anticipated (2010 to 2015) ? Consumption is exceeding rate of discovery, mine development and reserve replacement ? These fundamentals are driving increased capacity and production at existing mines in South Africa, Botswana and Russia and new areas such as Canada ? Canada is now the third largest diamond producing country in the world ? These fundamentals are also driving record levels of exploration expenditures throughout the world with particular focus on Africa and Canada

May 1, 2006

By G. R. Rawsthorne

"The Con-Rycon mine is located on the north shore of Great Slave Lake in the Northwest Territories within the present city limits of Yellow-knife. Development work on the Con property started in 1936, resulting in a mine-mill complex which produced its first gold brick on September 5, 1938. Since that date 5,000,000 tons of ore have been mined yielding 3,000,000 ounces of gold. At present there are 220 employees at the mine.MineThe mine has 1.22 miles of vertical shaft, 41 miles of level development and 10 miles of inclined raises. There has been 1,000,000 feet of diamond drilling in search of ore. The temperature at the 4900 level (4400 feet below sea level) is 68 deg. F.The present mining method is cut and fill. The majority of the ore mined today passed through an internal winze before reaching the main shaft. The long haulage and double handling will be eliminated with the completion of a new shaft presently under construction to the 5800 level.MineralizationThe ore treated today is from the Campbell shear 1vhich is characterized by lenses and veinlets of coarse textured quartz containing some carbonate, sulphides and finely disseminated as well as visible gold. At the lower levels of the mine the arsenopyrite content in the ore is de-creasing with a~ increase in the levels of chalcopyrite and pyrrhotite."

Jan 1, 1974

By A. W. Fahrenwald

"The rate of progress in the last three years in the development of differential flotation has been rapid beyond the realization of most people. Differential flotation is no longer a ""delicate"" and unreliable process, but is now in wide use. Its ""safety"" is due to the wide use of chemicals which either depress or enhance floatability by definite modification of surfaces.The extent of the development and reliability of differential flotation methods any be emphasized by pointing out that there are now several customall-flotation"" plants in this country treating complex lead-zinc-iron ores from widely separated mines. While these ores differ in chemical composition and apparently in physical nature, the various ores treated in such a plant are passed through the same crushing and grinding equipment and through the same flotation machines and flow sheet with only slight changes, if any, in quantity and kind of chemicals and oils added.Some of the development in differential flotation is due to intelligent research on the part of well-trained chemists and metallurgists; much of It must be attributed to empirical testing.Much of the success in differential flotation is due to more care being given to constant conditions with regard to such factors as (1) fineness of grinding, (2) density of pulp entering flotation machines, (3) quantity and constancy of oils and chemicals added to the pulp, and (4) place of addition of reagents, and time of ""conditioning"" treatment of pulp with reagents."

Aug 1, 1925

By L. W. Burger

The need to establish and harmonise methodologies to quantify air emissions, atmospheric dispersion and the consequences of air pollutants (especially hexavalent chromium) from the ferrochrome industry became important aspects with the increasing demands for comprehensive impact assessments. The paper includes a synthesis of current knowledge on the following aspects: ? Locally and internationally accepted methodologies for the quantification of chromium emissions, including sampling methods and emission factors; ? A compilation of recognised and accepted air quality sampling and laboratory analysing techniques; and, ? Dispersion modelling and impact assessment tools. Depositing and removing materials from the chromium ore stockpile and wind erosion of exposed stockpiles result in mainly chromite emissions unlikely to contain significant amounts of hexavalent chromium. Pre-treatment processes such as drying, crushing and screening also produces chromium emissions, but mainly as trivalent chromium. The smelting of chromium is the major source of chromium emissions - open furnaces have the highest uncontrolled chromium emissions, followed by semi-closed and closed furnaces, respectively. Based on the current knowledge on emission rates, interim emission factors for particulate, total chromium and hexavalent chromium releases are provided. Ambient sampling and analytical methods to determine environmental exposure of the general public require that hexavalent chromium needs to be quantified in very low concentrations. Suggested sampling and analytical methods for both source characterisation and ambient monitoring are provided. The selection between dispersion models needs to be based on the size of the modelling domain and the complexity of the terrain. The discussion on dispersion models includes the US EPA?s Industrial Source Complex Model (Version 3), the AERMET/AERMOD suite of models and the CALMET/CALPUFF suite of models. Guidelines are also proposed for environmental exposure assessments including cancer and non-cancer health effects.

Jan 1, 2004

By Donald A. Ranta

Every mineral project or mine is based on a geologic entity-an ore (mineral) deposit. A well-defined mineral deposit and its associated geologic characteristics are the only aspects of a project that cannot be altered. Mine plans can be modified to exploit the deposit using alternative approaches and yielding similar results. A variety of processing methods also are often available producing generally comparable results. Major modifications can be made to other aspects of the project without substantially changing project economics. However, all engineering and metallurgical aspects of a mine must be accommodated to the spe¬cific location and geologic characteristics of the deposit. Geologic data and interpretations form the foundation for both mine evaluation and mine production by providing esti¬mates of reserves and essential information for mine planning and process design or control. Proper geologic work requires a keen awareness of and an ability to anticipate the technical requirements of geotechnical engineers, hydrologists, mining engineers, metallurgists, and other specialists. Geologists are inte-

Jan 1, 2008

By S. S. Cole, C. E. Wood, T. L. Joseph

"INTRODUCTION Iron ore containing titanium was first used in blast furnaces over a century ago. It is well known that TiO2 is a slag-forming material that will increase the amount of slag produced by the usual gangue materials, silica and alumina. Increase in the volume of slag due to the presence of TiO2 and a lack of information concerning its effect on the properties of the slag have prevented the general use of titaniferous ore. Also rather com¬mon belief among furnace operators that the bottom of the furnace builds up when ores containing TiO2 are smelted has militated against the use of titaniferous ore. This building up of the hearth has been attributed to the formation of copper-colored crystals of titanium cyanonitride, which have been observed in the salamanders of blast furnaces. Until recently the availability of nontitaniferous iron ore has left little incentive to use ore containing titanium.The presence of vanadium in certain deposits of titaniferous magnetite in New York State has created new interest in problems connected with the use of titanium-bearing ore. It appears that most of the vanadium in this ore can be recovered in pig iron, which can be blown in a converter to produce a slag containing vanadium in amounts suitable for the production of ferrovanadium.The Titanium Division of the National Lead Co. recently erected a largo mill to treat ore from Sanford Hill, in Essex County, New York, about 50 miles west of Port Henry. The ore deposit was acquired from the MacIntyre Iron Co. and is often referred to as Sanford ore. It is one of the largest deposits of Iron-bearing material to be found east of the Lake Superior region and is being mined by open-pit methods."

Jan 1, 1943

By David E. Albus, Ahmadreza Mortezaie, Bidjan Ghahreman

The structural evaluation of seismic performance of an existing hospital in Long Beach, California, required spring constants of foundation elements. The structure included support by deep foundation elements comprised of belled (underreamed) caissons. The available relationships in the governing building code (ASCE41-13) to compute axial stiffness is not applicable due to the belled configuration of the caissons. The large diameter of the bells required consideration of the foundation medium to the axial stiffness; a detail not clearly described in ASCE 41-13. Furthermore, prescriptive equations in ASCE 41- 13 used to estimate lateral stiffness only consider pile groups with the assumption that the only source of lateral stiffness is the axial reaction of individual piles. These assumptions were invalid for the project at hand where all caissons are configured as single foundation elements, not a pile group. In the present work, the approach taken to estimate seismic stiffness of single-belled caissons is described which accounts for the elastic behavior of the foundation medium below the bell base and lateral behavior of single-pile shafts. Results of the work provide a more satisfactory derivation of the spring constants consistent with current modeling methods. INTRODUCTION Seismic evaluation of an existing hospital in Long Beach, California, required geotechnical investigation followed by site-specific ground motion analysis. This evaluation was required by the Office of Statewide Health Planning and Development (OSHPD) in order to meet the requirements of the Structural Performance Category 4D (SPC-4D) published as a part of the 2016 California Building Code, CBC (Section 3412A). SPC-4D utilizes ASCE41-13, as modified by OSHPD, and involves two seismic performance objectives: BSE-1E (20% probability of exceedance in 50 years) and BSE-2E (5% probability of exceedance in 50 years). Spring constants and capacities of foundation elements were needed for evaluation of the structural performance of the building subjected to these two performance objectives. Our review of the as-built foundation plans indicated that both shallow footings and caissons were used for support of the structure. The plans demonstrated that all caissons are belled (under-reamed) and are individual, i.e. not part of pile groups. In this paper, the subject site condition and foundation elements are described first. This is followed by details of assessing spring constants and vertical capacities for belled caissons. The new requirements of the 2016 CBC concerning the evaluation of critical facilities will likely entail evaluation of other structures with belled caissons due to the more extensive use of these foundations in the past. This paper proposes a method to address the conditions of individual belled caissons not explicitly considered in the current code provisions.

Jan 1, 2018

By J. B. Clark

In multiphase ternary diffusion studies, plots of the variation bf the composition on the isotherm constitutes one of the most effective methods of presenting experimental results, especially if such plots are made in a manner which relates the composition path on the isotherm with the diffusion layer structure in the couple. Unfortunately, if different conventions for plotting are used serious misinterpretations occur readily, causing apparent disagreement between investigators who actually share the same viewpoint. A common convention for mapping these diffusion paths is needed at this time because with the increasing use of the electron-probe X-ray microanalyzer, a much greater number of ternary diffusion studies can be expected in the near future. In an effort to prevent unnecessary confusion in the future litera- ture, a convention for these plots is proposed, as outlined below. A hypothetical example of the use of these conventions is given in Fig. 1 where the path of composition through the diffusion structure of the 100 pct A/50 pct B, 50 pct C couple is plotted on the appropriate isotherm of the ABC system. The lower case letters relate the region in the diffusion layer structure to the appropriate composition on the ternary isotherm. 1) The diffusion path is plotted on the isothermal section corresponding to the diffusion temperature of the couple. 2) The terminal compositions of the plotted diffusion path are the initial compositions of the couple halves—provided infinite boundary conditions are maintained. If, in either couple half, infinite conditions are not maintained, then the path terminates at the composition of the exterior surface of the couple. If, at this surface, the composition varies with time or if the plotted path is time dependent, then the diffusion time should be noted beside the plotted path. 3) A solid line crossing a single phase field (e.g., line a-b in Fig. 1) denotes an existing layer of that phase in the diffused couple. 4) A dashed line crossing a two-phase field parallel to the tie lines (e.g., line g-h) represents an interface between the two phases with interfacial compositions designated by the ends of the tie-line. The line represents no spatial extent. 5) A solid line crossing a two-phase field so as to cut tie lines (e.g., line b-c or line j-k) represents a locally equilibrated columnar two-phase layer. The solid line should cut those tie lines which correspond to the lateral interfacial equilibria along the columnar

Jan 1, 1963

By M. R. TECK, N. Rudd, L. K. Thomas, D. L. Katz

The authors are to be congratulated for presenting the first comprehensive paper on the theory and practice of threshold pressure determination in connection with underground gas storage. It is of particular value since most previous experimental work on this subject has been proprietary to the commercial laboratories engaged in such testing and to their clients. This dlscussion is presented in amplification of the subject paper, not in criticism, and is based upon our experience with approximately 5,000 threshold pressure determinations. Our comments are directed primarily to the experimental procedures as described by Thomas et al. It should be noted that, while clay mineral-rich lithologies are the most common caprock materials, the samples used (Table 1) include low permeability sandstones and carbonates, but do not include shales or other formations in which clav minerals exert a dominant effect. While our experience on samples analogous to those investigated by the authors generally confirms their findings, we have found that even more rigorous experimental conditions must be imposed where clay minerals are the controlling factor. These additional conditions result from the well-known molecular character of the clay minerals themselves in which water is interlaminated with, and bonded to, silicate sheets, thus becoming an essential component of the molecule. In many clay minerals the character of the intersheet bonding, and thus the dimension of the lattice, is strongly affected by variations in the identity and concentration of cations present in the intersilicate water. On a supermolecular scale, adsorbed water films on particle or "flakes" of shale provide much of the cohesive force necessary to maintain mechanical strength. The thickness of these films is variable and inversely proportional to intergranular pressure within the dimensional limits involved in caprock investigation. The thickness of the intersilicate water layers may also be subject to pressure under some conditions. These considerations are reflected in several necessary modifications of the experimental procedures described by the authors. Two of these are, in our judgment and experience, of such importance that they cast real doubt on the validity of data obtained on argillaceous materials without their application. The very careful resaturation procedures proposed by the authors should give good results in connection with the relatively "inert" lithologies used in their experiments. Our experience suggests, however, that they would create more problems than they would eliminate if applied to argillaceous materials. 1. Drying of the sample at the temperature and for the duration indicated by the authors not only will dessicate the sample with consequent shrinkage cracking, parting along bedding planes, and even total disassociation in the case of fissile shales, but it may also alter the character of the clay minerals themselves — in some cases irreversibly. 2. Prolonged evacuation to 2 microns Hg further dessicates the sample and is even more effective in reducing the intersilicate water content. 3. Resaturation with water differing in pH or chemical content from that existing originally in the sample also serves to alter the nature of the sample, particularly its structure and strength. 4. Our experience has been that, even with the thorough precautions proposed by the authors, complete resaturation of very fine grained materials is rarely obtained. Yet our experience confirms the

Jan 1, 1969

By X. M. Zhou, T. Wu, He X. N.

"In order to study the support effect of concrete in the surrounding rock of a metal mine, the concrete and surrounding rock were comparatively studied. Firstly, the general situation of the ultra-kilometer deep shaft in Xincheng, surrounding rock and geological conditions are introduced. Secondly, the experimental scheme of material mechanical properties of surrounding rock and shaft lining concrete based on same standard dimension and shape are examined, and the mechanical tests of rock and concrete based on different shapes and sizes are carried out. The study shows that the compressive strength value and elastic modulus of the rock cube are 1.28 times and 1.78 times that of the cylinder, and the Poisson's ratio is 0.77 times. The dimensional effect law of the concrete cube and cylinder test data is consistent with the rock law. However, the test results of the concrete are less discrete than the rock; the test also shows that the strength and elastic modulus of the concrete lining of the main shaft of the Xincheng are much smaller than the surrounding rock that is also used as the concrete aggregate, which indicates that the support of concrete lining in the surrounding rock shaft behaved weakly. Based on the development of the modern NATM rock support theory, it is suggested that the mechanical test standard of artificial support materials should be unified into the mechanics test standard of natural rock, which will help to improve the accuracy and practicality of scientific calculation of geotechnical engineering.INTRODUCTIONConcrete and rock mass are usually attributed to a class of materials called frictional materials or geotechnical materials, of these two kinds of materials, the first is man-maded and the second is natural. The attentive scholar can find that there are many differences in the test criteria for the mechanical properties of the two kinds of materials among different industries or departments, reflecting the differences in their sources, tradition, and the application thoery of material strength among them.There is a situation wordwide, that there are many testing standards of the same material mechanical parameters such as elastic modulus, compressive strength, etc. The cube with a side length of 150 mm is adopted as a common sample in the architecture department in China, while a cylinder with a diameter of 50 mm and a height of 100 mm is as a standard specimen in geotechnical department.Knowing that mechanical parameter values are strongly affected by the the size, shape of specimen and loading rate etc, that is to say the mechanical parameter values of the same material are completely different when obtained from different test with different standards. However, such a problem has been long neglected in geotechnical engineering."

Jan 1, 2019

By A-A Latscha, C Boyle

Geological modelling has historically been done using sectional interpretation of paper sections or on a computer screen. Boundaries of geological units or grade shells are interpreted by a geologist section by section and the shapes are drawn onto paper to be digitised later or they are directly digitised into a computer. This approach is referred to as explicit modelling. Such methods are time consuming if there are many section lines or boundaries to be interpreted. The number of metres drilled and resource models made is increasing each year and it will be difficult to keep up using explicit modelling methods. Alternatively, it is possible to use information carried in the drill holes, known geological relationships and point estimation methods in two or three dimensions, to create similar geology boundaries, while eliminating or at least greatly reducing the need to manually interpret and digitise detailed sectional interpretations. Such methods are referred to as implicit modelling and are available in a number of software packages. Implicit modelling approaches have been used in iron ore and found to significantly reduce the time needed for modelling while producing results that are comparable or better than standard explicit modelling approaches. A number of case studies have been undertaken of implicit modelling in iron ore deposits. Stratigraphic surfaces of bedded, folded and faulted iron ore deposits have been modelled in various deposits by Leapfrog Geo, GOCAD (with SKUA) and Vulcan Integrated Stratigraphic Modelling. Leapfrog Mining was used to model iron grade shells at particular cut-off grades. The modelled surfaces are of a high standard equivalent to those that could be produced by traditional explicit modelling but the time required by the implicit methods is far less. Implicit geological modelling is an active area of software development and improvements in software are likely.CITATION:Boyle, C and Latscha, A-A, 2013. Implicit geological modelling of iron ore deposits, in Proceedings Iron Ore 2013 , pp 57-66 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By D M. Marques, J F. C L Costa

The estimation of process plant head grade is not trivial and is a source of constant dispute within the mining industry. Grade estimates informed by the short term mine planning are frequently not reproduced by sampling the continuous flow of ore at the plant. Head grades are normally obtained by periodically sampling the continuous flow during a day or shift, and taking the average of the multiple increments collected. The standard error of this mean grade depends on the ore variability and the frequency (number) of aliquots extracted. The more increments are taken the higher is the precision on the calculated mean. Variographic experiments are normally used to map grade variability along a certain period of time and the extension variance is derived from this variogram. This experiment is time consuming, expensive and cumbersome. Mining industry personnel rarely apply this approach. Additionally, a temporal variogram can vary from day to day as different ores are mined along the life of the mine. This paper investigates a novel approach based on simulating the grades feeding the processing plant. In situ 3D grade models are built using geostatistical simulations. Grade spatial continuity and variability are reproduced in models that mimic the real deposit. These models are used in mine planning and scheduling transforming a 3D block model into an one dimensional string of values feeding the plant (one dimension flow). These grades have the statistical characteristics of the unknown real grades and can be sampled to emulate a variographic experiment. The results showed consistency and adequacy to estimate the sampling error (Gy, 1998 p 31) for various sampling intervals using the simulated grades. Also the results show a variographic experiment can change significantly from time to time, as ore changes and a selected sampling protocol can become obsolete if not adjusted for ore variability.CITATION:Costa, J F C L and Marques, D M, 2012. Defining a sampling strategy for a continuous flow supported by geostatistical simulations, in Proceedings Sampling 2012 , pp 3-8 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 21, 2012

By K. Morita, N. Sano

Thermodynamic properties of chromium oxides in molten slags are very important for optimization of stainless steel refining processes as well as reduction processes of chromium ores. The solubility of chromite into molten slags has been found to vary considerably with oxygen partial pressure and slag composition in former studies by the authors. In the present study, activity data and redox equilibria of chromium oxides measured under moderately reducing conditions, PO2= 6.95x10–11atm, at 1873 K are summarized. For the CaO-SiO2-CrOXsystem, the activity coefficient of chromium oxide increased with increasing basicity, and the optimized slag composition for stainless steel refining is assessed as that saturated with CaCr2O4and Cr2O3usingthe phase relations determined. On the other hand, the presence of MgO and Al2O3brings about different behaviour of chromium oxide activity and redox equilibiria and the 44 mass per centCaO-39 mass per cent SiO2-11 mass per cent Al2O3-6 mass per cent MgO slag is recommended toreduce the chromium oxidation loss in the practical stainless steel refining process at 1873 K. Keywords: chromium, activity, stainless steel, AOD, VOD, oxidation loss, redox, CaO-SiO2-Al2O3-MgO slag

Jan 1, 2004

By Kunihiko Takahashi, Gjergj Dodbiba, Hisayoshi Umeda, Toyohisa Fujita

"An increasing number of mobile phones is increasing the number of the discarded mobile phones. Many efforts are thus being made to collect and recycle these devices. This paper is a short introduction of the recycling system of precious metals from the discarded mobile phone, currently available in Japan. Moreover, an attempt has been made to compare the energy recovery and the mechanical recycling of plastic wastes from the discarded mobile phone. The assessment has been carried out in the context of the life cycle assessment methodology (LCA). The environmental impact of each option was assessed by calculating the following impact indicators: depletion of abiotic resources (ADP), and global warming potential (GWP). 1. Introduction In 2003, the demand for mobile phones was increased since the camera was included in a mobile phone and the 3rd generation of mobile phones was introduced. In turn, the number of discarded mobile phone is rising sharply. Generally speaking, all the metallic parts of mobile phones can be recovered and recycled by using smelting and purification techniques. The recycled materials are then used to fabricate other new products."

Jan 1, 2008

By H. S. Martin

The Phosphate Recovery Corporation operates three flotation plants, Nos. 1 and 2 concentrators about three miles northeast of Mulberry, Florida, and No. 3 plant at Wales, Tennessee. These plants represent the first commercial phosphate flotation operation and are also believed to be the largest nonmetallic flotation operation in the world at the present time. The details of this paper will be confined to plant No. 2, this being the newest and largest concentrator in Florida, and the flow sheet being practically the same as at plant No. 1. The No. 3 plant has been operated but a short time and has been shut down since December, 1932, on account of the decrease in phosphate rock production. The phosphate washers usually are located centrally on a known deposit so that about two hundred acres of ground can be mined economically to each washer location. The washers are moved to new areas when the distance becomes too great for economical pumping. The flotation plants are built either adjacent to a washer, so that current debris may be utilized, or on the site of a former washer where there is sufficient accumulated debris available for mining, and the flotation plants must also be moved from time to time. Most of the water used in the Florida flotation plants is recovered after passing through a circulating system where most of the fine suspended matter is settled out, but some make-up water is obtained from deep wells near the plant. Power is obtained from the Tampa Electric Co. through the distribution facilities of the International Agricultural Corporation. Flotation concentrate is hauled from the plant by trolley over the International Agricultural Corporation's trolley system, to the drying plant at Prairie, one mile northwest of Mulberry. Ore Treated In the pebble phosphate district of Florida, the phosphate mineral, or collophane, is usually found in horizontal beds of varying thickness

Jan 1, 1935

By S. Maurhofer

The Uetliberg Tunnel in Switzerland is the longest tunnel in Zurich?s new Western Bypass Expressway, connecting the Birmensdorf bypass in the west with the existing Zurich-Chur national motorway in the east. Thus the tunnel links the Zurich-West motorway interchange with the Zurich-South interchange (shown in Figure 1). The Uetliberg Tunnel project comprises two parallel tubes, each about 4.4 km long. The two tunnel tubes are connected every 300 m by a transverse walkway and every 900 m by a transverse roadway (Figure 2). The SOS niches are spaced 150 m apart. Portal stations with machinery rooms are located at the west and east portals. The tunnel falls with a gradient of 1.6% from the west portal at Wannenboden to the east portal at Gänziloo. The Project costs are about CHF 1.12 billion. The carcass construction started in March 2001. The Opening of the Uetliberg Tunnel is planed in spring 2009.

By Terry L. Muldoon

This report describes development and demonstration of an upgraded stench fire warning system for underground wines. Current systems, which have been used since before 1920, release an ethyl mercaptan mixture into the mines' compressed and/or ventilation air during emergencies. Miners, when smelling ethyl mercaptan, evacuate the mine according to predetermined plans. These systems, while simple, have problems with safety and reliability. The upgraded system overcomes these problems. The system uses a different stench agent, is less toxic, less nauseating, and less corrosive than ethyl mercaptan. These combined with the feature of thiophane not reacting with iron oxides, makes the upgraded system safer and more reliable. The system also uses a combination of two simple principles: a standpipe with pressure balancing to provide a constant head, and a sized orifice to control the rate of release of the stench agent. This system enables the mine to release the agent for a longer period which provides better coverage and to ensure that miners will not be exposed to potentially toxic concentrations of the stench agent. The system is easy to operate, requiring only the turning of two 1/4-turn ball valves. The upgraded system has been successfully tested during two evacuation drills at an underground uranium mine. Using three injectors (one on the compressed air line and one on each of two intake air shafts), the system exhibited significant improvements in warning times over the mine's existing system. This report provides a detailed description of the system design and its demonstrated performance in two mine demonstrations.

Jan 1, 1981

By Natesa I. Jayaraman

A field study was conducted by the Bureau of Mines to determine the feasibility and effectiveness of a secondary ventilation system retrofitted onto an Eickhoff EDW 340L double-drum shearer as a technique for controlling respirable dust generated during a longwall mining operation. An airflow duct was formed by enclosing the bottom of the undercarriage with steel plate and cutting air channels through the ends of the undercarriage frame. Air intakes were provided behind each cutting drum and at several locations along the undercarriage. Grills were installed at the intakes to prevent the broken coal from entering the ducting. A dust collector consisting of 5,000-ft3/min fan, water sprays, and a minicyclone panel was installed on the shearer at the tailgate end. Field results indicated that the secondary ventilation system reduced respirable dust more than 60% along the face. Reduction was less near the intake airway and when secondary dust sources occurred.

Jan 1, 1977

By E. Laine

Rock density determinations are necessary for ore resource evaluations from estimated block grades in g/t. Rock density depends on the mineral composition and, thus, it is specific for each rock type. The rock density distributions for different rock types are often symmetric. Hence, the arithmetic mean is a good approximation for the average density for lithological units. However, there may exist spatial variation in density values due to alteration, fracturing and original heterogeneities such as layering. This study compares the kriged density model with the one with constant density values for different lithological units in the evaluation of metal amounts in rock blocks. The case study consisted of rock densities measured from the drill cores at Ahmavaara PGE deposit in northern Finland. The used Ni contents were simulated in accordance with the spatial distribution of rock densities. The Ni amounts in 2x2x2 m3blocks are higher for the kriged densities than for the average densities. The difference is increasing with the increasing metal amounts due to the nonlinear correlation between Ni content and rock density. The final effect on the resource estimation depends on the cutt off grade and prices of the metal, for example, for a very valuable metal the small differences are significant

Jan 1, 2003

By G. Price

The Building Research Establishment installed a base load cell in a driven cast-in-place pile prior to it being tested under vertical load. The monitored base loads were found to be significantly less than could have been predicted by current design methods. The less than expected capacity was attributed to the drilling out procedure. An electro-level system installed in a second similarly formed pile, provided detailed information on the performance of the pile under lateral load. The information obtained was used to check several current design methods for laterally loaded piles. The findings show the potential dangers of attempting to improve design parameters from only limited performance data.

Jan 1, 2010