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By Robert Thomas

DURING the past 20 years the advantages of reinforced concrete as a substitute for timbering in so-called permanent mine openings have been fully recognized, and its use has become almost general practice in the larger mines. The term "permanent mine openings" is used advisedly and is assumed to embrace such openings as ventilation shafts, material shafts and main hoisting shafts, with their adjacent stations, ore pockets, etc. In the concreting of such openings, the actual cost as compared with that of timbering has been of secondary consideration, the support of large openings, elimination of fire hazards, and prevention of inter-ruptions to production being the primary objectives. The ultimate economy, however, of lining such openings with concrete when they are to remain in use during the entire life of the mine, and especially when they are in bad ground, will seldom be questioned. During this 20-year period there have appeared in engineering publi-cations a number of interesting articles on the use of concrete in mines, nearly always describing some specific project of major proportions, such as the concreting of ore pockets, large stations or main hoisting shafts. Such articles are unquestionably of interest, since the projects require considerable engineering thought, not only in the method of excavating large openings, but in their engineering design as well. Concreting of main hoisting shafts, particularly when this is done with the least possible interruption to production, provides some interesting problems. The concreting of haulage drifts of the dimensions commonly found in mines, on the other hand, soon develops into a routine operation, there-fore it is with some hesitancy that the author attempts to prepare an article on this subject. The writer can recall only one article on the concreting of mine haulageways, although several articles have been written concerning the concreting of tunnels considerably larger in dimensions than those required in general mine practice.

Jan 1, 1936

By H. Krogerus, P. Niemelä, P. Oikarinen

High carbon ferrochromium is produced by carbon reduction. No replacement for carbon as reductant has yet been developed. The reduction creates a considerable amount of CO-gas. In open and semi-closed furnaces the gas is burned when leaving the burden. In closed furnaces the formed gas is sucked out by a fan, washed and utilised as fuel. The formation of carbon monoxide is presented briefly starting from thermodynamic considerations up to solid and liquid state reduction. The volume, composition and energy content of the furnace gas are discussed, focusing on the raw materials and pre-treatment processes of the furnace feed as well as on the process equipment and control. Outokumpu has been using closed and sealed furnaces and utilising the CO-gas in its Tornio Ferrochrome Works since 1968. Today in Tornio with an annual ferrochromium production of 260 000 t CO-gas production is 186 million m3, representing 68 MWh an hour. At the same time the furnace power input is 95MW. About 98 % of the CO-gas is utilised, whereof 30% in the ferrochrome production itself. This paper focuses on the characteristics and utilisation of CO-gas. CO-gas is secondary energy, which on one hand saves primary electric and fossil fuel energy in ferrochromium production and, on the other, replaces other fossil fuels at the adjacent steel works. The characteristics of the fuel, requirements for utilisation as well as health and safety aspects are discussed. Utilisation of the gas has a high impact on the total dust and gaseous emissions and on the energy optimisation at the ferrochromium and steel works.

Jan 1, 2004

By Ronald Smeink, Ton de Gouw

"Reagents are an important cost-factor in the flotation of minerals. The mechanism of collectors and frothers has been studied extensively, but on depressants – probably the biggest cost-factor in the reagent suite – very little is actually known. Theories are frequently faced with the bare facts, pointing in another direction. Fundamental research is complicated by the fact that the amount of possible interactions in the flotation cell is almost unlimited and makes “change-one-parameter-at-a-time” experiments questionable and at least difficult to interpret. Also, the adsorption of depressants on the ore is very strong and desorption merely impossible. Detection methods therefore tend to be indirect and – therefore - non-specific about the location of the depressant on the ore.Depressants are supposed to adsorb selectively on gangue minerals; not on the valuable minerals in the froth. In order to be able to develop better and ‘’smarter’’ depressants, an analytical method is therefore required that will enable to detect which (=qualitatively) depressant, in which concentration (=quantitatively) sits where exactly (= selectively) on the mineral surface. (Answering the question: ‘’ Which minerals is located direct under the depressant?’’)And also: does the depressant compete with other reagents for that location? (like collectors) This analytical method is under development. The actual status of the method is promising and the results will be shown."

Jan 1, 2003

By Steven W. Hunt, Safdar A. Gill

Design and construction of temporary shafts for underground facilities often require evaluation of bottom stability due to rupture (blow-ins) caused by water pressure acting on a bottom plug. This paper provides an overview of shaft bottom stability evaluation methods for the case of a relatively watertight soil plug which overlies an artesian aquifer. Methods of considering plug perimeter shear, plug buckling and pressure relief are discussed. Minimum factors of safety are suggested. Future use of the shaft subgrade is also considered. Bottom plug failure case histories at several shafts are evaluated. This paper should be useful to project designers, ground support system design engineers and contractors involved with construction of shafts for underground facilities

Jan 1, 1997

By S. Narasimha Rao

Bored cast in situ piles are highly susceptible to construction defects like necking, discontinuity in concreting, poor compaction of concrete, improper end bearing condition due to inadequate cleaning of bore hole, exposure of reinforcement, segregation of concrete etc. There is a necessity to understand the behavior of piles so as to design effective foundation system. In this paper investigations of two field cases were discussed to bring out the effect of defective piles. In one case improper end bearing has been discussed for a concrete pile of length of 45m and diameter equal to 1.2 m and is reinforced with 32 no's of 28mm diameter steel bars and in another case necking of the pile has been discussed. Further model piles with preformed defects have been tested in laboratory to bring out the influence of defective piles.

Jan 1, 1996

By R. Rushforth

The surge of activity in the solar energy market, spurred by government incentives, has created new and more efficient solar technologies, but issues surrounding land- and water-use have backlogged the full-scale development of solar farms. This paper explores siting solar power plants on degraded or polluted lands, such as mine tailings impoundments. Historically, mining and has been integral to Arizona?s economy, but has dwindled in relevance due to urban pressures and environmental regulations. Currently, it is legal to site solar power plants on degraded or polluted lands, but the question remains whether the economics of this degraded lands solar development is more favorable than developing pristine land. Therefore, we explore economics of developing mine tailings impoundments at both the institutional and financial level. Methods of research for this paper were interviews with government regulators, environmental advocacy organizations, farmers, and mining company executives. Financial models using extant tax incentives show a positive net present value for the installation of solar power plants, even when accounting for the costs of land remediation.

Jan 1, 2011

By Luminita Calin

King County (Seattle, WA) is on a monumental task of building the new Brightwater System complete with a new treatment plant, three main conveyance tunnels, a new outfall into Puget Sound and other ancillary works. This paper will describe the first conveyance tunnel, Brightwater East currently under construction by the Joint Venture of Kenny (Sponsor) / Shea / Traylor that is scheduled for completion in early 2010. The project located in Bothell, WA (north of Seattle) is in both King and Snohomish Counties. It was the first of the major tunnel projects that was scheduled by King County for the Brightwater System. The East Contract consists of the following major elements: 14,000 ft of 19'-2' EPBTBM mined tunnel using 16'-8' ID bolted, gasketed precast concrete segments for a primary liner; installing and encasing 14,200 ft each of 48', 66', 27', 84' in diameter steel pipes inside the tunnel along with three runs of fiberoptic cable; 2,430 ft of 72' in diameter microtunnel including three caisson shafts and associated structures; one Intercepting Structure (IS) shell to mine from that is 74 ft deep and 74 ft finished in diameter with 130 ft deep slurry diaphragm walls, tremie slab and final concrete wall lining; one Influent Pump Station shell (IPS) 83 ft deep, twin 77 ft inside diameter cells, with 160 ft deep slurry diaphragm walls, tremie slab, and final lining; two short 12 ft in diameter inter-shaft connector tunnels; one extraction shaft 40 ft deep by 40 ft wide and 140 ft long for connection to the new treatment plant piping.

By R. Fernández, E. Marczak, A. Collins

Newmont roasting plant in Carlin, Nevada commenced operating in December 1994. Over the years, refractory ores and pyrite concentrates from different gold deposits constituted the feed to the facilities. Historical plant performance indicated that the roasting temperature was the main variable that affected the structural characteristics of the calcine which, in turn, affected the recovery of gold by cyanidation. Gold recovery as a function of roaster temperature was closely monitored since October 2000. Original design temperature was 550oC. Lower roaster temperatures of around 500oC resulted in gold recovery increase by more than 6 percent. This increase was directly related to an increase of the surface area of the calcine. The implementation of an “intelligent” process control system helped significantly in achieving steady low roasting temperatures thus achieving high gold recoveries between 92 and 93 percent. Under those conditions, several roasting campaigns with high-arsenic-containing ores were conducted, which resulted in a significant decrease of gold recovery. The reduced gold recovery was caused by the loss of surface area (e.g. porosity) of the calcine as the arsenic content of the roaster feed increased.

Jan 1, 2007

The extractive industry has been faced with a situation where there has been no systematic and formalised training and education structure available. Previous structures which were available, e.g. the quarrying diploma and the mining papers as a part of an engineering degree, have suffered the same fate as the Dodo. They are now extinct.   In providing for a training strategy, the past strategies need to be examined and reasons behind their demise examined. This paper examines the reasons for past failures in education and training in the extractives industry, the factors that need to be taken into account in creating an education and training culture, the strategies required, the Government regulations and trans-Tasman agreements, and the quality management which must surround the entire training programme.

Jan 1, 1997

By B Mohanty, G Yamin

A number of parameters, aside from blast design and pre-existing rock conditions, can change the performance of the explosives system in actual blasting practice. Sympathetic pressures caused by detonation of preceding holes have been identified as a major contributor to explosive system malfunctions, leading to uneven blasting performance. These effects can occur both within a hole or across several holes. These can consist of high transient pressures related to the shock phase of the explosion or the relatively longer or quasi-static pressures associated with the explosion gas expansion phase. This study presents the findings from an on- going investigation on measurement and analysis of these pressures between donor and receptor holes in a granitic outcrop for representative inter-hole distances and borehole conditions, employing single cartridges of emulsion explosive in 45 mm diameter holes. The results, despite wide scatter in the measured values, show the very short duration pressures to range up to 7 MPa and arriving within a few milliseconds after detonation, whereas the much lower amplitude pressures arrive after tens of milliseconds. Both have the potential to seriously affect the performance of an explosives system.

Jan 1, 2005

By Christopher Davey, Marian Mazurkiewicz, Yvonne Spooner, Dana Hankey, Peter Kanjorski

The concept of a high pressure liquid jet mill with highly unsteady flow, has been developed and recently patented by Cornerstone Technologies LLC (CsT), for the purpose of micron and sub-micron particle production. The mill accepts feed sizes up to 15mm for some materials and is capable of submicron production. Successful material range from precious metals such as silver and palladium to dielectric components and substrates such as Barium Titanate slips, zirconia, titania and silica. The process has also succeeded in adequately reducing the size of materials for both composite and coating uses such as anthracite coal, graphite, chrome metal, wollastonite and more than 100 others. A unique design approach has been taken to highly maximize the energy flux in the mill's chambers to create extremely high turbulence and destructive cavitation. This is assisted by shock waves, which cause particles to undergo ultra high frequency pressure pulsations, high frequency collisions and then abrasion, shattering, hydrowedging, and cleaving. Due to these extreme properties the processing occurs in just fractions of a second allowing throughputs up to 1000 kg/h on a machine that would fit inside a 60 cm box. The technical solution and technological advance, as well as the environmental and economic benefits indicate rapid and wide spread acceptance of high-pressure liquid jet milling in modern industry.

Jan 1, 2003

By Patrick A. Turner, Timothy J. Olson, Abraham J. Schutte, Roman van Ommen

"The use of classifying devices in grinding circuits dates back to the early 1900’s when classifiers were installed to close ball mills. The search for ways to further improve grinding circuits led to the use of hydrocyclones in place of mechanical classifiers in South Africa in the early 1950’s. Today Hydrocyclones are considered as the best classifying devices to close grinding circuits. After 50 years of development the hydrocyclone has changed significantly when compared to the designs of the early days, but the focus to circuit optimization must be expanded to an understanding of the integral system consisting of mill, cyclone feed pump and cyclone.The key to good cyclone circuit design and operation in primary grinding circuits will be discussed including individual cyclone design features such as cone angle or materials of construction, as well as orientation and manifold configuration.Cyclone performance issues as well as maintenance considerations will be detailed in an effort to achieve consistent cyclone operation with minimal coarse solids in the overflow. “The importance of constant cyclone feed conditions is unquestioned today. The challenge of Cyclone sizing is a large number of not fully known variables prior to startup. The most significant unknown variable is slurry viscosity. Because of this, engineers often specify a conservative cyclone system that produces a finer than required separation. However, this approach often leads to higher circulating loads and a higher overflow density in order to produce the required separation. The higher cyclone overflow density results in a less efficient cyclone separation. The average concentrator can pick up 2-4% finer overall grind by having a more aggressive cyclone operation.”"

Jan 1, 2003

By J L. Mauk

The Favona low-sulfidation epithermal deposit in the Hauraki Goldfield is less than one kilometre southeast of the world-class Waihi deposit. The veins are hosted by Miocene andesite of the Waipupu Formation, have a total strike length of over 900 m, a vertical extent of at least 350 m and are on average 1-3 m wide. Individual veins have been traced for 200 m with vein widths up to 25 m. The dominant vein textures are massive, crustiform and colloform banded veins and vein breccias, with subsidiary textures including comb, zonal, flamboyant, lattice-bladed, ghost-bladed, microbotryoidal, feathery, ripple and dune, and mosaic. Quartz is the dominant gangue mineral in the veins at Favona. Accessory gangue minerals include pyrite, chlorite, adularia, illite, calcite, and apatite. Electrum is the only gold-bearing mineral and is associated with acanthite, tetrahedrite, pyrite, sphalerite, chalcopyrite, and rare galena. Whole rock geochemical analyses indicate that gold grades correlate with textures/vein types. The highest gold and silver grades are associated with vein breccias and banded veins, with the former containing 28 g/t Au and 136 g/t Ag on average. To date, veins with significant base metal sulfide minerals, and massive and crystalline quartz veins lack significant precious metals (Au and Ag), except for one banded base metal sulfide-rich vein at Favona. An overall zonation of the veins exists, with base metal sulfide minerals dominant at depth (1050 m RL) of the system are characterised by massive quartz veins.Fluid inclusions from a total of 31 quartz, amethyst, and platy calcite veins reveal homogenisation temperatures of ~190-250¦C, with final ice melting temperatures between 0.0 and -0.8. Ice melting temperatures correspond to apparent salinities of 18O value of the water that formed these veins is approximately -4.3 per mil, which is similar to meteoric water-dominated, near neutral chloride fluids in geothermal systems in the Taupo Volcanic Zone.

Jan 1, 2002

By P. Huang, D. W. Fuerstenau

Various factors that control the natural flotability of talc, including differences due to crystal face and edge effects, were delineated. For study of talc depression phenomena, dextrin was used as a model depressant. For the enhancement of talc flotation, dodecylammonium acetate (DDAA) was used as the collector. The interaction of DDAA with talc was assessed by flotation experiments and electrokinetic (zeta potential) measurements, from which the role of hydrophobic bonding can be demonstrated. The results presented in this paper provide useful information on how the crystal chemistry and surface chemistry control the electrical double layer, adsorption phenomena, wettability, and flotation behavior of talc in aqueous media.

Jan 1, 2003

A Life Cycle Assessment (LCA) of stainless steel production, including that of the nickel, ferronickel, ferrochromium and iron feedstocks was carried out using inventory data derived from the literature. The environmental impact categories considered in the study were Global Warming Potential (GWP), Acidification Potential (AP) and total (or full cycle) energy consumption. The effects of different sources of electricity (black coal, natural gas and hydroelectricity) were also examined in the study. The results of the LCA showed that when ferronickel is used as the nickel source, the total energy consumption for stainless steel production is approximately 50% higher than when nickel metal is used as the nickel source (75 MJ/kg cf. 49 MJ/kg). This result comes about largely because the Fe units in ferronickel have a much higher energy intensity than do the Fe units in pig iron, and the greater the use of the former at the expense of the latter, the greater is the total energy consumption. The results also showed that the production of ferronickel made by far the largest contribution (59%) to the total energy consumption for stainless steel production when this feedstock is used as the nickel source, but when nickel metal is used as the nickel source the contributions of the various stages are more evenly distributed. It was also observed that the electricity consumption of the electric furnaces used in the production of ferronickel, ferrochromium and stainless steel contributed approximately 50% to the total energy consumed in stainless steel production. Given the relatively low efficiencies associated with electrical power generation, significant reductions in the total energy of stainless steel production could be anticipated if more direct use of thermal energy was made in the ferronickel, ferrochromium and/or stainless steel smelting stages, for example by utilising bath smelting processes.

Jan 1, 2004

By Harri J. Lehto, Marja I. Oja

"The purpose of grinding circuits is to produce a particle size distribution that has as much as possible the wanted particle size class. In practise, however, the production of the wanted size class is not at all as simple as it sounds. In the case of industrial minerals for example the end user may give very tight specifications for the particle size distribution and for the chemical composition of the product. This leads in many cases to a very demanding grinding process, if we want to reach and maintain these specifications. In other words, the required size distribution is not necessary the best possible for the chemical composition.Screen models aim to predict the size distribution and flow of the products when a feed size distribution, feed tonnage, and grade efficiency curve are known. The approach used in this study was to select the most suitable empirical model for classification. Suitability of the existing models has been evaluated and accuracy compared. The tests showed that best grade efficiency model was the Rosin-Rammler model.The performance of a screen was evaluated in order to minimize the amount of fine material in the screen overflow. The experiments were carried out using Derrick single-deck screen, first alone with recycling and then in the closed circuit with a rod mill using two different scales. The separate screen tests showed the expected behaviour of the grade efficiency curves. In the pilot tests the Leonard screen efficiencies stayed almost constant. This suggests that the screen works better in a milling circuit. However the loading of the screen turned the product of the mill coarser that helped screening. The grade efficiencies obtained from the pilot tests had the same general shape. The regression analysis of the pilot test runs did not give an acceptable correlation for the parameters. This suggests that pilot tests cannot be directly used to scale or to optimise industrial milling circuits. However they can be used to predict the trends of behaviour of an industrial circuit."

Jan 1, 2003

By K. L. Lownie

For research and test data to serve a useful purpose, it is essential that it be derived from some known standard test procedure that allows for comparative analysis as well as independent replication and verification. Fan performance data provided by manufacturers is not absolute, and is influenced by the geometry of the test installation. For these reasons, fan test standards have been prepared in order to establish a clearly defined test procedure that allows for comparison of different fan designs, and also allows for the independent verification of test data. Internationally recognized Standards such as BS848, ISO5801, and AMCA 210 etc. are highly prescriptive, and precisely specify test duct configurations, measurement procedures, measurement planes and instrumentation to be used. Provided the laboratory tests are conducted strictly in accordance with the relevant Standard, the performance data will accurately reflect fan performance within the appropriate tolerances for efficiency, pressure and flow when tested in the defined configuration. Major differences in performance exist between a fan tested in accordance with a Fan Test Standard, and an identical fan installed in a mine ventilation system. The aerodynamic performance of any fan will be influenced by the quality of the fan manufacture, the flow system within which it is operating, the location of measurement planes, and the system stability. The flow distributions present in a standardized Laboratory test are unlikely to be repeated in mine ventilation systems, and this will also disadvantage fan performance. Unless the fan supplier takes all of these influences into account, there will an inevitable reduction in fan aerodynamic performance, and the end user will experience a shortfall in expected flow through the mine. The effect on fan performance can range from minor inconvenience to catastrophic fan failure resulting in major rectification costs and significant loss of mine production.

Jan 1, 2009

By Wiliam L. Crentz

The importance of Somerset County, Pa., as a coal producer is due in large measure to the presence reserves of low-volatile bituminous coals. Although many coal beds of minable thickness are present, the important reserves are to be found in those beds underlying the Pittsburgh bed. The Kittenning beds and Freeport beds, which are responsible for the bulk of the present coal production in Somerset County and contain the largest reserves to meet future coal requirements, are usually thin and entirely free from impurities. The Pittsburgh bed, which has been such an important coal deposit in the coal areas immediately west and south of Somerset County, is of secondary importance in this county. Although generally rather friable, Somerset County coals have enjoyed wide receptability as excellent coals and to some extent have been utilized in the metallurgical market.

Jan 1, 1951

By Roger J. Morrell

Bureau of Mines laboratory experiments with reduced scale cutter and cutter forces were performed to (1) define the fundamental relationships governing disk cutter performance and (2) to develop a method of predicting disk cutter performance in soft, medium, and hard rocks. The rock cutting experiments were performed in four igneous and metamorphic rocks that ranged in compressive strength from 38,000 to 67,000 psi. A special testing machine called a linear cutter apparatus (LCA) was used to load and traverse a free rolling disk cutter across a smooth rock surface. Each pass of the disk produced a single crater, and runs were spaced to avoid breakage between craters. During each run the normal and tangential cutter forces were measured and recorded. The soft and medium rock data were obtained from previous Bureau experiments with disk cutters. Crater depth, tangential cutter force, crater volume, specific energy versus normal cutter force, and crater width versus depth are defined within this study. With the use of standard physical properties, performance prediction equations were developed using stepwise linear regression analysis techniques. A method of using these prediction equations to calculate the boring rate, the cutter spacing, and the torque and energy requirements of a full-scale boring machine was also developed.

Jan 1, 1974

[Separates of all the Technical Publications published in 1930 are available at Institute headquarters. All the papers are on file in public, university and technical libraries, and when so indicated in the list, may be found in the Transactions.] Metal Mining Technical Publi- Title Author Meeting Tran~. cation Volume No. and Page* 264-A.29 Quicksilver Industry in 1929. Im- L. H. Duschak San Francisco T30, 283, 319 provements in the Metallurgy of C. G. Maier and Oct., 1929 Quicksilver and Symposium on The others Present Status of the Quicksilver Industry (With Discussion) (37) 271-A.30 Observation on Ground Movement R. E. Palmer New York T30. 168 and Subsidences at Rio. Tinto Feb.. 1930 Mines, Spain (20) 274-A.31 Development and Installation of the C.L.Berrien New York T30, 139, 166 Hawkesworth Detachable Bit (29) Feb., 1930 276-A.32 Protective Measures . Against Gas 0. A. Glaeser New York T30, 129. 167 Hazards at United Verde Mine (11) Feb., 1930 287-A.33 Use and Cost of Compressed Air (12) R. S. Lewis New York Feb., 1930 314-A.34 Miami Copper Company Method of F. W. Maclcnnan New York T30, 39, YO Mining Low-grade Orebody (44) Feb., 1930 319-A.35 How Human Beings Respond to W. J. McConnell New York Changing Atmospheric Conditions Feb., 1930 (9) 324-A.36 Vertical and Incline Shaft Sinking at Arthur B. Foote San Francisco T30, 87 North Star Mine (21) Oct., 1929 32bA.37 Governmental Control of the Pro- W. E. Colby New York duction and Sale of Mineral Re- Feb.. 1930 sources (With Discussion) (16) 333-A.38 Some Recent Developments in Open- E. E. Hunner New York T30, 106, 117 pit Mining on the Mesabi Range Feb.. 1930 (25) 334-A.39 Mining Methods and Costs at Presi- V. D. Howbert El Paso dio Mine of American Metal Co. of R. Bosustow Oct., 1930 Texas (15) 339-A.40 Operation of Pressure Fans in Series W. 8. Weeks New York (8) V. 6. Grishkevich Feb., 1931 364-A.41 Top Slicing with Filling of Slices as H. Willey El Paso Used at the Charcas Unit of Com- Oct., 1930 pania Minera Asarco, S. A. (17) 373-A.42 Drill Sampling and Interpretation of H. T. Matson New York Sampling Results in the Copper G. A. Wallis Feb.. 1931 Fields of Northern Rhodesia (17)

Jan 1, 1930