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By S. E. Phifer

The Haile gold mine was the largest gold producer east of the Mississippi River before 1942. It was the first gold mine in the Southeast to reopen following deregulation of the gold price by the United States Government. The Haile mine was also the first gold mine in the Southeast to use heap leaching and carbon recovery for gold production. Current production involves mining and heap leaching about 1.8 kt/d (1600 stpd). Carbon is used as a recovery medium. Due to the clay and excessive fines in the oxidized ore, agglomeration using portland cement is required before leaching. Agglomerated ore ranges in screen size from 50 mm (2 in.) to less than 75 µm (200 mesh). The agglomerating step combined with certain other conditions has enabled Piedmont Mining Co. to achieve recoveries of about 90% or better.

Jan 1, 1987

By P. Somasundaran

Beneficiation by froth flotation, which exploits the difference in surface properties of minerals, has been a promising method for coal cleaning. However, dissolved mineral species present in coal flotation systems can interact with particles and other species leading to drastic effects on flotation. Particularly, precipitation or adsorption of such species on the particles can alter their surface properties and thus influence the efficiency of coal cleaning. In this work, the bulk and surface precipitation of the dissolved mineral species present in Pittsburgh No. 8 coal was investigated under controlled experimental conditions. Changes in the surface properties of coal due to the precipitation were monitored by following zeta potential. Solution potential data were used to elucidate the mechanism of the precipitation. The effect of the precipitation of the dissolved species on the floatability of coal was found to be marked.

Jan 1, 1995

By John S. Anderson

The need for fuels and minerals in this country is estimated to double, triple, or even quadruple by the end of the present century. Even assuming more recycling of scrap metals and some priority allocation of energy, as has been done, for instance in war time, the projected increase in the nation's population and ever-increasing wants of that population will require vastly more minerals than are now being produced. Since mineral ores are being mined at lower grades, and since all minerals, including fuels, are having to be mined from deeper deposits, the amount of surface land to be disturbed will, inevitably, be increased. We cannot depend on foreign sources to supply all the extra requirements, since the non-U.S. population is increasing, in most cases, faster than our own. Furthermore, starting from a lower base, their mineral needs may accelerate more rapidly than ours. Restrictions on exports may be applied in foreign countries, if it appears that remaining reserves are not sufficient to fill the national needs. In vice; of the opposition which the mineral industry is receiving, as has been well described at these sessions and elsewhere, what can we, as mineral producers, anticipate as regards our ability to continue to operate, to sway nothing of expanding production? Although not minimizing the problems involved, it seems obvious that, except under emergency conditions, the country cannot tolerate a reduction in the available

Jan 1, 1971

By Bob Gordon, Allen Furth, Dan Dobbels

A 4.8 m (16 ft) diameter hard rock tunnel was driven through granite bedrock to create the 1.7 kilometer (1.1 mile) long Hampton McCloy Retention Tunnel for the city of Richmond, Virginia. During the work the tunnel encountered narrow seams of partially decomposed granite that were not self supporting and could be dealt with using ribs and lagging. However, as the tunnel approached the receiving shaft, it encountered a large seam of highly decomposed rock, alluvial deposits and running sand which resulted in soil loss into the machine. As a result of this condition, a jet grouting program was quickly developed to allow the tunneling to continue. This paper will describe the manner in which jet grouting was used to solidify and stabilize the decomposed bedrock, alluvial soils, and running sand to allow the TBM to continue tunneling.

Jan 1, 2003

By M. S. Klima, B. K. Kim

The use of a 25.4-mm- (1-in.-) diam water-only hydro-cyclone for separating liberated 125 x 25- µm high-density particles from similar-size lower-density (2.65 g/cc quartz particles, as might be used in soil washing applications, was investigated. As expected, cyclone performance was greatly affected by changes in cyclone geometry and operating conditions. A single-stage separation recovered 75% of the magnetite (4.8 g/cc) while rejecting nearly 60% of the quartz. With ferrosilicon (7.0 g/cc) as the heavy component, the recovery improved to 85%. The use of dense medium in a single stage increased both ferrosilicon recovery and quartz rejection to approximately 90% each. In addition, computer simulations of a three-stage circuit were performed. The simulations showed that recoveries approaching 97% with quartz rejections of 95% were possible.

Jan 1, 1999

By William J. Taylor

Strictly defined, a stull is an inclined or horizontal timber support; a vertically placed timber is defined as a prop. Common usage allows the catchall term "stull" to refer to all such uniaxial mine support, regardless of orientation. Typically a stull is a round wooden column that is wedged in place to provide short-term auxiliary support between sill and back, or between hanging wall and footwall. Stulls may be used exclusively or in con- junction with other support systems such as roof bolts, shotcrete, or cribbing. Stulls are used both as local temporary support in stoping operations and for uniform systematic support installations. Where stoping areas are to be abandoned soon after excavation, stulls may be used to provide temporary support during mining operations. Where controlled caving and subsidence is required, stull supports are designed to fail in a systematic, predictable manner. Wood type is selected on the basis of availability, price, and load carrying characteristics. Coniferous woods are typically used, especially to carry heavy ground loads. Brittle woods are generally avoided because of their tendency to fail suddenly. Gradual yielding failure is preferable to sudden, unexpected failure of the support. Some usage of wood from deciduous trees such as cottonwood and other poplars has been reported in Grants, NM. These stulls reportedly mushroomed as the ground load increased but continued to maintain their structural integrity. Stulls fabricated from structural steel are used in special applications. Adjustable lengths are commercially available in mechanical, hydraulic, and pneumatic designs. The high cost of mechanical stulls limits their use to mining systems where recovery and reuse is possible. End blocking, also called headboards or footboards, uses wood blocks that are placed between the stull end and the ground they are supporting. The blocks are typically 50.8 to 101.6 mm (2 to 4 in.) thick, 203.2 to 304.8 mm (8 to 12 in.) wide, and 381 to 609.6 mm (15 to 24 in.) long. End blocking serves to distribute the support over wider back area. Compression of the end blocking gives visual indication of wall movement prior to failure of the stull. A common application of the stull is in flat-bedded uranium mining during pillar extraction. Many western US uranium mines use a pillar pattern development to delineate the irregular ore pods. After development of an appropriate sized pillar, the ore pillars are then sequentially mined out, leaving the undercut hanging wall or back to cave. Where thickness of the ore is less than 4.3 m (14 ft), stulls are generally used to provide ground control as the pillar is removed in slices. Experience dictates the density of stull placement. In general, the number and size of stulls should be sufficient to resist ground closure and to provide support for drilling and loading operations adjacent to the pillar. Stulls next to the mining face are often lagged 0.9 to 1.2 m (3 or 4 ft) up from the floor (or sill) to confine the blasted ore to a passage next to the pillar. Mucking is simplified by this confinement. Experience dictates whether back control along a mining face requires removal of stulls to allow con- trolled subsidence of the back or hanging wall. Without caving or closure, abutment pressure can create poor ground conditions near the pillar.

Jan 1, 1982

By B. R. T. Simoneit

The formation of petroleum is normally thought of as a geologically lengthy process, involving the accumulation of organic matter, its gradual burial, diagenetic breakdown via geochemical reactions, maturation, heating within a 75-150'C "oil window" induced by normal geothermal gradients in the subsiding basin, and slow product migration into structural traps (Tissot and Welte, 1984, Hunt, 1979). The entire process can take millions of years and, indeed, most oil reservoirs probably formed in this manner. How-ever, today in sedimented, submarine rift basins (Fig. 1), Cl to >C40 hydrocarbons with the chemical and physical properties of crude oil are forming in demonstrably much shorter time by rapid thermal maturation of immature organic matter in hydrothermal regimes that are unusually high for sedimentary basins (Brault and Simoneit, 1988a, b; Didyk and Simoneit, 1988; Kawka and Simoneit, 1987; Peter et al., 1988; Simoneit, 1983; 1984; 1985a,b; 1988; Simoneit et al., 1984; 1987; 1988).

Jan 1, 1989

By Alexander N. Winchell

"Location. The iron formation of the Gogebic district (including the Penokee) comprises a narrow belt south of the western part of Lake Superior extending from Michigan for a considerable distance into Wisconsin. From the mouth of the Montreal River (about twenty-five miles west of Ashland) the iron formation is only about twelve miles distant, but it is about twenty miles south of Ashland. Beginning on the east at a point about eight miles east of Wakefield, Mich., it extends through Sunday Lake, Bessemer and Ironwood in Michigan, and thence south of west through Hurley, Wis., and only a short distance south of Mellen, Wis. About eight miles westward from Mellen, the formation disappears, but six miles further west it is known to reappear and continue thence for about eight miles. The total length of the range is about sixty miles, two-thirds of this distance being in the State of Wisconsin; but nearly all of the ore has been obtained from the eastern third of the district, which is in the State of Michigan.History. This iron range was first noted in 1848 by Dr. Randall, assistant geologist to Dr. David Dale Owen, while following the fourth principal meridian northward. It was also reported by Charles Whittlesey in an account of a survey made in 1849, and published by Owen in 1852. Analyses of the iron ore are given with the following account. ""The bed of magnetic iron ore south of Lac des Anglais is of extraordinary thickness,25 to 60 feet. * * In the wild and deep ravines where the Bad River breaks through the range, there is a cliff of slaty ore * * * probably three hundred feet thick. * * * I estimate more than one-half of this face to be ore, and in places the beds are from ten to twelve feet in thickness, with very little inter-mixture of quartz * * * . The position of the best exposures of ore which I saw is such as to require from eighteen to twenty eight miles of transportation to reach the lake."""

Jan 1, 1920

By Brendan Demich, Brendan Macdonald, Timothy J. Orr, Jonathan K. Hrica, CASSANDRA L. HOEBBEL, Jason Navoyski, Jennica L. Bellanca

The paper describes the process of collecting detailed accounts of near-miss incidents and turning them into impactful visual stories using graphic simulation. The aim is to create high-quality training materials to reduce haul-truck-related accidents and fatalities in mining.

Sep 1, 2023

By J. Finch, J. Yianatos, N. W. Johnson, R. Espinosa-Gomez

A method of determining the maximum concentrate solids rate or carrying capacity is described for given column operating conditions. The method requires alteration of the feed rate of solids to the column at a fixed residence time by manipulation of the % solid of the column feed pulp or the bias rate. The carrying capacity was measured for five streams at the Mt. Isa Mines Pb/Zn and Cu concentrators. As a potential scale up parameter, the mass of solids per unit time per unit column cross section (Ca, g/min.cm2) is explored. Ca is tentatively related linearly to the 80% passing size (d80) of the concentrate. For d80 < 15 pm Ca was less than 4 g/min.cm2 (8 lb/min.ft2) which makes it a critical consideration in scale-up for such fine feeds. An alternative carrying capacity parameter, mass of solids per unit volume of gas Cg was not as useful as Ca since Cg varied inversely with gas rate.

Jan 1, 1988

By Vladimir Adamek

Due to the variability of subsidence characteristics across the U.S. coalfields, it was concluded that it would be practically impossible to develop a universal predictive model for mining-induced subsidence based on theoretical assumptions. Therefore, an effort was made to find a procedure to develop an empirical subsidence predictive model based on a sufficient Mount of field data from one mining area (in this case the Northern Appalachian Coal Region). It was also thought that this procedure, if successful, could be used as the template for developing predictive capabilities for other coalfields with different subsidence characteristics given a reasonable amount of field data. It has been found, in the Northern Appalachian Coal Region, that the variability of subsidence characteristics can be expressed by a polynomial equation developed through regression analysis of the variable subsidence coefficient and derived directly from the field data. In this study, field data were obtained from 11 Bureau longwall panel studies (16 half profiles) for static subsidence and 14 panels for dynamic subsidence. The effects of lithology, expressed in the form of a variable subsidence coefficient, have been separated for each test site by introducing a correlation between hythetically homogeneous overburden and existing ithological conditions. For each longwall panel, the characteristic of the variable subsidence coefficient was defined along individual static profiles. The definition of mean values with acceptable deviations is the substance of the predictive method. The same procedure was used to develop a predictive model for dynamic subsidence, since it war discovered that the rate of longwall face advance is not a necessary functional parameter. This paper presents the theory, development, and application of the static and dynamic subsidence prediction models.

Jan 1, 1986

By David De Lemos Pires

Mining is essentially a materials management process where materials are classified, excavated, moved to a desired location, processed at a cost and sold for a price hopefully to generate a profit. ?How much is that cost and can it be reduced?? is the age-old question. The requirement for a paradigm shift with regard to materials movement in search of low-cost production has not just happened by chance but, rather, has been driven by agents of change that include mining companies, consultants, governments and equipment suppliers. During the past 100 years of mining, surface mining technology has involved humans with hand tools, humans with machinery and unmanned automated equipment. In the past 50 years, surface mining technology has evolved and now takes the form of trucks and loaders (TL), in-pit-crushing conveying (IPCC) and autonomous haulage equipment (AHS).

Dec 1, 2013

By David J. Maguire, Ken Alexander, Maya Scherbakov

As conveyor systems continue to improve in reliability due to improved design, installation, maintenance, and operation, one of the more common modes of failure is the rubber carry cover being abraded away to the tension member. Various types of abrasion are discussed as well as current laboratory methods for measuring wear. New lab methods to mimic types of abrasion in service are presented and data from current and improved rubber covers will be presented. Actual wear performance of current and new cover compounds in multiple applications (coal, limestone, granite) will be compared to the new lab test methods and cost benefits shown.

Jan 1, 2002

By Richard L. Patterson, Alan P. Finch

Twenty years ago, when tunnel projects in the UK were generally procured by the public sector, many were completed late and over budget. Now a significant proportion of new infrastructure is developed by the private sector. Seeking more certainty in cost and programme, promoters have tried new and radically different methods of procurement and contract forms. The paper will review these developments, then examine the approach adopted for some of the largest current UK tunnelling projects (both in the public and private sectors) including the Channel Tunnel Rail Link, the Heathrow Terminal 5 Development and new highway tunnels.

Jan 1, 2003

By Shelley M. Burg, Dennis K. Poulton, Robert B. Gordon

This project includes the excavation and concrete lining of approximately 18 900 m (62 000 ft) of 5.5 m (18 ft) finished diameter subway tunnel for the Los Angeles MTA. The project required that four soft ground headings be excavated from a single shaft located near the mid point of the tunnels. The tunnels were classified "gassy" during the excavation phase. Because of the contract schedule requirements and the limited urban work site available, many logistical problems had to be overcome during the project while excavation was accomplished at a record setting pace. Some unique project features include the muck handling system and an access shaft using a high strength tieback support system. In order to accomplish the work, an extensive effort to plan and construct the main work site was required.

Jan 1, 1995

By Steven W. Hunt, Ronald E. Heuer, Safdar A. Gill

A 3.3 m (11 feet) diameter, 51 m (168 feet) deep temporary steel casing which had been sunk within glacial soils buckled and collapsed on July 29, 1985. The collapse occurred at the CT-8 Dropshaft site in Milwaukee while two workmen were contact grouting outside the casing in an attempt to stop groundwater inflows through a bottom plug. This paper describes the soil and groundwater conditions at the site, the casing design, the method of shaft construction, and probable causes of the buckling failure. Specific aspects of the paper include: slurry method of shaft excavation and casing installation, soil creep, earth pressure due to three dimensional arching, and buckling strength of a casing surrounded by slurry rather than grout and firm soil. The paper should be of interest to designers and constructors of temporary ground support systems for deep shafts.

Jan 1, 1995

By David C. McLean, Peter Penner, Martin de G. Salter

The Rogers Pass Project for C.P. Rail includes a 14.7 km tunnel and an 8.5m diameter concrete lined ventilation shaft to a depth of about 335m. The shaft collar is in bouldered water bearing glacial till to a depth of about 95m. Initial excavation in the overburden was with the aid of dewatering wells. When ground support problems arose the excavation was completed by a two stage freeze programme. Freeze holes were drilled from the shaft bottom. This most unusual method was successful in overcoming the difficulties safely and efficiently. The remainder of the shaft was sunk and lined conventionally. Finally, a central dividing wall was poured by jump forming from the bottom up. The wall was completed to a high standard at up to about 20 vertical metres per day.

Jan 1, 1989

By Steven Hart, Graeme Hill

Boddington Gold Mine is situated 130km South-east of Perth, WA. The operation is managed by Worsley Alumina Pty Ltd. The Direct Leach plant was commissioned in mid 1986 at a rate of 3 million tonnes per annum. The plant was upgraded to 4.5 mtpa in 1988 and almost immediately to 6mtpa in 1989. Subsequent debottlenecking resulted in further increases in throughput up to 7mtpa by 1991. The SupergenelBasement Plant was constructed in 1990 and commissioned in early 1991. It was designed to process both copper-gold-silver anomalies within the laterite gold orebody and future hard rock ores. The Supergene plant incorporated control potential s­ulphidisation (CPS) and flotation ahead of CIL to remove a host of copper minerals. It operated in that configuration for 2 years at rates up to 350,000 tpa and average grades of 6.0 git gold and 1.2% copper. Gold recovery averaged 90.7% and copper recovery averaged 80.0% before the flotation circuit was decommissioned in March 1993. Quartz hosted high grade, free milling oxide and basement ores were discovered at the northern end of the orebody in 1990 and now comprise the major feed source to the basement plant. Oxide ores are currently milled at a rate of 550,000 tpa, while basement ores are milled at a 420,000 tpa rate. Metallurgical testwork during the feasibility stages indicated that up to 30% of gold in plant feed could be recovered by gravity separation methods. It was also highlighted that signifi­cant improvements in overall plant recovery and reduced operating costs would be achieved by maximising gravity gold recovery ahead of cyanidation. To achieve this, rec;iesign and upgrade of the gravity circuit was necessary.

Jan 1, 1995

By Satid Therdkiattikul, Donald A. Dahlstrom

Many gold ores are known to be refractory so that conventional cyanide processing will result in serious losses of gold and silver values. A significant percentage of these refractory ores contain aresenopyrite and the gold and silver is usually encapsulated within this matrix as well as the pyrite matrix. Normally the values can be recovered as flotation concentrates because of the sulfide compounds with recoveries of over 90% and at very good grades. In order to free the gold and silver, the sulfide matrix must be destroyed. This can presently be achieved by (1) pressure­temperature leaching (2) roasting and (3) bacterial leaching. All of them have advantages and disadvantages as well as an obviously increased cost for the each processing method. However, the increased gold and silver recovery should and must more than offset this cost. It is believed that gold recovery should be well over 90% from the concentrate so that overall recovery from the ore should be in the 90-95% region. All three processes must consider pollution control of both sulfur and arsenic to prevent contamination of air, water or land through improper waste disposal. This paper will concern only bacterial leaching and its necessary control of effluents and solids. Sulfur does not appear to be a problem as the element is oxidized to sulfate and is precipitated with an acceptable solubility. Other important improvements that must be controlled are arsenic and iron which are present as significant values (1-12 g/1 of arsenic, 20-40 g/1 of iron). In addition much smaller values of base metals, aluminum and magnesium can be present as well as other elements depending on the ore and these must be low enough after treatment to meet EPA regulations.

Jan 1, 1993

By X. K. Jiang

Upgrading molybdenite ore can be technically difficult and expensive if talc is a major impurity in the ore. The layered structure of molybdenite and talc decreases the surface specificity of floatation and suppression agents, thereby making molybdenite ore beneficiation inefficient if under some wet processing methods. However, oxidic talc surfaces may be distinct from the sulfidic or oxysulfidic molybdenite surfaces, such distinction related to electron work functions and/or densities of electron donors/acceptors sites. If such differences are present, the upgrading of finely sized molybdenite ore by dry triboelectrostatic methods may hold advantages over traditional wet methods.

Jan 1, 1999