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By Richard Giffen, Boris CARO VARGAS, Terrence Carroll

"This paper takes an in-depth look at the $72 million design-build Norris Cut project, which includes the replacement of an existing 54-inch waste water sewer main to Fisher Island under the Norris Cut Channel. Tunneling through one of the country’s most unpredictable geologies created unique challenges in both the design and construction phases of the project. The paper presents the geotechnical and structural design considerations for the 100-foot deep secant piled TBM launch shaft in the highly permeable Fort Thompson formation limestone and sands. The structural design effort also included the design of the tremie slab, thrust wall and design of the largely unreinforced launch shaft to resist asymmetric loading from partial ground freezing. The retrieval shaft was designed as a deep soil mixed shaft and is thought to be the deepest soil-mixed shaft in Miami. From a construction perspective, this paper discusses the unique challenges of building two shafts with two different techniques and will compare some of the constructability aspects, costs and equipment schedule-considerations related to the use of two separate techniques. INTRODUCTION Nicholson Construction Company (NCC) was awarded a $72.1 million Design-Build contract to replace an existing force main from the Virginia Key Central District Wastewater Treatment Plant (CDWWTP) under the Norris Cut Channel to Fisher Island. The location of the project is shown in Figure 1. The project involves replacing an existing 54-inch diameter pre-stressed concrete sewer force main with a 60-inch diameter fiberglass force main. Arup USA, Inc. (Arup) is the lead designer for Nicholson on this design-build project. Arup is providing design services for the TBM launch and retrieval shafts, segmental tunnel lining, the fiberglass pipe, and the horizontal directional drill component. Miami-Dade Water and Sewer Department currently owns and operates the existing 54-inch sanitary force main that transmits sewage collected from Miami Beach and Fisher Island to the CDWWTP for treatment and disposal. The existing force main was subject to a condition assessment in December 2011 which revealed structural deficiencies in the pre-stressed concrete pipeline."

Jan 1, 2016

By D Teyhan, J Kirsch

Traditionally, most Australian iron ore mining operations have been surface-based. Processing plants were designed to handle dry ores. In recent years mining operations in the Pilbara have progressively moved below the water table exposing wet, sticky ores which have caused lost efficiency in screening operations as particles tend to agglomerate and adhere, blinding screening media. Miners and vibrating screen manufacturers have experimented with a shift from linear motion to elliptical motion screens. Elliptical motion conveys and lifts particles. Effective on flat deck (horizontal and inclined) or sloping decks it can be configured to provide a controlled transport rate, applying pressure in all directions to maximise screening efficiency. In practice, elliptical motion screens have proven to be effective in dislodging sticky particles from screening media, reducing blinding rates and improving screen efficiency. Moisture and clay content change during the life of a mine. These changes are sometimes the effect of seasonal rainfall, in other cases due to increased groundwater and clay content as mining operations go deeper. To compensate for such changes and optimise screen efficiency, changing the ‘shape’ of elliptical screen motion is required. This has traditionally required shutting down processing plants and making mechanical screen adjustments. Plant downtime is costly and machine adjustment has been a ‘trial and error’ practice. This paper will explore the results of a field trial that is currently underway in Brazil of a next generation elliptical motion screen design that allows operators to make changes to exciter rotational direction, speed and screen stroke angle, through electronic drive phase control. The machine’s electronic drive system synchronisation is enhanced for stability with a unique mechanical timing system. Operating at up to 6 g, screen adjustments can be made on the fly without stopping production. Early trial results are showing up to 50 per cent improvement in screen efficiency compared with traditional elliptical motion machines under certain feed conditions.

Aug 24, 2022

By D Teyhan, J Kirsch

Traditionally, most Australian iron ore mining operations have been surface-based. Processing plants were designed to handle dry ores. In recent years mining operations in the Pilbara have progressively moved below the water table exposing wet, sticky ores which have caused lost efficiency in screening operations as particles tend to agglomerate and adhere, blinding screening media. Miners and vibrating screen manufacturers have experimented with a shift from linear motion to elliptical motion screens. Elliptical motion conveys and lifts particles. Effective on flat deck (horizontal and inclined) or sloping decks it can be configured to provide a controlled transport rate, applying pressure in all directions to maximise screening efficiency. In practice, elliptical motion screens have proven to be effective in dislodging sticky particles from screening media, reducing blinding rates and improving screen efficiency. Moisture and clay content change during the life of a mine. These changes are sometimes the effect of seasonal rainfall, in other cases due to increased groundwater and clay content as mining operations go deeper. To compensate for such changes and optimise screen efficiency, changing the ‘shape’ of elliptical screen motion is required. This has traditionally required shutting down processing plants and making mechanical screen adjustments. Plant downtime is costly and machine adjustment has been a ‘trial and error’ practice. This paper will explore the results of a field trial that is currently underway in Brazil of a next generation elliptical motion screen design that allows operators to make changes to exciter rotational direction, speed and screen stroke angle, through electronic drive phase control. The machine’s electronic drive system synchronisation is enhanced for stability with a unique mechanical timing system. Operating at up to 6 g, screen adjustments can be made on the fly without stopping production. Early trial results are showing up to 50 per cent improvement in screen efficiency compared with traditional elliptical motion machines under certain feed conditions.

Nov 8, 2021

Roof bolting is a slow, expensive, and absolutely necessary mining activity. Roof-bolting activities also account for the largest percentage of lost-time injuries in underground coal mines. Dull bits result in the application of excessive force, which bends drill steel; and changing starter and finisher steel was the most significant source of injuries associated with roof bolting. The tungsten carbide (WC) roof-bolt drill bits currently used in American, Canadian, and Australian coal mines are capable of drilling only one or two 4-ft holes and then they are resharpened once or twice to drill another one or two holes. Often, in medium-hard rock formations (sandstone), as many as 20 to 30 bits may be required to drill a single 4-ft hole. Objective To compare the performance, longevity, and cost of newly developed polycrystalline diamond compact (PDC) roof-bolt drill bits against WC bits. Research and Background Diamonds for industrial use have been scarce throughout history and continuous attempts have been made to produce synthetic diamonds. The first synthetic diamonds were manufactured in 1953. Economically produced synthetic diamonds are 1 to 10 µm in size, but in this size range, they are totally unsuitable for industrial applications. In 1972, General Electric Co. developed a process to sinter the artificially developed, minuscule diamond particles into usable products. In this process, several layers of diamond-particles-and cobalt mixture are overlaid on WC substrates and sintered at 2,350° F and 1,000,000 psi. The final product is known as PDC. Today, PDC's are available in many shapes, but their size is limited to 3/4 in, or less, in length or diameter, because pressures greater than 1,000,000 psi are required to manufacture larger PDC's. At present, diamond and PDC arc the hardest and strongest commercial materials available for wear surfaces. The PDC used in this study had a hardness 3.61 times greater than that of WC.

Jan 1, 1992

By Claude Cunningham

Difficulty has always attended the evaluation of rock breaking energy available from explosives, owing to the complexity of the way in which it is released, and the destructive amplitude of the pressures. Many problems have arisen and continue with this difficulty, including the following: I. Formulation of improved compositions to deliver appropriate energy levels to the blasthole walls, or to deliver previous results at improved cost. How appropriate is it to use various ingredients, such as Aluminium, water, salt? 2. Claims over energy issues, resulting in wasted time and expense, over things that sound good in theory but are very difficult to tie down. 3. Purchasers of explosives make decisions based on claimed “Bang per Buck” from different manufacturers, where the estimate of “Bang”comes from simplistic numbers from various, very unequal detonation codes. The above problems are escalating as time progresses. Using the high level IDeX PC 2000 detonation code, we have found a way to portray the differences between formulations in a way which relates to their breaking effect in the field. The basic method is to plot the adiabat from the detonation state to full expansion in units which express the practical implications. Energy alone cannot deliver results, so we use the curve to examine its manifestations: pressure and temperature. Internal energy is plotted with these. The method displaces relative energy numbers, as it portrays the context in which the energy is available. It is used here to compare an ANFO, an emulsion and a doped emulsion, as well as the effect of Aluminium. The effect of the shock pressure regimes and temperature correlate well with what is seen in the field.

Jan 1, 2000

By Karin Soldenhoff

Recovery of uranium in conventional ion exchange circuits, using strong base or weak base resins containing quaternary or tertiary amine functional groups, is based on an anion exchange mechanism. In saline liquors, chloride competes with uranium for the active resin sites and reduces resin loading. This results in significant negative impacts on the IX process in terms of plant throughput and operating costs. In this paper we present the results of a study on the recovery of uranium from an acidic in situ leach liquor containing approximately 9 g/L chloride. A range of resins was tested, and a high capacity strong base resin was identified with significantly enhanced loading compared to conventional resins. Other process-relevant criteria such as loading kinetics and elution efficacy are also discussed. The process developed was successfully tested during a recent ion exchange pilot plant operated in conjunction with a field-leach trial.

By Charlie Watts, Ken Smales, Ron Fleming

The Manapouri Power Station is an underground hydro-electric station located in the South Island of New Zealand, and was constructed in the 1960s. Between 1997and 2002, a second 10m diameter tailrace tunnel was constructed to increase the out-put and to improve the overall hydraulic efficiency and output of the station. A critical economic and project approval consideration for the second tunnel was the outage time required for the breakthrough into the power station. The power station is in part dedicated to providing power to an aluminum smelter with the balance to the National Grid, and apart from the physical problems associated with providing an alter-native power supply to the smelter, the loss of generation revenue and supply risk were significant issues. Innovative planning reduced the planned outage time from several months to21 days, and the breakthrough was eventually achieved in 11 days as a result of additional value engineering measures implemented during construction. This paper describes the engineering optimization that took place during the planning stages of the project and later during construction, as well as describing the construction methodology used.

Jan 1, 2007

By Z. Chen

This study is concerned with the behavior of bubble clusters in a well-controlled turbulent flow. We used a specially designed cell where the bubble aggregates could be formed and exposed to breakage by a rotating impeller. The effects of impeller speed and the concentration of collector on cluster behavior were studied. It was found that the size of the clusters increases with the concentration of collector used. We also found that although the clusters could easily be destroyed under the action of impeller, they could reform, especially at lower impeller speeds. It was observed that the size of the bubbles arriving into the impeller region in the absence of particles before breakage was considerably higher than the size of the clusters formed at the same impeller speed. It appears that both cluster breakage and re-formation take place simultaneously, and the extent of formation and regrowth is mainly determined by the hydrophobicity of the particles and the impeller speed.

Sep 1, 2012

IN the course of his employment the Broken Hill Co. the writer has had occasion to use and instruct others in the use of the Shamrock rescue apparatus. This paper deals with the various types of apparatus tested. The common object of the various types of breathing apparatus is to enable the wearer to remain and work for varying periods of time in an atmosphere which is either deficient in oxygen or is poisonous that is, contains carbon monoxide or irritating and irrespirable vapours, such as the smoke from underground fires, sulphur dioxide or ammonia fumes. For any apparatus to be efficient as required in the above paragraph it must fulfil the following conditions;1. Air-tight as regards the passage of the air from the outside to the inside. In atmosphere containing carbon dioxide a slight leak would not render the apparatus useless; but where irritating vapours, such as the smoke from burning oregon and sulphides, are met with, even the slightest leak must be avoided.2. The oxygen supply must be ample, and so supplied that it is not checked by expiration.3. Expiration and inspiration must not be retarded.

Jan 1, 1911

By Roy H. Grau

Increased awareness of a healthy work environment is common to all industries and the stone industry is no exception. The presence of operating diesel equipment, welding, stone production blasting, and silica dust in a working environment all contribute to air quality issues in underground stone mines. Particularly recognized is the exposure of workers to diesel particulate matter (DPM). Recent regulations call for a DPM standard of 160TC ug/m3 (TC = Total Carbon). The National Institute for Occupational Safety and Health (NIOSH) has conducted research to improve the ventilation of these mines and consequently reduce the exposure of workers to harmful airborne contaminants. The results have shown that the ventilation of underground stone mines can be significantly enhanced using improved ventilation controls and techniques. Large-opening stone mines present specialized ventilation challenges because their entries are much larger than in other types of mines. Most stone mines have entries about 40 feet wide and up to 30 feet high, with bench areas that may extend even higher. These large entries present the positive opportunity to move large air quantities at relatively low mine fan pressures resulting in lower fan horsepower and reduced operating costs. However, the difficulty in ventilating large-opening mines is that even with large air volumes, the air velocity is often less than 100 feet/minute. Higher ventilation velocities more quickly dilute and remove contaminants from the face areas. Higher ventilation airflow velocities can be achieved by effective ventilation planning and proper choice of ventilation fans.

Jan 1, 2009

The Mount Kasi gold deposit in Vanua Levu represents an epithermal, high sulphur, gold-enargite system occurring within a volcanic caldera of Middle to Upper Miocene age. High level breccia pipes flare upward and form flat lying, near surface, mushroom shaped sheets parallel and near to the present land surface. The upper portions of the pipes contain explosion breccias which are capped by sandy siliceous sinter-like beds and are cut by alunite veins. Outlying intercalated scoriasceous lavas and breccia sheets show evidence of subsidence within a shallow basin. Detailed mapping of breccia types, intensity of silicification and the presence of multiple quartz veining and enargite abundance outlined blocks of more consistent gold mineralization within the breccias. This work has provided a model for mineralization which will aid future exploration and ore reserve estimations. A significant eluvial concentration of gold occurs in soils overlying the breccia sheet.

Jan 1, 1987

By W. J. Garmoe

Distinct areas of mineralized and non-mineralized brecciated rock are found in the Ontario Unit of the United Park City Mines. These breccias contain an appreciable fraction of the present ore reserves and probably will become even more important as deeper levels are developed. Three ages of breccia have been recognized in the Ontario Mine to date: ( 1) Pre-mineral breccia that may or may not be mineralized, (2) early post-mineral breccia with mineralized fragments, and ( 3) late post-mineral breccia that is younger than and cuts through ( 1) and (2) above. These age ,relations are known from detailed underground mapping. Locally, both pre-mineral and post-mineral breccias have sufficient lead-zinc-silver content, either as matrix or fragmental material, to constitute ore. Ore-grade breccias occur throughout a vertical range of over 1000 feet and are found in both the Humbug and Deseret formations from above the Ontario 1300 level to below the Ontario 2200 level. The mineralized breccias, which are difficult to distinguish on mine maps, are not well delineated by underground workings, and their horizontal outline and vertical extent are not known beyond the immediate mining areas. The greatest amount of truly mineralized breccia is exposed on the 2200 level.

Jan 1, 1968

By K A. Campbell, K A. Rodgers

The Plumduff sinter occurs at Whenuaroa, near Puhipuhi, approximately 30 km north of Whangarei. It is one of three residual sinters in the southern portion of a mid- to late-Pliocene geothermal system. The deposit consists of many large sinter breccia boulders, including rudrocks (coarse breccias), scattered around the flanks and summit of the small conical hill of Plumduff. Three types of sinter breccia occur: (i) rudrocks consisting of large, angular to sub-angular clasts of layered sinter up to 0.8 m across, as well as smaller clasts of sinter (20 - 100 mm dia), and fragments of stromatolitic structures; all clasts are supported in a matrix of microcrystalline, transparent to translucent to milky quartz; (ii) fragments of layered angular to irregularly mottled sinter of white to grey or bluish hue supported in a translucent to opaque silica matrix; (iii) smaller, matrix-supported breccias with clasts both partially surrounded and/or penetrated, by a clay-like weathering rind, and sinter conglomerates with rounded to oblate clasts. Three principal types of fabrics constitute the bulk of the sinter: (i) stromatolites, including columnar, palisade and filamentous networks, showing progressive silicification, in fenestral, tufted to clotted fabrics; (ii) peloids and pisoids; (iii) plant-rich facies in which various silicified plant species occur in a silica matrix. All fabrics have counterparts in hot spring deposits in the Taupo Volcanic Zone formed at temperatures from 75¦C to 35¦C. Also present is steam-condensate-produced alteration: kaolinite and alunite as well as boulders of quartz lattice texture. Cinnabar only occurs in sinter on the north and south central slopes of the hillside. No quartz veins or geyserite were recognised.

Jan 1, 2001

The Kidston breccia pipe is situated approximately 280 km west northwest of Townsville, north Queensland. It is currently Australia's largest gold producer with production varying between 8,000 and 16,000 tonnes of ore per day. Current reserves are estimated at 36.2 million tonnes averaging 1.74 C/t Au and 2.21 g/t Ag. Alluvial gold in the gullies surrounding the deposit was first discovered in the 1880's and between 1907 and 1948 small scale open cut and underground mining was undertaken. Advances in extractive metallurgy and an increase in the gold price were major factors influencing the recent exploration and development of large scale mining of the deposit by Placer Pacific and Kidston Gold Mines. The breccia pipe is trapezoid in shape with surface dimensions of 1100 m by 900 m. Clasts show only limited evidence of mixing during brecciation, with the pre-breccia stratigraphy still discernible on the basis of clast types. This lack of mixing together with the intimate association with intrusive activity, suggests that the brecia formed by collapse, probably associated with the escape of a large volume of irothermal fluid from a crystallising hatholith. Mineralisation and alteration are also sratially and temporally associated with rhyolite emplacement and brecciation. Pre-breccia mineralisation consists of laminated stockwork quartz veins associated with muscovite, quartz and orthoclase-epidote alteration. Stockwork veins contain either anomalous molybdenite or gold. Uneconomic early stage post-breccia mineralisation and alteration consists of cavity infill quartz-epidote and calcite associated with potassic and propylitic alteration respectively. Economic late stage post-breccia cavity infill and sheeted veining consists of quartz-carbonate-sulphide infill associated with phyllic alteration. The grade of gold mineralisation generally decreases downwards in the system with an increase in the amount of pyrrhotite relative to pyrite. Pre-breccia stockwork quartz veins mineralisation is genetically related to the

Jan 1, 1987

By Marcía García

El presente texto revisa la historia minera de Morococha. Aunque no se tienen datos exactos sobre el inicio de la explotación de esta minera, existen indicios primitivos de este proceso antes de la llegada de los españoles. Durante el Coloniaje se comenzaron a trabajar minerales oxidados que se beneficiaban por amalgamación en «circos»; asi como las galerías y pavonados que se fundían en horno de «pachamanca». Posteriormente, don Martín de Bidegaray, minero, azoguero y hacendado, solicitó licencia para levantar un Ingenio (Molino de metales) en el paraje San Martín de Tuctu de Morococha. El virrey le concedió y se construyó el molino de metales, constituyéndose la partida de nacimiento de la industria metalúrgica en Morococha y toda la región central del Perú. Sin embargo, la lucha por la Independencia Nacional paralizó por completo la naciente industria minera del Coloniaje, quedando en abandono las labores de extracción de minerales, sumándose la escasez de barreteros. Por ello, el señor Izcue, recurrió a Carlos Pflucker, hombre enérgico y emprendedor, quien pronto se convierte en el pionero de la Pirometalurgia al tratar de fundir minerales de cobre en hornos de Reverberación construidos por tres operarios fundidores traídos por él especialmente de Alemania. Finalmente muere el señor Izcue y Pflucker decide contratar más barreteros y convirtió a Morococha en una próspera Hacienda Minera, descubriendo nuevas minas de plata e instalando modernos procesos metalúrgicos de amalgamación y cloruración en Tuctu. Así, en 1905 el señor James B. Haggin adquirió las propiedades de la Compañía Minera de Santa Inés Y Morococha, y en el año 1908 por acción de los señores Haggin y A. W . McCune se constituyó la Morococha Mining Company, entidad de la que también formaron parte integrantes los miembros de la Cerro de Paseo Syndicate.

Nov 1, 1964

By J. R. Allan

Loki Gold Corporation of Vancouver, B.C. is developing the Brewery Creek Mine, an open pit heap leach gold mine, 55 km East of Dawson City in Yukon, Canada. Mineable reserves are 17.1 million tonnes of ore grading 1.45 grams/tonne, containing 24.8 tonnes (797 000 oz) of gold. Ore processing will employ a cyanide heap leach using run of mine ore. Permitting this mine has drawn significant attention because the heap leach technology, while proven in other jurisdictions, has not been used in Yukon. Engineering design of the heap leach was similar to that for heaps in more temperate climates, with the added issues of permafrost and cold weather operations. Solution balance with seasonal placement of ore and year -round leaching requires very large pond capacity for spring thaw conditions.

Jan 1, 1996

By H. Feldheiser

Acid resistant brick linings are state of the art for anti-corrosion linings in tanks for high pressure acid leaching (HPAL) treatment. The design of these brick linings has to take into account the almost non-elastic behaviour of the brick lining inside a relatively highly elastic steel vessel. There must be tools and data available to determine for the steel vessels the thermal growth plus the pressure expansion and for the brick lining the linear thermal expansion and the chemical swell. Thermal shocks and pressure drops are not regular operating events but their negative influence on the lifetime of a brick lining has to be a part of the engineering study. Finite Element (FE) models as well as a lot of research and development on brick lining materials is the only way to find a path through the complex engineering work for pressure vessels.

Jan 1, 2004

By Andrew Middleton, Mark Wyatt

"The Brickworks Marketplace Project is a significant shopping centre development in inner north west Adelaide constructed by Badge Constructions in 2014 and 2015. The site was a former brickworks with a deep pit containing various extents of uncontrolled fill which was to remain on site, and with a remaining void up to 6 m in depth. The existing uncontrolled fill was improved using the High Energy Impact Compaction system, and the pit backfilled using a quarry crusher byproduct selected by trial and a recycled crushed concrete and bricks and compacted in deep lifts. This approach resulted in significant savings in compaction time, cost and building foundations. The settlements of various parts of the completed works have been monitored since February 2015 and this monitoring has demonstrated small settlements which meet the user’s constraints.INTRODUCTIONThe Torrensville Brickwork Markets project involved the transformation of a former brickworks and clay pit site into a regional 17,000m2 shopping centre, opening in June 2015.The site was a former brickworks with adjoining clay borrow pit. The clay pit had been partially backfilled over many years with ‘uncontrolled’ fill comprising ‘clean’ soil, bricks and kiln dust typically of the following thicknesses:??of the order of up to 7 m to 10 m but locally up to 15 m in the western part of the site??2 m to 5 m in the south-eastern part of the site; and??less than 0.5 m in the north-eastern part of the siteAnecdotal reports suggested compaction of some of the fill may have been undertaken, although this not able to be confirmed nor records obtained.Initially it was proposed to take up the existing uncontrolled fill, sort and recompact or remove to landfill, followed by backfilling in conventional means over 500,000 cubic metres of imported filling to a thickness of up to approximately 6m to backfill the former pit. This work represented a significant cost and was not economically viable.During early negotiations, the contractor proposed an alternative to retain and ground improve the existing filling on site, and to backfill the pit with fill placed and compacted in deep lifts, thereby significantly improving the economics, environmental and community impacts of the proposed works.The developer agreed to the proposal with the following performance criteria:??a settlement of =10 mm after 10 passes by the Impact Compactor (on existing subgrade areas);??a bearing capacity of 250 kPa for high level footings;??a maximum long term differential settlement of 40 mm (measured over 16 m), ie. 1 in 400; and??a minimum modulus of 40MPa."

Jan 1, 1900

By Ron J. Elliott, Corry Coumans

The following is a detailed description of the blasting procedures used in the successful demolition of the Stave River bridge, Mission, British Columbia, Canada. This highway bridge spans a highly sensitive salmon-spawning river. Demolition of the bridge took place in a high liability situation in close proximity to sensitive structures. The new highway bridge carrying an exposed 150mm diameter gas line was located only 1.5 meters away. The bridge piers were blasted only seven meters from overhead power lines. Control of blast vibration, flyrock, and underwater overpressure was critical to the success of the operation. Electrical sequential blasting was used to ensure that blast vibration on the new bridge structure was kept below 50mm per second.

Jan 1, 1998

By Calvin Konya, Janos Foldesi

A bridge over a main line railroad system was scheduled for demolition. The bridge was made of reinforced concrete and spanned three mainline railroad tracks which could not be shut down due to blasting or demolition. To further complicate matters, the mainline tracks had high tension power lines running above the tracks, but below the bridge. These high tension wires provided the electricity for electrically powered trains. The tracks could not be damaged or disrupted, nor could the power line be broken.

Jan 1, 1992