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By David Yang

Commercially available flotation technologies for recovery of mineral fines have remained essentially unchanged for several decades. Recent studies have focused simply on improving mechanical and open column cells. Such studies have explored different control strategies and have aimed to improve reagent selectivity, fine air bubble generation and particle-air contact. However, no study has questioned whether current techniques are the most efficient technology for recovering mineral fines. Given that both mechanical and open column cells have a widely accepted carrying capacity limitation, the lack of extensive research into an alternative technology is surprising. Most recently, open column flotation has become an entrenched technology, and it is undermining the efficient recovery of mineral fines worldwide. An alternative exists. Packed column flotation overcomes the above-stated problems as the technology surpasses the carrying capacity limitation of current means by several-fold and almost always achieves the best performance in many comparative pilot tests and full-scale plant operations. Filling a column with packing plates creates a network of sloped walls capable of supporting a froth bed many times deeper than conventional machines. Having froth up to 75 percent of the total column volume tolerates all feed changes encountered in the plant environment and permits maximum flexibility in concentrate quality control. Furthermore, its scale-up is straightforward by increasing column volume or the number of interconnected small cells. As the air breaks upon rising and is distributed horizontally through packing plates, the air spargers can be replaced with a simple blower, resulting in considerable savings in operation and maintenance costs. Packed flotation technology provides a break-through solution for the separation of fine and ultra-fine minerals. Its simplicity, superior performance, and low cost structure make it an appealing alternative to current technologies and allow greater flexibility in downstream processing. Future industrial applications include a wide variety of metallic and non-metallic ores. This paper focuses on some recent scale-up campaigns for nickel and copper sulphide flotation applications compared directly to conventional equipment.

Jan 1, 2014

By Brendan Demich, MAHIYAR F. NASARWANJI, Alan G. Mayton

Nonfatal injuries from slips, trips, and falls (STF) that occur at surface mines can result from inadequate lighting. Mobile equipment operators are among the occupations associated with the nonfatal incidents reported to the U.S. Mine Safety and Health Administration (MSHA). In addition, getting on/off the equipment (ingress/egress) frequently adds to the highest proportion of nonfatal incidents. Accordingly, researchers at the Pittsburgh Mining Research Division (PMRD), National Institute for Occupational Safety and Health (NIOSH) conducted a field study to investigate lighting on haul trucks and wheel loaderswith regard to glare and illuminance levels recommended by the Illuminating Engineering Society (IES). The objective was to determine whether two light-emitting diode (LED) area luminaires—a Mr. Beams® (model MB390 Ultrabright) (area luminaire-1) and a NIOSH-developed Saturn (custom-designed for a mine roof bolter study) (area luminaire-2)—could complement a headlamp luminaire. Measured levels of visual tasks, with the headlamp alone and the area luminaires plus the headlamp, demonstrated that illuminance met or exceeded IES-recommended levels. Nevertheless, the area luminaires illuminated a much broader area, which is key to increasing hazard awareness. Discomfort and disability glare were lower with area luminaire-1 than with area luminaire-2. Differences in glare were more noticeable for newer models of haul trucks and loaders featuring updated ingress/egress system designs. This study demonstrates that commercially available luminaires, such as area luminaire-1, are capable of complementing headlamp lighting, and can thus improve a miner’s ability to detect and avoid STF hazards.

Jun 17, 2020

By D. M. Muir

The mineralogy of residues formed during the pressure acid leaching of arid region nickel laterite ore varies according to the salinity of the process water, alkali cation additives and the overall acid loading. In fresh water, hematite is the main iron-bearing leach residue component, together with amorphous silica and hydronium or sodium alunite/jarosite [(H3O,Na)(Fe,Al)3(SO4)2(OH)6]. As the process water salinity increases, or as NH4+ or K salts are added, alunite/jarosite is the kinetically favoured iron-bearing phase accompanied by an increase in acid consumption. The alunite/jarosite appears as two XRD distinct phases with different Fe:Al molar ratios. In weakly saline water, iron-rich alunite/jarosite slowly transforms to hematite and an aluminium-rich alunite/jarosite together with the release of acid. The addition of potassium salts forms a more stable alunite/jarosite whilst the addition of ammonium salts leads to greater transformation of alunite/jarosite at 250°C. Weakly saline process water gives enhanced nickel recoveries, whilst strongly saline process water gives lower nickel recoveries but higher soluble iron because of chloro-complexation. SEM and microprobe analysis shows very little nickel is associated with the alunite/jarosite and hematite phases. Nickel losses to the residues are attributed to adsorption on amorphous silica and to a lesser extent on alunite/jarosite.

Jan 1, 2006

By M. Gyenge, O. F. Coates, K. Barron

"It is suggested that artificial supports might be used to increase, with safety, the angle of hardrock open-pit slopes. Guidelines for designing such a support system, based on a simplified analysis, are given. The installation, construction and instrumentation of a trial support system is described and a breakdown of the construction costs is given. On the basis of this cost analysis, the economic benefits derived from reduced waste-rock excavation are compared with the support costs for a typical mine. In an example, it is shown that the slope angle in an open-pit mine 500 ft deep, with benches 50 ft high by 30 ft wide, could be safely increased from 37Yz degrees without support to an optimum of 53 degrees with support. In this case, the support costs would be approximately $900 per linear foot of pit wall and the savings due to decreased excavation of waste rock (at $0.34/ton) would be approximately $1,900 per linear foot, yielding an increased margin of profit of approximately $1,000 per linear foot of pit wall. This figure could be increased to $6,000 per linear foot if the steeper slope were used to extract more ore.More than 50 per cent of the support costs are accounted for by diamond-drilling the holes for the deep cable anchors. The use of percussion drills for this purpose would seem to offer a means of significantly reducing the support . costs and thus further increasing the profit margin available."

Jan 1, 1971

By John D. Campbell

Alberta Plains coals exhibit an almost rectilinear system of vertical fracturing called "cleat", which is best traced by mapping true bearings of underground coal mine rooms. The cleat pattern is approximately conformable with a pattern of surficial features and a pattern of bedrock jointing in the Alberta Plains, and with the trend of the Rocky Mountain Trench, but not with the distribution pattern of coal rank nor with the trend of the eastern boundary of the Rocky Mountains and Foothills physiographic province. The processes resulting in cleat remain in doubt, but cleat is always of practical importance in extracting coal from deeply buried deposits.

Jan 1, 1979

By E. Swartzman

"IntroductionGENERALLY, the necessity for mining coals of higher impurity content, the drive for lower costs by intensive mine mechanization, changing market requirements, and the increasing competition of oil and natural gas, have continued to result in an upward rise in coal preparation, and have necessitated a more intensive study of coal preparation problems.Increasing adoption of •continuous mining equipment, for example, is introducing new problems in coal preparation. Limited experimental work in the United States (1) shows that the effect of the continuous miner on size distribution varies with the characteristics of the seam. In some seams, the fines problem is lessened, in others it is greatly aggravated. Generally there is a decrease in the relative amount of the top sizes (plus 2 in.) and a substantial increase in the intermediate sizes (down to about 1/8 in.). Contrary to expected results•, where continuous miners with vertical-moving cutting heads are used, an increase in impurities in the slack sizes does not necessarily occur where draw-slate is taken. This is because the draw-slate tends to be kicked out in lump form. However, if a seam contains bands •and lenses of impurities they are bound to be in the mined product."

Jan 1, 1952

By Robert S. Sanford

In April 1948, the Bureau of Mines was requested to evaluate the graphite deposit' known as the Benjamin Franklin and Just mines in Chester County, Pa. After preliminary investigation, it was recommended that the Bureau core-drill, trench, and sample the deposit and make beneficiation tests on the ore. During the first and second World Wars, flake graphite was in short supply, and a number of deposits in the United States were exploited. In 1942, the Defense Plant Corporation, through its lessee, the Benjamin Franklin Graphite Co., purchased 70.263 acres of graphite-bearing land and built a complete mining and milling plant with a capacity of 300 tons of crude ore per 24-hour day at a cost of $426,250 (Plancor No. 1254).

Jan 1, 1949

By A. B. Campbell

The Bureau of Mines is developing alloys using ion implantation as an alternative to bulk alloys that consume large quantities of strategic materials such as chromium and nickel. These alloys are formed at the outer layer of relatively common materials. To more fully understand the corrosion characteristics and physical properties of this outer layer, it was necessary to deter-mine the alloy concentration as a function of depth into the substrate material. Also, since many of the ion-implanted alloys would be utilized at elevated temperatures, it was necessary to determine the diffusion behavior of the implanted element. Proton-induced X-ray emission and inert gas ion sputtering have been utilized to generate composition depth profiles for Fe-Cr, Fe-Ni, and Fe-AI ion implanted alloys fabricated by implanting 25-kev Cr+, Ni+, or AI+ into iron substrates. The data were fitted (utilizing a computer program) with symmetrical Gaussian profiles yielding values for the range and range straggle of the ions. These parameters were then compared with those calculated from theory. Changes in the profiles due to annealing were investigated and values for the diffusion coefficient were obtained assuming diffusion according to Fick's Law. For the Cr+ and Ni+ implantation, the profiles as-implanted agree reason-ably well with theory and exhibit ?norrmal" diffusion characteristics at 500° C. For the Al+ implantation, the profile as-implanted is much broader than predicted and exhibits substantial enhanced diffusion at temperatures up to 500° C.

Jan 1, 1979

By Adam Zagorski, Rusty Lucido, Curt Scheyhing

"The current California Department of Transportation (Caltrans) practice based on AASHTO LRFD Bridge Design Specifications is to use the O’Neill and Reese method (FHWA, 1999) for calculating the side resistance and base resistance of Cast-in-Drilled-Hole (CIDH) piles / drilled shafts. In this calculation, end bearing is typically neglected for piles constructed using a wet method due to questionable reliability of end bearing resulting from soil disturbance and inadequate cleaning of the base. Pressure grouting below the tips of drilled shafts in cohesionless soils has long been used worldwide to provide reliable end bearing capacity, but for decades it was relatively unused in this country. It has been used increasingly in the United States over the last decade. Before this project tip grouting has not been utilized on or accepted by Caltrans to maximize piles end bearing capacity. This project proved that tip grouting to mobilize reliable base resistance can be successfully implemented on a full-scale bridge project requiring over 350 large diameter shafts.For the Gerald Desmond Bridge Replacement Project, Shimmick/FCC/Impregilo, JV utilized a temporary Oscillator casing to the full depth to install CIDH piles. Piles were constructed by the wet method and then pressure grouted below the pile tip. A tip grouting procedure for these large diameter shafts was developed and tested to specifically address the geology and constraints of the project. This procedure was then proven during the Load Testing of test piles during the Test Shaft construction phase of the project. Tests showed a minimum reliable base resistance of 150 ksf could be mobilized in very dense sand at a downward movement of 5% of the pile diameter for piles ranging from 4.9 to 8.2 feet in diameter. By tip grouting, the length and diameter of the piles were significantly reduced."

Jan 1, 2017

By Kelly D, Moore C

The Golden Mile, which has been mined continuously for the past 100 years by both underground and more recently open pit methods, occupies an area of 1.2 km by 4 km adjacent to the city of Kalgoorlie Boulder in Western Australia (Figure 1). Large-scale open pit mining at the Kalgoorlie Consolidated Gold Mines (KCGM) Fimiston operations is currently extracting 7.8 million tonnes of oxide and sulphide ore for a total production of 522 000 oz per annum. The effectiveness of grade estimation techniques at KCGM has been examined with reference to existing 10 m bench sample data from all operating areas within the Eastern Lode System of the Main and North pits. The aim of the study was to recommend practical parameters for grade control estimation. The review included comprehensive variography and comparison of nonparametric estimation methods (Joumel, 1983) such as indicator kriging and probability kriging with ordinary kriging, leading to the development of improved grade control parameters and procedures for both daily quality control and short term mine planning. This paper reviews the geological, statistical, geostatistical, mining and modelling features studied in order to present KCGM's Mining Department with recommendations for improving grade control.

Jan 1, 1994

By Fred D. Wright

This paper describes research at the Bureau of Mines experimental oil-shale mine at Rifle, Colo., to improve blasting techniques and reduce breaking costs. Many of the conclusions are applicable to any mining operation. Experiments Were conducted on many phases of blasting. The effectiveness of various grades of explosives was compared, and several different drill-hole patterns were tried in heading rounds. An experiment was conducted to determine the maximum effective burden for various diameter blast holes. High-speed motion-picture studies were made of blasts, and the time for initial movement of rock after detonation of the explosive was measured. Experiments with millisecond-delay detonators in heading rounds proved that, when used properly, these detonators result in improved fragmentation, economical use of explosive, and compact, easily loaded muck piles.

Jan 1, 1953

By Steven J. Page

Accurate measurement of workplace respirable dust concentration is an essential step in eliminating lung disease in any occupational setting. In the United States (U.S.) coal mining industry, this measurement process has relied upon a personal sampler that includes a 10 mm Dorr-Oliver (DO) nylon cyclone operated at a flow rate of 2.0 L min-1 to collect a respirable dust sample. Dust concentrations measured with this sampler are multiplied by 1.38, which was empirically derived, to convert them to measurements approximating the United Kingdom British Medical Research Council (BMRC) definition of respirable dust upon which the health effects of coal mine dust are based. The International Organization for Standardization (ISO) subsequently refined the respirable dust definition and the U.S. National Institute for Occupational Safety and Health (NIOSH) 1995 Criteria for a Recommended Standard presented a conversion multiplier of 0.857 to apply to the 2.0 L min-' DO (in addition to thel.38 multiplier) to obtain equivalent ISO concentrations, as approximated by the 1.7 L min-1 DO. However, the conversion multiplier 0.857 was derived indirectly from a limited size distribution data set rather than a direct comparison of the DO samplers. The present analysis focuses on providing a more accurate conversion multiplier derived from direct comparisons of the 2.0 L min-1 (with 1.38 BMRC equivalency multiplier) and 1.7 L min-1 DO cyclones. A weighted linear regression analysis of this database suggests that a more accurate estimate of the conversion multiplier is 0.815.

Jan 1, 2009

By Louis A. Panek, John A. Stock

A flat slot is created in rock to cause stress relief effects in a pair of hydraulic borehole pressure cells (previously installed in drill holes above and below the slot ) , which act as sensing devices . This relief is annulled by repressuring the slot by means of a flat hydraulic cell . The slot pressure at annulment is taken to be the existing ground stress at right angles to the plane of the slot . A number of trial installations in the rib of a mine drift showed that for a valid determination of ground stress the sensing devices that respond to relief and repressuring must be within a specified zone close to the pressure transmitter ; otherwise the indicated ground stress may be excessive . By using an additional pair of borehole pressure cells , installed a few feet away , the existing rock stress can be redetermined at intervals , irrespective of a change of stress intensity subsequent to the initial installation . Based on these findings , equipment and procedures have been developed that make possible the installation and operation of a permanent rock stress monitoring station for observing mining - induced stress changes . The station consists of a 12 - in - wide hydraulic pressure cell cemented in a flat slot and four 2- by 8 - in flat hydraulic pressure cells in nearby drill holes . All drilling for the installation can be done with an air leg drill and conventional bits . Once the installation is completed , all required information is obtained by Bourdon pressure gage readings . The apparatus is simple , relatively inexpensive , and reliable under operating conditions in a wet mine . Unlike most methods of rock stress determination , this scheme permits periodic remeasurement of absolute rock pressure over several years , without additional drilling or instrumentation . Similar to other flat slot procedures , stress measurements are obtained without making auxiliary tests to determine elastic

Jan 1, 1964

By George L. Richert

The Minas de Matahambre is situated on the north coast of Cuba, in the Province of Pinar del Rio, approximately 150 miles west of Havana. This nine is the only producer of copper in Cuba, and has been worked for the past 15 years. In 1921 the property was affiliated with The American Metal Co., Ltd., and has been worked by them since that time under the direction of Mr. D. D. Homer, General Manager. Extracts from P. D. Wilson's ?Preliminary report on the geology at Minas de Matahambre? have been freely used in this report.

Jan 1, 1929

By P. L. Sibrell

Previous research by the U.S. Bureau of Mines has shown that autoclave cyanide leaching of used automobile exhaust catalysts for recovery of platinum-group metals (PGM) is technically feasible. The purpose of this work was to investigate the chemistry of the dissolution of PGM in cyanide solutions in more detail. Where possible, samples of pure, elemental PGM powders or foils were used instead of automobile exhaust catalysts, because of their greater purity. Ultraviolet spectra revealed that Pt and Pd were solubilized as the square planar tetracyanometallate (II) complexes, while Rh was solubilized as the octahedral hexacyanorhodate (III) complex. This explained the poor recovery of Rh from solution by carbon adsorption, solvent extraction, and ion exchange observed in earlier research, because of the higher anionic charge and size of the octahedral complex. Leaching rate studies showed that the rate of solubilization was greatest for Pd, followed by Pt and Rh. Although the rate of chemical reaction was the controlling step for the dissolution of elemental Pt and Rh samples, the rate of pore diffusion was rate limiting for PGM in catalyst samples.

Jan 1, 2010

By Chuan-Jian Zhong

Gold-based nanoparticles in the size range of a few nm have attracted increasing interests in catalysis, sensors and biomedical applications. The study of the unique catalytic properties of nanosized gold was inspired by the pioneering work of Haruta on the nanogold-catalyzed CO oxidation (1-4). There have been a number of excellent reports discussing both fundamental and application aspects of gold nanoparticles in catalysis (3-8). Our work reported herein is aimed at investigating the preparation and application of gold and its alloy nanoparticles for potential applications in fuel cell catalysis. Fuel cells operating by electrochemical oxidation of hydrogen or methanol fuels at the anode and reduction of oxygen at the cathode are attractive power sources due to their high conversion efficiencies, low pollution, lightweight and high power density. While methanol offers the advantage of easy storage and transportation in comparison with hydrogen fuel cell, its energy density (~2000 Wh/kg) and operating cell voltage (0.4 V) are much lower than the theoretical energy density (~6000 Wh/kg) and the thermodynamic potential (~1.2 V). The poor activity of the anode catalysts and inefficient activity or issue related to "methanol cross-over" at the cathode electrode are associated with the loss of about one-third of the available energy at the cathode and the other one-third at the anode. Extensive studies have been focused on Pt-group metals (Pt+Pd+Rh+Ru+Ir (PGM)) for both anode and cathode catalysts. A major problem is the poisoning of Pt by COlike intermediate species (9,10). Recently, oxide-supported gold nanoparticles in the <10 nm size range have emerged as one of the best catalysts for CO oxidation (1-3,11), and for water gas shift reaction in reforming stage using 5 nm Au on Fe2O3 (6). Gold and its alloy with other metals in the nanosize range present new alternatives (2,12). Whether the unique properties of gold nanoparticles can be exploited for addressing these problems is a focus area of our work. The ability to harness the large surface area-to-volume ratios and the unique surface sites of nanoparticles in <10 nm size range, especially in heterogeneous catalysis, constitutes a major driving force in fundamental research and practical applications of nanoparticle catalysts. It is this size range over which the metal particles undergo a transition from atomic to metallic properties. The understanding of factors controlling the morphological and surface reconstitution associated with such a size range is of fundamental importance to the ultimate exploration of nanostructured catalysts. We have been investigating the interfacial structures and properties of core-shell types of nanoparticles consisting of gold or alloy nanocrystal cores and organic monolayer shells that were prepared by twophase synthesis (13) and processing (14) protocols. Important attributes of such nanoparticles include controllable size monodispersity, processibility, and stability towards size- and composition-tunable catalysis (15-21). Some of these attributes were studied for understanding their electrocatalytic properties in the oxidation of methanol and reduction of oxygen, which are of fundamental interest to fuel cell technology.

Oct 1, 2003

By J Holdsworth, L Sutton, A Lavrinec, D Ilic

Air quality is a big topic of discussion in regional mining communities as well as urban environments situated close to port terminals handling bulk solids. Community perception of poor air quality can significantly affect the reputation of the mining operation and handling facilities. Dust monitoring for regulatory compliance relies on using a handful of accurate but very expensive sensors, usually situated at the boundary, relatively far from the activities that generate the airborne dust. These reference monitors measure dust leaving the site but dust mitigation and management on-site largely relies on operator judgement. At a fraction of the cost, small wireless solar powered units can be used to supplement reference monitors in real-time. Due to their compact nature, portability and low price, these units can be implemented on a mass scale to increase spatial resolution of dust measurements and, more importantly, in much closer proximity to both the dust generating activity and the sources of dust. This can provide valuable insights into the origins and timing of dust generation thus producing datadriven decision-making while minimising subjectivity. Similarly, light detection and ranging (LiDAR) is another supplemental technology that can be used to increase the spatial resolution of dust measurements in near real-time, however, the cost of commercial systems even exceeds that of regulatory monitors. LiDAR also presents difficulties in quantifying dust plume concentrations. This study presents learnings of implementing both technologies for dust emissions management. Several low-cost sensor units and a fast-scanning custom-built 3D LiDAR system operating at a range of 1.5 km with a resolution of 1.5 m were deployed on a surface mine to monitor dust emissions from different activities. The project explores the use of real-time sensor data to quantify LiDAR measurements in parallel with integration into mine planning. The approach can assist in prioritising dust mitigation activities thereby reducing instances of emissions exceedance and minimising water use through databased and targeted application. Demonstrated is an opportunity for a step-change in industry best practice as well as commercialisation and operationalisation of the method across different industries, including future mineral extraction.

Sep 18, 2023

By Oliver C. Ralston

The growing popularity of perlite (sometimes spelled pearlite) as a raw material for thermal expansion into pumicelike products in the Western States has prompted a preliminary investigation of the properties of such material and the problems that want solution to put a perlite industry on a firm foundation. The Bureau of Mines is undertaking the gathering of data and the solution of these problems, and the following paper records some of the available information. and the promise of the material, with some comparisons of advantages of the various competing lightweight aggregates that can be made from siliceous volcanic glasses and rocks containing entrapped or dissolved water that causes their expansion on&apos; quick heating to their softening points. This new industrial rock has caught the fancy of the mineral industry in the western States because it has Fume advantages over natural pumice. Chemically, it is typified as rhyolitic in composition, and one may find obsidian, rhyolite, pumice, pumicite, and perlite from the same vant and contemporaneous in origin. The material need not be rhyolite but should be a siliceous or acid lava and contain 2 to 5 percent water still in "solution" in the rock. On quick heating to the softening temperature the material puffs, due to conversion of the contained eater into bubbles of steam. Slow heating causes gradual release of the imprisoned water by decrepitation and. cracking and-results in, very little puffing. Perlite is often in the form of ovoid volcanic bombs formed by explosive eruption of large masses of lava into the air, where they, quickly cool, with escape of little of the contained water, exceptt perhaps for a hollow interior. Since they cool in layers they have an onion-type structure and a pearly luster from interference of light between the. layers, which is&apos; the origin of the name "perlite." Perlite may occur in intruded flows that have been quickly cooled and partly expanded but retained most of their magmatic water content. Obsidian may be the same lava cooled quickly under conditions that prevented crystallization of feldspars and other minerals, leaving the volcanic glass that may or may not retain all of the original contained water.

Jan 1, 1946

By Joshua C. Adams, Les Chernauskas, Edward L. Hajduk

"Drilled shafts are increasingly being used to support bridge and building foundations. Because these foundations usually carry very high design loads and often serve as non-redundant, single load carrying units, these foundation systems need a high level of quality control (QC) and quality assurance (QA) during construction. One such method for providing QC/QA is crosshole sonic logging (CSL) testing, in which ultrasonic signals sent across the drilled shaft concrete assess concrete quality.CSL testing is an effective tool to evaluate the integrity of the in-place drilled shaft concrete. While typically used to evaluate drilled shaft concrete after construction, CSL testing can also be used to evaluate drilled shaft repairs. This application can be difficult, given the variability of repair methods and material properties. CSL testing can also be adversely affected by the condition of the concrete/access tube bond, leading to false anomaly detection and/or inability to evaluate concrete integrity effectively. This phenomenon, called access tube debonding, is often located in upper portions of the drilled shafts where large changes in groundwater occur, such as within tidal zones.Two case histories showcase innovative uses of CSL testing to deal with consistent access tube debonding and to evaluate drilled shaft repairs.CSL OverviewCSL testing involves placing ultrasonic transmitters and receivers in access tubes installed in the drilled shafts prior to concrete placement. Concrete quality is assessed by examining the First Arrival Time (FAT) and relative energy of the signal sent between the transducers. If the distance between the access tubes is known, an apparent signal velocity (i.e., wave speed of the ultrasonic signal through the concrete) can also be determined and used to assess concrete quality.Common CSL testing practice consists of simultaneously raising the ultrasonic transmitter and receiver and recording the ultrasonic signals with respect to depth. This results in a 2D examination of the"

Jan 1, 2009

By Y. J. Wang

The selection of a shaft size for ventilation purposes is a classic problem of concern to mining engineers. This presentation is concerned with the sizing of conventionally-sunk circular shafts with concrete or shotcrete linings. Costs of sinking shafts of three different depths (from 500 feet to 1000 feet) and six different diameters (from 14 feet to 24 feet) were obtained through questionnaires to shaft contractors. The primary objective of the economic model presented is the balancing of detailed annual capital and operating costs to achieve the minimum overall cost of the shaft installation over its life. The economic model is similar to previous analyses but treats several of the individual cost categories in an updated fashion. Included in the paper is a detailed analysis of the effects of varying power costs on optimal shaft size. Also included are a statistical analysis of current shaft costs and comments on the choice between shotcrete and concrete linings.

Jan 1, 1977