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By T. Moller

There are differences in design aspects between steel and rubber linings in grinding mills. This paper describes the basic design rules for rubber liners for different grinding applications. When converting a mill from steel to rubber liners, the design must be changed from such familiar steel liner shapes as wedge bars and plates, wave liners, ship-lap, etc. to take advantage of the characteristics of rubber. Very little of the knowledge of the wear properties of steel can be used for the design of rubber mill liners.

Jan 1, 1989

By Colin C. Brooks

The Ok Tedi gold/copper deposit of almost 800 million tonnes was found in I968 because at that time technology had just developed sufficiently to enable exploration of such an area, world markets and prices for copper encouraged exploration for large deposits of low grade ore, Papua New Guinea law encouraged exploration by groups with men, money, management and expertise necessary for successful prosecution of such a search and such groups were already operating in the country.

Jan 1, 1990

By J. Peshel

This paper presents a regulatory perspective of the design and construction of the Exploratory Shaft Facility which may become part of the future high-level waste repository. Site characterization concerns and long-term waste isolation concerns require the consideration of various shaft design and construction aspects quite different from that of conventional shaft sinking.

Jan 1, 1989

By W. G. Pariseau

Regression analysis of calculated on measured displacements were used to assess the influence of fill and fold plunge on shaft pillar mining at the Homestake Mine. These effects were neglected in the original three-dimensional finite element analysis undertaken in 1991. An average fold plunge of 15? and a 24K fill (Young’ modulus of 24,000 psi or 165 Mpa) were used in the reanalysis. Measured displacements were obtained from an array of 36 m (120 ft) multiple-position borehole extensometers installed in June 1994 and read to March 2003. Results indicate the effects of both on calculated displacements and thus on regression parameters are noticeable. However, these neglected effects would not have changed the original inference of Ross Shaft stability during pillar mining.

Jan 1, 2004

By Steven A. Tesdahl

Maintenance means keeping equipment running or restoring it to operating condition. However, the 21st century will usher in a broader need for equipment management, a cradle-to-grave strategy to preserve equipment functions, avoid the consequences of failure and ensure the productive capacity of equipment. Profitable future mining operations will have reduced the 35% of operating costs typically spent on maintenance and the unfavorable impact of downtime that often multiplied these costs by 300%. They will survive those operations that tried to carry outdated "maintenance" thinking beyond the year 2000. These surviving operations will have applied modern management techniques, technology and information to align the efforts of people with the needs of equipment. Future managers will use equipment management as an integral part of an overall production strategy. They will see it as a means of raising productivity, improving performance and minimizing downtime to maximize profitability. This global thinking will characterize all operations planning to survive in the competitive world of mining of the next century.

Jan 1, 1998

By Q. Yuan, B. Yarar

Steric stabilization is a phenomenon observed when relatively high doses of flocculants are added to fine particle suspensions. Experiments were conducted to establish conditions under which medium viscosity and the sedimentation properties of black sand components in a slurry could be controlled so as to enhance the selective sedimentation of gold grains. It was shown that black sand concentrates containing as low as 2.65 g/mt gold could be upgraded by selectively hindering the sedimentation of non-gold components in an aqueous slurry. This paper presents data describing the theory and practical implementation of this cyanide or mercury-free novel approach where gold could be concentrated by as much as 15 times with relatively high recoveries. The relationships of solids content of slurries, type and dose of polymers with the recovery process are documented. Key words: Gold, black sand, selective flocculation, steric stabilization.

Jan 1, 1993

By Lorenzo Pellegrini

The respect of EPB reference pressure during TBM advance and hyperbaric activities, the complete and effective filling of the annular gap between tunnel lining extrados and the excavation section and a well organized monitoring system, to control surface settlements and ground distortion, are items of utmost importance in EPB tunnelling process. The paper describes how these concepts have been applied while excavating in the difficult underground conditions found at Sao Paulo (Brazil) during the execution of the Sao Paulo Metro Line 4-Lot 1. In this project, the annular gap has been filled by two components type, cement grouting. The back feed of the extensive monitoring campaign carried out to check the surface settlements during the excavation and hyperbaric maintenance operations will also be described in the paper.

Narrow vein mining, with enough challenge and also where the cutting edge technology can be applied, is still a very important and exciting portion of the mining industry. Based on the deposit characteristics, the most flexible mining method, cut and fill, has been being tested mining this high grade Northern Nevada property, Hollister, since the year of 2008. In the last three years, 254,000 tons of ore were hauled out of the portal and 23,000 feet of development were excavated underground with the winning of several safety and environmental awards. Together with mine geology, the essential segments include mining cycle, ground control, ventilation, grade control and backfill method in cut and fill stopes were covered in this paper.

Jan 1, 2012

By S. Monette, D. B. Dreisinger, D. Vleeschhouwer, G. B. Harris, G. A. Kordosky

A new process for the recovery of pure (>99.95%) palladium and platinum is described. The process, which has been tested at the pilot scale, comprises (i) the simultaneous solvent extraction of palladium and platinum by a new Schering Berlin reagent, TN 1911, (ii) washing of the loaded extractant to remove co- extracted impurities, and (iii) differential stripping of first platinum at pH 3, and secondly palladium with strong hydrochloric acid, and (iv) precipitation of palladium and platinum salts, followed by reduction to metal. The process is, unusually, a non-ammonia one requiring only small amounts of ammonia at the end where final purification may be necessary for particularly complex feed solutions.

Jan 1, 1993

By J. Parker

Gentlemen; Rainy day in Upper Michigan, a good time to catch up on reading. Am doing that, and have a couple of questions concerning the K and P paper on roof problems and supports. I wonder if the authors can enlighten me. The compressive strength of the coal was reported as 4.4 MPa (633 psi) and compressive stresses measured in the coal seam were reported at around 27.6 and 48.2 MPa (4000 and 7000 psi ). Can such a soft coal actually contain such a high level of stress? Can it be measured as if the material were elastic, or does the coal behave plastically? Can that stress level be confirmed with hydraulic load cells? And if the coal is so soft, and if it is plastic, why is the stress field not hydrostatic? The intact roofrock appears to be unusually strong, with compressive strength reported at around 145 MPa (21,000 psi), and some failures were noted as soon as the rock was exposed. Were tests run to find out how that rock responded to the addition

Jan 1, 1991

By Eric Gilmore, Ron Tudor, Gregory E. Korbin, Bill McCormick, Brad Bush

INTRODUCTION Las Vegas has recently been termed the “Construction Capital of the Country”. It has also been acknowledged as the fastest growing city in the country for several years running. The rapid growth improves the economic picture of the region but it also imparts unusual demands on the area’s infrastructure. In 1994 the Southern Nevada Water Authority (SNWA)was working on a master plan to address the rapid growth. A long range analysis revealed the need for additional water treatment capacity and delivery systems. Short term projections showed that the current system would reach capacity in the summer of 1997 with the possibility of demand exceeding the supply. The River Mountains Tunnel #2 is part of a $150M scheme to quickly upgrade the system to meet the short term demand, improve the overall system operation and allow for a smooth transition into the larger additions being planned for the future. The SNWA selected Carollo/Black & Veatch (CBV) to provide detailed design and construction management for the upgrades. The River Mountains Contracts consisted of five separate contracts broken out separately to stream line a very aggressive (just 34 months) design and construction schedule. Necessary work included four miles of excavated and lined tunnel, connections from existing pipelines to and from the new tunnel including large diameter (to 3.66m(144 in)) valves, a 18 927cu m (5 million gal) regulating reservoir, a surge tank and a 170 343cu m (45 million gal) reservoir to add additional storage to the system. Notice to Proceed was given to Kajima Engineering and Construction (Kajima) on May22, 1995 for the construction of the River Mountains Tunnel #2. The design called for a tunnel to be driven 6070m (19 915ft) in rock and lined to a finished diameter of 3.71m (12.17ft).Excavation began on December 14, 1995 and holed through on April 30, 1996. Lining began on June 25, 1996 and a notice of Substantial Completion was issued on December 13,1996. This paper describes the measures taken to complete the tunnel in 18 months from Notice to Proceed to Substantial Completion. THE RIVER MOUNTAINS SITE The River Mountains are a low range of rugged mountains separating the Las Vegas Valley from its main supply of water, the Colorado River at Lake Mead. They are volcanic in origin and the harsh desert environment has left them as expanses of exposed bedrock rising 305m (1000ft) above the valley with little or no vegetation. An existing 3.05m (10ft)

Jan 1, 1997

By S. K. Sharma, D. A. Stanley

The US Bureau of Mines is investigating the fundamentals of the flocculation process. The objective of this study was to determine the effects of various physico-chemical parameters, namely, shear rate, polymer dosage, and polymer concentration, on floc growth and to determine the applicability of a model for predicting polymer flocculation behavior. A rapid in-line particle size analyzer was used to follow the progress of both the floc growth and the breakage as a function of time. A genetic algorithm (GA) was used to determine the unknown parameters in the model and to fit a curve to the experimental data. The results showed that the model reproduces the experimental data with only reasonable accuracy and that it was relatively insensitive to the parameters. Results of the flocculation study showed that increases in the polymer dosage had a greater effect on the time required to reach the maximum floc size than on the floc size itself: It was also determined that, given all the above parameters, the degree of slurry mixing during the flocculation process had the greatest bearing on floc growth.

Jan 1, 1995

By Irwin R. Higgins, Joseph C. Milbourne

The selection of a suitable nitrate removal process depends on a variety of site-specific chemical and environmental issues. The dominant technologies for nitrate removal include biological denitrification and continuous countercurrent ion exchange. The decision to apply either of these technologies, or both together, depends on the nature of the waste water to be treated. Factors that affect the selection of the biological system include the feed composition and feed temperature. Ion exchange nitrate removal systems ere less sensitive to the feed composition but require disposal or destruction of the concentrated pregnant eluate. The paper discusses Tetra's continuous countercurrent ion exchange technology (CCIX™) and fixed film biological reactor, Denite®. The treatment of the ion exchange pregnant eluant is also discussed.

Jan 1, 1995

By S. P. Liebenberg

During the past fifteen years significant progress has been made on carbon-in-pulp (CIP) technology for the extraction of gold. While most research on the mechanisms and kinetics of CIP sub-processes has focused on the adsorption step only, auxiliary unit operations such as elution have received less attention. The mathematical models which have been developed for elution at the University of Stellenbosch can be used for design as well as process optimisation by incorporation into an overall CIP simulation program. Except for these models, no other comprehensive models for the complex elution process are available. It is the aim of this paper to review recent modelling work on competitive elution from activated carbon.

Jan 1, 1995

By T. C. Eisele

The use of column flotation was considered for the ?reverse flotation? of iron ore, where the gangue (quartz) was recovered in the froth product. This use of the froth for carrying the gangue mineral rather than carrying the valuable concentrate significantly changes the operational requirements of the column. The objective of this work was to determine which of several column flotation technologies would be most suitable for this type of flotation operation. Studies were carried out using both the Jameson column and the Deister column. Comparative results are presented that show the capabilities of both column types in this application relative to conventional Wemco flotation cells. Columns were demonstrated to have grade-recovery performance superior to what could be achieved with conventional cells. Two-stage flotation with the columns could produce a concentrate that was up to 70.2% Fe at 87.5% iron recovery, compared to 70.4% Fe at only 77.7% iron recovery for four stages of flotation in conventional cells. It was shown to be particularly important to operate the columns to recover a maximum of the quartz gangue into the froth. It was noted that there are often problems in scale-up of laboratory columns to plant scale, because the increase in height and the decrease in the ratio of height to diameter at the larger scale allows more axial mixing and bubble coalescence, both of which degrade the column performance. Horizontal baffling was shown to improve column performance by reducing axial mixing and breaking up large bubbles, and so the use of such baffles in the reverse flotation application was investigated.

Jan 1, 2007

By H. Bogart

The Golden Sunlight Underground Mine located near Whitehall, Montana was portalled from the bottom of the existing Golden Sunlight Pit in July 2002. Gold was mined by sublevel stoping in the larger ore zones and longhole back stoping in the narrower ore zones. The stopes varied from 30 feet to 100 feet in width, extended up to 200 feet in height, and were completely unsupported. Underground production averaged 1,500 tons per day with a staff of35 people. The mine operated with a break-even cut-off grade of0.080 ounces per ton.

Jan 1, 2004

By Randy Sandrik

Sampling has evolved at two large underground limestone mines as conditions and product requirements have grown tougher over 100 years of mine life, requiring innovative techniques to insure delivery of high purity limestone. Sampling insures delivery of consistent product to customers at the lowest possible cost. Statistical considerations have evolved from simple data collection to predictive and process capability analysis. Sample methods include borehole samples, face (using a proprietary face-sampling device), and total plant feed automatic, process, and final product sampling. Lessons learned, while keeping costs at historically low numbers, include the importance of geological models, exploration drilling density, face sampling, and blending of ore.

Jan 1, 2005

By Atta Ur Rehman, Kwame Awuah-Offei

This paper examines the effect of bucket geometry (cutting-blade profile, floor profile and blade thickness), speed, motor power output and muckpile particle sizes on bucket penetration and draft for rubber tire loaders. The work uses a 1:16 scale model of a load-haul-dump (LHD) in full-factorial experiments to examine the effect of the variables on penetration and maximum draft. The results show that speed and motor output are positively correlated with penetration and draft, and muckpile particle size is positively correlated with penetration and negatively correlated with draft (p < 0.0014).

By Mona M. Fawzy, Ahmed A. Eliwa, Ebrahim A. Gawad, Ahmed H. Orabi, Amal E. Mubark

The growing demand for rare earth elements (REEs) has led to numerous recent studies to recover these elements from various bearing ores and wastes. Therefore, the recovery of REEs from Ras Baroud polymetallic concentrate has been investigated in the current study. Physical beneficiation for the Ras Baroud pegmatite sample was carried out, yielding a concentrate for euxenite (Y), fergusonite (Y), xenotime (Y), monazite (Ce), allanite, thorite, uranothorite and Hf-zircon, which resulted in raising the concentrations of REEs, Th, Zr, U and Ti in the sample. Fusion digestion processes with sodium hydroxide were studied using the conceived predictive diagonal (CPD) technique. The three experimental digestion groups proved the dissolution of 99.9, 95.6, 99.9, 52.5 and 0.47 percent for REEs, Th, U, Ti and Zr, respectively, under fusion conditions of 723 K, 120 min, 1/1.5 ore-to-alkali ratio, and smaller than 100-μm particle sizes. Fusion kinetics, isotherms and thermodynamics were investigated using several suggested models, namely, pseudo reversible first order, uptake general model and shrinking core model, which matched well with the experimental digestion results. Selective recovery of actinide content from the REE content of the digested concentrate chloride solutions was accomplished using solvent extraction with di-2-ethyl hexyl phosphoric acid. About 99.9, 99.9 and 4.2 percent extraction efficiencies for Th, U and REEs were realized, respectively, using 0.3 mol/L solvent concentration in kerosene as a diluent, 1/2 organic-to-aqueous ratio, aqueous pH of 0.2 and contact time of 15 min. Thorium and uranium ions were stripped with 2.5 mol/L sulfuric acid solution with 94 and 98 percent stripping efficiency, respectively. A highly purified REE precipitate was obtained from the raffinate solutions. Zircon mineralization tailings were obtained as a byproduct through the alkaline digestion process.

Oct 1, 2024

By Carlo Grandori

Foreword In loose ground and soft rock formations, mechanical tunnel boring is necessarily dependent on the adoption of shield machines and the application of adequate support or lining structures. These structures are erected either within or immediately behind the rear portion of the shield and provide the required reaction to the forward thrust. In competent rock formations where systematic support is not a requirement, hard rock tunnel boring machines generally advance by thrusting from a structure gripped against the tunnel walls. These machines may feature a more or less extended cutterhead shield or roof support, but when in weathered, fractured or otherwise weakened ground, or in fault zones filled with soft gouge, the gripper mechanism often cannot provide enough thrust reaction to advance the cutterhead. Under these conditions, early support of the arch and walls is generally required in the form of rock bolts, steel rings and laggings and some times of a primary concrete lining placed in the short section between cutterhead and grippers. Such tunnel support measures generally fail to produce an adequate increase in thrust reaction capacity, but

Jan 1, 1976