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By Simón Díaz‑Quezada, Ernesto Arancibia, HUMBERTO ESTAY, Tomás Vargas

In situ leaching (ISL) is an attractive technique that enables copper recovery from copper oxide ores that are either low-grade or located at depths too great to be economically exploited through conventional methods. At present, in situ leaching (ISL) has been applied to intact copper oxide ores, in particular, those which (i) present a good natural permeability and (ii) do not require preconditioning. Many copper oxide ores present low natural permeability. These are located above the water table and need preconditioning for the ISL application. The present work shows an economic assessment of the application of ISL to this type of copper ores. The preconditioning technique considered here involves the application of partial mining by sublevel stoping by removing a small fraction of the ore. This technique results in forming an ore bed with good permeability and good solution collection at the stope base. The economic assessment of this approach suggests that it can be implemented with positive net present values to copper oxide ores located at depths in the 100–300 m range, with copper grades above 0.4%. The maximum acid consumption values are below 52.5 kg/t, with blasting procedures designed to produce an ore bed with an average particle size below 6″. The breakdown of operational costs indicates that the mining cost is still very high, accounting for up to 60% of the total operating costs. Therefore, optimizing mining procedures is still necessary for improving the economic outlook of this approach and thus expanding the application field of ISL.

Feb 4, 2023

By R. D. Irvine

Enhanced concern for protection of the environment and attendant actions by environmental regulatory authorities in support of this concern are influencing to varying degrees the demand and supply of a range of industrial minerals in a number of jurisdictions. These influences take a variety of forms. In this paper, the author seeks to delineate certain broad trends which are occurring relative to industrial minerals and the environment and then, through a series of examples, outline opportunities, developments, and impacts respecting a number of industrial minerals produced and consumed in Canada and the United States.

Jan 1, 1995

By Lawrence W. Aldrich

At the San Francisco meeting of the Institute last year, I presented, through the courtesy of Dr. James Douglas, some results of experiments on the roasting and leaching of concentrator tailings. After it became apparent that flotation rather than leaching was clearly the better method of handling the particular problem under consideration, before dismantling the experimental equipment, some data were secured on roasting and leaching the concentrate itself in competition with smelting. Some of the results obtained are given in the following paper and they are of particular interest at this time in view of the large quantities of flotation concentrates with their somewhat difficult smelting characteristics now being produced. A complete wet processt consists of roasting and leaching the calcines in dilute sulphuric acid produced from the roaster gases, roasting the residue with salt and leaching with dilute tower liquors (the well-known Longmaid-Henderson process) and recovering the copper, silver and gold by cementation or electrolysis or a combination of both. It is evident, however, that the residue from the first leaching, carrying about 20 per cent. of the copper and all of the silver and gold, can be smelted if preferable. In considering the application of the scheme to individual cases, it must be remembered that freight plays a large part in any reduction process wherein smelting is not conducted at the mouth of the mine, and that it is not practicable today to build small smelting plants for individual operations, The experiments may be grouped under four main heads: Roasting, leaching, chloridizing residue, and recovery of copper from solutions. The products of two concentrators were used: The Nacozari concentrates were the product of a large modern mill not using flotation, the copper mineral being largely chalcopyrite; and the Tyrone concentrates, the product of an experimental mill including flotation, the copper mineral being chiefly chalcocite. Typical analyses are given in Table 1. Fig. 1 shows screen analyses of calcines obtained by dead roasting the

Jan 1, 1917

By John S. McCartney

This paper focuses on the seasonal thermo-mechanical response of two energy foundations installed at the new Denver Housing Authority Senior Living Facility in Denver, Colorado. The two drilled shaft foundations, which have diameters of 36 inches and depths of 45 ft and are end bearing in the Denver shale formation, include a closed-loop series of polyethylene tubes through which fluid is circulated to exchange heat with the surrounding ground. The tubes within the foundations are coupled together with the conventional ground source heat pump system for the building and were installed to evaluate the heat exchange response of the foundations as well as any thermo-mechanical soil-structure interaction effects. A series of vibrating wire strain gages and thermistors were installed at different depths in the foundation to record the thermo-mechanical strain and temperature at different depths. Also, pipe-plug thermocouples are used to measure the inlet and outlet temperature of the heat exchanger fluid entering each of the foundations, which is necessary to evaluate the total heat exchange for the foundations and the efficiency of the heat pump. This paper will describe the energy foundation construction processes, the strain distribution and ambient temperature profiles during building construction and the seasonal strain and temperature distributions during heating and cooling of the building. The data indicates that typical heat exchange associated with heating and cooling operations leads to strains which are within acceptable limits, and that the foundations can provide a clear option for absorbing the base heating and cooling load for the building.

By E. W. Newman

DURING 1943 and 1944, there was an urgent need for certain grades of optical calcite (Iceland spar) for instruments for military uses. To find a supply of this material, prospecting was carried out in Montana, California and Colorado. Although some production was obtained by the work in California, the best results were from prospecting the large calcite veins of south central Montana. The bulk of the optical calcite mined during World War II has come from that area. The Bureau of Mines took an active part in the search for optical calcite in Montana. It examined most of the known calcite veins in the 70-mile distance between Wilsall, on the Shields River, and Absarokee, on the Stillwater River, and conducted exploration on several of the deposits. The Geological Survey also took an active part by mapping many of the veins. Actual mining of the calcite was performed at first by Calcite Operators, Inc., and later by the Metals Reserve Co., through an agent. A sorting plant was established at Clyde Park, where custom material could be sold. These activities stimulated mining by private operators. To be suitable for military uses, the calcite mined had to meet rigid specifications as to both size and quality. Individual crystals had to be clear and transparent and if in the form of rhombs had to measure at least 7/8 in. on each edge. Some color and a few inclusions in the calcite were allowable, but material with incipient or developed cleavages, or showing twinning other than parallel to the base, was unacceptable. HISTORY OF DEPOSITS The existence of large veins of calcite in south central Montana has long been known, and for many years the farmers of this region have used the common vein calcite for producing grit for chicken feed. According to reports, the first optical calcite produced from Montana came from the Cartwright deposit near Greycliff,1 but until recently the mining of optical calcite in Montana has been limited to spasmodic searching for small crystals suitable for making nicol prisms for saccharimeters and microscopes, or for mineral specimens. The possible need of substantial amounts of optical calcite for military uses began to appear late in 1942 and early in 1943, therefore the Polaroid company began searching for a source of supply in Montana and California. Work on the Wade property near Clyde Park was started on a small scale in the fall of 1942, by A. H. Hansen, of Clyde Park. During the winter and spring of 1943, a modest quantity of optical calcite was mined and shipped to the Polaroid Corporation, Cambridge, Mass. Most of this was produced from the "Hansen vug," which was found close to the surface. Early in the summer of 1943, mining on the Wade property was undertaken by Calcite Operators, Inc., a company organized for mining optical calcite from the Montana and California deposits. This com-

Jan 1, 1945

By James C. Bradbury

Tripoli is a naturally occurring, finely divided form of silica found chiefly in midwestern and southeastern states and used commercially in fillers and abrasives. The name comes from the location of a silica deposit in North Africa and was applied in the latter part of the 19th century to similar material near Seneca, Missouri. Subsequently, the North African material was found to be diatomite, composed of siliceous skeletons of microscopic marine plants called diatoms, and the material's name was changed to tripolite. The name, tripoli, remained with the Missouri silica, which is inorganic in origin, and tripoli is now used to designate all naturally occurring silica that is similar in characteristics and origin to the Missouri material. Just to confuse things further, in commercial trade tripoli usually designates silica from the Missouri-Oklahoma field, whereas silica from southern Illinois, the other major producing area, is called amorphous silica. Each term, however, may be used commercially for any material, regardless of place of origin that has the characteristics or uses ascribed to material from either major producing area. For example, Engineering and Mining Journal routinely lists under "tripoli," prices "f.o.b. Elco, I11." and "f.o.b. Seneca, Mo. and Rogers, Ark.", and under "silica, amorphous," prices "f.o.b. I11 and "f.o.b. Dierks, Ark." "Soft silica" is another term that has been applied to tripoli from Illinois, west central Arkansas, and Tennessee, presumably to distinguish it from the more compact Missouri material. It has also been used in the ceramic trade to distinguish tripoli from "hard" silica, or silica flour, which is produced by pulverizing silica sand. Tripoli is produced mainly in extreme southwestern Illinois, in the Missouri-Oklahoma district in Newton County, Missouri, and Ottawa County, Oklahoma; and in the novaculite belt of west central Arkansas. Some tripoli is produced for local and specialized uses near Austin, Texas.

Jan 1, 1980

By T. J. Batchler

"INTRODUCTION A variety of standing supports are being applied in underground coal mining operations to assist in providing stable mine entries. Standing support performance requirements depend on the nature of the ground deformation behavior, and therefore require a good understanding of the interaction between the support and ground to achieve an optimum roof support system. Mining operations often employ standing support strategies that are unique to their mine. A support system that functions successfully in one situation could fail in another situation. It is important that the design and installation of the standing support systems provide the highest probability of preventing roof falls. Considerable research and development has been conducted by support manufacturers to develop standing support technologies for the mining industry. The National Institute for Occupational Safety and Health (NIOSH) researchers, with the cooperation of various support manufacturers, have developed a testing protocol that evaluates performance characteristics of these standing support systems.. Using this protocol, each of these support systems has gone through rigorous safety performance testing under controlled loading conditions in NIOSH’s Mine Roof Simulator (MRS). It is important to understand the unique performance characteristics of each type of standing support. This information allows mine operators to determine if the support system is compatible with the conditions in the mine and to compare each support system and determine if that support will provide equivalent or improved support capability. This paper provides a comprehensive summary of support performance to facilitate this objective. SUPPORT DESIGN CRITERIA AND THE GROUND REACTION CURVE Standing roof support systems are designed to prevent unplanned roof falls. The selection of the standing support is based on the interaction of the support with the surrounding rock mass, and its function is to assist the primary support system in maintaining the integrity of the immediate roof. The standing support works to control the immediate roof structure by resisting deformation that contribute to delamination of the bedded layers and displacements that lead to separation of the bolted zone from stable roof structures above the bolted horizon (Barczak, 2005). Standing supports should be installed early enough and develop sufficient capacity to bring deformation of the ground into equilibrium before a critical deformation is reached that leads to a detached block condition, at which point the standing support will be required to carry the entire dead weight of the detached rock mass to prevent a roof fall from occurring (Mucho, 1999). The ground reaction curve (GRC) can be used to assist in determining the compatibility and design requirements for a support system. It is important to understand the significance of the ground reaction relative to the support design requirements. The ultimate objective is to match the support behavior to the ground response and create equilibrium (stability) of the rock mass. This equilibrium is accomplished when the support loading intersects the ground reaction curve (Figure 1). Essentially, the ground reaction concept implies that the convergence in the mine entry is controlled by the magnitude of the support resistance. However, as a passive support, the standing support develops its loading through convergence. As such, the support needs to maintain its load capacity through the associated deformation of the ground and resulting entry convergence until the equilibrium condition is reached. This requirement causes factors such as the support stiffness, peak capacity, yielding characteristics, and stability to be fundamental to proper support design and application. NIOSH contributes to providing this understanding through full-scale performance testing of support products in the Mine Roof Simulator."

Jan 1, 2017

By Thi Hien Tran, Huy Hoan Nguyen, Thi Thu Hien-Dinh, Hong Son Nguyen, Duy Anh Dao

"Lithium discovered in La Vi deposit, Quang Ngai province in the Central of Vietnam was estimated with a reserve of approximately 1.5 million tones of lithium ore, which was characterized by mainly lepidolite with muscovite, albite, and quartz. This study investigated reasonable flowsheet and optimal conditions of enrichment technology for lepidolite from the mined ore by flotation process, and producing Li2CO3 and LiCl from lepidolite concentrate by hydrometallurgical process. The significant conditions for froth flotation of lithium ore including particle size, pH of ore slurry, pulp density, chemical spending (collectors, activators, depressants, and frothers), stirring and flotation time were investigated. The identified reasonable flowsheet and optimal conditions for froth flotation the La Vi lithium ore processed lepidolite concentrate containing up to 4 wt.% Li2O with a recovery of 87.61 wt.%. The processes of sulfation roasting lepidolite concentrate using FeSO4.7H2O, then leaching in H2SO4 solution, and removing impurities were carried out to prepare a pure lithium-bearing solution for producing Li2CO3 and LiCl. The products containing 99.05 wt.% of Li2CO3 and 99.02 wt.% of LiCl were obtained with recoveries of 82.97 wt.% and 85.77 wt.%, respectively. The obtained results indicated that lithium ore in La Vi deposit can be processed to produce commercial lithium products and lead the study to develop technology for a new industry of lithium processing in Vietnam.INTRODUCTION Lithium is the lightest metal, which has many superior properties in both metal and compound (such as Li2CO3, LiCl...) states since its discovery in 1817 by Swedish chemist Johan August Arfwedson. Lithium is a favourable material for many high technology fields such as aerospace industry and chemical industry. Some industrial fields which present the main consumptions of lithium include ceramic, glass, aluminum alloy, lubricants, rechargeable Li-ion batteries, synthetic rubber, and pharmaceuticals. The worldwide production of lithium in 2014 was 31,700 tones, continually increased in 2015 of 5% presented 32,500 tones (USGS, 2016). The demand for lithium tends to increase because of the raising in consumption of lithium batteries. Lithium is mined from salar brines, mainly in Chile and Bolivia, but also from granites and pegmatites, which contain minerals with high lithium content such as spodumene - LiAlSi2O6 (Heinrich et al., 1978; Linnen et al., 2012); petalite - LiAlSi4O10 (Sitando & Crouse, 2012); zinnwaldite - KLiFe2+Al(AlSi3O10)(F,OH)2 (Paukov et al., 2010; Kondás J. & Jandová J., 2006); lepidolite - K(Li,Al)3(Si,Al)4O10(F,OH)2 (Luong et al., 2013); and amblygonite - LiAlPO4F (Garrett, 2004)."

Jan 1, 2018

By D. G. Hartley

The major copper loss at Mount Lyell is in the coarsest particles presented to flotation. An analysis of data collected from the five primary and six secondary ball mill circuits showed that grinding was limited by low breakage rates in secondary mills, possibly due to oversize balls. For 5 months, the make-up ball size for one secondary mill was reduced from 50 to 30 mm. Frequent steady-state tests indicated that overall average breakage rates could be increased by about 70% using smaller balls. A mathematical simulation of the whole circuit with increased breakage rates showed that the resultant finer grind was likely to improve copper recoveries by about 22.

Jan 1, 1981

By Joseph T. Duncan, Syd Peng, Larry G. Stolarczyk

The mining business has numerous risks: equipment availability, labor disruptions, foreign exchange rate, etc., but one of the more important risks is assessing the geology. Improving the “intelligence” of geology can and will have significant positive effect on reducing mining risk and thus enhancing operational and financial performance. The use of the advanced Radio Imaging Method (RIM-IV) on coal seams and ore bodies can create useful two-dimensional (2-D) and three-dimensional (3-D) high-resolution images that provide mining engineers with additional intelligence to better plan and improve operations. Improved operational performance will reduce costs and enable mining companies to meet market and financial commitments. For the past decade the underground coal mining industry has been moving toward “super panels” in long-wall mining, and “super sections” for room-and-pillar mining. These mining conventions employ wider faces, longer gate roads, greater room-and-pillar density, and an increased scale in the amount and complexity of mining equipment. An obvious economy of scale exists: amortization of setup investments over greater volume of coal enables mine management to reduce fixed cost per ton. Restricted by equipment considerations, face widths have currently reached about 1,100 ft. Wider longwall panels are planned, with 1,400-ft widths, but this requires an incremental step in hardware that the original equipment manufacturers will soon bring to market. However, longwall panel length has not yet reached its limits, with some panels planned up to 25,000 ft. While longwall panel length is generally dictated by reserve size and extent, practical restrictions in mine planning also include seam thickness, ventilation requirements, or restrictions involving methane drainage. Super panels have certainly enabled the industry to keep pushing the limits of productivity improvement. However, important considerations in mine planning, now and especially in the future, will be driven in large part by geological factors. While larger developments improve productivity and capture economies of scale, the fact that super panels can contain at least four times the area or coal volume means that the probability of encountering serious anomalies is at least four times greater than with the “conventional” panels. Given the increased probability of encountering anomalies, improved assessment of geology is important for super panels and super sections. Proper due diligence requires a thorough and competent evaluation of a mining property and its ore reserve. Using improved geostatistical techniques is most important, and improving the base data for the analysis is equally important. The old cliché “garbage in, garbage out” certainly applies. Also, the quality of coal reserves is (or has been) declining, so, in the future, mining will be in deeper and most likely thinner seams—and these seams appear to contain greater anomalies that threaten efficient operations. To counter the impact of reserve deterioration, the industry is moving toward greater use of geophysical tools and services. Fortunately, tools such as the Radio Imaging Method™ (RIM-IV) system have been improved and can provide the industry with enhanced 2-D and 3-D images of coal seams and ore bodies. To identify and profile the best areas of a coal reserve, geologists, engineers, and mine managers need greater intelligence in the form of RIM-IV tomographic maps of longwall panels and room-and-pillar sections. These images have enhanced the understanding of in-seam features, which in turn has improved operational plans and performance.

Jan 1, 2005

By Sanja Miskovic, Manjunath Basavarajappa

In this study, a coupled CFD-DEM (Computational Fluid Dynamics-Discrete Element Method) approach is used to simulate two-phase, solid-liquid flow within the flotation cell. Turbulence plays a key role in flotation cells and level of turbulence is affected locally by the presence of particles. Turbulence in the flow is modelled using Reynolds Averaged Navier-Stokes (RANS) based k-e model. Using particle transport and spatial distribution, mixing mechanism for differed sized particles are analysed. By including the effects of particle-particle collision, particle rotation, and particle translation, as well as the volume occupied by the particles in the fluid, CFD-DEM approach can be used to accurately predict the motion of particles in the turbulent solid-liquid flows with strong coupling. Electrical resistance tomography (ERT) is used to investigate the effect of impeller size, shape, off-bottom clearance and impeller speed on mixing and suspension behaviour inside flotation cell. The effect of flotation impeller design, impeller size, and off-bottom clearance on flow hydrodynamics is investigated. In the case of moderate and high solids loading (> 10 %w/w), energy is dissipated through inter-particle interactions and four-way coupling becomes important (Derksen 2003). The main goal of this study is to understand the effect of particle size and concentration on flow dynamics at high Re in highly turbulent systems using advanced modelling and measurement techniques. Experimental measurements obtained by ERT) system allowed detailed mapping of temporal hold-up profiles of the dispersed phase. Impeller size and off-bottom clearance are found have significant effect on the particle suspension characteristics.

Jan 1, 2014

By Gary Anderson

??Privately Held Corporation ??Incorporated in Delaware, May of 2002 ??HQ in Malvern, PA (just outside Philly) ??Approx 40 employees ?9 Field Engineers ?MSHA Certified ?10 Development/NOC Engineers ?Site Survey/Site Design ?RF Engineers ??Standards Based ?IEEE 802.11 ??Commercial Off the Shelf (COTS) ?Gateworks, Ubiquity, Atheros, Linux Based ??Technology was developed and inspired by the lack of communications during the terrorist attacks of Sept. 11, 2001

May 1, 2009

By R L. Calhoun

A paper on High Pressure Air must start with the industry accepted definition of High Pressure Air and, for the reader who is unfamiliar with High Pressure Air systems, include basic information on which type of Drilling Rigs can benefit from the use of High Pressure Air. The operation of a modern Downhole Drill must also be reviewed.

Jan 1, 1976

By Steven T. Mitchell

The introduction of Vertical Crater Retreat (VCR) Stoping at the Homestake Mine in Lead, SD, constitutes a major advance in Homes take Mining Company's efforts to improve productivity and reduce costs through underground mine mechanization. The work to date indicates that Vertical Crater Retreat Stoping is one of the safest methods of underground hardrock mining today, and is competitive with all other forms of stoping in terms of cost and productivity. Homes take anticipates that VCR stoping rill account for approximately 30% of the total mine production in 1980.

Jan 1, 1980

By B Shi, Y Li, L Ma, F Zhou

Subsurface fires are a common threat to coal mining, as spontaneous combustion of coal can potentially result in gas combustion and explosion. Fire-proof techniques, such as grouting, foam, or colloid injection, are not in a position to function ideally, due to the limited coverage and stopping the extinguishment substance from reaching the fire location. Liquid nitrogen, as a kind of all-submerged fire prevention or extinguishing method, can rapidly extinguish fires, thus preventing gas explosion and minimising extinguishment time. Injecting liquid nitrogen through boreholes is an important way during the period of mine catastrophe. But liquid nitrogen is not effective enough in infusion; technical issues restrict the development and utilisation of liquid nitrogen fire prevention and extinguishing technology. Immediate infusion of liquid nitrogen is usually associated with ‘air slug’ (the balloons and bubbles in the pipeline which hinder the flow of low-temperature liquid), which blocks pipelines for liquid nitrogen injecting. Another issue is that the pipeline tends to be damaged due to freezing, which undermines the injecting efficiency of liquid nitrogen and its application result. In order to solve the problems of the low efficiency and some other related field issues in liquid nitrogen perfusion, the ground–underground high efficiency liquid nitrogen injection technology were developed. Implementation of liquid nitrogen infusion techniques in Chinese coalmines achieved the goals of fire prevention and air-cooling. The technique presented in this paper is efficient in absorbing heat, and consequently, displacing oxygen and combustible gases. Field tests at Rujigou and Yangchangwan Coalmine justified the efficiency of the technique. By using this technique, there was no waste left behind, which may impede the subsequent production. The presented technique is of great benefit to the social, economic, and environmental aspects of mining operations, and will have broad applications in fire prevention for large-scale coalmines.CITATION:Zhou, F, Shi, B, Li, Y and Ma, L, 2015. Key techniques and engineering applications of stereoscopic liquid nitrogen infusion for coalmine fire prevention, in Proceedings The Australian Mine Ventilation Conference, pp 291–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By Woolsey Johnson

THE object of this paper is to, describe the several necessary characteristics of the zinc-retorting charge and to show how by certain improved methods; the large excess of coal, over that theoretically required, can be reduced, thereby effecting an increase in the smelting capacity of a retort plant as well as other economies. In the Southwestern zinc works a charge of roasted zinc ore with a side mixture of carbonates and silicates, analyzing on the average 50 per cent. Zn, is mixed with 55 or more per cent. of its weight of a mixture of coal and coke analyzing 60 to 70 per cent. fixed carbon. . The ore is of varying fineness and the coal and coke are usually crushed in a semi-moist condition through a 3/8 -in. screen. With ores of a slaggy nature, this coal proportion is increased, sometimes to as much as 100 per cent. of, the weight of the ore. With carbonate ores, or where anthracite screenings with higher carbon content are cheap enough, the percentage of reducing agent is cut to 45 per cent. or even somewhat lower. The average charge per retort for a monthly run of a plant on ore, as distinguished from retorts on blue-powder, ladle-skimmings and other between-products, runs from 60 to 66 lb., with a mean of 63 lb. for the Southwest with standard retorts of 8 ½ -in. inside diameter and 50 in. long inside, using roasted sulphide ores. Conditions will change these figures, but 40 lb. of ore per cubic foot of retort space is, I believe, an average in the better-operated plants. Since the rise in. the price of spelter, the tendency has been to overcharge. To remove the slag that is formed when retorts are overcharged, extra men are put on to "gum-chisel" the retorts to prevent "set" furnaces and "butchered, retorts." Taking the above conditions as premises, we find that from four to six times the amount of coal necessary for the reduction is used, as is evidenced by the fact that the residues analyze as high as 35 per cent, fixed carbon. There are good reasons why this excess of fixed carbon must be used and perhaps these can be best explained by a description of the metallurgical requisites of a zinc charge. We may enumerate these as follows: 1. High reducing power, especially at the end f the shift, to reduce any carbon dioxide to monoxide and bring about a good condensation

Jan 2, 1918

By B. O. Pickard

WITH more than a score of shafts and numerous stope openings to the surface, all inter-connected underground; with underground temperatures high, often exceeding 100° wet bulb; with an ore presenting a dust health-hazard; with certain rocks giving off inert gases; with an altitude of 6000 ft. above the sea level and a dry desert climate, the Tonopah mines offered an interesting, problem to the student of metal-mine ventilation. Tonopah is not an old mining district relatively speaking. It was discovered in 1900 and Tonopah soon was a boom camp. By 1910 the mines of this district had paid many millions of dollars in dividends. At the time of the 1921 ventilation study, mining had passed its peak of production and the operators were striving to reduce costs, to discover new ore bodies, and to attract desirable workmen. In 1925, the camp was operating on a still less prosperous basis, but the several managements had not relaxed in their efforts to keep the mines on a paying basis, neither had they lost their faith in the ability of the mines and the price of the silver to "come back." Early in the fall of 1921 the Bureau of Mines was invited by the mine operators at Tonopah, Nevada, to make a detailed study of the under-ground air conditions in the Tonopah silver district. D. Harrington,? who was then directly supervising the ventilation studies of the bureau, detailed district engineer B. 0. Pickard, mining engineer E. D. Gardner, surgeon C. E. Kindall, and petrographer H. Insley to carry on the study. G. S. Rice, as chief mining engineer of the Bureau of Mines, was in general charge of the work. Upon the completion of the study each operator was furnished a report on conditions in his mine.

Jan 2, 1927

By V. Korobko, M. Byantogtokh, N. Byambadorzh, V. Bysov

A three-stage operative planning of mining operations in ore opencasts is considered. The hierarchy of monthly-weekly, weekly-daily, daily-shift planning is offered. For the fastest elimination and deviations in problematic situations a level is analysed and weekly-daily or monthly-weekly operative plans are being constantly updated. Operative planning is formulated on information received of preparation and working of mining panels. The electronic maps of these panels are considered for automated operative planning. On the data of the registration of blasthole drillings on a panel, the position of blasthole entry, their depth and the number of a line are determined. The geologist specifies boundaries of ore grades by the bored silt. The qualitative characteristics of ores are determined by the chemical analysis of slime or magnetic logging of blastholes. The missing geologic information is obtained by interpolation on the data of detailed and operational explorations. During working of the mining panel the technologists mark the movement of shovels, associating this movement to blastholes. For this purpose technological attributes are used: when was the blasthole drilled, what drill-rig participated in drilling, what shovel was used and when was it worked? Around each blasthole the zone of its influence is built up. It represents a discrete, elementary volume of ore or waste. The discrete form of the data is most convenient, as it allows step-by-step methods to be employed of the scheduled tasks in many and various combinations. The account panel working technology avoids ‘combination’ explosions. The elementary blocks should be placed in a trajectory of shovel movement and the trajectory can not be arbitrary. It’s determined by the technological rules of extracting and loading of mine mass. In linking to blastholes, the trajectory of shovels is simulated by the sum of step-by-step moving from one elementary block to another. For this purpose a geometrical linkage of blastholes is used. At a railway haulage, or complete mining with truck haulage, the trajectory of movement is a shuttle along the front of operations in the panel. At a selective mining of ores the number of possible directions is limited to three: moving of a shovel by idle running along the front of operations in the panel, frontal pull all the way down of the panel, and withdrawal. The technologically acceptable trajectories of shovel movement are stored for the following estimation and selection of the best. The estimation is carried out on mathematical models with criteria on the method of the least squares of deviations based on preset parameters from the plan, uniform loading of shovels, and mixing of ore at unloading points. The equations of balance type and directive parameters of the plan, as well as technological restrictions of solid and of elementary blocks within the limits of a trajectory are the restrictions of the model. Depending on an industrial situation it is possible to choose one of the predetermined models. The presented technique is used for longitudinal shovel bench at the Erdenet ore-dressing company.

Jan 1, 2003

By R. G. Vardiman, M. R. Achter

THERE has been interest recently in the conditions under which dislocation pipe diffusion may be observed. In order to extend the measurements to temperatures below Tm/2, where pipe diffusion becomes more important, a chemical sectioning technique was developed for silver single crystals which makes possible the removal of layers of 100A or less. The procedure is briefly as follows. Silver single crystals of 99.995 pct purity were cut in the form of discs t by 4 in., electropolished, and electropolated with Ag110 to about 1000A thickness. The thickness was determined by calibrating the activity with the weight of heavier platings, up to 10,000A. Both diffused and undiffused samples were sectioned in a two-step process. Reaction with a solution of iodine in alcohol formed a thin, even layer of AgI, which was then dissolved in a KCN solution. The reaction rate of the iodine solution varied slightly over a period of time, so that the thickness of the stripped layers, while quite even and regular for a given specimen, ranged from 65 to l00W for different specimens. This variation was checked by using a thickly plated standard with each run. Layer thickness was determined from undiffused samples by the point where the layer activity drops to half the maximum. This maximum intensity also provides, with appropriate corrections, the initial concentration per layer co. Because of the small penetration distances, it is necessary to use the exact solution of Fick's law for a source of finite thickness.' For a plating of thick- where c is the concentration at depth x. flj the error function, D the apparent diffusion coefficient, and t the time. The diffusion coefficient was obtained from the concentration-penetration data by extrapolating to x = 0 where c/co = erf h/2(Dt)1/2 Enough points were taken to impart confidence in the accuracy of the intersection, generally about ten layers. Four temperatures were used as in Table I. For best accuracy, t and h were chosen to give values of the parameter (Dt)1/2/h between 1.0 and 1.7. A typical concentration-penetration curve is shown in Fig. 1. The diffusion coefficients calculated from Eq. [I] are plotted in Fig. 2. For comparison, the high-temperature data of Tomizuka and sonder 2 which go down to 630°C are plotted as the solid line 2(a) from their expression D = 0.40 exp (-44,090/RT). Also for comparison, the lowest temperature point of Hoffman and Tumbull3 is plotted. It is apparent that our data diverge appreciably from the high-temperature extrapolation by 373°C. A better straight line fit for the low-temperature portion is obtained by subtracting the extrapolated volume diffusion coefficient from the apparent. or measured coefficient, and plotting the difference, curve (h) of

Jan 1, 1970

By J. J. Pelley

NOT being a scientist, an engineer or a metallurgist, I consider it a very great honor indeed to be asked to address the American Institute of Mining and Metallurgical Engineers. Your program indicates that any lack of intricate and technical knowledge on my part in the field of metals will be well taken care of by others. Therefore, I believe any remarks that I have to make might well be devoted to the practical side of metals in railroad service and to the general railroad situation as I view it today. The experiments now being conducted on the railroads with so-called streamlined, light-weight trains and cars would not have been possible had it not been for scientific and engineering research in the past that made these lighter weight metals available. The railroads now have approximately forty units of these new trains in operation. Experi-ence with them will no doubt be a guidepost for future construction in that direction. While the best known experiments are in the passenger service, they are being extended into the freight service. Within the past three years there was constructed for the Association of American Railroads a new standard box car of ordinary carbon steel, in which, by reason of superior design, weight was reduced by 3500 to 4500 lb. under that of existing cars of like capacity. The Association is now testing a box car that weighs approximately six or seven tons less than practically all of the box cars of like capacity in service today. If these tests are successful a very large field for the use of lighter weight metals will immediately be opened, provided the costs of such metals are not too high. The fact that various experiments are being carried on with other classes of equipment constructed with so-called light-weight and non-corrosive metals no doubt will have a considerable effect upon the rebuild-ing of old equipment. The question then will be: How much can we afford to spend on the rebuilding of an old car weighing six to seven tons more than a new car constructed with the latest available materials?

Jan 1, 1936