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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

By P. Marcheselli, Jean-Yves Peron

A twin tube tunnel of 2 000 meters long and an internal diameter of 6.90 m has been excavated through alluvial ground, with low overburden, using a 8.0 m diameter Earth Pressure Balanced tunneling machine with foam injection and extruded concrete behind segment.

Jan 1, 1995

By Lawrence W. Teufel

Knowledge of in situ stress and natural fracture distribution at depth improves our ability to stimulate and produce low permeability reservoirs. The focus of this study is three closely spaced, 2.5 km deep vertical wells in the Piceance Basin of Colorado. The wells were completed through the tight lenticular and blanket gas sands of the Mesaverde Group. In situ stress directions and magnitudes were determined from hydraulic fracture tests and anelastic strain recovery measurements of oriented core. The distribution, orientation, and characteristics of natural fractures in the subsurface were determined from detailed observations of over 1300 m of core, of which 400 m was oriented. Stress measurements clearly show that horizontal stresses are strongly influenced by lithology. In a sandstone/shale sequence at a depth of about 2.0 km in situ stresses in sandstone formations are anisotropic, with the average ratios of the minimum and maximum horizontal stresses to the overburden stress being 0.82 and 0.96, respectively. In sharp contrast bounding shale formations are lithostatic. This stress contrast between sandstones and bounding shale formations could act as a barrier to hydraulic fracture propagation during stimulation and impede vertical fracture growth. Natural calcite-filled fractures are present in over 7 percent of the core, with several horizons having a much higher frequency of fractures. Fractures are found primarily in sandstone. The fractures have a strong preferred orientation of N 1060E[+]110, which is aligned with the maximum horizontal stress and direction of hydraulic fracture propagation. The interaction between a well developed fracture fabric and anisotropic stresses in sandstone formations produces a permeability anisotropy, with the maximum permeability aligned with the fracture fabric and maximum horizontal stress.

Jan 1, 1986

By Gill G. Geesey, Michael R. Hankins, Paul L. Wichlacz, Anita Gianotto, John G. Jolley, Randy B. Wright

Thin films of copper [2.0 nm on germanium internal reflection elements (IREs) and 3.4 nm on germanium discs] were exposed to 10% gum arabic (aqueous solution) , 2% alginic acid (aqueous solution), 1% bacterial culture supernatant (BCS, simulated seawater solution) and 0.5% Pseudomonas atlantica exopolymer (simulated seawater solution). The IRES were monitored in situ, in real time using fourier transform infrared/cylindrical internal reflection/attenuated total reflection spectroscopy as a function of time at ambient conditions. The discs were characterized (pre- and post-exposure) by X-ray photoelectron and Auger electron spectroscopies. Ancillary graphite furnace atomic absorption spectroscopy was used to monitor the removal process of the copper thin film from the germanium substrates. Results indicate that Cu was oxidized by gum arabic, alginic acid and BCS. Furthermore, Cu was removed from the Cu/Ge interface by all four polymers. The Cu was found associated with the polymer solutions.

Jan 1, 1989

By Steve Meador

West Virginia's basic coal mining regulatory programs are not unique when compared to Federally approved programs implemented by other coal producing states. In fact, the language in The West Virginia Energy Act governing subsidence mirrors that written in the Federal Surface Mining Control and Reclamation Act as well as other states' statutes. Certain legal and administrative issues, how¬ever, combine to make West Virginia's regulation of surface subsidence a singular approach.

Jan 1, 1986

By K. S. Mortensen

The softwall mining system is a novel, new method of mining mineral deposits in soft, shallow, nonrock ground conditions. This method can mine the ore layer without substantially disturbing the existing overburden. The softwall mining system consists of machinery that is hydraulically controlled and powered, that can be buried (or used on the surface) to extract the ore or mineral from a layered deposit. The method is essentially an application of the longwall mining concept, modified for loose overburden and ore conditions, combined with hydraulic mining.

Jan 1, 2003

By R. D. Hagni

Introduction The ore deposits of the Viburnum Trend in the Southeast Missouri Lead District constitute the world's largest lead producing district. Six or seven mines currently are in production in the Viburnum Trend. The principal minerals are few in number, simple in composition, and form simple superposition and replacement textures. The economically valuable minerals in the typical lead-zinc ores of the Viburnum Trend are the sulfides, galena, sphalerite, chalcopyrite, and siegenite. The most abundant gangue minerals are dolomite, marcasite, pyrite, calcite, quartz, and dickite. Four concentrates, lead, zinc, copper, and cobalt are produced from the ores, and they contain an interesting suite of trace elements, of which silver and cadmium are recovered at the smelter and refinery.1 Emphasis is given here to the variations in directions of ore fluid flow based upon interpretations of the positions of orebodies due to the ore fluids being impeded by Precambrian basement relief and upon patterns of ore mineral/metal zoning. The Precambrian basement relief and Lamotte Formation pinchout has exerted an important control upon the specific locations of orebodies in the Southeast Missouri Lead District. The locations of some orebodies along one side of Precambrian knobs or ridges strongly suggests that they are positioned on the side from which the ore fluids flowed. Other orebodies are located in positions that suggest that they formed where the ore fluids passed around or between Precambrian knobs. Patterns of mineral and/or metal zoning have been used in many mineral districts to interpret the directions of ore fluid flow. The mineral/metal zoning pattern correlates closely with that of the mineral paragenesis. The earliest deposited minerals tend to be deposited nearest to the source, the later deposited minerals next closest to the source, and the latest deposited minerals furthest from the source. In the Southeast Missouri Lead District, it is interpreted here that the early-deposited copper-rich ores are closest to the source of the ore fluids, the subsequently-deposited zinc-rich ores are next closest to the source, and iron-rich ores are furthest from the source.

Jan 1, 2006

By S. Devasahayam

Acid production or acid drainage is a major environmental issue that also has negative implications on the aquifer system surrounding the mine tailings area. The approach to controlling acid mine drainage involves physical and geochemical characterization that affect acid production. The material permeability determines the availability of oxygen, which is paramount in acid production in coal rejects, and varies with depth. In this paper the author presents the variation in oxidized pyrite/acid production with depth in black coal mine washery wastes. Chemical kinetic parameters and the diffusive parameters have been used to obtain the variation in oxygen content and the oxidized pyrite content with respect to the depth and time. Its dependence on porosity and moisture content is illustrated.

Jan 1, 2007

The Coeur Rochester Mine is one of the largest and lowest cost primary silver mines in the United States. In January, the mine surpassed 3.1 kt (100 million oz) of historic silver production. Rochester is owned and operated by Coeur d’Alene Mines, the world’s largest primary silver producer. Rochester is the world’s seventh largest silver mine. It also produces gold — more than 31.1 t (1 million oz) in historic production. Cash operating costs have averaged 8 cents/g ($2.58/oz) of silver since operations began in 1986.

Jan 1, 2004

Floor heave events in underground mining often happen suddenly and cause risk to workers and equipment. Reducing the risk of floor heave must be addressed in mining layout design. To improve that design one must understand the significant parameters that are correlated to the occurrence of floor heave. To accomplish that goal, researchers from the National Institute for Occupational Safety and Health (NIOSH) completed a numerical study using FLAC3D, taking advantage of its strain softening and ubiquitous joint capabilities to better simulate the floor heave and caving mechanisms involved at an actual mine site.

Jan 7, 2020

By None None

Use this month wisely — go online and take advantage of your new member benefit. As an SME member, you can read and download for free all of the full-text papers of the Mining, Metallurgy & Exploration (MME) journal, including the 22 papers in the launch Special Issue on Mineral and Metallurgical Processing in Honor of Professor Emeritus Douglas W. Fuerstenau as well as the archived articles of Minerals & Metallurgical Processing (MMP), all the way back to Vol. 1, No. 1. Just follow the instructions on this page.

By Wilbur I. Duvall

This paper discusses general principles of underground opening design based on the concept that with the necessary input data regarding the geology of a site, the physical properties of the rocks, the in situ stress field in the rock and the general geometry of the underground openings, the rock formation can be classified into six major categories which are useful for design purposes. Using simple theories for the criteria of failure for rock In compression and tension, general elastic theory for stress concentration around openings and In structures, beam theory for stability of roof rock, and elementary inelastic theory for creep phenomena, basic design techniques are outlined for the various rock classifications. The need for field evaluation of the theoretical design is stressed and some general techniques that should be used in these field evaluations are discussed. Where appropriate, the need for additional studies and research is noted.

Jan 1, 1977

By Hiroyuki Kawata, Toshiyuki Ueno, Mikio Yamazaki

INTRODUCTION For the construction of several kinds of structures which pass through under railways, we have recently developed an effective and new tunnel construction method, aiming at more secure train operation during the construction as well as the rationalization in the construction works for such structures. Most important in carrying out the construction works for the structures under railways is how to maintain the safe operation of trains. For such construction works, temporary supporting structures and supplemental works have been often applied, for which high cost and long period for the construction have been required. While, this new tunnel construction method has the feature that it is capable of constructing definitive structures for various purposes, which, at the same time, acts as the temporary supporting members for protection of railways. Therefore, this method is now drawing much attention in that higher safety of train operation, low construction cost, and shorter construction period are accomplished, minimizing the period required for slackening the train speed during the construction works.

Jan 1, 1979

By H. Hejny

The objective of the project is to construct and operate a pan-European underground drainage and minewater management research centre, which would be the hub for data gathering and dissemination in real time of new data to users for analysis and interpretation, as well as serving as a model for consistency, for other centres at key water management sites throughout Europe which would feed data in real time through the hub. The data from the centre will be essential for informing River Basin Management Plans arising from the EU Water Framework Directive, which is an important driver for the project. The implementation of this Directive sets out a requirement for all Member States to develop River Basin Management Plans for all water resource systems. The facility would be a major contribution to sustainable water management in Europe.

Jan 1, 2007

By Stephen W. Kline

Rock suitable for crushed-stone aggregate is almost entirely restricted to the Highlands region of Arkansas, mostly from Paleozoic sedimentary units, but also from a few Cretaceous igneous plutons. Reserves in the state are sufficient for local needs, and Arkansas is geographically well situated for export markets to the south, where resources for crushed-stone aggregate are lacking. A study of 423 quarries, test pits, and exploration sites in Arkansas has been completed to evaluate the relative quality of bedrock units for producing crushed aggregate. Of these, 274 sites have records of engineering tests for stone evaluation done by the U.S. Army Corps of Engineers and/or the Arkansas State Highway and Transportation Department (AHTD). Of the 1,775 sample records from these sites, the most commonly reported parameters are the LA abrasion test and the Na-sulfate soundness test. Many records also have absorption and specific-gravity data, and, for some, petrographic information helps identify the potential for alkali-silica reactivity in portland-cement concrete. By determining the bedrock sources of the tested samples, comparison is made between the various geologic mapping units as to their relative quality for crushed stone.

Jan 1, 1999

By T. Malterer, R. Adams

Peat has unique physical, chemical and biological properties. These include high porosity and water retention, high absorption and adsorption properties, and high buffering capacity. In addition, peat is a rich medium for microorganism activity. Peat has traditionally been used for horticultural purposes. However, in recent years, peat is increasingly being used for waste- treatment purposes. This paper reviews North American literature on the use of peat for waste-treatment applications. The literature indicated that peat has potential for use in the treatment of municipal and on-site effluents, for the removal of low concentrations of heavy metals and for the adsorption of liquid and gaseous hydrocarbon pollutants.

Jan 1, 1997

By R. Kingman

At Tahawus, New York, National Lead Company operates the MacIntyre Development, This operation produces 10,600 long tons of ore per day for crushing, 8,000 tons for grinding and processing, of which 2,000 tons per day reports as tailing for disposal in an impounded tailing storage area. With the change in location of mining operations at the mine of National Lead Company, a change in the area for tailing disposal by gravity became necessary, This called for the diversion of tailing from near the proposed mining area to areas more favorable for long term storage by gravity. In order to avail the operation of maximum storage for the future, a uniform minimum grade launder was proposed with a minimum velocity and maximum outfall at the discharge. Disposal of the gravity and flotation tailing was formerly accomplished in open ditch from the concentrator at a grade of 1.5 percent. It was desirable to design the new launder at grades less than this for the greater storage elevation.

Jan 1, 1966

By Steve R. La Brooy

Techniques for dealing with copper-gold ores are reviewed. Cyanide has little selectivity of gold over copper, and depending on the reactivity of the copper minerals cut-off grades for gold recovery by direct cyanidation are generally below 0.5% copper for oxide ores and 1 % for sulfide ores. Non-cyanide gold leachants also tend to be reactive to copper. The cheapest option for sulfidic ores is to produce a flotation concentrate for smelting, while transition ores generally need a sulfidisation pre-treatment. The requirement for the concentrate to have a high enough copper grade to be acceptable to a smelter may compromise copper and gold recovery. This can lead to significant gold grades in the flotation tailing, and copper levels in the tailing that are too high for direct cyanidation to be able to recover the gold. Oxidised ores, flotation tailing or other material not amenable to flotation represent the greatest grey area for gold recovery. Copper removal by acid, alkaline or ferric pre-treatment is possible though not generally used. Cyanide pre-leaching to remove copper, followed by copper and cyanide recovery represents a potential option that has been installed at one Australian gold plant, where copper is recovered onto carbon, ahead of the slower leaching gold. Actual cyanide recovery depends on ore mineralogy, allowing for losses as cyanate, thiocyanate, carbonate and ferrocyanide. Alternative options for gold recovery following cyanide leaching include precipitation, ion exchange and solvent extraction of the gold. Ammonia-cyanide leaching may offer another option for more selective gold dissolution from flotation tailing and oxidised materials. A plant is currently under construction in Mauritania.

Jan 1, 1992

By A. D. Hoagland

There are large areas on all of the continents with environments which are favorable for deposits of zinc and lead of Mississippi Valley type. In the developed countries, these environments have for the most part been quite thoroughly explored for the near surface deposits, and it will be necessary to direct more effort to the search for deeper buried deposits from which much of our future production must come. The difficulties of exploration for deep ore of this type are many and formidable, but the area of permissive environments beneath deep cover is many times as great as the area of the known near surface ore districts. It is a reasonable assumption, therefore, that numerous deposits wait for discovery and development. The finding cost, however, is certain to increase, and it is essential that concepts and techniques of exploration be improved if we are to sustain a reasonably strong productive capability into the 21st century. Exploration for deeply buried deposits requires at the outset relatively large areas of favorable geologic environment. The favorable horizons must be within economic limits of depth for the exploration as well as for the mining techniques which are currently available; and there must be some condition, design or strategy which will assure the explorer a reasonable chance of obtaining maximum benefit from discoveries which he may make.

Jan 1, 1973

By Vincente M. Jr. Lim, Brain W. Lawrence

Underground mining operating costs consist pri¬marily of direct costs such as labor, supervision, ma¬terials, and supplies, plus indirect costs. The material and supply costs vary substantially between mines but commonly range from 35 to 60% of the total direct costs. As part of the preparation of accurate operating cost estimates for a project, information must be as¬sembled to select the material and supply items and to determine the quantities of these items that will be required. Cost data then can be incorporated with the estimated material and supply requirements to determine the total material and supply costs for the project. Estimated quantities will vary considerably between mining projects depending upon factors such as the type of material being mined, the mining method, the equip¬ment selected, drilling and blasting techniques, mucking and haulage methods, ground support requirements, number of men employed, etc. Valuable information often can be obtained from suppliers and manufacturers, including data on current operating practices for similar projects, recommenda¬tions for the specific project, and preliminary cost quota¬tions. However, quotations obtained for estimates are generally higher than the prices paid at the time of purchase. Mines operating in the area, or those mining under similar conditions, also can provide essential design information, but it often is difficult to obtain cost information from the operators. Estimated costs for the most common major items of underground materials and supplies are presented in the accompanying tables. They represent current costs or cost ranges and are intended to be used only as a guide when preparing budgetary estimates for materials and supplies. Cost data were obtained mainly from suppliers and manufacturers, with up to three quotations being ob¬tained for each item whenever possible. In most cases, as noted in the table footnotes, prices were based on quantities representing normal requirements for me¬dium-size mine operations. Every attempt was made to assure accuracy. However, the cost for most items, especially those with multiple sources, can deviate sig¬nificantly for various reasons such as geographical loca¬tion, current market conditions, quantities ordered, size of the customer (which could influence the ultimate quantities purchased), and the ability of the purchasing department. It is also for these reasons that the actual amount individual mines are now paying for specific items may vary from the estimated cost in the tables. The cost for specific sizes of items that do not appear in the tables often can be factored from the data pre¬sented. Costs for many items can be converted easily to a unit that sometimes is more basic, but not as com¬monly used, such as from a length to a weight unit. Other items not listed, such as repair parts for equip¬ment, will involve contact with suppliers to determine specific recommended requirements and to obtain costs for these items as related to each individual project. Costs are expressed in terms of US dollars as of 1978 unless otherwise specified. All measurements, sizes, and weights are expressed in conventional units (i.e. feet, inches, pounds) ; applicable metric conversion fac¬tors follow each table. Costs are represented for drill steel and bits; mining explosives; blasting caps; blasting supplies; ground sup¬port items; ventilation equipment; utility pipe, utility hose, and accessories; mine track and accessories; tires for underground equipment; lubricants and fuels; and miscellaneous supplies.

Jan 1, 1982