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By S. K. Kawatra

Outokumpu Electronics has designed a new on-line coal slurry ash analyzer, based on an instrument developed at Michigan Technological University. The primary goal was to build an accurate instrument at the lowest possible cost. The instrument determines ash content from measurements of X-ray backscatter, iron K, fluorescence, and low-energy y-ray absorption. It is capable of measuring the ash content with a standard error of 1.1% ash over an analysis range of 9-21% ash and 7-22% solids. The analyzer was tested on coals from United States, Poland, Great Britain and the USSR.

Jan 1, 1993

By R. A. Metz, M. A. Bryant, J. C. Goodwin, T. B. Faddies, L. D. Kornze

The Mercur Gold Mine is located 56 km (35 air miles) southwest of Salt Lake City in north central Utah. In July 1981 Getty Mining Company made the decision to put Mercur into production. The first gold bar was poured in April 1983. This paper provides details on: 1) the history of the camp, 2) past production, 3) geology of the deposit, 4) the exploration and development program, 5) ore reserve estimates, 6) detailed geologic pit mapping, 7) production blasthole sampling techniques and 8) the use of geostatistics (kriging) in handling assays and gold extractions to produce the required mill feed.

Jan 1, 1992

By J. A. Frew, G. I. Orrock, R. M. Glen

The zinc flotation circuit was sampled to provide sized information on its metallurgical performance. A good balance was obtained and the roughing, scavenging, cleaning and regrind sections were assessed. Substantial losses of sphalerite occurred in all sizes. The limitations were poor recovery in the cleaning section which resulted in substantial recycling of 15-30µm sphalerite and iron sulphides, and inability to float +38µm sphalerite in the roughers. Regrinding increased sphalerite recovery by 7% with no loss in grade. Liberation measurements enabled balances for six size fractions to be calculated and the role of liberation on the metallurgical performance was assessed.

Jan 1, 1993

By R. Larry Grayson

A survey of 1250 surface and underground coal mines across the United States was made according to a stratified sampling technique based on national coal districts. A total of 171 responses (13.7% response rate) have been returned and summarized, giving a picture of computer usage in the coal industry. Overall, 63.5% of the respondents use computers, but the percent varied from 100% for large mines to only 44.1% for small mines. As expected, a proliferation of microcomputers has pervaded the industry. Importantly, in spite of the high usage of computers in the industry, sophisticated engineering applications have not yet burgeoned.

Jan 1, 1989

By Alvaro Souviron, W. W. Atkinson

The porphyry copper deposit at Los Pelambres is a resource exceeding 2 Gt (2.2 billion st) of 0.7% copper and 0.02% molybdenum. It includes a high-grade zone of +1% copper that is amenable to open-pit mining with a low stripping ratio. Metallurgical testing has indicated that the ore has exceptional characteristics, and that recoveries of 96% for copper and 93% for molybdenum can be obtained by conventional flotation methods. This paper summarizes the history of the prospect, the geology of the ore body and the surrounding area, and the procedures and results of exploration.

Jan 1, 1987

By M. E. Kuchta

Research is currently being conducted at the Colorado School of Mines in the use of high-pressure water for scaling down loose rocks in underground mine openings. In addition to improved miner safety, the adhesion strength of shotcrete applied to rock surfaces treated with high-pressure water is also increased significantly, resulting in improved overall support capabilities of the shotcrete layer. Test results show an increase in adhesion strength by a factor of four on a concrete test wall cleaned with water at 21 MPa (3,000 psi) as compared to a surface cleaned at 0.7 MPa (100 psi).

Jan 1, 2003

By John E. Roberts

People are not a novelty. But the phenomenal numbers thereof, who have approached, settled, and been born in California in the past twenty-five years, are such a problem as to be a novelty in the broadest sense of the word. California, with less than 7,000,000 people in 1940, and over 19,000,000 in 1966. In 5 1/2 years, (1960-65) the southerly 14 counties of California, which together comprise one-half the land area of our state, had an increase in population greater than Colorado, or Arkansas, or Oregon, or any one of 19 other states.

Jan 1, 1967

By Odd G. Askilsrud, Steinar Johannessen

New powerplants, tunnels and dams are currently under construction at Meraaker to triple the annual power production of a nearly 100 year old power scheme. A total of 44 km tunnels with cross sections varying from 7 m2 to 32 m2 have been excavated in hard rock formations. Ten kilometers were excavated by a High Performance Tunnel Boring Machine (HP TBM). The remaining tunnels have been completed by the drill and blast method, using modem proven equipment and procedures. This paper gives special attention to the TBM drive and equipment selection, including, planning, site organization and performance.

Jan 1, 1993

By Jeremy Cawley, Horry Parker Jr., Clint Wilson

The 5180 m EPBM drive on the Lower Olentangy Tunnel (LOT) is predominantly within glacial overburden. To connect LOT with the existing OARS deep tunnel in limestone bedrock, the upper 15 m inside diameter Vine Street retrieval shaft telescopes down to 6.7 m in diameter and extends into the karstic Columbus Limestone to a depth of 51 m, where a 104 m SEM tunnel will connect to OARS shaft 6. Pre-excavation grouting was reuired prior to lower shaft excavation to reduce potentially high groundwater inows. This paper discusses the secant pile installation, grouting program, shaft excavation, and hydrogeologic observations.

Jun 23, 2024

By Christian Heinz, Doug Harding

TBMs can last for decades and be rebuilt project after project with proper maintenance. How successful can rebuilt TBMs be? At the DigIndy Tunnel System in Indianapolis, Indiana, USA, a rebuilt TBM was used to great effect. The 6.2 m diameter Main Beam, originally manufactured in 1980, bored 40+ km of tunnels and set three world records in its size class of 6 to 7 m, including a best month of 1,754 m. In this paper, the authors analyze the TBM rebuild, performance and lessons learned to make recommendations for future projects seeking to use rebuilt TBMs over long distances.

Jun 23, 2024

By M. J. Sapko

The US Bureau of Mines conducted, through joint funding with the Colorado Mining Association, large scale oil shale rubble fire tests to investigate flammability characteristics and different methods of extinguishment. Ignition of large rubble piles was easily accomplished. Foam blankets could he used to control surface flames. The results of these large scale tests confirmed that water was effective but not particularly efficient in extinguishing deep seated oil shale fires. It took up to 1.7 times as much water to extinguish afire as anticipated on the basis of a simple cooling model, assuming 100% utilization.

Jan 1, 1990

By R. J. Wesely, A. D. Zunkel, Tracy B. Braun, Philip L. LeHoux

An overview of gold processing operations at Barneys Canyon Mine is presented with particular emphasis on ore agglomerating experience, leaching and metallurgical accounting practices, and carbon column plant operating approach. The mine, located thirty kilometers from downtown Salt Lake City, is just eight kilometers north of the Bingham Canyon copper mine. Mining was initiated in February 1989 and the first gold was poured in September 1989. Through year-end 1992, approximately 7 million tonnes of ore have been processed and 12,000 kg of gold have been produced. Gold recovery is in excess of 85 percent.

Jan 1, 1993

By Martin Herrenknecht

The world?s growing population and rapidly proceeding urbanization are boosting an enormous demand for new and high-capacity infrastructures to secure the mobility of goods and people. Densely populated areas face the challenge to provide efficient traffic infrastructure, such as a modern public transportation system. At the same time, the maintenance and modernization of supply and disposal structures for water, sewage, energy and communication are also essential. Additionally, supra-regional transportation routes such as long distance water diversion schemes are the challenges for the future. All these projects are as demanding as they are characterized by a tight time schedule.

Jan 1, 2010

By James G. Sack, Donald G. Wieland, James H. Meinholz

The paper will describe the $1.7 billion Milwaukee Program. Past contracting practices of the Milwaukee Metropolitan Sewerage District are discussed. To minimize costs and claims, the MMSD has implemented some recommendations from Better Contracting for Underground Construction. Currently implemented are: full disclosure of subsurface data including interpretations, the deletion of disclaimers relating to subsurface information, use of the federal Differing Site Condition clause, payment for mobilization. Also considered was the recommendation concerning Wrap Up Insurance. The MMSD shares and allocates certain designated risks through the Contract. A claims handling methodology has been developed and used on this major construction program.

Jan 1, 1983

By George S. Austin

Perlite is rhyolitic glass with 2 to 5 percent by weight (wt.%) bound water held within the silicic-glass structure. It is often distinguished by vitreous, pearly luster and concentric perlitic fractures ("onionskin"). Occurrences worldwide are associated with Tertiary to middle Quaternary volcanic rocks. Perlite is in silicic domes, plugs, laccoliths, flows, vitric tephra, chill margins of dikes and sills, and welded ash-flow tuffs. It is a hydrated volcanic glass formed through secondary alteration of obsidian by the incorporation of water into the glass/silica structure. Post-emplacement hydration (weathering) of cooled glasses by meteoric water is the principal alteration process, but some hydration by magmatic or meteoric water during or shortly after emplacement, or hydration by water exsolved during cooling may occur. Commercial "perlite" is any volcanic glass that expands or "pops" when heated quickly to plasticity while evolving steam and thus forming a lightweight, frothy material. The expansion temperature typically ranges from 1,100 to 1,500°F. An expanded volume increase of 10 to 40 times the original volume yields expanded densities of 1.5 to 11 pounds per cubic foot (lbs/ft3). Perlite is mined by eight companies at 10 operations in six western states. New Mexico accounts for more than 80% of the total tonnage mined. The rest comes from Arizona, California, Colorado, Idaho, and Nevada. In 1992, domestic production was 571,000 short tons (st), domestic apparent consumption was 591,000 st, and the value of crude perlite was $15.3 million. In 1991, with about the same production and price of crude perlite, the gross value for expanded perlite was $101.7 million. Perlite exports in 1992, primarily to Canada, are estimated an 30,000 st; and imports, from Greece, are an estimated 50,000 st. In 1992, 70 plants in 33 states expanded crude perlite. Construction uses of expanded perlite accounted for 66% of total domestic sales. Expanded perlite used as filter aid accounted for 15%. All other markets, including use as a filler and in agriculture, accounted for 19%. Leading states for expanding perlite, ranked by order of sales, were Mississippi, Pennsylvania, California, Illinois, and Georgia. Domestic perlite encounters transportation disadvantages in some areas of the eastern United States compared to perlite imported from Greece. However, western U.S. perlite exports to Canada offset this in large part, and net import reliance for perlite is about 3% of domestic consumption. Perlite grab samples were tested at the New Mexico Bureau of Mines and Minerals Resources (NMBMMR) for their basic suitability in horticulture, construction, filter aids, and fillers/extenders using Perlite Institute techniques modified by the NMBMMR. Most commercial perlite ranged from 2.5 to 3.0 wt.% bound water for all major types (classical, granular, and pumiceous). Expanded density varied widely, but the lowest density of 1.9 lbs/ft3 was for granular. Average brightness of expanded perlite was 47.6 to 69.3%. Nonexpansibles, commonly obsidian or "dead" perlite, ranged from 18 wt.% to less than 1 wt.%, with granular perlte generally the lowest. Compacted density was not related to either perlite type or nonexpansibles present. Sieve analyses of the -50+100 mesh product showed that, in general, pumiceous perlite produces more fines and classical and granular perlite average 60 to 80% -30+100 mesh after expansion. Samples were tested for crystalline silica that ranged from below the detection limit of 0.5 wt.% to nearly 0.2 wt.%, but most tested below 0.5 wt.%. Although quartz content can be lowered in the expanded product by the expansion process, producers can further lower crystalline silica in the product by mixing low-quartz crude with high-quartz perlite before expansion. Chemical analysis by x-ray fluorescence confirms the rhyolitic composition of perlite, but indicates that surface weathering may increase the concentration of some elements, such as potassium and calcium, by infilling cracks or fissures developed during or after perlite emplacement.

Jan 1, 1995

By C. J. Dungey

INTRODUCTION The County of Cornwall is situated in the South Western extremity of England, see Fig. 1, and has for hundreds of years been an historical centre of mining activity. In the last century many thousands of Cornish miners emigrated to Canada, U.S.A., Australia and numerous other countries throughout the world to form the nucleii of mining industries in those lands. At present there are four active underground mines within the county, all mining tin, together with a relatively large china clay industry. All the operations are directly or indirectly associated with the three main granite intrusions, namely the Land's End Granite, the Carnmenellis Granite and the Bodmin Moor Granite. The report which follows relates to two mines, owned by the South Crafty Group of Companies, namely the South Crofty Mine itself and its smaller subsidiary, Wheal Pendarves. Both these mines are adjacent to the Carn Brea Granite ridge, see Fig. 2, which is an off-shoot of the main Carnmenellis Granite mass. The Carn Brea Granite has provided one of the most intensive areas of copper and tin mineralisation anywhere in the world. Many of the mines worked during the last two centuries and the early part of this century were situated close to the metamorphic aureole surrounding the granite intrusion. Both South Crofty and Wheal Pendarves have their shafts collared in the overlying slate, locally known as killas, but the major part of their workings are in the granite beneath. The ore bodies, or lodes, of both mines are generally steeply dipping and approximately one to four metres in width. They have been, and continue to be, worked by either back or under-hand stoping with the major level interval being approximately 37 metres. A feature of both stoping systems is that they require no back filling and in many cases the completed working areas have remained open for many years due to the competent wall rock conditions. The stoping operation necessitates having box-holes or draw points at regular intervals along the strike length at 4 to 7 metres centres; thus a stope some 50 metres long may typically have ten box-holes or draw points through which air can percolate into the empty stopes above. The granite country rock contains traces of uranium minerals, namely pitchblende or uraninite, and it is the decay of this uranium mineral which leads to the formation of the mobile radon gas which, together with its short lived daughters, may create a hazard. The presence of uranium minerals has long been known, but the quantities being so minute, it was not appreciated until some ten to fifteen years ago that these might present a hazard. The Mines and Quarries Inspectorate approached Management approximately ten years ago with a view to taking samples in areas of the mine that they felt might contain the highest concentrations of radon. Samples were thus taken in several areas of both mines, normally well away from working areas and where there was no through ventilation. The results of these initial tests were published by the National Radiological Protection Board in a paper entitled "Radon and Its Daughters in Various British Mines". The results of the initial surveys made it apparent that improved ventilation was the most important factor in reducing radon daughter concentrations within the mine atmosphere, with increased flow rates having three beneficial functions, viz. (1) To dilute radon daughter concentrations. (2) To prevent radon and its daughters reaching a state of equilibrium. It is not uncommon for radon and its daughters to have a disequilibrium factor of 1,000 in some uranium mines.

Jan 1, 1981

By Dan Preston, Shane Yanagisawa, Robert Marshall, Don Deere

Geotechnical Baseline Reports often estimate the number of cobbles that will be encountered in terms of volume or weight. These estimates are practically impossible to verify in the field. ClaroVia Holdings in conjunction with Frontier Kemper Constructors Inc. developed Digital Geologist 2.0 to classify and count cobbles discharged from an EPB TBM at the RSC7 project in Burbank, CA. The system worked by using two stereoscopic laser sensors with a global shutter to scan and count cobbles at 12 frames per second. Results of the effort are revealed along with lessons learned and paths for improvement.

Jun 13, 2023

By V. M. Torres

Arapiraca ore deposit has a mixed chalcopyritelbornite mineralogy, with a copper head grade of 0.7%. The reserve size does no allow profitable exploration by grinding/flotation. The technical feasibility of exploring the reserve by heap leaching was studied. Preliminary agitation tests indicated 85% copper recovery. To simulate heap leaching, column tests were performed. The tests included different ore types and acid addition levels. Operating at pH range 1.6-1.8, 67% copper extraction was achieved. Also, it was found an empirical correlation between the operation pH range, copper extraction and acid consumption.

Jan 1, 1996

By Ted DePooter, Mun Wei Leong, Chad Frederick

Downtown Bellevue Tunnel (DBT) is part of Sound Transit’s $3.7 billion, 14-mile light rail transit system from downtown Seattle, across Lake Washington, to the cities of Mercer Island, Bellevue, and Redmond. The tunnel was the first Sound Transit East Link project and posed significant construction risk. This paper discusses implementation of design changes to the soft ground tunneling method, implementation of several technologies such as the use macro-synthetic fiber initial shotcrete lining, use of spray-applied waterproofing, and use of shotcrete for the final tunnel lining. These efforts allowed for significant time and cost savings to the project.

Jun 13, 2021

By Francesco Chiappalone, Marco Invernizzi, Franco Gasperin, Fabrizio Fara

As part of the Ship Canal Water Quality Project, 2.7-mile Combined Sewer Overflow tunnel is excavated with a 21.5-foot diameter EPB Tunnel Boring Machine. Due to the difficult geological and hydrogeological conditions, the tunnel is excavated maintaining a ground support pressure between 1 and 3 bar imposing significant challenges to the projects. The first part of the paper describes the general characteristics of the project while the second part focuses on the challenges and technical details of the pressurized breakthrough that took place in a deep shaft excavated in urban environment as part of the project.

Jun 23, 2024