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By Antonio De Biase

In October 2006, a 7m Double Shield TBM, boring through very poor volcanic formations, was pushed back by fluid mud, which presence had not been detected during previous field investigations, due to the high covers characterizing the majority of the tunnel axis. The present work describes the investigations made to gain better knowledge of the conditions in front and all around the TBM, the special measures implemented, the exploratory and bypass tunnels excavated, the extraordinary occurrences came true during the execution of these tunnels, the drainage campaigns, the design of the chamber excavated to free the TBM, the dismounting and restarting of the TBM.

By Steve Kral

U.S. mines are among the most efficient, productive and safest in the world. Much of that efficiency is due to the high-technology equipment and processes available to the industry. The U.S. mining industry can produce more material now with fewer people than it could a few decades ago. And that material can be produced more safely. However, the workforce is growing older and fewer young people are filling the holes created by retirements. Even though mining is one of the highest paid occupations in the United States, young people believe they can find jobs that pay almost as well without the risks and the often remote locations associated with mines.

Jan 1, 2002

By W. J. Miles

At the beginning of the 20th century, barite was a mineral of minor importance in the United States. Its primary use was to extend lead oxide in white paint. Barite also added the special qualities of hiding power and flatness to paint. Because white lead sometimes turns black or yellow and barite does not, ground barite became a pigment on its own merit. Barium chloride was added to bricks before fi ring to stop efflorescence when exposed to weather. Barium carbonate or nitrate added luster and brilliance to glass. Barium chemicals were added to refining sugar, enameling iron, making oilcloths and paper collars, and in the manufacture of paper, artificial ivory, rubber and lithopone. Lithopone became a major paint ingredient in the 1920s; its use lasted until the 1950s, peaking at 150 kt (165,000 st) of barite in 1937 and 1947 for the manufacture of lithopone. Later in the 20th century, titanium dioxide replaced lead oxide, barite and zinc oxide in the coatings industry. In the 21st century, barite is used as a filler, extender or weighting agent in products such as paints, plastics and rubber. Some specific uses include its use in brake and clutch pads for automobiles, automobile paint primer for metal protection and gloss, to add weight to rubber mud flaps on trucks and to add weight to the cement jacket around petroleum pipelines under water. In the metals casting industry, barite is part of mold release compounds. Because barite significantly blocks X-ray and gamma ray emissions, it is used as aggregate in high density concrete for radiation shielding around X-ray units in hospitals, nuclear power plants and university nuclear research facilities. Ultra-pure barite consumed as liquid is used as a contrast medium in medical X-ray examinations. Barite is the raw material for barium chemicals, such as barium carbonate, which is an ingredient in faceplate glass in the cathode-ray tubes of televisions and computer monitors. In the 21st century, barite industrial uses accounts for an estimated 78 kt/a (86,000 stpy) in the United States.

Jan 1, 2009

By F. B. Olender

Idler engineering, operation, and maintenance cannot be covered in depth in a short paper. Therefore, this will be a general look into the subject matter in light or the present-day technology. Depending on the source or reference used, belts for handling bulk material underground came into being between 1900 and 1920, while strip mining appeared in the thirties. The conveyor belt speeds in that era were in the 300 rpm to 500 rpm range. Belt speeds or 600-700 rpm were in vogue in the thirties, and the early sixties saw speeds or 800-900 rpm. Today, speeds or 1000 rpm are not looked at with dismay; in fact, speeds or 2000 rpm are being discussed. Among the driving forces moving the bulk materials handling industry to these greater heights have been the mining operators and engineers. Their appetite to increase output, yield, and reduced per-ton costs has constantly challenged the bulk material handling industry to develop products capable or handling these increased capacities. One or the products affected by this movement is the idler. Apart from the conveyor belt itself, it is one or the most significant parts or a conveyor system because or the sheer numbers needed in an installation.

Jan 1, 1971

By J. Kern, M. Cain, T. Torries

Until recently, the generation of electricity was regulated in all states and the value of generation assets in a regulatory environment for ad valorem taxation were based largely on the book value of the plant plus the rate of return on capital allowed by the state regulatory agency. This method of appraising utility generation assets is inappropriate in a competitive environment because past capital expenditures are not relevant in a competitive environment. However, it is not clear what valuation methods are appropriate after restructuring. This paper identifies key problems and advantages of other appraisal methodologies and makes comments on various valuation and taxation methods.

Jan 1, 2001

By Horst Pöchhacker

The largest structure along the Tauern highway section between Salzburg and Villach is the 6.4-km-long Tauern Tunnel. The major geotechnical problems that came up surprisingly while driving the headings of that tunnel and their successful solution form the content of this article. A detailed discussion is presented of the special construction methods developed by systematic application of the principles of the New Austrian Tunneling Method with which even very heavily squeezing ground with large excavation areas can be mastered reliably and economically.

Jan 1, 1976

By T. M. Yegulalp

A new explanation of the scale dependency of the strength properties of rock is presented based on the theory of extremes. A review of past work on specimen size strength relationship is followed by an introduction to the fundamentals of the underlying theory of extremes and its relationship to the scale effect on the statistical properties of the strength distribution. It is shown that the weakest link theory is directly related to extremal statistics and properties of strength distributions of rock can be derived as a function of the specimen size. Three sets of Brazilian test data are used to demonstrate the use of this approach.

Jan 1, 1992

A series of gas inrush events occurred during development at Grosvenor mine resulting in exposure to elevated levels of methane at the production face. A total of 22 gas inrush events occurred releasing between 15 and 130 m3 of methane during each event. The presence of an undrained seam in the immediate floor, geotechnical characteristics of the floor, and the stress environment all contributed to these dynamic floor events, while the geological characteristics of the seam below, such as the seam thickness and ash content of 75%, prevented effective pre-drainage. However, events only occurred in headings mined parallel to the principal horizontal stress direction. In cut-throughs (C/Ts) perpendicular to the principal stress direction, no events occurred, and higher methane levels were observed at the production face.

Jan 7, 2020

By Irwan S. Halim

For tunnels in horizontally bedded rock, geologic factors affect the selection and design of the initial supports, including the rock propensity toward parting along bedding and the resulting high potential for rock slabbing during excavation. To evaluate this ground behavior, numerical analyses and results with Mohr-Coulomb, Hoek-Brown, and Ubiquitous Joint constitutive models were used, using the Upper Rouge CSO tunnel in Detroit, Michigan as an example. The different rock models and other geologic considerations are shown to impact the selection of the tunnel initial support and design. This paper emphasizes the appropriate selection of an analytical model based on the site specific geology to achieve an optimum initial support design.

Jan 1, 2008

By Jean Habimana

The Detroit Upper Rouge Tunnel CSO Control Project will capture and store up to 201 MG of combined sewer overflow from 28 outfalls in Detroit, Dearborn Heights and Redford Township during wet-weather events. The history of rock tunneling in the area is associated with high groundwater inflows, artesian pressure, and hazardous and combustible gases. This paper presents the geotechnical considerations for designing the 11.28-km (7-mile) long, 9.14 m (30-ft) finished diameter tunnel and its associated adits, chambers and shafts, including the discussions of geotechnical investigations, rock mass characterization, estimated groundwater infiltration during construction, and the selections of excavation methods and lining system based on anticipated ground behavior to be encountered.

Jan 1, 2008

By T. M. “Mike” Gurr

"U. S. marketable phosphate rock production for the 2018 crop year (July 1, 2017 to June 30, 2018) showed an increase to 27.7 Mt (30.5 million st) from the 2017 crop year production of 27.1 Mt (29.8 million st), as reported to the U. S. Department of the Interior by the mining companies operating in the United States during crop year 2018 (Table 1). Domestic consumption decreased in the 2018 crop year to 23.9 Mt (26.3 million st), as compared to the 27.2 Mt (30 million st) consumed in crop year 2017. U.S. imports of phosphate rock increased to 3 Mt (3.3 million st) for the 2018 crop year from the 1.81 Mt (1.9 million st) for crop year 2017. Imports of phosphate rock were from Peru and Morocco. There was an increase of 2.85 Mt (3.1 million st) in producers’ stocks from 7.45 Mt (8.2 million st) in crop year 2017 to 10.3 Mt (11.3 million st) in crop year 2018 (Table I).For calendar year 2018, Florida and North Carolina phosphate rock production accounted for 75 percent of the total U.S. production, with the balance being produced in Idaho and Utah. The Florida and North Carolina percent of U.S. production is declining. U.S. production of 25.7 Mt (28.3 million st) in calendar year 2018 was produced by five companies at 10 mines in four states and accounted for approximately 9.6 percent of the world production of 267.7 Mt (295 million st) for calendar year 2018 (Table 2).In calendar year 2018, U.S. phosphate production decreased by 2.2 Mt (2.4 million st), while companies increased stocks of phosphate rock by 1.7 Mt (1.9 million st). The domestic production for calendar year 2018 of 25.7 Mt (28.3 million st) represents 78.4 percent of the domestic production capacity of 32.8 Mt (36.1 million st).At present, China reportedly produces more than 50 percent of the world’s phosphate rock. As a result of planned expansions, Morocco production has increased from 27 Mt (30 million st) in 2017 to 33 Mt/a (36 million stpy), which is approximately 12.3 percent of the world’s production, moving ahead of the U.S. production. In calendar year 2018, the U.S. phosphate rock production was 25.7 Mt (28.3 million st), which is less than 10 percent of the world’s production of phosphate rock (Fig. 1)."

Aug 1, 2019

By Lei Pan, Venkata Atluri, Xuming Wang, Yuesheng Gao, Jan D. Miller

The wetting characteristics and water film stability at the talc surface have been studied, particularly the effect of polysaccharides such as guar gum, starch, and dextrin. Talc is a gangue mineral in the flotation of base metal sulfide ores, precious metal sulfide ores, and platinum group metal (PGM) sulfide ores. Talc surfaces were investigated using surface analysis techniques including atomic force microscopy, high-speed video bubble attachment measurements, and wetting film stability measurements using a synchronized tri-wavelength reflection interferometry microscope (STRIM). In the presence of polysaccharides, there is a significant increase in bubble attachment time at the talc surface, but only a slight change in contact angle, which suggests that polysaccharide depression of talc is due primarily to the slow rate of bubble attachment and not due to a change in contact angle. The critical rupture thickness (hc) for a hydrophobic talc surface was found to be 56 nm, while the hydrophilic phlogopite surface of similar structure has an equilibrium film thickness (he) of 25 nm. At low polysaccharide concentrations, the wetting films formed on the talc surfaces were unstable, but at high concentrations the wetting films became stable with similar thickness values as the critical rupture thickness, and bubble attachment did not occur. However, it was found that the critical and equilibrium film thickness values do not change significantly with the polysaccharide type or concentration. The results from this research help us understand further details of film rupture and displacement during bubble attachment.

By Mutombo Nombe, Avimanyu Das, Rick Honaker

Enhanced gravity separators (EGS) provide a more efficient separation than froth flotation when cleaning coal in the 150 x 25 µm particle size range. To improve the performance of an EGS unit, air bubbles were injected into the feed stream in an attempt to decrease the apparent density of the coal particles due to the formation of bubble-coal particle agglomerates. Air injection had a significant impact on operating characteristics and separation performance. Coal recovery was increased by 10 to 20 absolute percentage points while a 2 percentage point drop in the minimum product ash content was also achieved.

Jan 1, 2005

By J. Kretschmann

Around the world, mining has been done for thousands of years for the benefit of humankind. The winning process in mining operations ends with the depletion of the deposit or its closure if the operation becomes economically unprofitable. After that, a period of post-mining follows which may last for a very long time and which is generally regarded as a period of hazards, risk and high cost. In the USA alone, approximately 500,000 abandoned mines do exist; worldwide, there are millions. In Germany, too, we have had to deal with abandoned mines for a considerable period of time now.

Jan 1, 2012

By Robert M. Valentine, Randall L. Lentell

Interpretive geotechnical investigations were performed for the construction of approximately 15,250 m (50,000 ft) of wastewater interceptor tunnels in Austin, Texas. Subsurface materials consist of claystone (or clay shale), siltstone, altered volcanic tuffs, chalk and limestone. Special conditions include multiple crossings of Onion Creek with cover ranging from about 1/2 to 3 m (2 to 10 ft.), and the potential for mixed-face conditions consisting of water-bearing gravels overlying clay shale or siltstone. The methods and results of the geotechnical investigations are discussed and the inferred construction conditions are compared to those encountered during tunneling. A suggested format is presented for interpretive geotechnical reports for underground construction projects.

Jan 1, 1985

By Paul Headland

The Washington Suburban Sanitary Commission (WSSC) has recently completed design for the Bi-County Water Tunnel Project. The project will include a 10-foot diameter, 5.3-mile long hard rock tunnel located within the Piedmont Physiographic Province in Montgomery County, Maryland. The rock formations present along the alignment are comprised of igneous and metamorphic lithologies. This paper presents the steps taken to characterize the complex geology along the tunnel alignment into a single ?Engineering Unit? based upon the intact rock and rock mass properties. The Rock Mass Rating (RMR) system is planned to be used as the basis for dividing the ground into three ?Excavation and Support? classes. This RMR approach was selected to establish contractual baselines as presented in the Geotechnical Baseline Report (GBR) and is intended to facilitate management of the ground support characterization during construction.

Jan 1, 2008

By L. Ozdemir, M. Cigla

This paper presents and discusses some of the computer models developed and currently used at the Earth Mechanics Institute (EMI) of the Colorado School of Mines (CSM). These include the performance models for full and partial face machines. Examples of input and output of these models will be illustrated for typical mining operations by using machines such as Tunnel Boring Machines (TBM), Continuous Miners (CM), Marietta borer miners and longwall drum shearers. The general approach to modeling and the available models are discussed and some examples of these models are presented. The comparison between the estimated and achieved performance, as well as the degree of improvement in the performance due to balancing and modification in cutterhead design are also discussed.

Jan 1, 2000

By A. Wahab Khair, John G. Oldsen, John C. Stankus, Song Guo

During the last several years, implementation of trusses, in lieu of wood cribs, has been successful for supplemental tailgate support in the Pittsburgh seam. This paper reviews, the truss support system provided by the new high strength 0.6" tensioned cable truss, which is now also being used in cribless tailgates. Cable loading and roof deformation were monitored to evaluate roof and floor performance. The test results indicate that the cable truss system successfully controlled the roof and floor during the first and second panel extraction. This paper will describe the advantages of cable trusses and their load transfer mechanism as well as mine evaluation.

Feb 24, 1997

By Rolando Gonzalez

Mexico’s role in the world economic community continues to grow. And it is important that the country makes use of its natural wealth, including its large underground deposits of minerals and metals. With that in mind, Industrias Peñoles S.A. de C.V.(Peñoles), a mining, smelting and refining company, began mining lead, zinc and other metals from the Francisco I. Madero Project (FIM). The mine is located about 600 km (370 miles) northwest of Mexico City in the state of Zacatecas. Peñoles plans to remove about 3 Mt/a (3.3 million stpy) of ore from FIM. To achieve this goal, the company needs to optimize its processing, to maximize the amount of metal it extracts through FIM’s large flotation lead-zinc concentrator. To ensure high productivity, Peñoles and its contract engineering firm, M3 Engineering and Technology, of Tucson, AZ, have implemented anore processing system.

Jan 1, 2003

global mining boom and in-creased demand for iron ore has lead to a resurgence in the mining industry in Minnesota. At the combined 81st Annual Minnesota Section of SME Meeting and 69th Annual University of Minnesota Mining Symposium, April 15-16 in Duluth, MN, this resurgence was the hot topic as new mining projects were featured in the keynote session. The meeting attracted more than 400 mining industry professionals, including engineers, executives, mining managers and suppliers from around the world. This year?s theme was ?New Ventures in Mining.? The meeting included concurrent technical papers sessions, a keynote session that featured three distinguished speakers and a panel discussion that provided updates on new mining developments in the state. The Minnesota Section of SME technical papers were presented in concurrent sessions, one on mining and one on mineral processing. The mining session included papers on drilling, ore blending, slope stabilization, dust control and operations management. The mineral processing session included papers on plant-control technology, ball mills, pellet strength and fans. Also offered was an SME short course titled ?Simulation based pellet induration optimization.? The Minnesota Section of SME held its annual business meeting during the conference. The 69th Annual University of Minnesota Mining Symposium technical sessions were held on April 15 and also consisted of concurrent sessions on mining and mineral processing. Mining session topics included logistics management, real-time performance measurement, uses for taconite aggregate and environmental issues. The mineral processing session included papers on ore liberation characteristics, zeta potential studies, induration modeling, fuel optimization and conveyor belts. The combined conference included a tradeshow with more than 80 booth spaces featuring vendors offering products and services to Minnesota?s booming mining industry. More than 900 people, including conference registrants and special invited guests of the vendors, at-tended the tradeshow opening reception. This was the largest trade show in many years ? an indication of the vitality of the mining industry in Minnesota.

Jan 1, 2008