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By B. Valentim

Policies for reducing NOx emissions have led power plants to restrict O2, resulting in high-carbon fly ash production. Therefore, some potentially useful fly ash, such as the economizer fly ash, is discarded without a thorough knowledge of its composition. In order to characterize this type of fly ash, samples were collected from the economizer of a Portuguese power plant burning two low-sulfur bituminous coals. Characterization was also performed on economizer fly ash subsamples after wet sieving, density and magnetic separation. Analysis included atomic absorption spectroscopy, loss-on-ignition, scanning electron microscopy/energy-dispersive X-ray spectroscopy, optical microscopy, and micro-Raman spectroscopy. Key words: Fly ash; Petrology; Petrography; Economizer fly ash

Jan 1, 2009

By Qingqing Huang, Mohammad Rezaee

The Mineral & Metallurgical Processing Division (MPD) of the Society for Mining, Metallurgy & Exploration held the 12th MPD Student Poster Contest on March 2, 2022, during the MINEXCHANGE 2022 SME Annual Conference & Expo. The event showcased the work of 32 graduate and undergraduate students from U.S. and international institutions. The contest began in January when the students submitted one‐page abstracts for judging. In February, they prepared and presented posters that explained their research, and each student had five minutes to explain their research to a panel of judges during the conference. Recognizing the students’ efforts in working hard on their research topics and setting aside time to complete the necessary steps to enter the poster contest, the MPD provides monetary rewards to all participants. For graduate students, first place receives $1,000, second place $500, and third through seventh places $200 each, and for undergraduate students, first place receives $1,000 and second place $500. The main authors of nonplacing entries receive $125 each. Participation in the contest includes a free ticket to the MPD Luncheon, where the winners are announced.

Nov 22, 2022

By R. Fedors, T. Ghezzehei, D. Or

The phenomena of dripping into cavities (e.g. tunnels and drifts) within an unsaturated fractured porous medium under ventilated conditions is studied to improve estimates of dripping rates, drop sizes, and chemical composition of droplets that could affect the integrity of high-level nuclear waste packages placed in drifts. The sensitivity of dripping rates and water chemistry to ventilation is analyzed at various flow rates using analytical expressions linking flow on fracture surfaces to drop formation and evaporation. The model was tested using laboratory experiments involving machined aluminum slabs designed to represent a simplified morphology of a fracture face intersecting a cavity and using natural fracture surfaces from a welded tuff. Comparison with ten years of data on dripping in natural caves showed good agreement with model predictions. In particular, for low dripping rates, evaporation due to ventilation leads to larger drop sizes and alters drop chemistry by increasing the concentration of solutes in the drop relative to that in the water flowing on the fracture face.

Jan 1, 2000

By Kira Mizell, James R. Hein, Tracy Conrad

"The Ninetyeast Ridge (NER) extends roughly N-S as a topographic feature for 5000 km, from 31° south to 10° north (Fig. 1) where it becomes buried beneath the Bengal Fan at its northern end. These two geographic characteristics make the NER an ideal natural laboratory for determining the influence of latitude and terrestrial input to ferromanganese (Fe-Mn) crust formation and composition. In addition to study of geographic controls on crust composition, the NER is the largest feature in the Indian Ocean that may host crusts of economic interest.Crusts were collected from 9 of 33 dredge sites from 1.4° north to 26° south latitudes during the 2007 R.V. Roger Revelle Knox06 cruise. Nineteen samples were analyzed for 69 elements each. Nine bulk crusts and 10 layers from four crusts were analyzed. Three of the crusts sub-sampled for layers did not have the bulk crust analyzed and the weighted means for those layers were calculated to obtain bulk compositions. One sample was left out of the statistical analyses because it is phosphatized and chemically quite different from the other samples (Table 1).In order to determine changes in composition with latitude, Pearson product-moment correlation coefficients were calculated for the chemical dataset and latitude of dredge sites, as well as water depth. At the 95-99% confidence level, the following elements increase in crusts moving north along the NER: Mg, Ti, S, Cd, Ni, Tl, Mn, Ba, Co, Cu, In, Li, and Zn; and the following elements decrease northward: Fe, Fe/Mn, P, As, Sc, the rare earth elements plus yttrium (REY), Bi, Ge, and Pb. These correlations indicate that the iron oxyhydroxide component and its associated elements are more prevalent to the south, and the manganese-oxide phase and associated elements increase toward the north end of the NER. This change occurs between dredges D20 and D14 (Fig. 1), with crusts from D20 and south having Fe/Mn !1.0 and those north of D20 ""1.2, with the exception of the phosphatized crust. Crust composition also changes with water depth: Th, Ge, Pb, and the middle rare earth elements (REEs) increase with increasing water depth. Thorium commonly increases in deeper water crusts, which explains the higher Th concentrations in Atlantic and Indian ocean crusts in general compared with Pacific crusts (Fig. 2 and Hein et al., 2012), including the samples analyzed here with a mean water depth of 3584 m. However, water depth does not explain the latitudinal changes because the mean water depths of samples along the northern and southern segments of the NER are roughly comparable. Surprisingly, Si and Al, representing the aluminosilicate/detrital phase, do not correlate with latitude; that is as the ridge approaches and is buried by the Bengal Fan the Si and Al contents do not increase. However, overall, Si and Al have higher concentrations in NER crusts than in central Pacific crusts. Ba can be used as a proxy for primary productivity and statistically does increase to the north along the ridge in the direction of the equatorial zone of high biological productivity. Correlations of Mg, Li, and Zn with latitude may also reflect increased primary productivity at lower latitudes."

Sep 1, 2014

By Yoginder P. Chugh

Most mines are large producing 0-25 mmt annually. The coal is mine.) at depths ranging from .0-150 m 120-500 ft mining at 300 m .(,1000 ft) depth is anticipated in the future. Single and multiple seams ranging from 3-12 m 10-40 ft) in thickness are mined. Most overburden is unconsolidated and consists of sands, and sandy or silty clays. The stripping ratio (volume of overburden to volume of coal mined) varies from 3-L. The overburden and coal is mined in benches 8-12 m -(24-40ft) high; the high-wall angle is about 45 degrees. Bucket wheel and bucket chain excavators are commonly utilized for overburden and coal removal, Some of the large overburden stripping machines nave capacities. Ranging from 4400-10,000 bank cu ( 6000-14,000 BC) per hour. The overburden from the upper benches is transported around the pit using the trains and belt conveyors. It is deposited in the spoils using large stacker-conveyor systems capable of handling 2550-7300 cu m/hour (7500-10,000 cu yds/hour). The overburden from the bottom two or three benches is transported across the pit using the conveyor bridges which are computer controlled. Conveyor bridges capable of handling overburden up to 60 m (200 ft) high are currently in use; a 60 a (20e ft) high conveyor bridge has a capacity of 85 x 10 cu ( 118 x 10 cu yd) annually. The coal is loaded in the trains directly and shipped to power plants or coke oven plants.

Jan 1, 1980

By D. Bessinger, J. M. A. Geldenhuis

High titania slag is produced from the smelting of ilmenite. These slags contain approximately 85 per cent TiO2 and consist mainly of a M3O5 solid-solution phase. During cooling the slag can decrepitate to a fine particulate material, which decreases the value of the product. Based on X-ray diffraction analyses of the decrepitated slag after cooling, it was found that the M3O5 phase had almost disappeared. The disappearance of the M3O5 phase was linked to oxidation of the slag. A M6O11 phase formed in the decrepitated slag. It is postulated that decrepitation of high titania slag is caused by volume changes due to the oxidation of the M3O5 phase in the slag.

Jan 1, 2005

By A. Moergeli

The Swiss are building the world’s longest tunnel, the 57-Kilometer (35-mile) long Gotthard Base Tunnel. Lot 252, Tunnel Amsteg: Two Hard Rock Tunnel Boring Machines (TBM) crossed hydro-thermally decomposed granite. While the East TBM advanced slowly but steadily, the West one got stuck for five months and had to be recovered by special means and methods. Both TBMs have finished their more than 11-Kilometer (7 miles) long drives successfully. Lot 360, Tunnel Sedrun: For the first time in tunneling, roadway support machines are used through most challenging, squeezing geology. They constantly advance in full face mode for about one Tunnelmeter/24 hours.

Jan 1, 2007

By Jerry C. Tien

Mining in China dates back at least 4,000 years. Today, with no less than 103,000 metal/nonmetal mines and between 40,000 to 80,000 coal mines, China’s mining industry is undoubtedly the largest in the world. Despite improvements in recent decades, seemingly endless mining accidents continue to make the news. Official coal mining deaths were 6,702 in 2003, and 6,027 miners died in 2004; actual figures may be much higher. Added to these were the 2,699 deaths in the metal and nonmetal industries. Most of these accidents were due to CH4 (methane gas) explosions and fires as a result of inadequate mine ventilation de-sign or practices. A good portion of these accidents occur in small, privately run and often technically illegal mines. During the past 10 years, the Chinese government has attempted to crack down on small and often technically illegal mines without much success. The number of accidents and associated fatalities has not significantly reduced. However, there appears to be a new urgency in China’s efforts to step up mine safety in the country. After its worst reported mine disaster in more than a half century, the government quickly paid reparations to families, suspended high-level officials in charge and announced additonal reforms. One of those was the elevation of the central government’s work safety office to cabinet-level status. There has been increased transparency in reporting and investigation of mine accidents and disasters in recent years. There has also been an increase in public criticism by labor leaders concerning the neglect of mine workersafety.1 This article examines the causes of China’s many mining accidents, current legal and enforcement structures, respective mining health and safety related laws and regulations, recent mining industry developments and the latest effort to curtail small mining operations.

Jan 1, 2005

By Steve Dubnewych, Jon Kaneshiro, Calvin Jin

The Joint Water Pollution Control Plant (JWPCP), operated by the Sanitation Districts of Los Angeles County (the Districts), treats wastewater generated by over3 million people and processes wastewater solids generated by over 5 million people. The JWPCP Tunnel and Ocean Outfall Project, if constructed, would be one of the major marine outfall projects in the world. The new tunnel and ocean outfall system would provide relief to the existing outfall and allow inspection, maintenance, and repair of the existing tunnel and outfall system, portions of which were constructed as early as the 1930s. Geologic conditions are challenging along the alignments within the study are a being considered. Conditions include saturated alluvial soils, weak sedimentary rock, mixed face conditions, and squeezing ground conditions. Other significant challenges include the potentials for encountering up to 11 bars of water pressure, crossing seismically active faults, and encountering gassy and contaminated ground conditions. This paper discusses the details of the proposed project and the associated challenges.

Jan 1, 2007

By Larissa Koroznikova, Steve Durkin, Patrick Bouwmeester, Michael Tuck

In currently used mining methods, blasting techniques often causes dilution of valuable ore and results in costly processing requirements. In the context of narrow vein mining of thin and highly concentrated orebodies there is a need of a mining method that can reduce dilution in order to remain economically viable. This research project explored the viability of a new mining technology, thermal fragmentation, in narrow vein mining. Thermal fragmentation technology uses a flame jet to produce extreme heat that spalls the surrounding rock to a strategically located drill hole, as an alternative to traditional blasting. This paper creates a net present value (NPV) model of a mining method using thermal fragmentation, as well as for an existing method used for narrow vein mining; comparisons and evaluations were made regarding the feasibility of the new technology. It was found that while overall costs for thermal fragmentation were relatively high, reductions in wages, haulage and processing costs, as well as increased productivity and ore recovery, meant that the new method would improve the financial performance of any operation. These results identify that there is an opportunity to introduce the thermal fragmentation technology to narrow vein mines within Australia, in order to lower costs and increase profit.

Let’s start off with your assessment of the mining industry. Today, the status of the mining industry is stronger than it has been over the previous few years. While mining continues to be a major part of the world’s economic foundation, the industry is gaining strength due to rebounding metals and minerals prices. And now, with these rising prices and the changes the industry instituted during the years when mining-related commodities were selling at low prices, our stronger, more productive and internationally competitive industry should flourish. Mining remains an essential business and the industry is far ahead of the game when it comes to the trend of globalization as a key to sustained growth. Also, the industry continues to realize increased productivity through technological innovations. And an increasing number of countries are moving towards capitalism, which opens doors for exploration and mining within their borders. After looking at all of these factors, I believe that the mining industry will only continue to gain momentum in the future.

Jan 1, 2004

By Larry H. Heflin

The Washington Metropolitan Area Transit Authority's Wheaton Station and tunnel design was completed and offered for bid in the Spring of 1983. The format was unique to the Authority: a four part, four fiscal year contract developed in response to funding limitations with construction divided into four stages allowing the maximum amount of work to be done each year for the funds available. The bid was based on the entire contract, but was orginally awarded for only the first year's work. Each year's work had a maximum funding limitation thus safe guarding the Authority from a grossly unbalanced bid. The Authority's estimate for this work was $83,871,524. The low bid came in at 61% of this for a total low bid of $51,512,058. The low bidder was ILBAU America Corporation whose home offices are in Austria. Following receipt of the bids (and resolution of objections cited by other bidders who felt that the job could not be done for the $51 Million dollar figure), a Notice-To-Proceed was given on October 5, 1983. The construction contract allows a Value Engineering Change Proposal, called a VECP which is initiated and developed by the contractor to change the drawings, specifications or other requirements of the contract. Among other things the VECP should decrease the contract price while maintaining the service life, reliability, ease of maintenance, and standardized features and appearance and not require an unacceptable extension of the contract time. A VECP must estimate the amount of the net savings

Jan 1, 1985

By Paul Gribbon, Julius Strid, Greg Colzani, Jim McDonald

Portland, Oregon’s $370 million West Side Combined Sewer Overflow Tunnel Project has completed the final phase of construction and commissioning. The construction contract, which began in September 2002, was a reimbursable cost plus fixed fee contract that followed a qualifications-based contractor procurement process and apre-construction planning phase. This paper addresses the final results of the contracting method and provides a lessons-learned case history. Specific items addressed include the benefits realized from the contracting method, areas of improvement, final costs compared to the original contract estimates, design changes and schedule impacts, and subcontract management issues.

Jan 1, 2007

By B. Caro Vargas

The Toulon South Tunnel in France is the second part of a project started 20 years ago. After the problems and delays suffered during the construction of the North Tunnel, due to a complex geologic context of highly fractured and soft rocks under a highly urbanized environment, a very dense automatic monitoring system was implemented to control the settlements of surface (more than 1000 points), the structures adjacent to the tunnel alignment and the underground galleries being constructed. The latest automatic instrumentation systems were installed, using for example AMTS capabilities in terms of ?automatic prismless settlement monitoring?. All the data (geotechnical, structural and geological) was gathered in a global automatic data acquisition system and continuously available on a web based interface. Three different threshold levels (notification, anomaly, alert) were set up, each one with a differential and an absolute value for settlements. Depending on the actual geological site conditions and the actual monitored settlements, different supporting systems and excavation techniques were used. Furthermore, the monitoring data was also used to predict and anticipate the future settlement, by comparing it continuously with the theoretical Peck settlement curves. This method allowed a better risk management by limiting the settlement on existing structures and helped to secure the Works progress schedule, for a project that lasts from July 2007 to March 2011. The implementation of this observational method application is presented in this paper.

Jan 1, 2012

By D. E. Poole

Injury Prevention: Dependent, Independent and Interdependent In recent years, management-directed (dependent)safety programs have lost ground to the more successful self-directed (independent) programs, where employees take responsibility for their own safety. Today, with the growth of the team concept in industry, a mutual-caring (interdependent) approach to workplace safety is gaining wide acceptance. This presentation compares characteristics and results of the three progressive levels of safety responsibility and explains how to develop a successful interdependent program. The presentation will also detail the common principals that are necessary for safety excellence under any of the management styles.

Jan 1, 2000

By R. L. Howell, L. C. Atkinson

Typical sedimentary sequences overlying coal seams consist of interbedded sandstones, siltstones, shales, and rider coal seams. In many surface coalmine settings, these sediments are saturated; and prior dewatering of them is necessary for effective and economic mining, including the stacking of saturated spoils. Such sedimentary sections usually have a very low vertical hydraulic conductivity that does not allow them to drain in a timely manner prior to their being stripped. One potential solution is installation of drainwells. Drainwells are small diameter wells that can collect water laterally from the various more permeable layers in the overburden and then gravity drain it to a lower layer – often the coal seam being mined – where it can be removed by pumping wells or sumps located in the bottom of the pit. A ground-water flow model utilizing the 3-dimensional finite element code MINEDW has been used to evaluate the effectiveness of usingdrainwells in a hydrogeologic setting that is typical of the Powder River Basin. A series of numerical simulations were completed using various combinations and spacings of drainwells and pumping wells to dewater the overburden and coal seams. The numerical simulations suggest that drainwells can be a very effective method of overburden dewatering.

Jan 1, 2000

By Arthur Darby

The city of Kuala Lumpur was founded in 1857 by miners seeking tin near the confluence of the Klang and Gombak rivers. The rapid development of the city and surrounding area since independence has led to more rapid runoff during rainstorms and to gradual canalisation of the rivers with some restricted sections. The outcome has been more frequent and more severe floods (Abdullah 2006). At the same time the centre of Kuala Lumpur has become a modern inter-national city with tall office buildings, hotels, and shopping centres connected by a network of wide roads and commuter rail systems. With these the cost of dislocation during floods has risen as has the cost of making good damage afterwards. The Government of Malaysia considered these consequences unacceptable and sought ideas from the private sector for a solution. Potential solutions consisted of variations on the themes of bypassing the city centre with a flood relief tunnel or of providing off channel storage or a combination of both. Since under Malaysian law a tunnel cannot be constructed under private property unless this is first purchased or agreement reached with the owner, it was necessary for most of the tunnel alignment to run below existing heavily congested roads. After considering these facts Gamuda Berhad and MMC Berhad, two leading Malaysian development and construction companies, decided to propose to Government an innovative solution in which the tunnel would be used to carry road traffic except during floods.

Jan 1, 2008

By Li Jiuping, Zhong Gang, Chen Yong Zhang, I. Michael Gowring

The Liaoning Dahuofang Reservoir Water Transfer Project is an important development for the Department of Water Resources of Liaoning Province in northeastern China. The 85.3 km water conduit will transport water from the Hun River downstream of the Huanren Reservoir to the outlet on the Suzi River leading to the Dahuofang Reservoir. The additional water is required to sustain the growing cities of Fushun, Shen-yang, Liaoyang, Anshan, Panjin and Yingkou. The project is divided into seven contracts. Three TBM contracts comprise almost 75% of the work and the others are drill and shoot. The focus of this paper is about the creditable TBM performances achieved and some of the problems encountered by Chinese contractors; notably two having had no previous TBM experience.

Jan 1, 2007

By S. Maurhofer

The Uetliberg Tunnel in Switzerland is the longest tunnel in Zurich?s new Western Bypass Expressway, connecting the Birmensdorf bypass in the west with the existing Zurich-Chur national motorway in the east. Thus the tunnel links the Zurich-West motorway interchange with the Zurich-South interchange (shown in Figure 1). The Uetliberg Tunnel project comprises two parallel tubes, each about 4.4 km long. The two tunnel tubes are connected every 300 m by a transverse walkway and every 900 m by a transverse roadway (Figure 2). The SOS niches are spaced 150 m apart. Portal stations with machinery rooms are located at the west and east portals. The tunnel falls with a gradient of 1.6% from the west portal at Wannenboden to the east portal at Gänziloo. The Project costs are about CHF 1.12 billion. The carcass construction started in March 2001. The Opening of the Uetliberg Tunnel is planed in spring 2009.

By J. Philip Neal

Feldspar is no example of special mineralization in isolated spots: it can usually be found within a mile or so of almost anywhere. Along with silica sand, it is a major part of our world's total mineral composition. This fact imparts to it an economic status different from a sulfide ore, or potash, or phosphate. While every feldspathic "stringer" does not possess economic potential, the generous distribution does yield a high statistical frequency of good feldspar ore bodies: the adjective "good" being subject to some flexibility of interpretation. The strong chemical bonds of this alkali aluminum silicate give it certain use advantages, but under present technology its individual elements cannot practically be separated to create aluminum, potassium, sodium, silicon - or their oxides. Its present uses rely upon chemical inertness - as in fillers; and on its physical melting characteristics and their effect in glass, enamel, or ceramics.

Jan 1, 1973