Search Documents

By H. Akbari

Ordinary portland cement (OPC) is the key pozzalonic component of the concrete mix widely used as a construction material worldwide. B illions of tons of OPC are used in the construction industry each year. However, calcinations of limestone and silica that produce OPC also produce almost an equal amount of C O2 during the cement manufacturing process. Thus, OPC production accounts for nearly 7% of all anthropogenic C O2 emissions each year. The main objective of this study was to develop a geopolymer-based composite to be used as a substitute for OPC in concrete application to significantly lower the carbon footprint of the construction industry. A waste material produced during the coal combustion process was used as the main raw material for the geopolymer-based composite. It was mostly the nonmetallic content of the F-type fly ash produced from the combustion of bituminous coal. The authors envisioned extracting some of the valuable metal oxides from fly ash prior to using the major nonmetallic portion of the fly ash for geopolymer concrete application. The results obtained from this study showed that the compressive strength of geopolymer concrete compares favorably with that of conventional concrete prepared using OPC.

Dec 1, 2013

By J. J. Gusek

There are hundreds of passive treatment systems accepting mining influenced water (MIW) throughout the world. Some systems do not perform to design expectations while others, including volunteer systems, have successfully operated relatively unattended for decades. The primary reasons for this situation include the common misconceptions that (1) a “cookbook” approach to design is valid for a wide array of MIW chemistries and site conditions, and (2) low maintenance means “no maintenance.” Passive treatment systems for MIW are typically manmade ecosystems that are designed to handle a specific range of metal loading conditions and MIW geochemistry. Thus, when design conditions are exceeded, the suite of microbial to macroscopic ecosystems may be slow to recover or mature. This should be no surprise to designers. But when a particular system fails, it may be inappropriately attributed to the technology, not the design. This paper presents a standard “phased” design protocol that appears to work and provides examples of sub-par performance of selected passive treatment systems.

Jan 1, 2002

By R. J. Sweigard, C. T. Justice, T. Beckham, E. D. Thompson, T. C. Hopkins

Fine coal refuse is often pumped, as slurry, into surface impoundments as a means of permanent disposal. As the available volume is filled, the height of the embankments are frequently increased. Many times the additional embankment material is placed upon consolidated fine coal refuse. There has been some concern about the long-term effect of consolidation of this material at or above the liquid limit upon its shear strength. A laboratory investigation was performed using three different types of fine coal sluny taken from Central Appalachian coal preparation plants. The refuse was consolidated in 10-foot plexiglass columns under incremental amounts of surcharge loading. The incremental loads were designed to simulate the effect of increasing the height of a refuse embankment on top of the consolidating coal slurry. After the refuse in the columns had consolidated for several months, the columns were cut apart and triaxial tests were performed on both the consolidated material and unconsolidated material for comparison of their shear strength parameters.

Feb 24, 1997

By T. McCallum

Crud is a common concern in SX processes and is formed as a complex solid stabilized emulsion of aqueous and organic.1,3 Crud formation is highly dependent on the amount of solids entering the circuit and is influenced by a number of other operational factors. A common practice for crud processing is interfacial pumping, wherein crud, organic, and aqueous are pumped from the settlers for treatment and utilizes a variety of equipment. These mechanical means of crud processing are effective, however, require significant processing time and require oversight to prevent the return of contaminated organic. Cytec has developed a unique crud treatment process utilizing both chemical and mechanical means to enhance the solid/liquid separation. The use of ACORGA CB? 1000 crud busting reagent allows a rapid separation of solids from the organic phase and provides similar volume recovery to current practices. The process allows operations to return clean organic back to the plant more efficiently and may enable operations to process more crud. In addition, the organic quality of the recovered organic is higher than that recovered by typical means, which can lead to operational cost savings.

Feb 27, 2013

By Cem Şensöğüt, Özer Ören, Yaşar Kasap

The mining sector, which has an important place in terms of raw material and energy supply, is referred as a sector with one of the highest fatal accidents in comparison with other sectors. In this century, where occupational health and safety awareness has increased, it is important to review the past accident statistics and to determine the current deficiencies by using the information in the inventory. In this study, the Malmquist total factor productivity index (MPI) has been utilized to investigate the changes in the work accidents occurring in the Western Lignite Corporation (Turkey), where underground and surface production methods are applied, and to determine the measures to be taken. According to the results obtained, both the decrease in production amount and the increase in the number of accidents caused inefficiencies during the period in concern due to the expected 10-year economic life of the mechanized system operating in the underground production panel that came to an end in 2007 and the flooding took place in early 2017. Compared with the underground operations, it has been determined that production can be carried out at the appropriate scale despite the heavy working conditions encountered due to the changing climatic conditions and the progress of production in the surface operations.

By Mark Rybak

On August, 31, 2006, Tropical Storm Ernesto hit the City of Richmond, Virginia. The Battery Park area was hit particularly hard, as flooding forced an evacuation of the area. A large sinkhole collapsed a sewer line in the Battery Park area, blocking the pipe and causing more serious flooding. This case history describes the fast track design, bidding, and construction of an emergency tunnel to bypass the collapsed sewer. Innovative value engineering, tunneling and shaft sinking methods, and final lining design all contributed to the success of this project. The storm inundated Richmond, Virginia with up to twelve inches of rain in some areas causing widespread flooding and damage. One of the hardest hit areas of Richmond was Battery Park. A major trunk sewer in the Battery Park area collapsed causing local combined sewer and storm-water flooding. The collapsed sewer was an 8'-3" wide by 9'-6" high arch sewer that was constructed in the nineteen twenties and later filled over with municipal solid waste and a soil fill cap to current elevations. A sinkhole was created in the area of collapse approximately sixty feet deep and one hundred feet in diameter causing the existing arch sewer to become blocked. As a result of this blockage contaminated flood waters reached depths in low lying areas in excess of twenty five feet. [ ]

Jan 1, 2008

By S. Yerel

In a mineral processing plant, the determination of a preventive maintenance schedule is one of the most important maintenance policies. In this study, to determine the preventive maintenance schedule for the Emet Colemanite Mineral Processing Plant in Turkey, a mean quality control chart was constructed using the historical concentrate B2O3 grade data. The effect of preventive maintenance scheduling on B2O3 grades was monitored using the mean quality control chart. It was determined that recovery increased after each preventive maintenance scheduling. Close examination of the mean quality control charts indicated that there were three periods that showed different grade characteristics. These were identified as the period ?prior to preventive maintenance,? the period ?after preventive maintenance? and the period ?requiring preventive maintenance.? These periods were compared as two independent samples by using the Kolmogorov-Smirnov test. Application of this test for interpretation of the mean quality control chart enabled the authors to analyze the system effectively, and it showed that the preventive maintenance for this plant should be scheduled at four-month intervals.

Jan 1, 2007

By Sohta Takatsu, Hachiroh Mizubata, Shigeki Kudoh, Kazuya Takekuni, Yoshinori Yamada

A special type of shotcrete is used to improve the performance of open-type TBM in difficult situations. The Hakamagoshi and Johana tunnels are expressway evacuation tunnels of 3.2 km and 5.1 km in length, respectively (total 9.1 km) that were excavated by one open-type TBM. The geological conditions at the sites were estimated to be good before excavation. However, 95% of the rock turned out to be two ranking orders worse than the estimated classes. Therefore, we used a special shotcrete for bad rock conditions, and succeeded in excavating the tunnel at an average rate of 270 m/month.

Jan 1, 2001

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 Robert Schnab

ASFINAG is responsible for the construction and operation of the Austrian highway system. It is approx. 2,400 km of highways and 65 tunnels with a total length of 200 km including the Tauern Tunnel. In order to improve the documentation of the tunnel construction, ASFINAG chose to use a state of the art tunnel scanning system to record the various stages of construction: excavation, initial shotcrete lining, smoothing layer and final cast in place concrete lining. The geometric and photogrammetric documentation is provided on a daily basis to all par-ties involved. This innovative concept provides accurate & complete information in real time. The tunnel scanner documentation of the 2nd tube at the 6.4 km long Tauern Tunnel will be presented in this paper as a part of the survey contract.

Minerals contribute to the U.S. gross domestic prod-uct (GDP) at several levels?mining, processing and manufacturing finished products. In 2008, the estimated growth rate for the real GDP of the United States was 1.1 percent and the nominal GDP was about $14.3 trillion (Table 1). Trends in various sectors of the domestic economy are often reflected in mineral production and consumption rates. For instance, continued declines in the U.S. housing market during 2008 were reflected in further reductions in the production and consumption of cement, clays, construction sand and gravel and crushed stone (mineral commodities that are used almost exclusively in construction), and those associated with the related manufacture of goods, such as ceramic tile, heating and air conditioning equipment, paint, plumbing and sanitaryware, roofing, wiring and wallboard ? all used by the housing industry. The widespread effects of the slowing domestic economy became more apparent in the last three to six months of 2008 when prices for many mineral commodities declined sharply after reaching record highs earlier in the year, indicating significantly lower demand for those materials or products containing them.

Jan 1, 2009

Ceremonies for the induction of five mining industry pioneers into the National Mining Hall of Fame will be on Sept. 12, 2009 at the Charles F. Barber Pavilion of the Museum Convention Center in Leadville, CO. The five inductees are: Paul A. Bailey, 82, Richard T. Moolick, 89, William Braden and Alonzo Pawling and Henry Harnischfeger. Paul A. Bailly was president of Bear Creek Mining Co., the U.S. exploration subsidiary of Kennecott Copper, from 1961 to 1967. In 1968, he joined Occidental Petroleum Corp. and was tasked with creating the company?s international mining division, Oxymin, which he led as president through 1983. During his distinguished career, Bailly participated in numerous significant mineral discoveries, developed a new exploration philosophy and made important additions to the mineral exploration literature. William Braden was the first to recognize the immense potential of the El Teniente orebody in Chile. He founded Braden Copper Co. and developed the El Teniente Mine which now, 100 years later, remains the world?s largest underground copper mine. Braden?s endeavor survives to-day as the El Teniente division of the Chilean state copper company, CODELCO. T. (Dick) Moolick established a lasting legacy in the mining industry, first during a 35 year career with Phelps Dodge Corp. and then as the driving force in establishing the National Mining Hall of Fame and Museum in Leadville. The Hall of Fame and Museum ? a monument to the memory of the men and women who pioneered the discovery and development of the United States? natural resources ? has become one of the fi nest museums in the western United States.

Jan 1, 2009

By Yousef Ghorbani, Jafar Abdolahi Sharif, Fatemeh Kazemi, Ataallah Bahrami

Kinetic models are the most important tool for predicting and evaluating the performance of flotation circuits. Gilsonite is a natural fossil resource similar to an oil asphalt, high in asphaltenes. Here, in order to determine the kinetic order and flotation rate of a gilsonite sample, flotation experiments were carried out in both rougher and cleaner stages. Experiments were conducted using the combinations of oil–MIBC and gas oil–pine oil, with one test without collector and frother. Five kinetic models were applied to the data obtained from the flotation tests using MATLAB software. Statistical analysis showed that the results of the experiment with oil–MIBC were highly in compliance with all models. Kinetic constants (k) were calculated as 0.1548 (s−1 ) and 0.0450 (s−1 ) for rougher and cleaner stages, respectively. Rougher and cleaner tests without collector and frother also matched all models well (R2 > 0.98), with k values of 0.2163 (s−1 ) and 0.284 (s−1 ), respectively. The relationship between flotation rate constant, maximum combustible recovery, and particle size showed that the maximum flotation combustible recovery and flotation rate were obtained in the size range of −250 + 106 μm in the rougher and cleaner stages. The combustible recovery and flotation rate were higher in the rougher flotation process than in the cleaner stage.

By Yousef Ghorbani, Jafar Abdolahi Sharif, Fatemeh Kazemi, Ataallah Bahrami

Kinetic models are the most important tool for predicting and evaluating the performance of flotation circuits. Gilsonite is a natural fossil resource similar to an oil asphalt, high in asphaltenes. Here, in order to determine the kinetic order and flotation rate of a gilsonite sample, flotation experiments were carried out in both rougher and cleaner stages. Experiments were conducted using the combinations of oil–MIBC and gas oil–pine oil, with one test without collector and frother. Five kinetic models were applied to the data obtained from the flotation tests using MATLAB software. Statistical analysis showed that the results of the experiment with oil–MIBC were highly in compliance with all models. Kinetic constants (k) were calculated as 0.1548 (s−1 ) and 0.0450 (s−1 ) for rougher and cleaner stages, respectively. Rougher and cleaner tests without collector and frother also matched all models well (R2 > 0.98), with k values of 0.2163 (s−1 ) and 0.284 (s−1 ), respectively. The relationship between flotation rate constant, maximum combustible recovery, and particle size showed that the maximum flotation combustible recovery and flotation rate were obtained in the size range of −250 + 106 μm in the rougher and cleaner stages. The combustible recovery and flotation rate were higher in the rougher flotation process than in the cleaner stage.

By Steve Kral

President Bush’s National Energy Program and his Clear Skies Initiative both emphasize the use of coal to help meet the nation’s growing energy needs. And why not? Coal is currently responsible for more than 50 percent of the nation’s electricity generation. That fact, though, seems to be lost on policy makers, the environmental community and the public. Critics of coal advocate the increased use of renewable energy sources and the increased use of natural gas. Renewables, though, are only capable of generating a tiny fraction of the power required. Natural gas is expensive. And natural gas production cannot keep up with demand, especially given the nation’s increasing energy needs.

Jan 1, 2003

By C. -G. Zhang

This paper presents the results of a study on cellular acclimation of Acidithiobacillus ferrooxidans to sulfur biooxidation in terms of cells growth and changes in surface properties and morphologies of both cells and sulfur particles. The results showed that A. ferrooxidans cells were grown faster and demonstrated higher concentration in the soluble thiosulfate substrate than in nonsoluble hydrophobic S0 substrate. The results showed that A. ferrooxidans cells acclimated to the sulfur biooxidation by actively expressing some extracellular polymers substance and maybe some outer membrane proteins that modified the surface properties of both sulfur particles and the cells themselves. In addition, the results showed that the A. ferrooxidans cells were able to dynamically adsorb to or desorb from the surface of sulfur particles. The cells aggregating onto the S0 surface enhanced the use of S0 substrate by the bacteria cells. This mode may be one of the most important characteristics for the better growth and propagation of the cells in solid sulfur-containing media.

Jan 1, 2009

By Derek. C. Arnold

In order to meet increasing demands for water supply in the next millennium, the Government of the Hong Kong Special Administrative Region have identified the need for a major new water treatment and transfer scheme. The project now under construction will comprise a 1.2 km long raw water aqueduct, a major new 0.25million cubic metres per day water treatment works (with space for upgrading to 1.2Mm³/d), a 12.1 km long treated water aqueduct and a primary service reservoir. In order to meet increasing demands for water supply in the next millennium, the Government of the Hong Kong Special Administrative Region have identified the need for a major new water treatment and transfer scheme. The project now under construction will comprise a 1.2 km long raw water aqueduct, a major new 0.25million cubic metres per day water treatment works (with space for upgrading to 1.2Mm³/d), a 12.1 km long treated water aqueduct and a primary service reservoir.

Jan 1, 1999

By F. D. Ayhan

The aim of this study was to investigate the effects of various water mediums on desulfurization and deashing of a coal sample using flotation. For this purpose, experimental studies were conducted on a coal sample containing high ash and sulfur contents. The effects of pH, solid concentration, collector amount and frother amount on the flotation were investigated separately in Mediterranean Sea water, Çermik thermal spring water, snow water and tap water. Flotation results indicated that, when comparing the various water mediums, the following order for the ash content was obtained: snow water < Çermik thermal spring water < tap water < the Mediterranean Sea water. For the reduction of total sulfur, the following order was obtained: snow water > Çermik thermal spring water > Mediterranean Sea water > tap water. When snow water was used as a flotation medium, it was found that a concentrate containing 3.01% total sulfur and 27.64% ash with a total sulfur reduction of 57.06% was obtained from a feed containing 7.01% total sulfur and 41.17% ash.

Jan 1, 2009

By Steve Kral

Mining is a risky business. The cost of exploring for new mineral deposits is high and the success rate of finding one worthy of development is relatively low. And once a deposit is identified, there is no guarantee that it will become a mine. Mining companies have to spend a lot of time and money on due diligence, prefeasibility and feasibility studies, and sustainable development and environmental issues before deciding whether the deposit will become a profitable mine. And then there are the millions of dollars spent in developing the deposit and building a mine. No wonder the mining industry has trouble attracting investment capital. Companies take a large risk in developing reserves and investors take a similar risk in investing in them. So mining companies must be as accurate as possible in determining mineralization that makes it to reserve status. After all, reserves are a company’s most important asset and one of the critical factors analysts and funding sources look at when determining if a mine or mining company is worth the risk.

Jan 1, 2003

By Wojciech Klecan

Cobb County, located on the northwest side of Atlanta, GA, is continually growing and, like many other metropolitan areas, it needs to increase the capacity of its waste water system to meet future demand. The Cobb County Water System (CCWS) is the responsible agency for water distribution, waste water collection and treatment in most areas of the county. CCWS, one of the most progressive agencies in the metro-Atlanta area, is addressing its future waste water capacity needs in the southern part of the county with the construction of the South Cobb Tunnel and Pump Station. This project consists of an 8.8-km- (5.5-mile-) long, 8.2-m- (27-ft-) diameter, tunnel boring machine (TBM) excavated waste water storage and conveyance tunnel; six tangential vortex-flow intakes ranging from 1,533 to 5,700 L/s (35 to 130 mgd) peak flow capacity, two construction shafts, six 1.8-m (6-ft) finished diameter connecting tunnels ranging in length from 6 to 975 m (20 to 3,200 ft) and a 5,700-L/s (130-mgd) wet/dry pit pump station. The pump station will have a semi-circular wet well with a dividing wall that extends almost to the top of the shaft and a spilt dry well for reliable operation. Roller gates will control the flow to the wet well from the tunnel. The pump station will have six 1,420 L/s (32.5 mgd) pumps and two sets of stair wells and elevators. With a finished diameter of 32 m (104 ft) and a depth of 62 m (204 ft), this is the largest pump station shaft constructed so far in Georgia for the dewatering of a waste water tunnel. The pump station shaft was also the highlight of the well attended and successful 2009 Shaft Design and Construction Short Course held in Atlanta, Sept. 10-11. The two-day course was sponsored by the Underground Construction Association of SME and Pennsylvania State University and concluded with a field trip to the pump station shaft. The tunnel starts south of the city of Austell and finishes at the South Cobb Water Reclamation Facility (WRF), located on the banks of the [ ] Chattahoochee River just north of Interstate 20 (Fig. 1). The South Cobb Tunnel will run 30 to 137 m (100 to 450 ft) below the surface, with an average depth of about 91 m (300 ft), through metamorphic rocks (Fig 2). The construction contract was awarded to Shea-Traylor JV with the lowest bid price of $305 million and notice-to-proceed was given on July 14, 2008. Jordan Jones & Goulding, Inc. (JJG) is the project designer and performed the geotechnical investigations. Parsons/Jacobs Associates is the construction manager. The South Cobb Tunnel is CCWS?s second deep hard rock tunnel. The 15.3-km- (9.5-mile-) long, 5.5-m- (18-ft-) diameter TBM excavated the Chattahoochee Tunnel was the first deep tunnel to be construced in Cobb County. Construction began in 2000 and the project was completed four years later. It is located about 16 km (10 miles) northeast of the South Cobb Tunnel in similar geology. It was designed by JJG to meet east Cobb?s long-term waste water capacity needs and provide flow equalization to the R.L. Sutton WRF. The Chattahoochee Tunnel was named ?Outstanding Civil Engineering Project of the Year? by the Georgia Sec-tion of the American Society of Civil Engineers in 2006.

Jan 1, 2009