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By James Withers, Dongbo An, Jinhong Zhang

A micro-scale investigation was carried out by applying atomic force microscopy (AFM) to study in situ the adsorption of various collectors, i.e., oleic acid, octanohydroxamic acid (HA), and salicylhydroxamic acid (SHA), on bastnaesite in aqueous solutions. The obtained AFM images show that the surface morphology of bastnaesite changes greatly after it comes into contact with the solutions of the collectors, suggesting that all these collectors can effectively adsorb onto bastnaesite. Increasing temperature can facilitate the adsorption of oleic acid onto bastnaesite. Results from attenuated total reflectance–Fourier transform infrared spectrometry (ATR-FTIR) also show that all of these collectors adsorb strongly onto bastnaesite, with strong absorbance spectra being detected. The ATR-FTIR results confirm those obtained by AFM. In general, hydroxamic acid collectors (HA and SHA) adsorb onto bastnaesite mainly in the form of insoluble metal hydroxamate. This specific adsorption mechanism explains that a high selectivity with a moderate collectivity will be achieved with a hydroxamic acid collector for the flotation of bastnaesite.

By James Withers, Dongbo An, Jinhong Zhang

A micro-scale investigation was carried out by applying atomic force microscopy (AFM) to study in situ the adsorption of various collectors, i.e., oleic acid, octanohydroxamic acid (HA), and salicylhydroxamic acid (SHA), on bastnaesite in aqueous solutions. The obtained AFM images show that the surface morphology of bastnaesite changes greatly after it comes into contact with the solutions of the collectors, suggesting that all these collectors can effectively adsorb onto bastnaesite. Increasing temperature can facilitate the adsorption of oleic acid onto bastnaesite. Results from attenuated total reflectance–Fourier transform infrared spectrometry (ATR-FTIR) also show that all of these collectors adsorb strongly onto bastnaesite, with strong absorbance spectra being detected. The ATR-FTIR results confirm those obtained by AFM. In general, hydroxamic acid collectors (HA and SHA) adsorb onto bastnaesite mainly in the form of insoluble metal hydroxamate. This specific adsorption mechanism explains that a high selectivity with a moderate collectivity will be achieved with a hydroxamic acid collector for the flotation of bastnaesite.

By R. W. Fedors, S. T. Green, R. A. Hart, D. B. Walter

Computational fluid dynamic (CFD) modeling of a potential nuclear waste repository drift may be an important tool to estimate moisture redistribution caused by natural convection within the drift. To refine and support CFD techniques, a small laboratory cold-trap experiment was developed. Results from numerical modeling of the laboratory experiment show the sensitivity of the bulk air flow rate and average air temperature within the drift to several key parameters, including various boundary condition assumptions and surrounding porous media properties.

Jan 1, 2004

By Bruce Geller

Attending the Prospectors and Developers Association of Canada (PDAC) meeting and exhibit has become an annual tradition for many in the mining industry. Similar to last year’s synopsis, this report is an overview of the 2003 conference from the eyes of a consulting mineralogist. It is supplemented by conversations with other participants. And it examines the conference handouts. Certain segments of the mining industry have seen improvement throughout the year in terms of metal prices, stronger demand and renewed interest by the investment community. Other segments continue their decline due to depressed commodity prices, higher oil prices, a continued weakness in the global economy and war uncertainties. SARS was known to the world, but it was not a Toronto epidemic during PDAC. In short, this year’s PDAC was permeated by an air of anxiety about the Middle East.

Jan 1, 2003

By P. Dhar, H. R. Kota, M. Thornhill

Precipitated calcium carbonate is used as a filler and coating material in the manufacturing of paper because of its high brightness and light scattering characteristics. However, beneficiated calcite has similar potential, given the fact that the industrial specifications are already achieved. For paper industries, the requirement is that the desired product should be pure and have a brightness of 93 to 95 percent. A very-high-grade calcite deposit of around 92 percent is located in the north of Norway, which is used as the raw material for ground calcium carbonate (GCC) feed for the paper industries. There is a substantial amount of calcite resource, which has pyrite and pyrrhotite as major impurities. These sulfides, even when present in minor concentrations, impart color to the end product (paper). Removing these minerals is estimated to increase utilization of the deposit by 10  percent, which represents several million tonnes of calcite marble. Due to the requirement for environmentally friendly reagents and chemicals by the mineral industry, fatty di-amines are being tested for pyrite and pyrrhotite flotation. The interaction mechanism of diamine with the main components of the ore were studied and optimum conditions for removal of sulfide impurities are outlined.

The National Institute for Occupational Safety and Health conducted laboratory and field tests to evaluate the effectiveness of dust collector bags for reducing dust liberation and operator exposure from a roof bolter?s dust collection system. The laboratory tests evaluated the bag?s effectiveness to contain dust and the effect on canister filter loading in both a bag and bagless condition. The dust emissions from the collector?s exhaust were also measured in each condition during laboratory testing. Laboratory results show that nearly 100 percent of the test dust fed into the collector was captured by the dust bags. Loading and pressure drop on the dust collector?s canister filter is greatly decreased when using the bags, enabling longer periods of drilling without filter removal/cleaning. The field results showed that, even though dust standards were met, respirable dust in exhausted emissions was reduced around the bolter. Laboratory and field results show that benefits from use of the bags are realized in all areas of operator exposure.

Jan 1, 2008

By Joseph J. Feiler

Historical mining operations in Colorado and other western states have resulted in thousands of remnant mine openings. Many are sources of metals loading and acid water generation in surface and ground waters. It is estimated that more than 965 km (600 miles) of streams in Colorado have been impacted by past mining activities. The Animas River watershed in southwestern Colorado is one of the most heavily affected areas in the state. Abandoned mine features pose significant safety hazards to those who enter them. These hazards can include bad air, unstable rock or falls into open shafts, stopes and winzes. Backcountry skiers and snowmobile enthusiasts are particularly vulnerable to falls into snow covered mine openings.

Jan 1, 2006

By D. Rutledge

Discrete (digital) signal processing techniques are proving to be very valuable tools for miners using the block cave method. Waveform analysis of different measured signals associated with active mining provides valuable information on production dynamics and safe operation of the mine. For example, correlation of the three-dimensional surface displacement velocity waveform and the production output waveform reveals a remarkably predictable time-varying physical process. In this paper, the authors discuss the signal processing techniques used to study these relationships, as well as the related implications for mining.

Jan 1, 2008

By None None

Life as a mining/mineral professional doesn’t leave much time for perusing 20-page technical papers. Yet, being technologically savvy is part and parcel of a successful career in this industry. What’s an intelligent, well-informed person to do?

By J. W. Hawkins, K. B. C. Brady, M. W. Smith

The Pennsylvania Department of Environmental Protection (PaDEP) has been issuing surface mining permits since 1984 that authorize remining in areas that will affect preexisting pollutional discharges. These permits require the mine operator to employ best management practices to reduce pollution loading from abandoned mine discharges. A total of 110 completed mining operations with 233 discharges were evaluated to determine the impact to water quality. Overall, acid loading from these discharges was reduced by 7,200 kg (15,900 lbs) per day or 61%. Metals loadings were also reduced. For acidity, 49% of discharges improved or were eliminated, 52% showed no significant change, and fewer than 1% got worse. Loading reductions resulted from a combination of reduced concentrations and lower flows.

Jan 1, 2002

In 2005, CANMET-MMSL used its pool of expertise in ground control, open pit and underground mine engineering, mineral processing, information technology and applied mineralogy to launch a mine-to-mill research project. The objective of the project was to optimize the distribution of rock breakage energy among blasting, crushing and grinding activities, thereby maximizing the efficiency of energy utilization within comminution processes. Tests were designed to demonstrate that this approach could reduce energy consumption, thus contributing to the reduction of green house gas (GHG) production in the Canadian mining industry. The project was accomplished in collaboration with DynoConsult and Dyno Nobel Canada Inc., a world leader in commercial explosives. Data analysis from 12 blasts (six with electronic and six with pyrotechnic detonators) in three different geological formations of a quarry (soft, medium and hard rock) shows that electronic blasting technology increases rock fragmentation by 15% (in hard rock) to 20% (in soft rock). A more uniform rock fragment size distribution is also obtained. The impact of the improved quality blast product on downstream processes of the quarry is a productivity increase of 5% in rock excavation and transportation, an energy reduction of 10% at the primary crusher and an increase of 15% of the primary crusher throughput. Extended to the Canadian mining industry, such results would represent a GHG emission reduction of about 0.05 Mt/y. A soft-sensor prototype, based on primary crusher data (i.e., energy consumption, throughput, feed and product size distribution) and a simplified computerized process model, was developed for on-line measurement of the rock operating work index. Additionally, 385 rock samples and specimens were collected and prepared to determine the tensile and compressive strength of the rock material, to evaluate the aggregate crushing work index and to examine the development of micro- and macro-fractures by means of binocular and SEM microscopy. Blast-induced rock damage was evaluated at the end of the laboratory-testing program. Even though a reduction of rock hardness of around 30% was observed after blasting, the impact of the blasting method (i.e., use of electronic or pyrotechnic detonators) on the induced rock damage could not be observed. It is either absent or not perceptible with the accuracy of the measuring techniques and the number of samples analyzed.

Jan 1, 2008

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

By Stig Eriksson

In Switzerland two major railway systems as shown below in Figure 1 has recently been completed or is under construction: ¦Lötschberg, south of Bern which was commissioned in 2007 ¦Gotthard, south of Zurich which is scheduled to be commissioned in 2016The aim is to increase the transport capacity of the railway system and to transfer more transport of goods to the railway by offering transport of trailers and lorries on the new railway systems. It will have a positive environmental impact but also improve the congested traffic situation of the highways in north-south directionThe Gotthard tunnel is totally 57 km (35 mile) long and the Lötschberg tunnel is 35 km (22 mile) long. Both tunnel systems consist of two parallel single track tunnels connected with cross tunnels at every 333 m (1 093 ft). Additionally there are cross-over tunnels and caverns for installations and operation. In the Lötschberg tunnel, the majority of the excavation has been by Drill & Blast and in Gotthard tunnel the major part is being excavated by TBM.

By A. R. Biggart, A. Walters, G. J. E. Kramer

The Owner Procurement Process or OPP is a proven, viable alternative contract delivery method that is potentially applicable to many tunnel projects. Using the OPP, the owner specifies and procures major tunnel construction items such as tunnel boring machines and tunnel linings and provides them to a tunnel excavation contractor in order to manage risk and accelerate project schedule. However, due to industry perceptions regarding potential owner risk, it is seldom considered or is rejected out of hand. In fact, past performance demonstrates that the process significantly minimizes owner, contractor and over-all project risk and mitigates the impact of any claims and differing site conditions. The paper outlines how the process should be structured to achieve schedule, cost, quality and risk management benefits. Potential and perceived disadvantages are discussed and how the process can be structured to mitigate or avoid them. The planned implementation of this process on the tunnels for the Silicon Valley Rapid Transit Project in San Jose, California is discussed.

Jan 1, 2005

By B. A. Ridolfi, S. M. Alvarez

The Moon Creek Reclamation Project provides a case study in the development of creative cleanup solutions for an abandoned lead and zinc mine and mill site located in northern Idaho. Innovative design features include construction of a 88,000cubic yard combined waste containment facility on soft in-situ tailings, water-balance cap, limestone gravel drains, a geocell mattress for stability, and a below-grade scour protection berm. The stream, including a wetlands buffer, will be relocated within an existing road alignment and rehabilitated to provide trout habitat. These elements allow for the integration of reclamation and stabilization measures into an effective site design.

Jan 1, 1999

By William R. Yernberg

Santa Fe Pacific Gold, headquartered in Albuquerque, NM is expanding its operation at the Twin Creeks Mine in Nevada. The $250-million sulfide expansion project, including the Sage Mill, is under construction and is 80% complete. Also, additional mining equipment has been purchased to haul the sulfide ore to the mill. With the expansion, employment at Twin Creeks is expected to reach approximately 970 people by the end of 1996. Santa Fe Pacific Gold now owns and operates three gold mines in the United States and is involved in several other gold projects. The three currently operating mines are the Twin Creeks, Mesquite and Lone Tree mines. The Mesquite Mine is located in California’s Imperial Valley. Lone Tree is located 55 km (34 miles) southeast of Winnemucca, NV. The company’s total gold production from these operations is expected to be in the range of 26.3 to 26.6 t (845,000 to 855,000 oz) in 1996. This compares to a total production of about 124 kg (4,000 oz) for the company in 1989. Production costs range from $6.90to $7.25/g ($215 to $225/oz). At the end of 1995, the company reported proven and probable reserves of 556.7 t(17.9 million oz) of gold.

Jan 1, 1996

By B. J. Dave, Ashok J. Desai, Allen J. Hulshizer

This paper presents various design and construction considerations involved in developing an underwater installation of lined, large diameter shafts not known to have been previously accomplished for the diameter size, depth or ground conditions identified with the Seabrook Power Station. Outlined approach provides for driving tunnels independent of shaft sinking operation, permits the use of prefabricated shaft lining and incorporates a safe dry tap method for connecting the shafts to the tunnels. INTRODUCTION The Seabrook Power Station, located two miles inland from the Atlantic Ocean, at Seabrook, New Hampshire, is a two unit, nuclear powered, electric generating plant, each unit having a capacity of 1150 megawatts (electric). Typical to all steam driven generators is the requirement for large quantities of water. Requirements for the Seabrook Plant will be met by intaking and discharging approximately 850,000 gpm of ocean water at a considerable distance from the shore line in water depths that render the environmental impact inconsequential. Obtaining, conveying and discharging such large quantities of water represents a major undertaking, particularly under today's environmental controls. Tunnels are well suited to reducing the environmental impact at the Seabrook site by conveying the water about 250 feet deep under the salt marsh (a valuable ecological feature) and under the beach well out into the ocean without any noticeable ground surface disturbance. An alternate approach utilizing trenched piping would have created some disturbances and was environmentally less desirable. The tunnels connect to intake and discharge

Jan 1, 1976

The safety of personnel is the most important matter during a mine fire. However, there is not enough research on a case when a fire occurs near a shaft and the behavior of the fire gas is not well understood. Therefore, a series of experimental study using a scaled ventilation circuit model was carried out. The behavior of ventilation air during a mine fire near a shaft was investigated. The model consists of two vertical shafts, three horizontal ducts connecting the shafts and an exhaust fan from the shaft bottom. The cross section of the shaft and duct is a square of 200×200mm. The height of the shafts is 3400mm. The length of the ducts is 1540mm. The lower duct is set at the same level as the shaft bottom. The middle and upper duct are set at 750mm and 1760mm above the shaft bottom respectively. The airflow rates through the ducts can be adjusted by regulators installed in each duct. The behavior of the fire gas was measured by anemometer, thermometer, and visualized using laser light .The air was ventilated downward in both shafts before the initiation of the fire. Some amount of fire gas of high temperature rose upward gradually along the shaft wall regardless of the downward ventilation after the initiation of the fire. Then the direction of main ventilation air suddenly reversed upward in the shaft. The direction of ventilation reversed in many places in the model and the fire gas reached even the part not anticipated.

Jan 1, 2009

By X. Zhou

In this study, the cyclonic static microbubble flotation column (FCSMC) was investigated for fluorite beneficiation. The structure and principle of the specially designed column are described. Fluorite samples from the tungsten separation tailings of the Shizhuyuan Mine, Chenzhou, Hunan Province, P.R. China, were tested using a small-scale continuous flotation test unit, and concentrates with a fluorite grade higher than 98% were obtained. One rougher and three cleaner stages in the FCSMC achieved the same separation performance as one rougher and eight cleaners in conventional flotation cells. This greatly simplified the flotation circuit and reduced operating costs.

Jan 1, 2007

By Andrew E. Nevin

The government of India convened a precedent-setting meeting in New Delhi on Nov. 12, 2001.The meeting brought together regulators and the mining industry in an attempt to fix the industry’s mine development problems in that country. More than 150people attended the all-day session. Ram Vilas Paswan, Minister of Coal and Mines, chaired the meeting. Ravi Shankar Prasad, Minister of State for Coal and Mines, was also present. The secretary of the Department of Mines and the Joint Secretaries and Additional Secretary also participated. The Department of Mines’ mandate is for economic growth: to get new mine development going and to make investment in mining attractive for both domestic and foreign-owned companies.

Jan 1, 2002