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By E. Sarris

Tailings dams are large-scale earth-fill embankments that are designed to contain mining wastes from ore dressing plants. Most commonly tailings dams are constructed in stages in order to keep up with the increasing volume of mine tailings. Staged construction using various methods (like up-stream, down-stream, and centerline) is generally considered as a very effective way to construct this kind of embankments. The present study is devoted to the investigation of the behavior and the stability of these geostructures under static conditions. In order to accomplish this task, elaborate two-dimensional numerical models are examined, utilizing the geotechnical finite-element code PLAXIS. Numerical analyses are conducted for all three types of tailings dams in order to obtain the potential modes of failure, while the corresponding factors of safety are determined by the shear strength reduction technique.

Jan 1, 2005

By S. R. Rao, J. A. Finch, E. El-Ammouri, K. Ngoviky, P. A. Disten

Sludges produced by lime treatment of acid mine drainage (AMD) can contain significant quantities of base metals which represent both a potential hazard and a loss of values. A new technique for metal recovery from sludge is proposed by combining selective acid leaching and adsorption of metal ions by activated silica sol. The process is demonstrated on two AMD sludges, one containing primarily nickel and the second zinc. They were first treated with sulphuric acid (pH 3.5) to selectively leach the target metals and then activated silica sol was added to the leach solution to adsorb the nickel and zinc. Thickening and centrifuging gave about 90 percent rejection of the input volume to effluent. The adsorbed metals were redissolved by strong acid into a concentrated solution relative to the feed and the silica sol was recycled.

Jan 1, 2000

By Osvaldo Bascur

Large metallurgical complexes have more data than a small city and much of it is "real time," changing rapidly as internal and external conditions evolve. As corporations buy and sell assets and reengineer their staff, the structures and tools that were used to understand these data are lost. This results in significant deterioration in the ability to maintain a "smart" operation. The solution is to use the sophisticated new tools built for the Internet so as to leverage information in a familiar browser format that people can use and understand. This paper describes the use of Internet technologies with plant data. Examples are drawn from existing industrial sites. Users must project where this technology will lead - standing still is the most dangerous philosophy and the only one guaranteed to be obsolete. These examples show the way to leverage existing workers with information technology.

Jan 1, 2000

By S. P. Fleming

An acid mine drainage sludge containing 0.26% nickel, 0.21 % cobalt and 4.5% manganese was leached in a one-liter reactor with sulfuric acid in the absence and presence of sodium sulfite. The effects of temperature (25°C and 52°C) and sodium sulfite concentration (up to 0.03 molar) on the leaching rate were particularly investigated. The leaching rates of nickel and cobalt with sulfuric acid have been determined to be controlled by diffusion through product layer. It has been found that effective leaching conditions to give more than 90% extraction of nickel, cobalt and manganese while keeping the iron extraction below 10% come with an elevated temperature and a low sodium sulfite concentration at pH 3; for example, 52°C and 0.01 molar sodium sulfite.

Jan 1, 1992

By Sara J. Heinlein, George Malkos, James E. Lindell, Tony Pestonatto

The 79th Street Water Tunnel Extension Project was initially designed by the City of Chicago, Department of Public Works, to increase the capacity of the City’s south side water distribution system. MWH preformed a design review, prepared the final design and provided construction management for the City of Chicago Department of Water. Construction commenced in September 1995 and was completed in October 1999. The Project connected two existing water tunnels with a new 5.8 km (19,044 ft.) long, 4.9 m (16.08 ft.) finished diameter concrete lined rock tunnel utilizing TBM, drill-blast and mechanical hoe-ramming methods. In addition, approximately 61 meters(200 feet) of concrete lined variable cross section tunnel, a new gate shaft and a temporary construction shaft were constructed. This paper describes the construction of these features and the geological conditions encountered.

Jan 1, 2003

By Thomas A. Simpson

Hydrogeological techniques were used to solve problems of slope stability in open-pit mines of the Eufaula bauxite district, Alabama. Geologic and hydrologic data were evaluated and used to design a system of dewatering wells to enable the operators to mine bauxite more efficiently and economically. Walls of open-pit mines in the district were subsequently stabilized by the operation of the dewatering system. Three open-pit mines, each at varying stages of the mining process, of the A. P. Green Refractories Company, were used to develop a sequential series of guidelines that indicate how to effectively remove ground water from the formations surrounding the ore bodies in the district. The use of sound engineering principles in well design, in combination with the correct interpretation of the pit hydrology provided the basis for solutions of the slope- stabilization problem aided in the economical removal of bauxite from mines of the district.

Jan 1, 1975

By Gary Repetto

Hiring trends in the construction materials industry have remained steady through the years, with some seasonal and geographical variances. However, after several years of a depressed market, the base metals industry has begun to actively hire only over the past two years, due to the continued strength in the prices of copper, lead, zinc, molybenum, etc. The expanding precious metals industry, which for the most part escaped the depressed markets of the mid-1980s, actually preceded the base metal companies in hiring of engineers and operations personnel. The coal industry has not seemed to rebound much from the cutbacks of the early 1980s. And the uranium industry, which began its decline a year or two earlier than the other mineral industries, has remained nearly nonexistent in the United States. In nearly all of the mineral industries, new hires have been mostly in the engineering and operations areas, not exploration.

Jan 1, 1990

By Greg T. Saretzky, Wilson G. Ward

A comprehensive hydrologic study was completed far the waste rock dump at Equity Silver Mine, BC. Characterization of the hydrologic system included geologic structure. topography, surface hydrology and groundwater systems. The results of the study conclude that the cover system is restricting net infiltration to approximately 5%. However, significant discharge continues to occur from the perimeter of the dump. A three dimensional seepage analysis was carried out to illustrate the influence of groundwater discharge associated with the regional topography and geologic structures. The results of the modelling program show that groundwater discharge occurs from the waste rock dumps when high recharge rates are specified for the surrounding topography- This groundwater discharge strongly influenced by the high hydraulic conductivity assumed far the fractured bedrock. The modelling results are considered preliminary and field drilling and piezometer installation is being conducted to determine the groundwater regime in the vicinity of the waste rock dump.

Jan 1, 2000

By Duk-Won Park

Ground water has been a problem in underground mines (Anon., 1981; Aughenbough, 1973; Stansbury, 1981). Water migrates from water-bearing formations and surface water bodies such as lakes, ponds or creeks into the underground workings through fractures and cracks. As a result, under- ground workings become plagued with the necessity of having the water pumped out in large quantities. Underground workings become flooded when unexpected amounts of water flow into the openings, especially when mines use pillar extraction or longwall mining methods. It is difficult to detect water bodies above the coal mine roof before water problems take place. The resistivity method was used as a method for detecting water saturated rock layers and bodies of water above the roof of a coal mine in northern West Virginia, where the multiple seam mining method was being used.

Jan 1, 1983

By Norbert Steiner, Roy Norcross

For the desulfurization of weak SO2 gas streams, Degussa developed a process using dilute H2SO4 solution containing H2O2 instead of conventional gas scrubbing with all solid absorbent medium (limestone, MgO). The process is based on fast reaction of H2O2 with SO2 yielding H2SO4 up to 70% strength, depending on off-gas tem­perature. Compared to the conventional systems with typically < 95% efficiency, independent on the raw gas SO2 concentra­tion, residual SO2 concentrations of less than 20 mg!Nm3 can be easily achieved, corresponding to nearly 100% removal. These features render the H2O2 process a very attractive, low capital cost technology to retrofit existing conventional desulfurization plants.

Jan 1, 1996

By R. J. Matetic, Peter G. Kovalchik, Jeffrey Shawn Peterson

The National Institute for Occupational Safety and Health (NIOSH) has initiated a study of a roof bolter to reduce noise exposure to mine roof bolter operators. An important segment of this research entails determining the affect of various drilling configurations on the performance (penetration rate) and sound power emissions when drilling into granite. Test conditions included various combinations of rotational speeds and thrusts; hex and round drill steels of one inch (1.) and one and three-eighths inch (1 3/8.) diameters; vacuum and wet conditions; and using drill media of differing compressive strengths. This paper will detail the affects of each of these on the performance and sound power level emission. When drilling into granite, it was found that wet drilling generated lower sound power levels and performed better than vacuum drilling.

Jan 1, 2005

By E. J. Peuraniemi, J. T. Yli-Penttilä, A. Jokilaakso, K. M. Riihilahti

Dust formation and the reaction mechanisms of copper matte particles were investigated in simulated flash-oxidation conditions. The granulated and ground matte consisted of 72% Cu, 4% Fe and 21 % S (by weight). Experiments were conducted by using a laminar flow furnace with a reaction-gas composition ranging from 20% to 75% O2 (by volume) in nitrogen. The particle feeding was carried out by a single-particle method, and samples were quenched after a specified reaction time ([~] 0.05 to 0.4 s) in a cold water film. Experimental temperatures ranged from 800o to 1,300o C. Chemical analysis was used to determine the degree of oxidation, and optical and scanning electron microscopes, combined with energy dispersive analysis, were used for characterization of the reacted particles.

Jan 1, 1999

By Paul Zick

The Port Authority of Allegheny County North Shore Connector (NSC) Project involves TBM excavation of twin 690 m (2,240 lf) precast segment lined light rail tunnels through soil and rock under the Allegheny River and a narrow, downtown city street. The $435 M project is funded 80% ($348 M) by the Federal Government, 17% ($72.5 M) by the State of Pennsylvania and 3% ($14.5 M) by Allegheny County. Along the tunnel alignment are a historic building on shallow foundations, modern buildings on deep foundations, and one building constructed directly over the alignment. The project includes construction of twin 369 m (1200 lf) cut and cover concrete box tunnels and an underground station shell. This paper provides an overview of general site conditions, current project status and construction challenges for the Twin Tunnels and North Shore Light Rail Station.

By T. H. Eyde

Worldwide production of natural zeolites during 2001 was estimated to be about 3.5 Mt (3.85million st). Construction and agriculture continued to be the major consumers. Estimated production in North America during 2001, including the United States, Canada and Mexico, was about 40 kt (44,000 st). In the United States and Canada, the zeolitic tuffs are ground, extruded or modified for use as adsorbents, desiccants, ion-exchange media and carriers. In Mexico and the rest of the world, the zeolitic tuffs are cut into dimension stone that is used in construction. Zeolitic tuffs are usually composed of the minerals clinoptilolite, mordenite or both. They occur in a variety of colors and are easy to cut and shape. And they have low thermal conductivity. This construction application is classified with dimension stone rather than with chemical and agricultural uses.

Jan 1, 2002

By D. C. Hogeman

Growing Greener is the single largest investment of state funds in Pennsylvania’s history, allocated to address the Commonwealth’s critical environmental concerns. Signed into law by Governor Tom Ridge on December 15, 1999, Growing Greener will enable the Department of Environmental Protection (DEP) to appropriate nearly $240 million over five years, to watershed restoration and protection, abandoned mine reclamation, and oil and gas well plugging projects. DEP has utilized these allocations in some remarkably innovative ways, as it: involves the cooperation of several state agencies, local governments, and grassroots organizations to address environmental concerns of the Commonwealth, provides funds directly to watershed groups based on locally determined decisions for local watersheds and offers a user friendly process. In three years, over $130 million in watershed restoration and improvement projects have been initiated.

Jan 1, 2002

By A. K. Sheik, W. G. Pariseau

A small underground mine in northern Idaho was used as an experimental facility for studying the role of water in the analysis of mine opening stability. Laboratory test data, borehole measurements and geological mapping assisted in constructing a coupled finite element model of the rock mass. The model was used to make quantitative estimates of: 1) rock stress, strain and displacement changes, and 2) water pressure and flow velocity changes that occurred during historical mining. Stope cuts and wet fills were included in the analysis. Stability of crown pillars between stopes was of particular interest. The relatively low effective stress and high rock mass strength showed that water pressure changes were of no great consequence in agreement with experience. The computational tools used in the analysis may be applied to other wet mines with appropriate changes to site-specific input data.

Jan 1, 1999

By D. W. Boening

Xanthate salts have demonstrated effectiveness as a flotation reagent in the recovery of heavy metals from mining wastewater. However, due to their strong ionic potentials, they are generally toxic to aquatic life. Under ambient environmental conditions, the half¬life of a xanthate is approximately four days. As a soluble salt, xanthates will complex with the metallic ions contained in water and fish. Some researchers have proposed that this complexing may extend the halflife, as well as optimizing the transfer of a given metal from solution across the gill surface. Leakage of xanthate treated wastewater into the surrounding surface waters is the most common route of exposure for aquatic plants, invertebrates and fish. Because this is an emerging mineral-recovery technology, more information is needed regarding xanthate toxicity and environmental fate before environmental impacts can be assessed with any degree of certainty.

Jan 1, 1999

By D. D. Banerjee, S. K. Kawatra, T. C. Eisele

A high calcium fluidized-bed combustor ash was shown to be an effective binder for iron ore pellets at dosages of 1 % to 2% of the magnetite concentrate weight. Magnetite pellets that were between 1.1 and 12.7 mm (7/16 and 1/2 in.) in diameter were produced with dry crushing strengths greater than 22.3 N (5.0 lb-force) per pellet, which is comparable to the results produced using conventional bentonite binder. The effectiveness of fly-ash-based binders was considerably improved when calcium chloride was added as an accelerator. The addition of calcium chloride at a rate of 0.1 % to 0.2 % of the total powder weight increased the strength of the dried pellets by as much as 22 % compared to the strength of pellets made using fly-ash without accelerators.

Jan 1, 1999

By J. S. Anderson

Size reduction models of cone and impact crushers have been developed using Whiten&apos;s generic computational structure for the description of crushers. They incorporate a laboratory single particle breakage test and the t-family of curves to describe the breakage behaviour of the feed ore. A quantitative model of 7-foot cone crushers has been developed, based on surveys of Svedala (Kobe) and Nordberg machines. Survey data on a Canica vertical shaft impact machine have been used to validate the impact crusher model. Given the crusher operating conditions, such as tonnage, feed size, set and liner condition, or rotor speed and radius, plus breakage information on the feed, the models provide good predictions of product size distribution, and appear to be robust over a wide range of conditions. They are incorporated in commercially available computer simulation packages.

Jan 1, 1998

By John A. L. Campbell

Surface dependent processes, such as froth flotation and flocculation, are important or potentially important techniques for combating some of the current major problems in coal preparation. In order to correctly apply or imporve a surface dependent process, it is of paramount importance to understand the interfacial phenomenon, especially the double layer properties, exhibited by the solid. The specific objective of this research was to determine the properties of the bituminous coal/liquid interface by an electrokinetic method, streaming potential, and to relate the findings, wherever possible, to the existing unit operations of froth flotation and flocculation. The electrokinetic properties of both the whole coal and its lithotypes were investigated. As part of the total investigation, the role played in the double layer by the reagents commonly employed in the surface dependent process was also established (1). These data will be presented at a latter date.

Jan 1, 1969