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By Richard Louis Viner, William D. Leech, Walter A. Mergelsberg

With the construction management team established and a full funding agreement secured the Washington Metropolitan Area Transit Authority (WMATA) now has the manpower and the financial resources to continue Metrorail construction into the 1990's. This paper describes WMATA's new role as construction manager after the transition from Bechtel Associates and gaining the full funding agreement with the Urban Mass Transit Administration (UMTA) and regional governments to complete 84.7 Metrorail miles (136km). The authors review the most recent station and line tunneling projects. WMATA's contractors have employed the state of the art soft ground and hard rock tunneling equipment and methods - an earth pressure balance TBM, a closed face TBM, and the New Austrian Tunneling Method (NATM). In final, the paper previews future underground work to be let under the funding agreement.

Jan 1, 1987

By U. F. Beichmann

INTRODUCTION The City of Oslo together with the neighbor municipalities, Baerum and Asker, are presently building a jointly owned sewage treatment plant located on the west side of the inner Oslofjord. The project is scheduled for completion late 1981. Because the location of the treatment plant is at a distance of about 20 miles (30 km) from the city center, a discharge of more than 13 yds 3/sec (10 m3/sec.) of sewage and storm water will have to be transported over considerable distances. The topography of the area and the geological conditions early indicated that the only realistic transport method had to be through tunnels. As planning proceeded, full face tunnel boring emerged more and more as a favorable alternative to conventional drill and blast medhods. Today the scheme comprises nearly 25 miles (40 km) of tunnels being excavated by full face tunnel borers. In addition a number of access tunnels and cross cuts are to be excavated by conventional methods.

Jan 1, 1979

By Jorma Miettunen, Reijo Kalapudas, Pertti Koivistoinen

A new method for measuring the mill filling was developed by Outokumpu’s Pyhäsalmi concentrator during 1989-90. The method utilizes the power draw oscillation which is caused by the mill lifters. Each lifter bar causes a peak in the power draw and thus a continuous oscillation results. In a fixed time scale, the oscillation peaks will shift as the lifter bare hit the mill charge sooner or later depending on the volumetric filling of the mill. Thus the measuring method is based on the phase shift of the power oscillation. So far the measurement is utilized for maximizing throughput of the primary mills at Pyhäsalmi and Enonkoski concentrators and at Harjavalta slag concentrator. The paper describes the new method and the results achieved.

Jan 1, 1992

By J. W. Merks

Spreadsheet software is an effective tool for simulating dynamic stochastic systems such as mineral processing plants. The two-product formula is used to show how to set up a Monte Carlo simulation in a spreadsheet template and how to calculate variances of dependent variables. The key to a reliable and realistic simulation model is to obtain unbiased estimates for all independent variables and variances in the set that defines the stochastic system. Monte Carlo simulation is also a powerful tool for optimizing sampling procedures, for applying sensitivity analysis and for designing and evaluating experiments.

Jan 1, 2000

By N. K. Davé

Water quality impacts of shallow water submersion of partially weathered and oxidized waste rock containing reactive sulphide minerals were investigated in laboratory column lysimeter studies. The waste rock investigated was highly reactive, contained oxidation reaction products from previous exposure and weathering, and had a low sulphur content of approximately 2 % S, mostly as pyrite. The submerged waste rock, though previously weathered, had high oxygen consumption, resulting in rapid depletion of dissolved oxygen in its pore water, within a shallow depth of ~2?5 cm from the surface. The surface and pore water qualities of the submerged waste rock were significantly impacted by the dissolution and release of previous-oxidation-reaction products, which contributed to their rapid acidification and having increased concentrations of dissolved SO4, Fe total and other metals: Al, Mn, Ca, Cu, Ni, Zn and Pb. Despite the high porosity and permeability of the waste rock, the diffusion controlled mass transfer from the submerged waste rock to the overlying water cover was relatively low for most ionic species. Additional surface oxidation of the sub-merged, partially weathered waste rock was on-going, but its impact on the overall surface water quality was low and masked by the dissolution and release of previous oxidation reaction products to both surface and pore water regimes.

Jan 1, 2006

By Patrick J. Doig

The NS9 Drop Shaft contract formed part of the Waste Pollution Abatement Program (WPAP) conducted by the Milwaukee Metropolitan Sewerage District (MMSD). The contract involved the construction of two shafts, a deaeration chamber and connecting tunnel, and ancillary facilities. Portions of the construction were located in saturated overburden where dewatering was prohibited. Ground freezing was utilized for temporary support of the excavation. This paper concentrates on the freezing system and the excavation of frozen ground, with particular emphasis on the use of mechanical cutting equipment, including a raiseborer and a roadheader.

Jan 1, 1991

By Indranil Roy

Gua supergene enriched iron ore deposit from Jharkhand, India has been geostatistically modeled. Population modeling shows a negatively skewed 3-parameter log-normal fit for Fe and positively skewed 3-parameter log-normal fit for Al2O3 and SO2. Semi-variographic studies for Fe indicate spherical function fit using point kriging cross-validation technique with Co=4.06(%)2, C5.11 (%)2, Co+C=9.1 7(%)2 and 'a'=348m. Kriging with 50mx50mx 10m block size at 740mRL led to a global mean kriged estimate of 61.98% and kriging variance of 4.04(%)2 for Fe with central 90% geostatistical confidence limits at 61.39% and 62.24% for that level. This led to an ore inventory at 740mRL as 7.29 million tonnes of ore.

Jan 1, 2002

By Ron Robinson, Trevor Harrison

The planning, installation and commissioning of the first scheme of controlled recirculation of air flow in a section of coal mine in Great Britain is described, together with the proposals for a second installation. The work updates a previous paper (Robinson and Harrison, l986) on the subject. The special problems of ventilating the increasingly distant faces of the undersea mines in the North East Area of the British Coal Corporation are discussed and the alternative solutions stated. The advantages of using a system of controlled recirculation of air are proposed together with the safety features considered necessary. Design and installation details of the recirculation fans and a new booster fan are described.

Jan 1, 1987

By Regina N. Tempel, Laurie S. Balistrieri, Lisa L. Stillings, Lisa A. Shevenell, Maggy F. Lengke

Dexter pit lake, within the townsite of Tuscarora, Nevada, has been in existence since 1990 and provides a natural laboratory for the study of cycles of trace elements associated with ore deposits (e.g. As, Cu, Pb, and Se). Our goal in this study is to develop and calibrate methods of geochemical modeling that may be applied to estimating the concentrations and fluxes of trace elements in pit lake systems. Our initial modeling work considers limnology, hydrology, wall rock mineralogy and geochemistry, benthic fluxes, and colloid composition. Results from our work may be useful in evaluating water quality in the arid West.

Jan 1, 2000

By A. T. Yu

Two key components make up the core of a rapid excavation operation. They are: the breaking up of the rock and its removal. Owing to the complexity inherent in mechanical rock-breaking and the relative infancy of the art, for a number of years the first of these two components has received virtually undivided attention from the industry. Only recently has some concern been expressed about the technology and the economics of the much ignored second component: muck removal. As the continuous boring machine's percentage downtime continues to trend lower in the future, the need for adequate and more effective materials handling systems in rapid excavation will become increasingly more acute. (1) Recognition of the need for a broader and more far-sighted approach to our problem has been eloquently underscored in the conclusions of the Committee on Rapid Excavation sponsored by the National Research Council: "Ultimate attainment of the desired cost and speed improvements is significantly dependent on recognition of the excavation process as a system whose subsystems are critically inter-related. Substantial amounts of full-scale field testing of integrated driving, muck removal, and support subsystems are required." (2)

Jan 1, 1997

By J. E. Murphy, L. A. Walters, F. H. Nehl, G. B. Atkinson

The US Bureau of Mines investigated the selective electrowinning of Ag and Au from cyanide solutions contaminated with Cu with the goal of decreasing the amount of Cu codeposited. Decreasing Cu codeposited will reduce refinery costs. Direct current was applied to the cell in pulsed and square wave voltages at 0.7 A h/150 mL of solution. Times tested for each cycle ranged from 1 to 10,000 msecs. Graphite, lead and stainless steel were evaluated as electrode materials. Square wave electrowinning at 70°C (158° F) gave the best separation of Ag and Au from Cu. Applying 2.5 V during the duty cycle, 0.0 V the rest of the period, a duty cycle of 10% to 30%, and a period of 100 msecs to 1000 msecs gave the following results: Ag concentrations decreased from 34 µg/mL to 0.1 µg/mL. Au concentrations decreased from 54 µg/mL to 0.2 µg/mL and Cu concentrations remained almost constant at 560 µg/mL.

Jan 1, 1995

By F. F. Aplan, T. H. Wentzler

Limestone is potentially a low cost material for the neutralization of acid mine drainage and other acidic waters such as steel pickling liquor. Unfortunately, when limestone is reacted wit9 these waters containing large amounts of Fe , Fe+3, and SO4-2 , a coating of gypsum and iron hydroxides form on the surface of the limestone inhibiting further neutralization reactions. The nature of these coatings, their morphology, composition and thickness were evaluated using the scanning electron microscope and microprobe, and the kinetics of limestone dissolution was studied both in the presence and in the absence of the reaction-inhibiting coatings. These data were then correlated with the solution chemistry.

Jan 1, 1992

By W. Jack Wilkes, Gilbert L. Butler

TRANSPORTATION TUNNELING The use of tunnels for transportation, namely rapid rail transit systems and highways is on the increase. How much that increase might be through the 1980's is the question that is discussed in this paper. In 1975, there were 218 route miles of subway tunnels for rapid rail transit and 154 lane-miles of highway tunnel. From the viewpoint of many transportation planners and designers, the tunnel is one of the tools which may be used to by-pass many types of obstacles: a mountain, a body of water, or a Central Business District (CBD). Therefore, the transportation tunnel is a rural as well as an urban solution with major emphasis on the latter because of the current transportation needs of our cities. In the case of rural locations, tunnels are usually constructed through mountains in order to eliminate miles of steep grades and dangerous curves, such as the Eisenhower Tunnel which cuts through the Continental Divide in Colorado along 1-70 and saves 10 miles and 40 minutes of driving time. Tunnels also provide an excellent transportation link across bodies of water in order not to interfere with shipping lanes. The Chesapeake Bay Tunnel and Bay Tubes of the BART system are excellent examples of this type of tunnel.

Jan 1, 1976

By Thomas J. Regan

The first stage of the Massachusetts Bay Transportation Authority's Red Line Extension Northwest, is a two-track rapid transit extension from Harvard Square in Cambridge, through three stations, to the Alewife Station/Garage complex in North Cambridge. The extension, about 5.0 km. (3.1 miles) in length, is entirely in tunnel, with the Alewife Station/Garage complex and adjacent line sections of tunnel constructed by cut-and-cover methods. The Station/Garage complex, just west of Alewife Brook Parkway, is in an area underlain by deep deposits of very soft highly sensitive clays. It is proposed to construct the station and adjacent tunnel sections by the slurry trench method, using the slurry wall as the permanent structural wall of the station and tunnel. The unusual nature of the underlying clay and its very high sensitivity raised questions concerning the feasibility of the proposed construction. Since research failed to reveal any construction precedent for the specific conditions encountered, a test section was undertaken to determine construction problems, resolve uncertainties, and to establish acceptable parameters for the construction of the slurry walls. PROJECT ORGANIZATION Sverdrup & Parcel as tunnel and transit systems consultant for the Red Line Extension-Davis Square to Alewife had overall responsibility for determining program objectives, project management and test implementation.

Jan 1, 1979

By C. H. Rawlins

The total amount of ferrous slag generated in the U.S. is about one-third the amount of iron ore mined, thus ferrous slag can be considered a significant mineral body for processing. Steelmaking slag contains up to 30 wt.% metal of which only the >25mm fraction is commonly recovered. A grinding study was conducted of BOF, EAF, and LMF slags using the Bond Work Index method to determine grindability to 106µm. Work Index values obtained were 13.8-24.9 kWh/ST, depending upon the slag type and composition. Steel particles were magnetically recovered from the crushed and ground samples for size-by-size analysis, yielding up to 18 wt.% of the slag weight recovered as magnetic. The recovered material, as characterized by inert gas melting, was found to be 61-96 wt.% metallic.

Jan 1, 2008

By S. K. Sharma, D. A. Stanley

The US Bureau of Mines is investigating the fundamentals of the flocculation process. The objective of this study was to determine the effects of various physico-chemical parameters, namely, shear rate, polymer dosage, and polymer concentration, on floc growth and to determine the applicability of a model for predicting polymer flocculation behavior. A rapid in-line particle size analyzer was used to follow the progress of both the floc growth and the breakage as a function of time. A genetic algorithm (GA) was used to determine the unknown parameters in the model and to fit a curve to the experimental data. The results showed that the model reproduces the experimental data with only reasonable accuracy and that it was relatively insensitive to the parameters. Results of the flocculation study showed that increases in the polymer dosage had a greater effect on the time required to reach the maximum floc size than on the floc size itself: It was also determined that, given all the above parameters, the degree of slurry mixing during the flocculation process had the greatest bearing on floc growth.

Jan 1, 1995

By Mohammad Irshad, Larry H. Heflin

INTRODUCTION The planned 166 kilometer (103 mile) Metro rapid rail transit system in Washington, D.C. is being designed and constructed by the Washington Metropolitan Area Transit Authority. At the present time, 112.6 kilometers (70 miles) of this system is in operation and contains 21 route-kilometers (13 miles) of rock tunneling, and 14.5 route-kilometers (9 miles) of soft ground tunneling. An additional 2.4 kilometers (1.5 miles) of single track tunnels in rock are planned and 6 additional contracts will consist of some 8 kilometers (5 miles) of twin tunnel, resulting in 16 additional linear kilometers (10 miles) of single track tunnel in soft ground. The Authority plans, upon its evaluation and the recommendation of the General Engineering Consultant, to include an alternative design incorporating the convergence confinement method of construction known as the New Austrian Tunneling Method (NATM), for Sections E-5, E-6e and E-8a of the E-Route. The Metro system is constructed in a variety of geological conditions and crosses the boundary of two major geographic provinces. Rock tunneling is to the west of this "fall-line" boundary, soft ground tunneling to the east. The soft ground tunneling portions of Metro construction lie in the coastal plain which consist of a

Jan 1, 1987

By A. H. Shapiro, W. –F. Leung

A decanter centrifuge of novel design was developed for the dewatering of fine-solids slurries having micrometer-range particles that form pastelike, flowable, hard-to-dewater cakes. The design combines a compound beach with a cake flow control structure that allows expressed liquid, from the cake in the dry beach region to be returned to the liquid pool while maintaining a high-solids throughput. To provide optimal performance with various operating parameters (i.e., feed rate, centrifugal gravity, pool, differential speed, concentration of feed solids and slurry type), the cake flow control is adjustable. The second part of the beach is preferably at a zero angle. Tests showed that the new design allows increases in solids dryness and solids throughput. Key words: Dewatering, Centrifuge, Slurry, Fine particles, Beach decanter, Cake-flow control

Jan 1, 2003

By J. W. Leonard, C. L. Jiang, B. K. Parekh, X. H. Wang

The selective depression of pyrite from the Kentucky No. 9 coal seam was systematically examined using various kinds of inorganic and organic chemicals. Most of the organic chemicals tested showed little selectivity in pyrite depression. It was found that both orthophosphate and pyrophosphate were effective for the selective depression of coal pyrite in coal flotation using fuel oil as a collector. At substantially low concentrations of pyrophosphate, the flotation of coal pyrite was completely depressed over a wide pH range, while the coal flotation remained unaffected. The mechanism of the selective depression of pyrite by phosphates was explained with the help of thermodynamic calculations of iron-phosphate-water systems and zeta-potential measurements. It was shown that pyrophosphate reacts strongly with the iron ions of pyrite to form stable hydrophilic iron pyrophosphate complexes on pyrite surfaces.

Jan 1, 1999

By H. H. Murray

Tactical R & D is research and development for a specific application or applications. The mineral scientist has to define and understand the physical and chemical parameters required for a specific or potential application. Then the researcher must know the structure and composition of the mineral and its physical and chemical properties. Can these properties be changed by processing particle size and shape modification, and surface chemical treatment? Examples of tactical R & D in the industrial minerals area will be described.

Jan 1, 2003