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By John S. Egbert

Many of you are familiar with the Washington Metro Project. However, inasmuch as some may not be, and others may want to refresh their memories regarding certain facets of the project, I will cite a few summary details about the rail transit system we are constructing. That summary will also give each of us a common point for departure as I develop the principal thoughts that I want to leave with you. The Washington Metropolitan Area Transit Authority (WMATA) is an interstate agency established by Compact between the District of Columbia, Maryland and Virginia and approved by the United States Congress. Currently, the Authority has approval to build and operate a 101-mile (162.5 km) regional rapid rail transit system as shown on Appendix A. Of that total, 38 miles (61.2 km) will be in D. C., 32 miles (51.5 km) in Maryland and 30 miles (48.3 km) in Virginia. (Mileage figures, because of rounding error, do not add to 101 miles.) Referring again to the 101-mile total, 48 miles (77.2 km) will be underground, 42 miles (67.6 km) on the surface and 10 miles (16.1 km) on aerial structures. Of the 48 miles (77.2 km) that are underground, 15 miles (24.1 km) are rock tunnel, 14 miles (22.5 km) are earth tunnel, 0.5 miles (0.8 km) 9.s sunken tube and 19 miles (30.6 inn) are cut-and-cover construction. The system will include 86 stations, with 51 of them underground. Referring again to the full 86 stations, 43 will be in D. C., 23 in Maryland and 20 in Virginia. We currently have 37 miles (59.5 km) of line and 41 stations in operations as shown on Appendix B. Also shown on Appendix B is another 16 mile (25.7 km) increment and 13 stations which have been substantially completed, but are not yet in service. Additionally,

Jan 1, 1981

By Tianzu Yang, Weifeng Liu, Lin Chen, BOYI XIE, DUCHAO ZHANG, HUI XIAO

In this study, the oxygen-rich bath smelting process of copper dross was simulated using Factsage software. It was found that the two-step simulation results agreed better with the industrial data, especially in the speiss. Bismuth (Bi), lead (Pb), antimony (Sb), arsenic (As) and copper (Cu) contents in the speiss by two-step simulation differed from the industrial data by 0.6, 0.8, 2.6, 7.2 and 8.6 weight percent, respectively. The two-step simulation results indicate that the speiss partitioning of Sb, As and Cu increased from 60.1, 32.3 and 27.5 percent to 81.6, 67.8 and 47.2 percent, respectively, with the smelting temperature increasing from 1,050 to 1,250 °C, while the metal partitioning of Sb and Cu increased from 0 and 2.7 percent to 15.2 and 13.3 percent, respectively, with the separation temperature increasing from 400 to 700 °C.

By Thomas D. Henderson, Wayne R. Hopkins, Arthur Lynch

Brought on stream in 1975, the 10,000-tpd copper oxide processing plant of Anamax Mining Co. at Twin Buttes, Ariz., is now at design capacity. Based on acid agitation leaching, solvent ion exchange, and electrowinning, the Anamax plant bridges an ore to metal gap by producing mine site copper cathodes from lime-bearing oxidized feed. Until recently, such material was considered submarginal because copper recovery was uneconomic using conventional methods. The new Twin Buttes oxide plant, the largest of its kind in North America, is one stage in the expansion of Anamax, a joint venture owned equally by The Anaconda Co. and Amax Inc. Other phases include an accelerated stripping program in the pit, an expansion of the sulfide concentrator from 32,000 to 40,000 tpd, and construction of a 57 MW diesel generating station for the oxide plant. Once the basic oxide flowsheet had been selected, Anamax awarded a contract to a joint venture of Arthur G. McKee and Co.' (Western Knapp Engineering Div.) and Davy Powergas' (a member of the Davy International group). The contract covered process design, engi¬neering, procurement, and construction. The property, identified by Banner Mining Co. in the 1950s and developed by Anaconda, was put into production in 1965 as an open pit mine equipped with a 32,000-tpd sulfide flotation concentrator. The Twin Buttes mine has since become one of the largest earth¬moving operations in the world, excavating some 10 tons of waste per ton of ore. At the original sulfide mill feed rate, the mining fleet moved 375,000 tpd of material (225,000 tpd alluvium and 150,000 tpd of rock). The most significant copper mineral in the ore body is chalcopyrite, which is scattered in pockets of weak mineralization. Cap oxidation has progressed to depths of several hundred feet, principally as chryso¬colla. Present estimates place minable reserves at 347 million tons of sulfide ore grading 0.6% copper and 55 million tons of oxide ore grading 0.9% recoverable copper from 1.25% total copper. The nonre¬coverable fraction is composed of native copper and insoluble copper oxides and sulfides. The oxide ore has been partially stripped, and 25 million tons having a copper content greater than 0.6% have been stockpiled. The stripping of oxide ore to expose sulfides will continue for several years. The copper oxide studies launched by Banner Mining in the 1950s were continued by Anaconda. Process routes investigated included: acid leaching; cyanide leaching; segregation roasting; chlorination, oxidation, and reduction; flotation in combination with leaching; cal¬cite flotation plus leaching; copper oxide flotation; and sulfidization flotation. By late 1968 test work favored a low temperature roast followed by an ammonia-ammonium carbonate leach of the ore. During this period, acid leaching had been discounted because of excessive con¬sumption of expensive acid by the high limestone ore matrix. Restric¬tive SO2 emission controls in 1971 suggested an increase in acid production and availability at a lower cost. Research then switched to acid leaching, resulting in development of the present flowsheet. Mechanically agitated leaching in a cascaded series of tanks was selected in preference to vat leaching after piloting a stirred-tank system. Preliminary testing of vat leaching indicated that inter-vat solution clarification problems could be caused by gas evolution from leaching of high limestone ore. Lack of research time for resolution of this problem, plus success of the pilot agitation system, dictated the final flowsheet selection. In 1973 Anamax decided to proceed with agitation acid leaching to produce liquor for a solvent ion exchange (SIX) and electrowinning (EW) installation. At that time, such systems were proving their eco¬nomic viability, and they allowed direct recovery of high quality cath odes while bypassing the smelting and refining of lower grade cement copper precipitates. The Anamax oxide plant processes a grade of about 1% recovera¬ble copper from stockpiled sources and new mine production. Unit operations include size reduction, agitation leaching, countercurrent decantation washing of residue, pH adjustment of solution, clarifica¬tion, solvent ion exchange, and electrowinning of copper, with a mini¬mum of environmental impact. The feed to the primary crushers is composed of: 1) -10-in. stockpiled oxide ore, which has passed through the mine crusher and has been grade-segregated to allow blending for a consistent feed material. 2) -4-ft ROM oxide ore stockpiled in the early mining operation. 3) -10-in. ore currently being mined. Ore is delivered in 100-ton mine trucks to a dump pocket, where an apron feeder transfers the ore to an inclined 6-in. fixed grizzly. The grizzly oversize passes through a 48 x 60-in. primary jaw crusher, where it is reduced to -6 in. The fixed grizzly undersize and the crusher product are conveyed to a 4-in. vibrating grizzly. Oversize from this grizzly reports to a 7-ft Standard cone crusher, where it is reduced to -1 in. The crusher product and the vibrating grizzly undersize are conveyed to two 8 x 20-ft double-deck vibrating screens that operate in closed circuit with two 7-ft short head cone crushers. Screen undersize (-1/2 in.) is delivered to a covered conical fine ore stockpile with a designed live capacity of 15,000 st. Beneath the stockpile are ten Pioche belt feeders feeding two conveyor belts that supply the milling circuits. Each group of five feeders has two variable speed and three fixed speed drives. Grinding to 95% -48 mesh is done in two parallel lines, each consisting of an 111/1 x 18S -ft rod mill and a 12' x 30-ft ball mill in open circuit. Water is added to maintain a pulp density of 72% solids in the mills. Further water additions are made to the ball mill discharge sumps to create a 60% solids slurry for transfer to the leaching reactors. The nominal grinding rate is 440 tph solids. A splitter box on the product from the mills separates the incoming slurry into two streams, one for the leaching reactors and the other for the pH adjustment reactors. This split is determined by the lime content of the feed material and the pH of solution entering the pH adjustment reactors. Five 30-ft diam by 31-ft high mechanically agitated, rubber-lined leach tanks are arranged in cascade, with gravity transfer from one to another by enclosed launders. Concentrated sulfuric acid (93.2%) from storage is added to the pulp principally at the first leach tank, and the reacted slurry leaving the cascade after a 5-hr residence time at 50% solids is pumped to countercurrent decantation (CCD) wash thickeners.' At this point, most of the soluble copper has been leached from the ore. Up to 250 lb of sulfuric acid is consumed per ton of ore, the acid being supplied in tank cars from a nearby smelter. Leached slurry at 50% solids is washed countercurrently with return raffinate from the SIX plant in a series of four Doff-Oliver center caisson, 400-ft diam thickeners. Solids advance from thickeners No. I through No. 4 to the tailings dam. SIX raffinate advances from thickener No. 4 to thickener No. l, where a pregnant solution overflows to pH adjustment. To optimize solvent extraction, the pH of the pregnant solution from CCD thickener No. I is adjusted from 1.5 to 2.5 by adding unreacted ground slurry (split from the grinding circuit) to the preg¬nant overflow of No. I CCD thickener. The resulting slurry is retained for 45 min in three mechanically agitated leach tanks. CO, generated during leach and pH adjustment is ducted to a demister, where entrained acid droplets are removed. The cleaned CO, and the No. 4 CCD underflow are the only effluents from the plant. The underflow of No. 4 thickener mixes with tailings from the sulfide concentrator and is neutralized. Slurry exits the pH adjustment vessels at about 10% solids and

Jan 1, 1985

By Georgios Kafantaris, Carsten Bonde, Nataša Katic

Within the investigation works for the Copenhagen Cityring metro, Geo/CMT have carried out 90 geotechnical boreholes. Together with the previously available investigation, this resulted in more than 15 km of vertical drillings and several thousands of laboratory tests. The design is made for 17 stations, four shafts and two parallel 16 km long tunnels. The geotechnical investigation and design have been carried out in several stages comprising appropriate refinement of structural design and design of excavation operations, including TBM break-in and launching operations at each station shaft. Acceptance of the solution and / or refinement of the investigation and design schedule in the next stage were based on the geological conditions, area availability at surface level, planning and cost-control criteria. The applied recursive design refinement is presented herein with an example of the Østersøgade shaft location.

Jan 1, 2016

From some of the largest tunnel projects in the some of the most vibrant cities, to smaller projects in remote corners of the globe, the Robbins Co. announced two tunneling projects in which its tunnel boring machines will be used. Robbins earth pressure balance (EPB) machines undercut Downtown Zhengzhou. Zhengzhou, a city of 7 million people, is set to become a crossroads for rail commerce in China. The country?s future main routes, traveling between Beijing and Guangzhou (North-South), and between Xuzhou and Lanzhou (East-West), will intersect in the city. The plan includes up to four rail lines in Zhengzhou itself, which will eventually link up to the national lines. Excavation of Zhengzhou Metro?s new Line 1 tunnels began on Sept. 28, 2010, when the first of two 6.3-m (20.7-ft) diameter Robbins earth pressure balance (EPB) machines was launched from a 16-m- (52-ft-) deep shaft.

Jan 1, 2010

By Ralph T. Buscarello

For practical purposes, the terms "natural frequency," "resonance" and "critical speed" are synonymous. A part passing though its "critical" or "critical speed" may also be said to be "resonant" or "resonating." The vibrations of a precisely balanced part can be magnified by the structure in which it is assembled. Anyone who has driven an automobile knows that it will vibrate more at a certain speed than at others. According to the formula for centrifugal force, vibration should increase steadily with a rise in rpm. What happens instead is that the vibration not only in- creases with r m. but suddenly rises at a much higher rate through the critical speed, and then apparently smooths out as the rpm passes beyond it. To visualize what happens, consider a simple flat spring with a weight mounted at one end. When the spring is deflected by pulling down on the weight and then letting it go, the spring will oscillate, and the spring-and-weight system will vibrate at its natural frequency. If the timing or direction bf the impulses imparted to the spring did not coincide with its natural frequency, the result would be an irregular vibration that would not build up. If, on the other hand, the timing and direction of the impulses did coincide with the spring's natural frequency, the result would be a larger and larger amplitude. If the impulses were continued indefinitely, the amplitude of the spring's vibrations would go on rising [while its frequency stayed the same] until the spring broke or the amplitude of the vibrations reached an equilibrium [because frictional or other forces would tend to damp it]. Resonance magnifies the amplitude of vibrations in a relatively undamped system between 100 to 200 times over that of nonresonant vibrations. Frictional or viscous damping often reduces the magnification [from 10 to 20 times], but even with this reduction the amplitude would still be large enough to cause excessive wear, and sometimes even fractures. For example, a blower might show only 0.001 in. of vibration on the manufacturer's test stand. Installed, the blower could pass into its critical speed [the speed at which the frequency of the vibrations caused by the rotor coincides with the supporting structure's natural frequency], and the 0.001 in. of vibration could be resonated to 0.010 in., or as much as 0.020 in. The cure for such a condition would not be to lower the vibration of the blower by further balancing or better alignment but to separate the two frequencies by at least 20 to 30%.

Jan 1, 1970

By E. D. Stephenson

As part of the British Steel Corporation?s development plan during the 1970?s, it was decided to concentrate its bulk steelmaking processes based on the BOS at 4 major Works with access to deepwater ore terminals, for the supply of high-grade imported ores. These 4 sites were at: - 1. Rarenscraig Works in Scotland where the ore terminal would be hilt at Hunterston on the west coast some 50 miles away. Bavenscraig was already an integrated Works but suffered from having to discharge ore 27 Glasgow tenxinus on the River Clyde, which could only accommodate vessels up to 25,000 tonnes. In the future, ore was to be unloaded at Runterston and shipped by a rail-link into Ravenscraig, The new ore terminal would have the potential to unload vessels up to 300,000 tonnes. - 2. Port Talbot Works in south Vales where the existing harbour was developed to discharge large ore carriers. This again was an existing Integrated Works and the benefits of the new harbour also applied to Llanwern Works which was another integrated Works some 50 dies to the east, which would now receive ore from Port Talbot.

Jan 1, 1980

By H. R. Hernandez-Guerrero, S. A. Robles-Salazar, M. Marín-Pasillas, P. J. Pompilla-Rosales

Peña Colorada is a company dedicated to the exploration, exploitation, and beneficiation of iron ore, serving the national steel industry. Established in 1975 as a stateowned enterprise, it transitioned to operating as a private organization in 1991. It is jointly owned by two investors, ArcelorMittal and Ternium, each holding a 50% stake. The mining operation is situated in the municipality of Minatitlan, in the northwestern part of the state of Colima, Mexico (Figure 1). It comprises an open pit mine and a concentrator, covering an area of approximately 2,300 hectares. The pellet mill is in the town of Manzanillo, Colima state, a port on the Pacific coast, about 46 km southwest of the mine. The pellet mill occupies its own property with a total area of 60.4 hectares. A gravity-driven concentrated slurry pipeline connects the mine and the pelletizing plant, located at an average elevation of 1,020 meters above sea level and 20 meters above sea level, respectively. Currently, Peña Colorada produces 4.1 million tons of pellets and 0.4 million tons of iron concentrate annually. In 2018, due to a change in the cutoff grade, the processing volume of the beneficiation plant increased from 9 million tons to 16 million tons annually. This led to a greater amount of information to process and characterize the ore extracted from the pit before its processing in the beneficiation plant. Consequently, Peña Colorada sought new ore control technologies to enhance ore selection, optimize human resources and data management, as well as minimize discrepancies between planning and execution. To ensure adherence to quality agreements with stakeholders, it is crucial to understand the ore characteristics before initiating mining activities.

Feb 1, 2024

By R. Venkataramani

Crushed stone operations have become more difficult due to rising costs of labor and equipment, with the consequent reduction in profit margins. Competition from other operators and the encroachment of vertically integrated companies place severe restrictions on available markets. The seasonal demand for stone precludes any definite production level, and changes in productivity have to be accommodated. These influence profitability, and therefore production plans must be continuously adjusted to keep pace with rapidly changing conditions. The basic problem of stone companies seeking to maximize profits is one of balancing stone production costs, costs of inventory holding and stock-piling, marketing costs and any other charges accruing over time against the selling price of stone. Because of high peak demands, slack period production must be stored and then distributed to supplement peak period production. For a multi-plant operation, there is a need to evaluate at the same time the interaction between the plants and the various marketing sectors. In a multi-plant operation with different production capacities and production costs, stone producers are interested in the answers to the following questions: 1. How much stone should be produced at each plant in each time period? 2. What should be the optimum stone shipment from each plant to each market? 3. What are the effects on net returns and shipping plans, if production capacities are altered at the plants? These questions have many different answers that, will satisfy demands. From the point of production scheduling, the minimum production cost may be the objective. From the inventory standpoint, the best solution will be to synchronize production with sales. However, when the transportation of stone is also considered, the desired end is to achieve that delivered cost which maximizes the company f s net return. Besides, only an extremely naive analysis ,wouId attempt to

Jan 1, 1971

By X. Wang, Y. Luo

The propensity of coal spontaneous combustion can be evaluated using various laboratory testing methods, such as R70 adiabatic tests, thermal gravimetric analyzer (TGA) tests and critical self-heating temperature (CSHT) methods. Each of the methods has its unique characteristics and index for classifying the propensity of self-ignition of coals. Accountable relationships among the propensity indices of different methods should be established. Using the newly established R70 and TGA testing setups in our ventilation laboratory, samples from U.S. coal mines have been collected and tested. The TGA is a relatively new quantitative method. A test can be conducted in a relatively short time, within about one and a half hours, compared to the adiabatic tests. The temperature and weight of the sample can be measured with high precision and then used to determine the activation energy of the coal, which is a good indicator of the potential for self-heating. Under a specific experimental design, the TGA technique could perform the proximate analysis for determining coal quality parameters (e.g., moisture, volatile matter, fixed carbon and ash content). These parameters can be used in an empirical equation for assessing the potential for coal self-ignition. The trend of activation energies determined using TGA techniques is reasonably consistent with the trend of activation energies determined using adiabatic tests. As a case study, a comparative analysis of these two methods for determining activation energy was made on coal samples collected from Indiana. The kinetics of the spontaneous combustion mechanism has been explained. If the functional groups of a coal such as hydroxyl (-OH), carboxyl (-COOH), methyl (-CH3), etc., activate more easily with a small amount of activation energy at a relatively low temperature, the coal will have a higher potential for self-heating. With the kinetic and coal quality parameters determined by the TGA setup, it has been found that the coal with a low potential for self-ignition has low self-heating rate, a high activation energy and a high minimum self-heating temperature.

Jan 1, 2012

By Brenton Cook, Nate Long, Larry Applegate, Aaron K. McCain

"The Northgate Link Extension project is the third phase of the Sound Transit master plan to extend light rail throughout the greater Seattle metropolitan area. When completed, the Northgate Link Extension will extend the existing light rail system north by about 7 km (4.3 miles) from the University of Washington to the Northgate neighborhood. A general overview of the project alignment is provided as Fig. 1. The project was funded by a combination of federal grants and allocations from local taxes. The general contractor on the project was JCM Northlink LLC (JCM), a joint venture between Jay Dee Contractors, Frank Coluccio Construction Company and Michels Corp. SoilFreeze, Inc. was retained as a subcontractor to provide ground freezing design and construction services.The project involved the construction of two parallel 5.5-m, 25-cm (18-ft, 10-in.) (inside) diameter tunnels using earth pressure balance (EPB) tunnel boring machines (TBM) and precast segmental concrete tunnel liners. The two tunnels maintained roughly the same elevation along the alignment and were spaced roughly 12 m (40 ft) apart (centerline to centerline). A total of 23 cross-passages connecting the two tunnels were included at approximate 244-m (800-ft) intervals. Cross passage excavations were elliptical in shape with dimensions of approximately 5.6 m (18.5 ft) in height and 5.3 m (17 ft) in width. The cross-passages were 5.8 to 6.1 m (19 to 20 ft) long as measured between the exterior of the tunnels at springline elevation. Cross passages were intentionally located directly beneath public right-of-ways thus avoiding buildings. Many of the cross passages were located beneath narrow roads in residential neighborhoods with mature vegetation, existing utility structures and piping and limited parking areas. Excavation and support for each cross passage was completed using the sequential excavation method (SEM).The subsurface soil and ground water conditions at the cross-passage locations were described in the Northgate Link Geotechnical Baseline Report (GBR) prepared by Jacobs Associates and the Northgate Link Geotechnical Data Report (GDR) prepared by Shannon and Wilson, Inc. Soils along the project alignment were glacially overridden and characterized as very dense or hard. Subsurface soils consisted of cohesionless sand and gravel (CSG), cohesionless silt and fine sand (CSF), cohesive clay and silt (CCS) and till and till-like deposits (TLD)."

Dec 1, 2018

By Aditya Rana, A. K. Mishra, M. M. Singh, N. K. Bhagat

Many cases of derailments, train accidents and traffic interruptions due to the slope failure and rockfall have been reported in the past on Konkan Railway trackline because of unstable rock slopes. The authorities installed stability enhancement measures such as wire netting, rock bolting and shotcreting which were found insufficient. The failed geotechnical measures prompted authorities to excavate the unstable slopes. Rock blasting is generally not preferred for the excavation of slopes along the transportation route. Stabilisation and widening of slopes by blasting need closure of the route for a considerable time. Discontinuing traffic on Konkan Railway route was undesirable as it connects two important port cities Mumbai and Mangalore. The paper presents an innovative directional controlled blasting (DCB) technique for excavating three unstable slopes (i.e. cuttings) in hilly terrain without disturbing the traffic. New empirical formulae for small geometry blasting to estimate burden and throw have been developed. A unique sequence of firing and excavation with powder factor varying between 0.04 and 0.39 kg/m3 irrespective of the actual free face was used for rock blasting. The process controlled the throw of blasted material over the track and resulted in a smooth and stable wall. The slope angle has been changed from 80 to 82° to 45–47° and probability of wedge, planar and toppling failures was eliminated. About 100 such accident-prone slopes (52 km cumulative length, 7% of total route) situated at discrete locations along Konkan Railway route were stabilised using the technique. No incident of rockfall and slope failures along these slopes has been observed after the stabilisation.

By H. Vigil Fernandez, G. Peach

The Musaimeer pump station and outfall project located in Doha Qatar, was designed to collect and manage ground and stormwater and then discharge the treated waters offshore. The project constructed a long outfall tunnel using an EPB TBM with segmental lining, each tunnel ring being 1.35 m in length with an internal diameter of 3.7 m.. The diffuser structure was a 6-arm structure, measuring 294m by 40 m connected to a central manifold in turn connected to the TBM constructed tunnel via a riser shaft drilled from an off-shore barge. This technical paper will discuss the planning, methodology and construction practices employed to connect the TBM tunnel to the diffuser structure 10.2 km offshore.

Jun 13, 2023

By S. Chatterjee

Mining represents the first industry in the United States to have federally mandated training for its workers. Although the topics to be covered are specified in 30 CFR 48, course content is left to the discretion of the individual mine operators. Unfortunately, certain topics to be covered, such as prevention of accidents, are usually mine specific, making it very difficult to use the same course content in every mine. Further, training requirements may change from one mine to another, due to changes in the demographic characteristics of the workers, or changes in job and organizational characteristics. Therefore, if the intention of safety training is to modify the behavior of workers, it is expected that there should be some changes in the content of safety training programs in order to address the specific requirements of individual mines, or at least mines of similar worker and job characteristics. This study has been directed towards the development of a systems-based procedure for conducting a needs analysis. A special effort was made to understand the psychology of worker behavior by analyzing worker reactions to various organizational and job characteristics.

Jan 1, 1994

By David L. Kuck

Siderophyle platinum-group metals and sane gold are a thousand times more abundant in metal and chondritic meteorites than in terrestrial or lunar rocks. Type I and II carbonaceous chondrites contain granules of the high boiling point metals W, Re, Mo, Ir and Os. Metal meteorites and the metal fractions of other chondrites contain siderophyle Pt, Pd, Ru, Rh, Os, Ir and Au. Spectra of sunlight reflected from asteroids, when compared with those of meteorites and specific minerals, provide a rough classification and guide to sources of precious platin-group metals.

Jan 1, 1982

By Claus Becker

The new, 2.600 m long pipe under the river Elbe in Hamburg/Germany required for 2 traffic lanes, emergency lane and space for utilities a boring diameter of 14,20 m(46,6 ft). According the geology (glacial deposits consisting of clay, sand and marl, all containing big boulders) a Slurry-Shield with crusher was selected. With a minimum cover of 7 m and a maximum pressure of 5,6 bar extensive ground treatment was necessary to make the drive feasible. The machine contains a lot of new developments. The drive was finished in spring 2000 so all experiences can be reported. A special risk sharing contract avoided completely litigation.

Jan 1, 2001

By B. Govindarajan, L. S. Rao, T. C. Rao, B. R. Rao

Laboratory leaching experiments were conducted to extract potassium from glauconitic sandstone, and the effects of important variables were studied. The reduced time plot (RTP) for all of the variables obtained from the experimental data has been quantified by this simple equation: R = 100 (1 - exp (-0.693 *(T/T50)0.605) The time required for 50% extraction (T50) has been correlated by a regression equation to variables such as acid strength, temperature, fluorite: glauconite ratio and % solids. Both of these equations were used to predict the extraction percentage at different process-variable levels. In addition, several other experiments were conducted at arbitrary levels of the variables to verify the equations developed.

Jan 1, 1994

By J. R. Johnson, C. G. Stewart, D. K. Myers

INTRODUCTION Radon-222 is an inert, radioactive gas formed by the radioactive decay of radium-226, a long-lived member of the uranium-238 decay chain. Radium is present in varying amounts in virtually all soils and, on the average, about 36,000 pCi (1330 Bq) of radon per square meter of soil diffuse into the atmosphere each day (UN 1977). Radon decays with a half-life of 3.6 days through four short-lived daughters to lead210 and it is these short-lived daughters[ [Ra A, (218Po, t, = 3.0 min) , Ra B, (214 Pb, t;, = 27 min), Ra C, (214Bi, t] = 20 min) and Ra C1 (214Po, t] = 2.5 x 10-6 min)] ]which cause the major health hazard associated with radon (Bale 1951). Atoms of these daughters, either unattached or attached to the ever-present particles in air, are deposited on the surfaces of the respiratory tract; alpha particles emitted in their decay can result in large doses to the cells of the bronchial epithelium lining the respiratory tract. These daughters will be present in air in varying relative concentrations depending on the "age" of the air (time since radon emanated into it) and on the amount of mixing of radon and radon daughter contaminated air with clean air. [The practical unit developed to quantify the amount of radon daughters in air is the Working Level (WL). This unit was historically related to the equilibrium concentration of 100 pCi (3.7 Bq) of the short-lived daughters of radon in one liter of air (cf. Holaday 1969) and is defined as any mixture of the short-lived daughters in a liter of air that have a-potential alpha energy of 1.3 x 105 Mev (2.08 x 10-5J) in their decay to lead-210. The working level month (WLM) was developed along with the WL, and was defined as an exposure to one WL for a working month (170 h). This is equivalent to 2.2 x 107 MeV•h•L-1 (3.54 x 10-3 J.h.m-3). If the average breathing rate is taken as 1.2 m3.h•1 (ICRP 1975), then one WLM is equivalent to inhalation of 4.24 mJ of potential alpha energy.] It is now generally agreed that the inhalation of radon daughters is the major potential radiation hazard in uranium mining, and contributes a substantial fraction to the natural radiation exposure of the general population due to the accumulation of radon and radon daughters from natural sources in buildings. Radon daughter concentrations in modern mines are controlled by ventilation, and by blocking off old working areas (cf. Simpson, 1959). However, before the hazard from radon daughters was recognized, considerably higher concentrations of radon daughters were present in some uranium and non-uranium mines. These high radon daughter concentrations resulted in an increase in lung cancers in the mining population, and it is these results that are our main source of information on the risk of inhaling radon daughters. HISTORICAL REVIEW Many excellent reviews of the history of understanding the health effects of inhalation of radon daughters are available (see, for example, Hueper 1942, Lorenz 1944, Sikl 1950, Stewart 1964, Holaday 1969, Lundin 1971, Cross 1979) but a brief summary of some of the highlights in this area may be of interest. [a] 1556: Agricola describes an unusual and fatal chest disease occurring among underground miners in the region of Schneeberg and Joachimsthal (Jachymov) in the Erz mountains in Central Europe. (It is of some historical interest to note that Agricola's book was translated from Latin into English by a mining engineer and his wife; the engineer later became President of the U.S.A.) [b] 1879: Haerting and Hesse indicated that the majority of deaths among Schneeberg miners were due to lung cancer; the lung cancers in these miners (who were incidentally not cigarette smokers) were observed twenty to fifty years after they began working in the mines. [c] 1896: Discovery of natural radioactivity by Becquerel, followed by discovery of radon by Dorn in 1900. [d] 1924: Ludewig and Lorenser report high concentrations (400 - 15000 pCi or 15 - 570 Bq per liter) of radon in the air in the Schneeberg mines and suggest that radon could be responsible for the high rate of lung cancer among miners. However, the reason why radon should cause lung cancer specifically was still not really understood up to twenty years later (Lorenz 1944). High concentrations of radon in the air in the Joachimsthal mines were reported by Behounek in 1927 and a high incidence of lung cancer among Joachimsthal miners (similar to that among miners at Schneeberg, which is only some 30 km distant but in a different political district) was noted at about the same time (Sikl 1930; cf. Sikl 1950). It is estimated that about half of the Joachimsthal miners died from lung cancer and about half from silicosis and tuberculosis (Sikl 1950). [e] 1930's and 1940's: Radioactive ores are deliberately mined in the U.S.A., Canada and other countries primarily as a source of radium for medical purposes and for luminescent dials; other radioactive ores are mined as a source of several non-radioactive minerals, while extensive uranium mining did not begin until the late 1940's. [f] 1940: Based on crude epidemiology and dose calculations, Evans and Goodman propose 10 pCi L-1 as a maximum permissible concentration of radon in continued human exposure. This is the first known recommended maximum permissible concentration for radon. This recommendation was adopted by the U.S. National Bureau of Standards in 1941 and reconfirmed in 1953. [g] 1945: Mitchell identifies the short-lived daughters in radon as a likely cause of the increased lung cancers in the Schneeberg-Joachimsthal miners

Jan 1, 1981

By William R. Groseclose, Cecil E. Tackett

Since 1965 when the first mole was used on Bureau work, the Bureau of Reclamation has completed 17 tunnels of over 5,000 feet in length. The longest was 12.8 miles. Total length of the 17 tunnels was 376,207 feet, or over 71 miles. The finished diameter varied from 7 feet 0 inch to 18 feet 0 inch with 82 percent (58 miles) being less than 12 feet 0 inch in diameter when lined. All of these tunnels except one are gravity flow, water conveyance tunnels with relatively flat gradient. One is a low-head pressure tunnel. All were constructed by contracts resulting from fixed-price bids. Starting in 1964 the Bureau of Reclamation initiated the practice of giving several options in the specifications on methods of tunnel excavation. Since that time, construction work has been completed on 17 tunnels. Of this number, 11 were mole excavated and 6 were excavated by conventional drill and blast methods. In general, there has been 2 feet of mole excavation for every 1 foot of drill and blast. Cost comparisons are based on only 13 tunnels because the Bureau has 4 recently completed tunnels that have pending claims; therefore, final cost data are not available. Some definite trends show from the data available; however, the number of completed tunnels in some categories is so small the results cannot really be considered a trend. As more data become available, the indications will become more reliable. The information is presented to indicate general trends and comparisons and cannot be meaningfully used for a one-on-one comparison because of individual tunnel differences not considered.

Jan 1, 1974

By John S. Burton

Mineral policy in Canada has been in a state of transition and change over the past several years. 1976 has witnessed some settling of troubled waters and the pattern of the currents of change is becoming more clear. The provinces play a key role in this process and have provided much of the thrust for new initiatives. On the other hand, the federal government in Canada in recent years has taken a much more active interest in mineral affairs than previously and has asserted its powers on a number of key policy questions. Some of the initiatives from the two levels of government in Canada have come into conflict with each other and, thus, contributed materially to a state of affairs that includes change, uncertainty and conflict.

Jan 1, 1976