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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 Godwin Beene

During recent years, copper and acid production from Nkana Smelter has formed a significant proportion of ZCCM's total output, but a number of problems affecting the smelter over the last decade have only been recently overcome. This paper discusses recent developments in the smelting practice, highlighting some of the operational problems experienced and associated solutions. The smelter performance over the decade is discussed and the innovations in the smelting technology employed to sustain production in the wake of limited re-capitalization are dealt with in detail.

Jan 1, 1999

Mining Subscribes to Murphy?s Law Personal observations on the past ?Perfect, benign deposit mines can be screwed up-spills and concentrate handling issues ?Long term contamination and water management assessments inadequate ?The ?permitting mentality? and its effects on the application of proponent and regulator resources ?Reliance on simple principles but nature and chemistry is more complex

May 1, 2010

Bag stackers who use semi-automated palletizing machines and air slides may be exposed to high concentrations of dust. To reduce dust exposure, use an exhaust ventilation system in conjunction with an envelope of clean air over the bagstacker provided by an overhead air supply. Description of Hazard Mineral processing plants in the United States and throughout the world process material that is finely ground and placed into bags for shipping to the consumer. These bags normally range from 50 to 100 pounds in weight. Once the material is placed in these bags, a bag stacker loads the bags onto pallets. A bag stacker is exposed to a lot of dust that is mainly released by the force from loading the bag onto the pallet. The two main sources are the dust on the outside of the bag and the dust that escapes from inside the bag as it is loaded. The Mine Safety and Health Administration's (MSHA) records indicate the bag stacker's dust exposure is one of the highest of all workers at mineral processing operations. Ways to reduce the dust exposure and strain to the bag stacker are in constant development. Recently, automated systems have been built. These systems range from fully automated, which totally remove the worker from the bag-stacking process, to semiautomated systems, in which the bag stacker still performs some of the functions. This Hazard Control deals with controlling the bag stacker's dust exposure during use of a semi-automated palletizing machine. The worker slides the bags into position on the palletizing machine. Once an entire layer of bags is positioned, the bag stacker operates the controls on the palletizing machine to lower the layer of bags onto the pallet. An air slide is built into the semi-automated palletizing machine so the bags are easier to move. This slide uses a metal table with air jets that exit through small holes at high velocities, similar to an air hockey game. The dust problem occurs because the air slide causes dust to blow up onto the bag stacker, significantly increasing the dust exposure.

Jan 7, 2001

By S. Kelebek

Efficient separation of minerals is the essence of mineral processing. Separation of hexagonal pyrrhotite in processing of Ni-Cu sulphide ores was investigated together with particle size effects with respect to selective flotation recovery of pentlandite and nickel. The recovery by size response was compared for sodium metabisulphite (SMBS), triethylenetetramine (TETA) and their combinations with amyl xanthate as a collector. The pyrrhotite recovery for all sizes was lower than that of pentlandite for the blank case as well as individual cases with SMBS and TETA. For pyrrhotite, the recovery by size relations in the case of individual uses of reagents were mainly determined by recovery losses at coarser size range (>74 um), which occurs at a coarser size for pentlandite (>212 um). The combined use of SMBS and TETA, and the associated synergistic effect very significantly knocked down the pyrrhotite recovery to less than 7% that was a maximum for the –10 um (attributable to hydraulic entrainment). High recovery of pentlandite in a wide range of intermediate sizes and drastically low recovery of pyrrhotite resulted in a very efficient separation of pentlandite from pyrrhotite in all sizes. Separation of this mineral is discussed in relation to fundamental functionality of the reagents used.

Jan 1, 2017

By M. E. Poad, M. M. McDonald, J. C. Johnson, W. G. Pariseau

A U.S. Bureau of Mines case study of pillar recovery in high-grade ore near the Ross shaft at the Homestake Mine, Lead, SD, has demonstrated the usefulness of the finite-element method for evaluating shaft pillar mining plans and shaft stability. This report focuses on mine measurements and calibration of the two-dimensional computer model and is the second in a series of three Reports of Investigations describing the Ross shaft study. In this study, borehole extensometers and other instruments were installed to provide data for model verification and to monitor the shaft. Results of the recalibrated two-dimensional model (UTAH2) confirmed the premining stability evaluation. However, after mining began, concern was expressed because cracks and other signs of ground motion appeared at considerable distances from the area of active pillar mining. In part 3 of the study, an intense three-dimensional modeling effort using UTAH3 was initiated. The results again showed that the observed effects were within expectations and that the shaft would remain safe. Three-dimensional analyses of alternative pillar mining scenarios indicated that more of the shaft pillar ore reserve could be recovered than previously thought.

Jan 1, 1995

Misiman society is matrilineal and despite relatively long contact with Europeans and mining, it retains its traditional consensus style of decision making. Many Misimans at least understand English, and this has encouraged comfortable communication between the people and the company (Misima Mines Pty Limited). Company care in monitoring the environment (mostly using Misiman staff), its policy of maintaining a largely Misiman workforce, and its emphasis on training and safety, have all created an environment compatible with Misiman society. In addition, the company has constructed and/or upgraded community facilities such as the airstrip, roads, the health centre, police station and schools, and has actively promoted local business endeavours. All these initiatives have been accomplished by constant dialogue with the largely Misiman workforce, and with the Misiman people, both before and during implementation. Constant, careful communication, using traditional Misiman consensus methods, appears to be the key to continued community acceptance of the project.

Jan 1, 1991

Recovery of Precious Metals from Chloride Solution by Magnetite The development of environmental-friendly lixiviants as alternatives to cyanide and the increasing recycling activities to recover precious metals from waste materials have prompted researchers to find efficient methods and alternative sorbents to recover precious metals, such as Au and Pt, from aqueous solutions. This study explored the use of magnetite (Fe3O4) as a sorbent to recover Au and Pt from chloride solutions. Magnetite is a semiconductor and has the capability of transferring electrons both within the solid state and across the solid-liquid interface and has the ability to reduce metal species on its surface. The sorption of AuCl4- and PtCl62- from NaCl solution on commercial grade magnetite powder was investigated by batch-sorption experiments. The effects of pH, contact time, NaCl concentration and precious metal concentration on the recovery were studied. Sorption experiments revealed that magnetite exhibited selectivity towards other metals with the strongest affinity for Au. Both Au and Pt recoveries showed similar pH dependence curves, with peaks at pH 6 - 7. At this pH range, a maximum of 4.4 ¦mol Au/g Fe3O4 and 3.0 ¦mol Pt/g Fe3O4 were recovered after 24 h at an initial metal concentration of 0.05 mol/m3. Increasing the initial precious metal concentration increased the Au and Pt uptake amount by magnetite. It was also observed that the recovery decreased with high NaCl concentrations. The SEM images of the magnetite particles after the treatment showed that gold, which was confirmed by the EDX analysis, agglomerated and were deposited on Fe3O4 surface.

Sep 13, 2010

By H. G. Oltmann

The equilibrium nitrogen solubility in the CaO-SiO2system was studied by a slag-gas equilibration technique, in graphite crucibles at 1823K under a CO-N2 atmosphere. The nitrogen content of the slags was determined by the Kjeldahl method. A reliable technique was used to obtain an initial nitrogen content in the master slags, from the addition and pre-melting of silicon nitride. Reduction of silica by graphite was found to occur during the equilibration experiments, resulting in compositional changes of the slags. The results were extrapolated to equilibrium by kinetic evaluation of the data. The nitrogen solubility showed good agreement with the result of Suito and Sano, while Fruehan?s results were lower. However, the results of the present study do not support the maximum nitrogen solubility values found by Sano.

Jan 1, 1999

By Binxu Zeng, Mark Jolly, Xiaojun Dai

"The traditional investment casting foundries use batch melting and chunky running systems to produce casting components. This method leaves the energy saving issue as subsidiary one. In our research project, one of the partners, the AEROMET international PLC provides the thin wall aluminium component ""filter housing"" for test. The AERO MET uses traditional casting route to produce the filter housing, which only gives 5% --10% yield. In this paper, numerical simulation method is used to analyse filling and solidification of the casting running system. The CRIMSON running system of the filter housing is designed by using casting simulation software, MAGMAS and Flow3D. By working with AEROMET, various configurations of the casting running systems were tested and analysed. Using them ultiple life cycle approach, the energy content of new process is compared with traditional one. It indicates that the CRIMSON process only uses 36% of energy consumed by the traditional route.IntroductionThe investrnent casting is a metal for ming process using expendable patterns, which is a standard casting technique and is widely used to produce quality parts. Its accuracy, versatility and integrity tie itself to important and precious engineering components in Aerospace industry. However, traditional investrnent casting process usually uses chunky runner system and gravity filling method. It not only reduces the casting yield of the product but also causes the pouring defect during the casting. As author's previous research showed that gravity filling method pouring basin and down sprue are two main resources of entraimnent defects generation. No matter how good the running system is, entraimnent defects such as double oxide films (DOF) and bubbles will I get into the casting to cause problem."

Jan 1, 2013

By M Fallon

The full history of exploration successes, failures and related costs from initial greenfield exploration in 1987 to the current brownfield stages was analysed for the Plutonic Marymia Gold Belt of Western Australia. This belt, which had escaped the attention of turn-of-the-century prospectors and had not produced any gold until 1990, is an ideal area for a collectively exhaustive, progressive value and risk case study of expected return on gold exploration. The study analyses the progressive screening of over 200 greenfield and near mine prospects, through various stages of exploration to the establishment of 38 mining sites, ranging from a few large mines to small satellite operations. It provides empirical estimates of the historical Bayesian probability of projects advancing to successive stages of exploration, eg from reconnaissance, to systematic drill testing, resource delineation, feasibility and mine development, given a successful outcome in any exploration phase. The ratio between the estimated value of the gold discovered and the corresponding historical exploration expenditure in each year and cumulatively, ie the average cost of discovery per ounce of gold, are then computed as measures of historical return on the exploration investment in this belt. These, together with an estimate of the æresidualÆ gold endowment, ie of the number and size of possible as yet undiscovered deposits, generated through the use of rank statistics (ie ZipfÆs law), provide a basis for future strategic consideration in exploration targeting in this and similar geological terranes.

Jan 1, 2009

By H. C. de Wet

The predevelopment and preparation of a total infrastructure in a deep level mining environment, prior to the shaft system being commissioned has major advantages. This paper intends to indicate these advantages and outline an understanding of the disadvantages. These benefits can be classified in three basic groups: the financial and timing advantages, a knowledge of the ore body and the development of required technology to meet the design parameters. The required technology in many aspects was still to be developed prior to successful application. Stemming from the technological evolution are some secondary advantages which will be described in each of the groups. Safety and health considerations and some practicalities made some of the new technology redundant prior to the actual application. In each case the actual achievements and the anticipated benefits will be indicated to allow the reader to distinguish clearly between planned and actual achieved advantages.

Jan 1, 1997

By Pieter-Jan Kleiterp

Highwall mining is a mining method to extract coal from a final boundary in opencut mining, trench mining or contour mining. This boundary may have been reached because of economic constraints (economic strip limit) or geographic constraints, such as spoil heaps and rivers. Coal is mined from visible, horizontal, or near-horizontal coal seams by making rectangular, parallel, unsupported drives with an unmanned cutterhead and coal transport system. This is controlled from a mining unit, or launch frame, positioned outside the drive, in front of the highwall. Removal of overburden is not required or is limited to small quantities only.

Jan 1, 2010

By Edward M. Dowey

The concrete lining for a long 8.05 km (5 mi) section of New York City Water Tunnel No. 3 was cast in place. The contractor, Grow-Perini-Skanska, placed over76,841 m3 (100,505 cy) of concrete, pouring 24 hours per day, 5 days per week. The concrete was dropped 204 m (670 ft) to the tunnel level, transported by rail to a concrete remixer and pump, and placed in 146.3m (480 ft) of full circle forms. Some of the many challenges include the sheer magnitude of the job, navigating through drifts, a raise and curves, dealing with ground water inflows, and placing the concrete within time limits.

Jan 1, 2001

By Mohsen Sanai, Paul Gefken

"SRI International has developed and patented* a castable dilute explosive tile @ET) that offersunique advantages over conventional high explosive. The primary advantages of DET are that itsdetonation pressure can be adjusted over a wick range and its impulse can be controlled independently by adjusting its thickness and configuration. Because DET has a much lower detonation velocity than conventional explosives, the pulse duration produced by DET is as much as 10 times longer than the pulse duration produced by conventional explosives for equal explosive weights. These features of DET present several advantages to the mining industry. For example, DET can be tailored so as to control fragment size and distribution to enhance extraction of desired elements from ore or breakup of specific regions."

Jan 1, 1995

By M. C. Mound

A recent development using XRD techniques, a unique fixed detector, specifically permitting full mineralogical information simultaneously for the first time, specially designed sample preparation and presentation system and Rietveld codes provide a continuous real- time analysis on the true contained mineral polymorphic composition of powder streams such as ore materials, cement, ground clinker or any other mineral stream conducive to XRD analysis. There are several COSMA systems currently operating in the US, Canada, Italy and Australia, proving service and reliability of this concept. The mineralogical information generated continuously in real time is used for automated efficiency, product quality and reduces costs. Quantitative Phase Analysis information is transmitted to the plant DCS via Modbus over RS422 or ethernet. Some limited information is stored in the on-board computers for optional future use at the operator?s option.

Jan 1, 2010

By Dante Santony

La empresa Pixis desarrolla para la SCM Miner Lumina Ccoper Chile, la creación virtual de treinta procedimientos de operaciones y mantenimiento de sus plantas de proceso. En ese sentido, el presente texto señala la aplicación de este entrenamiento virtual en la industria chilena - en tanto ofrece beneficios como una mejor capacitación del personal de planta en procedimiento de fallas, posibilidad de simulación de fallas y emergencias, el equipo puede ser entrenado antes del comisionamiento de la planta, sin riesgo y a menor costo y los cambios de planta y optimización en los procedimientos que pueden ser capturados, mejorando la efectividad de estos

May 1, 2014

By John C. Cook

Channel sand bodies ("wants" or "cutouts") are deposits of barren, hard sediments which interrupt production and pose safety hazards when encountered in underground coal mining. To locate these costly impediments to mining in advance, from the surface of the ground, the seismic reflection method is recommended. High-resolution (high frequency) techniques for shallow seismic exploration of coal beds have been worked out and are reported here, including a field example. Newly-developed high-frequency, digital recording equipment was used, together with light-weight shot-drilling equipment and a variety of down-hole seismic impulse sources. Techniques for rapid but complete coverage of a coal prospect area with a crew of 2 to 6 men n 2 or 3 vehicles are described in detail.

Jan 1, 1976

By R. Kalra

The current paper looks at evaluating the merits of large geared mills versus gearless driven mills by evaluating the following factors: The capability of currently available systems in terms of power and mill diameter Efficiency in terms of overall electrical power consumed vs mechanical output power Capital cost Running costs Cooling requirements in terms of air versus water cooling Installation and delivery time World?s largest geared drive ? 2x8500kW ? Wushan, China (operating) Among the many reasons that geared drives on large SAG mills are not favoured, is due to not having an efficient variable speed drive option (60 to 80% critical speed), which is required for process reasons. As technological advances have occurred quite rapidly in recent years, this paper uses the latest data in applying these comparisons and attempts to dispel some of the myths regarding Slip Energy Recovery (SER) and variable frequency drive technology on twin pinion drive systems. Early attempts to provide load sharing on twin pinion drives used primitive electronics which have since been developed to eliminate the problems encountered in earlier attempts. In particular, torque pulsations between the twin motors have been overcome using a higher number of devices (pulses) and better electronics. With successful operation of 2 x 6.5MW (Phu Kham, Laos) and three 2 x 7MW units under manufacture (Pascu Lama) and a further 40 projects worldwide, energy efficient Hyper Synchronous SER drives are now mature and ready for use on 2 X 10MW dual drive mills. Speed variation required is in the range of +/- 15% of synchronous motor speeds. VVVF drive packages from ABB and Siemens are also available for 2 x 10MW in low and high speed options. Dual hydraulic inching drives provide a much safer and convenient operation with the added advantage of locked charge detection.

Feb 27, 2013

By D. J. Goodings, R. J. Bonenberger, H. U. Leiste, W. L. Foumey

This paper describes a series of two-dimensional tests conducted and filmed with a high-speed (500 frames per second) video camera. The purpose of these tests was to provide a better understanding of the processes involved in creating craters and channels in water covered soils with explosives.

Jan 1, 2000