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By Leslie Burnside

Homestake Mining Co. set out to complete final reclamation at a former open-pit gold mine in west central Nevada. The goal was to exceed regulatory standards by satisfying the company's own high corporate standards for successful reclamation. Homestake's completion requirements challenged available technology due to the unsuitability of heap material as a growth medium, the harsh environmental conditions of the site and the region's lack of native growth medium. Accomplishing these goals required enlisting a multidisciplinary project team to develop, test and implement appropriate and cost-effective revegetation alternatives.

Jan 1, 1999

By Ihsan Berk Tulu, Mark Van Dyke, Ted Klemetti, Deniz Tuncay

"Longwall abutment loads are influenced by several factors, including depth of cover, pillar sizes, panel dimensions, geological setting, mining height, proximity to gob, intersection type, and size of the gob. How does proximity to the gob affect pillar loading and entry condition? Does the gob influence depend on whether the abutment load is a forward, side, or rear loading? Do non-typical bleeder entry systems follow the traditional front and side abutment loading and extent concepts? If not, will an improved understanding of the combined abutment extent warrant a change in pillar design or standing support in bleeder entries?This paper details observations made in the non-typical bleeder entries of a moderate depth longwall panel; specifically, it explores data collected from borehole pressure cells and roof extensometers, observations of the conditions of the entries, and numerical modeling of the bleeder entries during longwall extraction. The primary focus was the extent and magnitude of the abutment loading experienced due to the extraction of the longwall panels. Due to the layout of the longwall panels and bleeder entries, the borehole pressure cells (BPCs) and roof extensometers did not show much change due to the advancing of the first longwall. However, they did show a noticeable increase due to the second longwall advancement, a maximum of about 4 MPa of pressure increase and 5 mm of roof deformation. The observations of the conditions showed little to no change from before the first longwall panel extraction began to when the second longwall panel had been advanced more than 915 meters. Localized pillar spalling was observed on the corners of the pillars closest to the longwall gob as was an increase in water in the entries. In addition to the observations and instrumentation, numerical modeling was performed to validate modeling procedures against the monitoring results and evaluate the bleeder design. ITASCA Consulting Group’s FLAC3D numerical modeling software was used to evaluate the bleeder entries. The results of the models indicated only a minor increase in load during the extraction of the longwall panels. These models showed a much greater increase in stress due to the development of the gateroad and bleeder entries—about 80% development and 20% longwall extraction. The FLAC3D model showed very good correlation between modeled and expected gateroad loading during panel extraction. The front and side abutment extent modeled was very similar to observations from this and previous panels."

Jan 1, 2019

By Hamed Khodadadi, Hamid Ghadiri

In this study, a fuzzy logic self-tuning PID controller based on an improved disturbance observer is designed for control of the ball mill grinding circuit. The ball mill grinding circuit has vast applications in the mining, metallurgy, chemistry, pharmacy, and research laboratories; however, this system has some challenges. The grinding circuit is a multivariable system in which the high interaction between loops, the variation of the system parameters with time, and time delay are some of the problems that pose a challenge. Since the controller parameters are determined offline in classic PID control, these gains are unchangeable and cannot overcome the mentioned challenges in this system. Hence, a fuzzy logic self-tuning PID controller, which is a combination of fuzzy logic and a conventional PID controller, is proposed to control the grinding system, especially in the presence of model mismatch and disturbances. In addition, in order to solve the system challenges, a multivariable control approach based on an improved disturbance observer is proposed to suppress the effects of the disturbances. The most important feature of the algorithm proposed in this paper as the combination of fuzzy logic self-tuning PID and improved disturbance observer is its ability to eliminate system interaction, attenuate internal and external disturbances, and compensate the effect of system uncertainty on the performance of the ball mill grinding circuit. Simulation results in the cases of the set-point change in particle size and circulating load in the presence of model mismatch and external disturbances confirmed the controller performance compared to other controllers.

By Hamed Khodadadi, Hamid Ghadiri

In this study, a fuzzy logic self-tuning PID controller based on an improved disturbance observer is designed for control of the ball mill grinding circuit. The ball mill grinding circuit has vast applications in the mining, metallurgy, chemistry, pharmacy, and research laboratories; however, this system has some challenges. The grinding circuit is a multivariable system in which the high interaction between loops, the variation of the system parameters with time, and time delay are some of the problems that pose a challenge. Since the controller parameters are determined offline in classic PID control, these gains are unchangeable and cannot overcome the mentioned challenges in this system. Hence, a fuzzy logic self-tuning PID controller, which is a combination of fuzzy logic and a conventional PID controller, is proposed to control the grinding system, especially in the presence of model mismatch and disturbances. In addition, in order to solve the system challenges, a multivariable control approach based on an improved disturbance observer is proposed to suppress the effects of the disturbances. The most important feature of the algorithm proposed in this paper as the combination of fuzzy logic self-tuning PID and improved disturbance observer is its ability to eliminate system interaction, attenuate internal and external disturbances, and compensate the effect of system uncertainty on the performance of the ball mill grinding circuit. Simulation results in the cases of the set-point change in particle size and circulating load in the presence of model mismatch and external disturbances confirmed the controller performance compared to other controllers.

By W. Perkins

The Smoky Canyon Mine has recently installed a PROMPTED GAMMA NEUTRON ACTIVATION ANALYSIS (PGNAA) on-line analyzer as part of a long-term advanced process control program. The on-line analyzer was adapted from a continuous dry analyzer and a large on-stream wet analyzer to a compact, multiplexed 3" slurry analyzer. The analyzation feed system utilizes a multiplexer system to accommodate up to fourteen (14) different plant process streams. The corresponding sampling system also provides for dewatering of sample streams too dilute for timely analysis. Key analysis includes, but is not limited to, phosphorus, aluminum, magnesium, calcium, and potassium. This data currently allows plant operations to be manually evaluated and controlled. Future development of a plant-wide supervisory control system will utilize the data for plant operations. This paper discusses the design, installation, and operation of the PGNAA on-line analyzer at the Smoky Canyon Mine.

Jan 1, 1996

By Klaus Rieker

North of Antwerp central train station, two single-track tunnels for the high-speed train line between Brussels and Amsterdam were constructed. At the same time, the central train station was modified to a through station. Both 1.23 km tunnels are situated in the Antwerp sands and were constructed using a slurry shield machine. Due to the inner city location, the tunnels run over their entire length underneath structures, in some cases with only minimal clearance. The paper deals with these challenging situations. In addition, the tunnel boring machine, the tunnel lining and measures to limit settlements will be introduced.

Jan 1, 2007

By John Parianos

"Seafloor mining provides significant potential economic benefits for many Pacific nations that may be "land poor" but "coastline rich," meaning they have the potential to utilize and profit from the mineral wealth within their Exclusive Economic Zones that extend 200 nautical miles (360 km) out from their coastlines. The Independent State of Papua New Guinea (the State) recognizes this tremendous opportunity and is taking a leadership role in this emerging industry by becoming a 15% partner in Solwara 1 (with an option to increase their investment to 30%).The Solwara 1 Project has been gaining momentum since Nautilus Minerals and the State signed an Agreement on April 24. This new agreement with the State in which they have staked a minimum 15% interest as a meaningful partner, underscores the State’s continued and widespread support for the Project. Signing of this Agreement was a historical occasion and a milestone achievement for Nautilus Minerals and the people of PNG.The machinery being built for the Solwara 1 Project is taking shape. The Seafloor Production Tools are now over 90 percent complete. Assembly of the biggest tool, the Bulk Cutter, was completed in April this year and assembly work on the Collecting Machine and the Auxiliary Cutter commenced in May and June this year respectively. The Riser and Lifting system, which will be used to transfer the mined material from the seafloor to the surface within an enclosed system, is over 50 percent complete. The critical path for the Solwara Project is to secure a suitable vessel arrangement. Nautilus aims to have this completed by the end of this year."

Sep 1, 2014

By Jon Y. Kaneshiro, Ed Walton, Stephen J. Navin, Robert M. Sergeant, Storer J. Boone

The Coronado Traffic Tunnel is a proposed two-lane, reversible, road tunnel, which will relieve severe peak hour congestion problems on surface streets. The tunnel will take traffic from the Coronado Bay Bridge to Naval Air Station North Island. The project will include 12.5 m (41 ft) inside diameter by 1,112 m (3,650 ft) of tunnel, 552 m(1,815 ft) of cut and cover box structure, and 400 m (1,315 ft) of open cut structure. The geology consists of predominately clean and silty sand, saturated sand, with some clay layers, requiring Earth Pressure Balance or Slurry Shield tunneling technology.

Jan 1, 2001

By J. H. Schuenemeyer

Uncertainty estimates on coal resources were computed as part of the U.S. Geological Survey’s National Coal Resource Assessment study of more than 60 coal beds and zones in the Appalachian Basin, the Colorado Plateau, the Gulf Coast, the Illinois Basin, and the Northern Rocky Mountains and Great Plains. The estimates were made to provide zone specific measures of uncertainty on the historical categories of geological assurance, namely measured, indicated, inferred and hypothetical. Previous estimates were based solely upon distance from a drill hole. These new estimates incorporate site-specific variability and spatial correlation and indicate that there is considerable difference in variability within and between regions. Uncertainty estimates for the measured category are discussed in this paper.

Jan 1, 2001

By Y. Paul Chugh

NIOSH and the Illinois Clean Coal Institute are funding studies on characterization of coal and quartz dust in Interior Basin mines since 2009. Coal dust characteristics vary significantly and, are vital for the development of the engineering controls. This paper presents wettability characteristics of coal dust with respect to its chemical and physical properties, since wettability is considered to be a primary dust control technique. Particle size distribution, inter-particle interactions during wetting and quartz associations with organic and inorganic matter in coal seams is critical for understanding wetting phenomena. Silica content in the un-wetted fractions was found to be very high during wetting tests. Wetting of quartz may be limited by its association to hydrophobic materials as well as buoyancy forces resulting from particle size characteristics and particle-particle interaction in the wetting agent. Temperature of the wetting solution and effective contact time between dust particles and water droplets are found to be two important variables affecting the wettability. The characterization data obtained from this study can be utilized to develop engineering controls.

Jan 1, 2011

By Tom Ireland, Tony Rock

The proposed 1.83km long twin bore A3 Hindhead road tunnel planned for contruction in 2008 is being delivered under a Highways Agency Early Contractor Involvement (ECI) contract. The proposed construction methodology is progressive mechanical excavation of a horseshoe shaped tunnel with shotcrete installed close behind the face using robotic spraying equipment. The tunneling medium is a ‘soft rock’ sandstone for which there was little previous tunneling experience, requiring extensive geotechnical investigations and an innovative approach to lining design. A 240m long portal section though sandy material utilising a steel pipe umbrella is also required. This paper describes the development of the tunnel planning and design including the most recent developments in UK road tunnels, and the innovation included in the ‘permanent’ primary lining design.

Jan 1, 2007

By Steve Polegato, J. Coady Marsh, Gary Landry

The Donkin-Morien Mine in Cape Breton, Nova Scotia, has successfully completed the excavation of a 7.6m (25-ft) diameter access decline over a distance of 3.5km out under the Atlantic Ocean. The tunnel, completed in December 1984, was driven through a sedimentary sequence of sandstone, siltstone, mudstone and various gassy coal seams prior to intersecting the Harbour Coal Seam where development work will commence. The tunnel was driven by a Canadian prototype tunnel boring machine (TBM) manufactured by Lovat Tunnel Equipment, Inc., Toronto, Ontario. The 7.6m (25-ft) diameter full-face shielded TBM operated at various grades from 0-20%. This paper outlines the TBM design, excavation, support and backup system utilized in the drivage. Problems encountered and drivage rates will be addressed.

Jan 1, 1985

Electrostatically charged water droplets efficiently suppress breathable dust produced during open air rock crushing operations, according to recently completed independent tests conducted for the Environmental Protection Agency. Since a primary rock crusher produces very heavy clouds of dust, this application was selected as an appropriate test site to measure the efficiencies of new "charged fogging" equipment in mining and mineral processing operations. EPA's Industrial Environmental Research Laboratory, Research Triangle Park, NC, contracted TRC-Environmental Consultants Inc. of Wethersfield, CT, to conduct a full-scale demonstration of a recently developed electrostatic fogger, designed to project a charged fog spray at distances up to 15.2 m. Test results indicated overall fogger efficiencies of approximately 70%. The Fogger IV* employed in these tests is reportedly the largest charged logger ever made, with an extremely long operating range. The original fogger was designed for indoor dust control; this fourth generation version is designed for fugitive dusts, indoor and outdoor, and has an operating range up to 15.2 in.

Jan 6, 1981

By Leo R. Love

A comprehensive study of the environmental conditions of the area affected by the Colfax and Cheswick Power Stations is of extreme importance to Duquesne Light Company. The residents in the valley where the two plants are located have complained for many years about the emissions from the Colfax Plant which is of the 1920 to 1930 vintage and which has a capability of generating approxi¬mately 200 Mw. They were extremely happy to hear that the Company had plans for shutting it down, however, they were extremely unhappy to hear that we were planning to build another even larger one to take its place in the same vicinity, namely the Cheswick Plant with a capability of 570 Mw. They had visions of a plant twice the size of the Colfax Plant and belching out twice as much smoke. A few of the citizens from that area were most vehement at the public hearings that were held by the Allegheny County Air Pollution Bureau for obtaining an installation permit. With two power plants already existing in that area (Duquesne Light Company's Colfax Plant and West Penn Power's Springdale Plant), the primary concern of the Allegheny County Air Pollution Control Bureau was that the Cheswick Station might increase air pollution levels beyond what they considered to be dangerous limits. It became very evident that the Allegheny County Air Pollution Control Bureau would be extremely reluctant to grant installation and operating permits unless they were satisfied that the new plant would not increase local pollution levels and that we were taking sufficient steps to monitor the emissions from our plants and also the ambient air in the general area. We concluded that an extensive air pollution monitoring program must be conducted in the area to determine the effects of the operation of our plants. The program was conceived with our consultants, NUS Corporation of Rockville, Maryland, and was begun in June, 1968. It was designed to accomplish several things: 1. Determine the effect on the ambient air of the operation of each of

Jan 1, 1972

By D. Earley

High metal prices and new world trade standards and accounting for environmental liability in financial disclosures are creating markets for metals commodities that are produced using ?green technologies?. A promising "green" gold leaching system uses a polysulfide based lixiviant which is non-toxic and non-polluting. Laboratory testing has demonstrated selective gold extraction rates comparable to those of cyanide. The polysulfide lixiviant is a dilute aqueous solution which can be inexpensively produced from readily available chemical reagents and even mining wastes. The reagent system is self-buffering and maintains the optimal chemical environment for leaching. Treatment of residual leach solutions is not necessary because the lixiviant itself is not toxic, and breaks down as the system equilibrates. Simple closed system boiling is used to recover gold from process solutions. The polysulfide lixiviant can then be readily renewed and recycled back into the system, forming a closed loop system that conserves reagents and energy which minimizes operating costs. Economic projections have shown that the system can be used profitably for standard ore types and grades.

Jan 1, 2009

By Daniel H. Isreal

Because the federal government owns and controls nearly 80% of the most valuable oil shale reserves in the West, it is inevitable that federal leasing and siting will play a prominent role in development of an oil shale industry during the 1980s. Also, because of recent enactment of the Synthetic Fuels Corp. authorizing up to $88 billion in loan and price guarantees-federal financing will provide the critical incentive to permit private investment in a still infant industry.

Jan 1, 1981

By K. Freytag

The extraction of lignite in open-cast mines has a severe impact on the landscape. Proper landscaping after the shut-down of the mines has always been the statutory responsibility of the mine operator. The large area of the land used for open-cast lignite mining requires special regional planning procedures well in advance of the permitting procedure stipulated in the mining law. The lignite plan determines, among other things, the objectives of land reclamation. These objectives will then be outlined in more detail in the mine operation plans and implemented accordingly. Apart from the actual mining laws and regulations, a large number of environmental laws also determine the process of land reclamation. The success achieved in the field of land reclamation in all mining regions during the recent decades has shown that the lignite mining industry creates new landscapes that do not leave any scars in the countryside and merge very well with it.

Jan 1, 2005

By Simon Strong, Tim Brown, Luis Ignacio Sanz Vivanco

"One of the most significant technical and practical challenges facing the tunnel construction team on the Legacy Way road tunnel project in Brisbane, Australia was how to erect the pre-stressed precast concrete slabs to form the smoke duct in the tunnel boring machine (TBM) tunnels. An essential part of the tunnel ventilation system, the smoke duct, extends the full length of the 4.6km long twin, two lane tunnels. The vast majority of the tunnels (approx. 4.3km) were constructed using two 12.4m diameter double shield TBMs. The refurbished Herrenknecht machines broke several world records on the way to completing the tunnel excavation works in just over nine months. With the excavation complete the focus turned to solving the complex civil tunnel fit out challenges. A key component of the civil fit out of the tunnels was constructing the smoke duct in the TBM tunnels which was designed as a precast solution. The slabs which each measure 8.62m long by 2.0m wide by 200mm thick and weigh close to 9 tonne need to be erected above cast in situ corbels whilst other tunnel finishing works continue. The space proofing clearance offered by the design to the support corbels below and the precast segmental lining above was in the order of only 100mm. This paper details the events of how the Transcity JV tunnel fit out team, comprising some of Europe and Australia’s leading tunnel construction specialists, drew upon the global strengths of the existing JV member companies and the global reach of leading TBM manufacturer Herrenknecht to develop an innovative system to solve this challenging problem. This globetrotting story, which starts in Australia, visits Europe and mainland China before returning to Brisbane where it all began."

Jan 1, 2016

By Axel Nitschke, Josef Arnold

Bochum’s Underground Lot 306 was characterised by a confined site and unique tunnelling methods. A highly mechanized construction concept was developed to achieve high progress rates. Bespoke backup systems for muck disposal and material supply were used. For the first time in suburban tunnelling, wet shotcrete, batched onsite, was applied. A three-storey underground car park had to be undermined with only1.5 m of overburden and had to be lifted several times by “compensation grout in.” An existing operational two-lane metro tunnel was enlarged without any major impact on train operation.

Jan 1, 2005

By C. D. Litton

Laboratory experiments were conducted to determine the responses of a prototype smoke detector and a commercially available photoelectric smoke detector to smoke particles generated from various combustion sources. The prototype smoke detector combines optical scattering measurements with ionization chamber measurements in order to reduce/eliminate nuisance alarms due to the presence of airborne dusts or diesel exhaust particles. The commercially available smoke detector is designed for use in harsh environments where airborne dust represents a major problem due both to nuisance alarms and detector contamination. In the experiments, the responses of the two detectors were measured when exposed to smoke particles from the exhaust of a diesel engine and from a variety of fire sources, including wood, coal, styrene butadiene rubber, and No. 2 diesel fuel. For the solid fuels, data were obtained for both smoldering and flaming combustion. This report describes the experiments, their results, and the use of these results as they apply to early-warning fire sensors capable of the rapid and reliable detection of fires in atmospheres that may or may not be contaminated by either airborne dust or the products produced from diesel engines. Subsequent to these laboratory experiments, six smoke detectors were installed in an underground limestone mine for further testing and evaluation. DISCLAIMER: The findings and conclusions in this report have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.

Jan 1, 2009