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By A. Kevin Beaton, Robert W. Laakso

The desire for dry passageways promotes the NATM as it provides a final support system most suitable for the installation of a waterproofing membrane. Waterproofing during construction is a cost effective way to enhance safety and function as well as increasing the life of an underground structure. The NATM approach utilizes the surrounding mass as an integral element of the "ringlike" support system. At the Pennsylvania Turnpike Commission Lehigh Tunnel No. 2 various rock classifications were determined to require support measures ranging from 2 to 12 inches of shotcrete along with spiling, wire mesh, deformed bar, lattice girders and rock bolts as needed. Field instrumentation and monitoring programmes are a key factor for the success of the NATM. When the support "shell" stabilizes smoothing shotcrete, waterproofing and a final liner can be placed.

Jan 1, 1991

By Sukru Sumer

East Pit Lake is an artificially created lake that resulted from the remediation and reclamation of surface coal mining operations at TransAlta Utilities' Whitewood Mine in the Wabamun area west of Edmonton, Alberta. The original excavation resulted from the creation of a mine end cut at the northern extent of the mining operation. The area of the surficial drainage basin that feeds East Pit Lake was relatively small. Therefore, most of the inflow and outflow from the lake would result from regional ground water flow. There was a concern about the lake's ability to provide a suitable habitat for a sportfish population. To determine the final recovered water level and rates of recovery, a two-dimensional ground water flow model was used. Data supplied by nested piezometers in and around the mine were used to calibrate the computer simulation and assess predicted recovery.

Jan 1, 1995

By F. M. Jenkins

Improvements in miners? safety and health, as reflected by injury and illness statistics, have reached a plateau and even been reversed. Research into miners' OSH is a necessary adjunct to regulatory enforcement. Under the National Occupational Research Agenda (NORA) mining experts have come together to draft a national agenda for this research. The Mining Sector Council, one of ten NORA Sector Councils, has produced a draft national research agenda to guide all mining research entities: academia, government, and industry. The agenda has seven major objectives, each of which has a sequence of sub-objectives: Reduce the likelihood of disasters in mines; Improve mine disaster response; Improve the health of miners; Improve atmospheric control (ventilation) in mines; Improve health and safety through behavioral research; Improve mine design, systems operations, and management performance to enhance mine health and safety; Apply ergonomics, human factor engineering, to increase health and safety. Long-term maintenance of the Mining Research Agenda requires input from the public, both here and abroad, monitoring of the impact of research results using OSH data, and partners who will translate the research to practice.

Jan 1, 2012

By J. R. Parga

In mineral processing, poor froth-flotation performance translates into both an enormous loss of revenue and an unnecessary waste of the ore reserve. In this context, Bacís Mining Company developed a versatile new, high-performance flotation-cell design that can be incorporated into various flotation circuits. The main feature of this circular cell is that it is comprised of two separate sections, namely, a flotation cell that uses wash water to minimize the entrainment of fine gangue particles into the froth product and an external bubble generator that produces small bubbles of relatively uniform size at a specified aeration-rate. The air/water mixture is blended with the pulp by gentle agitation, so as to enhance particle-bubble aggregate-stability. Comparative metallurgical performance with conventional flotation cells show that the power requirements and operating costs for precious metal flotation are three times lower, while the concentrate grade is 7% higher and the recoveries of precious metals are 5% higher.

Jan 1, 2009

By B. Gigas, M. Preston, M. Giralico

Optimized mixer settler designs will now handle total flows of over 6,000 m3/hr.Computational Fluid Dynamics (CFD) is a timely and predictable tool for design development. Lightnin has the capability of using numerical analysis methodology to evaluate flow patterns and phase separation. CFD can show performance differences between changes, in mix tanks, in settler geometry, and in liquid depth, against variable flow rates. Understanding the differences allows the development of optimized designs. This paper focuses on the major design components of the mixer settler and how technological advances will lead to further improvements, when designing for today’s largest flow plants.

Jan 1, 2004

By P. C. Holloway

La Oroya zinc ferrite (19.5% Zn, 26.6% Fe, 0.052% Ga, 0.075% In) was roasted with coal under conditions more oxidizing than normally used in a Waelz kiln, and the roasted residues were leached with 200 g/L H2SO4. Overall zinc recoveries of up to 97% were achieved, with 35% of the zinc reporting to the fume after roasting at 1,100°C with a bituminous coal addition of 20%. Under these conditions, 93.2% of the Cd, 13.4% of the Cu, 33% of the Ga, 61% of the In and 18.2% of the Pb were recovered either in the fume or in the leach solution. At 2006 metal prices, the value of the recovered metals is comparable to that obtained from commercial Waelz kiln processing of this residue. Zinc in the franklinite (ZnFe2O4) mineral is reduced to zinc vapor, and, after oxidation, some of the zinc is found as ZnO or as Zn2SiO4 in the roasted residue. Iron reacts to form either hematite (Fe2O3) or magnetite (Fe3O4), with no metallic iron detected in the roasted residue, and less than 2% of the iron is solubilized during leaching. The residue produced after roasting and leaching is, therefore, much more stable than the residue from Waelz kiln processing and should be suitable for disposal in a landfill.

Jan 1, 2008

By Thomas Marcher

Stanford Linear Accelerator Center (SLAC) is located in Menlo Park, CA. In order to allow for enhanced experiments, the current facilities required expansion. Tunnels were excavated through very weak sedimentary rock interspersed with uncemented zones (Ladera Sandstone) employing the principles of the NATM. The overburden var-ied from 10 to 80 feet. The paper addresses the characterization of Ladera Sandstone that can exhibit the properties of dense sand and weak rock. The paper focuses on the challenges that were encountered during the NATM initial support design and the construction phase including the geotechnical instrumentation, monitoring and design verification process in particular the excavation of the junction between access tunnel and the FEH cavern (49 ft wide by 32 ft high).

By R. E. Mclvor

This is an update of an original dissertation on this topic by Lavallee, McIvor and Stolovitch (1992). A step-by-step, technical procedure used to measure and improve the performance of plant grinding circuits was adapted into a training program. ?Systematic Design of Instruction? was applied to: ? Determine if training was a suitable way to deliver this new technology; ? Define the technical content of the program; ? Select program specifications based on learner and context characteristics; ? Design, create and test prototypes of the training modules; and, ? Establish a process for plant implementation. The training program covers numerous skills that are extremely valuable for plant personnel, not only in the grinding area, but also for many other parts of the plant. This paper describes how new skills are brought into the workplace through designed instruction can be an effective alternative to hiring during severe skilled labor shortages.

Jan 1, 2008

By Jayant Khambekar

In a typical mining operation, run-of-mine (ROM) ore is crushed and screened to achieve a desired particle size distribution and then fed to processing equipment for further refining. For an operation to be profit-able, the ore handling system from the mine face to final product loadout must be reliable. However, the handling system components do not always perform as expected and production problems related to material flow occur. These problems include flow stoppages, limited live storage capacities, uncontrollable flow, segregation, spillage and dust emissions. These result in lost production, excessive maintenance, safety and environmental issues, and even structural failures, in some cases. Flow patterns Flow problems and their solutions can be best understood by first learning how bulk solids flow. As bulk solids discharge by gravity from a storage system, primarily two types of flow patterns can develop: funnel flow and mass flow. Figure 1 shows a schematic of these two flow patterns. In funnel flow, only a portion of the material is in motion during discharge, which flows toward the outlet through a channel that forms within the stagnant material. Funnel flow occurs when a hopper is not sufficiently steep and smooth to ensure flow along the walls or when the outlet is not fully effective. In mass flow, all of the material is in motion whenever any is discharged ? there is no stagnant material. Mass flow occurs when the hopper is sufficiently steep and smooth to ensure flow along the hopper walls. Shallow valleys are not permitted and the outlet must be fully effective. A third type of flow pattern, called expanded flow, can develop when a mass flow hopper (or hoppers) is placed beneath a funnel flow hopper or bin. The mass flow hopper is designed to activate a sufficiently large flow channel in the funnel flow hopper to avoid flow problems due to a rathole. The flow pattern in which a bulk solid discharges from a storage system strongly influences the flow problems that may occur in that facility.

Jan 1, 2009

By Q. Wu

Neural network methodology is used to predict mean particle size resulting from rock blast fragmentation. A blast data base developed in a previous study is used in the current study. A part of this blast data was used to train a single-hidden layer back propagation neural network model for each of the similarity groups obtained in the same previous study. Levenberg-Marquardt algorithm provided the most stable and efficient training out of the four algorithms evaluated. An extensive analysis was performed using a part of the blast data to estimate the optimum number of units for the hidden layer for each similarity group. The remaining blast data are used to validate the trained neural network models. Capability of the developed neural network models is determined by comparing predictions with measured values and predictions based on one of the most applied fragmentation prediction models appearing in the blasting literature. Prediction capability of the neural network models was found to be strong and better than the existing most applied model. Diversity of the blasts data used is one of the most important aspects of the developed models. The developed neural network models are suitable for practical use at mines.

Jan 1, 2011

By Verya Nasri

This paper presents analysis of damages and rehabilitation design for three major French rail-way tunnels built in mid-19th century. The La Nerthe tunnel underwent ovalization deformation with excessive displacement at the springline, and pinching and bursting of the liner bricks at the crown due to tectonic residual stresses with very high lateral earth pressure. The Saint-Louis les Aygalades tunnel invert was subjected to undulatory deformation resulting in tracks misalignment, which was caused by non-homogeneity of mechanical and hydraulic properties of the ground. The Roches de Condrieu tunnel required widening to comply with the increase in dynamic envelope of trains due to their larger cross section and higher speed. The applied rehabilitation methods and constraints of work in these busy mainline railway tunnels have been discussed in detail.

Jan 1, 2008

By Thomas P. Kwiatkowski, Joginder S. Bhore, Christopher D. Orlandi, Jose Velez

Three case histories of successful TBM tunneling for New York City Water Tunnel No. 3 are presented. The tunnels, costing about one billion dollars total, are the 5-milelong, 18'-11" OD Brooklyn Tunnel; the 5-mile long, 23'-2" OD Queens Tunnel, and the9-mile long, 12'-4" OD Manhattan Tunnel. The three tunnels are the first major tunnels constructed in New York City rock utilizing the TBM method of construction. This paper describes and compares the three tunnel projects in terms of geology, construction methods, TBM’s, rock and groundwater behavior, rates of advance and other performance data, and challenges and solutions encountered during the projects.

Jan 1, 2007

The largest investment in mining equipment in Caterpillar?s history ? The F series mechanical and electrical drive trucks ? is rapidly advancing. Caterpillar showcased the 793F and 797F mechanical drive trucks and the 795F ac electric drive truck at MinExpo in 2008 and have continued testing since then. The 793F and the 797F have accumulated more than 75,000 hours of field testing and have proven their performance capabilities and their durability. The new Cat C175 engine that powers them has racked up 130,000 hours of field testing in mining trucks and more than 120,000 hours in power systems. Because of the success of these field-follow programs, the 793F is targeted to go into full production within a few months and the 797F late this year. Caterpillar engineers have been testing two 795F ac prototypes at the Tucson Proving Grounds in Arizona. The development program has provided input for the construction of a new 795F ac in Decatur, IL. The new truck recently shipped to a copper mine in North America where it will serve as the first field-follow 795F ac as it works at the mine. The 313-t- (345-st-) capacity 795F ac will enter a new size class for Caterpillar, and, as a result, the primary focus of the Caterpillar ac electric program has been on the 795F ac. The commercial launch date will be defined as the field-follow program progresses. ?It?s fitting that soon after producing the 50,000th Cat off-highway truck, we are now shipping our first ultra-class ac electric drive truck to a mine,? said Chris Curfman, president of Caterpillar Global Mining. ?Our new trucks further solidify our position as the one manufacturer to provide unparalleled options and unmatched customer support.?

Jan 1, 2009

By J. L. Page, A. C. Marlowe

The Research and Development Services of South Africa has begun underground trials with a Robbins 52RE blindhole borer using a cutterhead fitted with high pressure water jets to assist mechanical cutting. The objectives of the work are to reduce cutter costs by increasing cutter life and to increase overall penetration rates. The paper reviews blindhole boring in South Africa and laboratory experiments in rock cutting assisted with high pressure water jets. The borer and its ancillary equipment are described. Initial results of underground boring experiments are presented. The paper concludes with the test programme for the future.

Jan 1, 1985

By D. Kwietnewski

The 4th bore of the Caldecott Tunnel is a 50-ft horseshoe shaped highway tunnel located in the hills east of Oakland, California. Tunnel excavation was mostly completed using one of the world?s largest commercially available roadheaders, a Wirth T3.20. The geologic profile included seven different geologic units, which displayed a range of different behavior with regard to excavation and initial support. Following a brief introduction to the excavation and support methods, this paper will discuss roadheader performance in the various geologic units encountered during excavation. Comments will also be made concerning the relationship between the roadheader method of excavation and observed ground convergence during excavation.

Feb 27, 2013

By Thomas D. Kelly

In 1900, the average U.S. citizen’s average life span was 47 years. He traveled about 1,900 km (1,200miles) in a lifetime and resided in a home with an ice-box for food storage and oil or gas for lighting. He communicated by mail, telegraph and crude telephones with limited availability and range. By 2000, the average citizen’s life span was 77 years. He traveled an average of 19,000 km/a (12,000 miles/year) by automobile alone. He resided in a home with many electrical appliances, including refrigerators and electric lights. And he communicated almost instantaneously with any other part of the globe by several widely available means, including portable phones and e-mail.

Jan 1, 2002

By F. W. DeVries, O. B. Mathre

Addition of Kastone® peroxygen compound and formaldehyde to cyanide gold extraction process effluents, containing at least 5 mg soluble copper per liter, will oxidize acid-dissociable cyanide to levels less than 0.2 mg per liter, without appreciable oxidation of thiocyanate. Most of the copper precipitates and is removed by filtration of the treated solutions. The treatment can be completed in less than 2 hours when the excess of hydrogen peroxide over the cyanide is about 75-100 mg per liter. The excess hydrogen peroxide destroys residual formaldehyde and then is catalytically decomposed by the copper-containing solids that separate, so it will not interfere with subsequent operation. A pilot plant using this technology has been operated for more than four months at rates from 1-2 gpm. Clear, filtered effluent containing less than 0.2 mg acid-dissociable cyanide per liter has been produced.

Jan 1, 1981

By R. Grandori, L. Pellegrini

The construction of the La Joya hydropower plant (Costa Rica) was awarded by the Spanish power company, Union Fenosa, to the Italian Joint Venture formed by the companies SELI SpA and Ghella SpA. The project, located in a mountainous region of central Costa Rica, includes a 7.9-km-long head race tunnel having an excavation diameter of 6.18 m. A double-shielded TBM was selected to perform the tunnel excavation, which involved mainly volcanic rocks in variable but generally very weak conditions. The tunnel crossed long and continuous sections in completely weathered rock masses with no residual cohesion and with high water inflows. The paper describes and analyzes: The special methods adopted to overcome these sections with the TBM includ-ing face stabilization by chemical grout and foams as well small by-pass tunnels in the crown combined with TBM advance/support The grouting design and the grouting method that was implemented to meet the waterproof design specifications and restore the original groundwater level in the mountain The additional geological investigations performed to improve the knowledge of the rock mass in front of the TBM and the outcomes of these investigations The performance of the TBM in different ground conditions and on average along the entire tunnel Finally, the author’s comment about the possibility of implementing and improving the technologies experimented with in this project in future similar applications.

Jan 1, 2007

By A. Moergeli

The Swiss are currently building the world’s longest tunnel, the 35-mile long Gotthard Base Tunnel. At Sedrun, for the first time in tunneling, four Roadway Support Machines will drive through most difficult ground, supporting variable diameters of up to 13 m. The machines are prepared for their first deployment. At Amsteg, two Hard Rock TBMs have successfully crossed a known fault zone by applying full circle steel arches and shotcrete immediately behind the cutter head. Comparisons between Drill& Blast and Hard Rock TBM are shown.

Jan 1, 2005

A large lab apparatus was designed using a scale-down methodology based on the design legacy of the current FLSmidth commercial forced air flotation machines. This new apparatus, along with a new test methodology, was used to evaluate new rapid prototype concepts. The apparatus was designed to monitor bubble size, power, pumping capacity, Jg, velocity profiles, froth character, and tip speed. The methodology developed follows a sequence that goes from hydrodynamic tests and solids suspension tests to a flotation kinetic test. This methodology has been demonstrated to be a good tool to determine the effect of machine design changes on flotation.

Jan 1, 2012