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By Todd Kilduff, Michael Tinney

The North Temple Tunnel pedestrian underpass in Salt Lake City, UT was built using a pipe canopy method that met significant challenges in potentially running ground conditions. Kilduff Underground Engineering (KUE) was the designer for the 20-foot-diameter SEM tunnel, Design-Build contract. Geotechnical data indicated ground conditions consisted of loose silty gravel for the majority of the face overlying soft to medium stiff clays in the tunnel invert. KUE designed a pipe canopy as pre-support to stabilize cohesionless gravels in the crown, a shotcrete initial liner with lattice girders to minimize disturbance of the finer-grained materials in the invert and a final liner with waterproofing system. The project was presented with a few unique challenges, primarily from the adverse ground conditions, but was successfully completed safely and schedule

Dec 1, 2022

By Michael Rehbock-Sander

The Gotthard Base Tunnel (GBT) is 57 km (35 miles) long and consists of two par-allel single-track tubes with an ex-cavation diameter ranging from 8.8 to 9.5 m (28.8 to 31.2 ft). These are interlinked by cross-passages every 312 m (1,000 ft). Two multifunction stations (MFS) are located in the sections Sedrun and Faido, at one-third and two-thirds of the entire tunnel length (Fig. 1). These will be used for the diversion of trains to the other main tube via tunnel crossovers, for the housing of tech-nical infrastructure and equipment and for potential emergency stops. To reduce construction time, the GBT was divided into five sections and was excavated from several sites simultaneously. The tunnel was excavated from the two portals, Erstfeld in the north and Bodio in the south, and also from three intermediate attacks, with their corresponding access tunnels, in Amsteg and Faido and two vertical 800-m (2,624-ft) deep shafts in Sedrun.

Jan 1, 2012

By R McDonough

DTL2 contract C916 was awarded in March 2009 for S$340 M. This contract includes two mass rapid transit (MRT) 1100?m long bored tunnels using two slurry tunnel boring machines (TBMs), with an internal diameter of 5.8?m, two cross passages and 135?m of cut-and-cover tunnels The contract also includes the design and construction of a new underground station including station entrances, subway links, architectural finishes and external landscaping. The station, located at Upper Bukit Timah Road near Jalan Jurong Kechil will also double as a civil defence shelter.The works included significant traffic management in a dense urban area in order to create the working areas whilst keeping the requisite number of traffic lanes. This involved numerous utility diversions and included the removal of a 33-year-old pedestrian overhead bridge (POB) over busy Bukit Timah Road. The station and tunnelling works were completed on time, including a ‘dock and dismantle’ TBM retrieval and subsequent breakthrough of the separating wall.This paper will detail the methods and solutions used to construct the tunnels and stations, with a focus on the requirements for construction of the station to be a civil defence shelter if required. This involved solutions to tying reinforcement and placing concrete to high standards in a restricted space, as well as the incorporation of heavy blast doors and other associated protective measures. The efforts of the management team resulted in the project being awarded first prize in the 2011 Land Transport Authority’s Annual Safety Award Convention and being named winner of the Safety and Health Award Recognition for Projects (SHARP) award at the 2011 Workplace Safety and Health (WSH) Awards. As well, McConnell Dowell won a Green and Gracious Builder Award (Excellent Category) from the Building and Construction Authority (BCA).CITATION:McDonough, R, 2014. Design and construction contract C916 Beauty World Station and Tunnels, Singapore, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 411–418 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By Georgia J. Lysay

The Kemess Mine tailings impoundment is retained behind an earthfill and rockfill dam that, when complete, will measure about 140 m in height with a crest length in excess of 1 km. Due to weak foundation conditions, the dam must be raised at a very flat downstream slope approaching 7H:1V. This requires an enormous volume of fill to construct the downstream shell of the dam, which has a low permeability clayey till core and is raised via the centerline construction method. For the initial years of annual dam raising, from 1996 through 2002, the downstream shell of the dam was constructed with non acid generating waste rock from the open pit, 7 km distant and requiring an uphill haul with obvious cost implications. To reduce costs, and to reduce waste haulage constraints on mining schedules, feasibility studies were initiated for raising of the downstream shell using cycloned tailings sand as opposed to open pit waste. This required inclusion of flotation cells for removal of residual sulphides from the tailings to produce the non acid generating product mandated for the downstream shell of the dam. These studies were positive, and cycloned sand construction was initiated in December of 2002. This paper describes the experience gained with cycloned sand construction for the dam. Unique aspects include environmental controls given the sulphide-bearing ores, preparation of the existing shell of the dam for subsequent placement of hydraulically placed cycloned tailings sand, on-dam settling ponds, water management issues, reclamation of the sand dam for erosion control commensurate with the wet climate, and use of the system to construct an above-water beach of non acid generating tailings to increase the closure security of the structure. A particularly unique aspect of the Kemess experience is hydraulic fill operations extending throughout the coldest winter months, as compared to other operations where such placement has traditionally been considered non-viable through the winter months

May 1, 2007

By R. C. Gilmore, J. McMack, G. E. Bogin, J. F. Brune, C. DeRosa

"Researchers at the Colorado School of Mines are designing and building a 1:40 scaled physical model of a fully operational longwall coal mine. The purpose of the model is to minimize the occurrence of methane explosion hazards by testing various ventilation strategies and determining optimal methane sensor placement throughout the longwall face. Fluid scaling factors were analyzed using Computational Fluid Dynamics software Ansys FLUENT™ at both full and 1/40th scales. Researchers were able to identify key scaling factors and subsequently developed suitable flow parameters that would maintain full scale accuracy of flow patterns in the 1/40th model. KEYWORDS Coal, Longwall, Methane, Explosion, Scale Model, Ventilation, Fluid Dynamics, Richardson, Gob, Porous INTRODUCTION Mine ventilation systems are a key component for ensuring a safe working environment by introducing fresh air from the surface and diluting explosive gases and hazardous contaminants. This holds true for longwall coal mines where the emission of flammable methane gas from the longwall face as well as the gob can create explosive mixtures of methane and air. Therefore, an effective ventilation strategy can help mitigate the potential for accidents within a mine. Developing an effective mine ventilation system (MVS) requires a detailed understanding of the physics of gas transport and how this relates to specific geometries and obstructions in the face. Researching this phenomenon requires the development of computational fluid dynamics models capable of simulating fluid flow and methane species transport that can be validated through physical experimentation. Unique site conditions determine ventilation layouts for every coal mine. Researchers have designed a 1/40th scaled physical model of a longwall coal face and adjacent gob that includes movable shield supports and a movable shearer with rotating cutter drums that can be adjusted to a variety of ventilation conditions. The proposed work will address the need for an improved Mine-wide Atmospheric Monitoring System (AMS), and provide the ability to link existing MVS models with AMS in real time. By accurately representing the coal face, the gob area and the mining equipment, gate roads and bleeder entries, the scaled model accurately represents all relevant structures, geometry, and dynamic conditions. A Plexiglas cover allows full optical access for sensor equipment as well as visual inspection of the fluid flow and species transport."

Jan 1, 2019

By E. Nolasco, J. Ouellet, T. Tikka

"Shaft bottom structural systems are used in underground mining to support transfer of personnel, equipment and ore to and from underground to the surface. This paper first summarizes the evolution of design philosophy from a concrete tower supported on a concrete plug to the current structural steel design arrangement with unlined shaft walls, clear shaft bottom area with only a concrete housekeeping pad. Then the paper reviews the design parameters, analysis and design, and construction methodology for this rather unique shaft bottom structural system consisting of three sets of hitch beams, with each having specific functional requirements. INTRODUCTION Shaft bottom structural systems are used throughout the world in underground mining operations to provide a means to support the transfer of personnel, equipment, materials, ore and waste entering and exiting a vertical shaft ready for transport to and from the surface via the hoisting system. The shaft bottom structural system, for the Service Shaft (SS) at the Jansen Mine, is designed to accommodate two skips, a personnel/equipment cage, counterweight, services, loading pocket, rope changing, arrestor system, crash (or catch) beams, access platforms, stairs and rope divider system. Stantec and BHP have engineered a unique structural steel shaft bottom system for hoisting system at a Potash Mine. The shaft bottom structural system connects to a fixed guide and cantilever bunton system, used in the vertical shaft (shaft barrel), above the shaft bottom. The geometry for the shaft bottom structural system, shown in Figure 1 a), features three sets of hitch beams, beams which span across the shaft excavation or barrel. At the top of the structural system are two upper hitch beams. These hitch beams support a 64 metre suspended rectangular braced tower (upper tower), complete with steel guides for the conveyances. The upper tower passes through the main station (potash or mining) level and then connects to the top of the arrestor (lower) tower structure via a sliding vertical connection. The potash level is supported by two hitch beams spanning the shaft and loading pocket excavations. The arrestor tower, a braced compression tower structure, is carried by a third set of hitch beams. Below the third set of hitch beams is a short suspended tower complete with access platforms, stairs and the rope divider system."

Jan 1, 2019

By J. Ouellet

The design of hydrostatic liner for a deep potash mine shaft in Saskatchewan poses tremendous technological challenges. Technology has evolved to a point where one could consider a new innovative approach to hydrostatic liner design. But there is still a place for conventional technologies such as cast iron tubbings. As will be discussed in this paper, improvement to manufacturing process, installation procedures and even new materials can bring this technology to an excellent level of performance. With the spur of new projects in the potash industry of Saskatchewan, the authors worked in various shaft liner designs from the conceptual stage through to the construction phase. They were either directly leading the design work on some of these projects or acting as an external reviewer on others. Most of these shaft liner designs involved cast iron tubbing technology and ground freezing. The major challenge in sinking potash shafts in Saskatchewan is to go through a water-bearing ground formation under high pressure, known as the Blairmore or Manville fm. The only proven stabilizing technology for these formations is ground freezing. For a potash shaft, dry shaft conditions are highly desired, so a fully waterproof hydrostatic liner is required. All the existing potash mine shafts in Saskatchewan, except for two with composite steelconcrete lining, used the cast iron tubbing technology. Two new shaft tubbing liners have been constructed recently, one in the Athabasca Basin and one for a potash mine in Saskatchewan. When the authors began working on these new projects, what became quickly evident is that the technological knowhow for designing and constructing tubbing liners was no longer available within Canada and that the past construction methods used to sink tubbing lined shafts was obsolete. The tubbing liner for the shafts sunk in the sixties were designed either by German or British companies. In both of these countries only few tubbing lined shafts were sunk in last 40 years and the technology used in the sixties was not improved. There are only few countries where tubbing is routinely produced and installed: China, Russia, Ukraine and Poland. Out of these countries Poland is the one where this technology is the most advanced. The authors, working in close collaboration with engineers from Poland, attempted to rebuild this knowledge for the mining industry in Canada. This process involved thorough analysis of old technical reports, literature review and study of current polish design and construction practices as well as site visits of existing shafts. Through actual construction experience, some lessons were learned as well as ideas for improvements. In this paper, the authors will present a succinct review of design and procurement process. But, the practical aspects of the construction and installation methodology will be treated with more emphasis, more specifically the practice leading to good liner performance. Some of the poorly understood technical aspects of tubbing installation will be discussed more thoroughly and some currently accepted myths dispelled.

Aug 1, 2013

By A. J. Williams

"Whenever a decision is made to bring a mineral deposit into production, the Owner in actual fact has decided to convert substantial sums of capital into productive capacity with the intenti6n of making a profit from such conversion.Escalating costs of construction, frustrating and costly delays in comp1etion, the increasing tempo of technological change and the increasing size and complexity of mineral processing projects have convinced Owners that the best way of implementing their capital must be sought and utilized. This requirement has stimulated a search for ways and means of applying modern management techniques to the design and construction of mineral processing plants.This search by consulting firms has resulted in the evolution of the concept of project management and the development of planning and con trolling techniques with the result that Owners can seek and obtain better assurance that their project objectives will be fulfilled.This paper will attempt to outline how a mineral processing plant can be brought into production through the implementation of project management techniques.Definition And Objectives Of Project ManagementThe design and construction of mineral processing plants is subject to the restraints of three inter-related parameters -Quality, Cost and Time each of which influences and is influenced by the other two.Project management is a technique where the Owner delegates complete responsibility to a single organization for all phases of a project (design, procurement, construction and commissioning) for the above parameters but retains freedom for major decision making. Normally, the consultant under-takes full responsibility for all phases, but partial project management services can be provided when the Owner so desires.The objective of project management is first to devise and define and then to implement a program in which the relationship between the three parameters of Quality, Cost and Time is optimized, i.e., the desired functional and other requirements are attained (but not exceeded) at the lowest practicable overall cost in the shortest practicable time. The measure of success of a project lies in the degree to which this objective is achieved."

Jan 1, 1974

By Timothy O’Rourke, Karrie Buxton, Chris Lynagh, Daniel Dobbels, Frederick Vincent

The Doan Valley Storage Tunnel Project in Cleveland Ohio was constructed to control Combined Sewer Overflows (CSOs). It is a complex system of three tunnels ranging from 8.5 to 18 feet in diameter with a total length of about 2.3 miles that was put into operation in mid-2021. The project lies within and below the cultural, educational, and medical hub of Cleveland, which presented unique design and construction challenges. This paper provides a case history of the design and construction, with particular attention given to lessons learned in devising a large tunnel system that can carry both dry and wet weather flows constructed in rock with limited cover, within a flood plain area and vibrant urban center

Dec 1, 2022

By Verya Nasri, Agustin Rey

Once completed, the Montreal Réseau Express Métropolitain (REM) will be the fourth largest automated transportation system in the world. The REM represents construction costs of approximately 7.0 billion Canadian dollars. The project consists of 67 km of twin tracks over four branches connected to downtown Montreal. The project includes 26 stations with 3 underground stations in downtown Montreal. One of the underground stations was built using the NATM method with thin permanent shotcrete initial and final liners separated by a sprayed on waterproofing membrane. The 2 other underground stations were built with the cut and cover approach including one using permanent secant pile wall with permanent walers and struts as the support of excavation and the final perimeter wall of the station. The project also includes the rehabilitation and enlargement of the Mont Royal Tunnel. This 100-year-old double track tunnel is about 5 km long. The REM also consists of 3.6 km new TBM tunnel connecting downtown to the Montreal International Airport through saturated soft ground and karstic rock. By the time of RETC, the construction of REM underground structures will be completed. This paper presents the design and construction aspects of the underground structures of this mega project.

Jun 13, 2023

By Earle J. Klohn

"The design, construction and operation of tailings dams is rapidly becoming a major consideration for most new mining developments, as well as for many existing operations. In North America, under pressure from public opinion, various government agencies have in recent years enacted legislation covering the design, construction and operation of tailings dams. In British Columbia, comprehensive legislation has been passed during the past year (1971). All of these new regulations may be placed into two broad categories: regulations concerning the safety of the dam and appurtenant structures, and regulations concerning the prevention of pollution. Both types of regulation affect the design of the tailings dam facilities. Consequently, they must be considered jointly by the designer. A good tailings dam design must satisfy the basic requirements of safety, pollution control, storage capacity and economy. To achieve this, 'the design must be based on a thorough understanding of both the geotechnical problems involved and the requirements of the mining development. Obviously, this requires close cooperation between the designing geotechnical engineers and the mining operators. This paper outlines the major engineering factors that should be considered in the investigation, design, construct ion and operation of tailings dams. Basic methods of tailings dam construction are reviewed and the advantages and disadvantages of each briefly discussed. Comparisons are made between the design and construction of conventional water supply dams and tailings dams. Examples are presented of some of the problems that may arise during construction and operation of a tailings dam. The paper also explains the need for basic instrumentation of tailings dams and for carrying out simple field tests and measurements during construction and operation. Of prime importance is the downstream monitoring of surface and subsurface seepage flows. These observations are invaluable where contamination of surface and/or subsurface water may become a contentious issue at some future date. Each tailings dam design must be based on a study of the particular requirements of that project. To make a proper evaluation, adequate data must be available concerning a large number of items•, including such things as: topography, hydrology, geology, subsoil properties, seismicity, government regulations, fineness of mill grind, mill water balance, availability of suitable construction materials, volume of water to be stored behind starter dam, downstream development or liability, and many others. The large number of variables involved in such an evaluation often result in the designer considering two or more alternative designs. Selection of the final design, which is usually based on detailed cost analyses of the alternatives, must be made in close consultation with the owner."

Jan 1, 1972

By W. L. Chong

For a project located in Docklands Victoria, a high-rise development was proposed where the geology comprised soils of various compositions and consistencies to approximately 50m deep before being underlain by a siltstone bedrock. Due to the structural loads and spatial constraints, the majority of the foundation piles were designed to be socketed into the siltstone. Key factors in selecting the Continuous Flight Auger (CFA) technique as an effective piling solution are explained. These factors included structural and geological considerations, piling rig capabilities, pile testing regime to verify load performance and integrity, the extensive suite of construction quality controls and instrumentation records required while also achieving an appropriate piling budget and program. This paper also described how these factors underpinned the design approach of the final piling scheme. Critical aspects considered during construction and post-construction quality and pile testing records required to meet and satisfy the strict project piling specifications are also presented. The project adopted what may be considered the “best practice” in deep CFA piling. To the author’s knowledge, this project achieved the record for the deepest CFA piles in Australia where multiple piles to 53.8m deep were constructed.

Nov 1, 2022

By David Mast, Amanda Foote, Mina Shinouda

The Michigan DOT’s I‑75 Modernization Project, Segment 3, is a 30-year, $1.2 Billion design-build-finance-maintain project in Southeast Michigan. The scope includes building a nearly 4-mile long, 14.5-foot ID stormwater storage tunnel. The tunnel and pump station are being built concurrent with new roads and bridges, requiring multiple levels of design and construction coordination. Underground risks include the poten‑ tial for encountering granular soils, groundwater, and explosive gases. The new tunnel will be mined by a new open-face TBM and lined with a one-pass steel-fiber-reinforced precast concrete segmental lining. Shaft construction began in early 2020 and tunnel mining in July 2020.

Jun 13, 2021

By Patrick O. Shires, Harry W. Schnabel

With stable building sites becoming scarce in the greater San Francisco Bay Area, the new Summit Senior Care Facility is being built into the side of an unstable hillside adjacent to the San Ramon Regional Medical Center in San Ramon, California. This hillside has had a long history of instability and the site of the new Senior Care Facility required excavation into both a historic old landslide and a more recent active landslide. After a thorough geotechnical study, it was concluded that the best way to build the new facility would be to construct a tied-back retaining wall in the area of the old landslide, since it extended off-site onto two adjacent properties, and remove the active landslide and replace it with compacted fill before cutting into its toe area with an additional tied-back retaining wall. The design was further complicated by the proximity of the site to several active faults. In the area of the old landslide, the combination of an ascending slope behind the wall, landslide forces and seismic forces resulted in total design pressures between 365 to 4,575 PSF for a wall with a maximum height of 30 feet. The wall for the old landslide was constructed by first drilling and placing steel soldier piles in concrete. The tip of the soldier piles extended a minimum of 12 feet below the landslide plane that was up to 36 feet below the bottom of the wall. Permanent double corrosion protected tiebacks were then installed through the soldier beams and anchored below the slide plane. A shotcrete facing was then installed on the face of the wall. BACKGROUND The site of the Summit Senior Care Facility is located on the southwest flank of Mount Diablo adjacent to San Ramon Valley which is characterized by gently rolling hills. The San Ramon Valley Regional Medical Center, which opened in 1990, is located to the north and an existing church is located to the southwest. There are also private residences located to the southeast. The site is shown in Figure 1. Numerous faults run close to the site, the most significant of which are the Calaveras and Pleasanton faults. The site has also had a long history of slope instability and has been the subject of numerous investigations. Studies conducted in 1979 and 1984 concluded that there was a landslide in the area and recommended that a buttress shear key be constructed between the subject site and the existing church for a sewer main as well as removal and replacement of the head area of the old landslide to stabilize the hospital site. While two previous geotechnical studies in 2008 and 2016 identified slope instability, they did not recognize the genesis and limits of the old landslide on the western portion of the site or the limits of the active landslide on the eastern portion of the site.

Jan 1, 2018

By Sivilay Sayavong, David Puller, Julian Gatward, David Hard, Martin Stanley

"AbstractThe Thames Water Tideway Tunnels programme involves the upgrade of London’s combined sewer and storm water system. The first section is the Lee Tunnel between the Beckton Sewage Treatment Works (STW) and the Abbey Mills Pumping Station. This will intercept the overflows currently discharging to the River Lee and has the capacity to store and transfer 350,000m3 of storm water and sewage. The project required 4 shafts and a 6.9km 7.2m diameter tunnel. The shafts are some of the largest ever constructed in the UK, with diaphragm walls up to 98m deep and 1800mm thick. As a result of the innovative methods of diaphragm wall design and construction adopted the 4 very large and deep shafts were able to be excavated and completed safely, with minimal water ingress and with extremely high quality.MVB, a joint venture of Morgan Sindall, Vinci Construction Grands Projets and Bachy Soletanche are delivering the £635m contract with Thames Water’s Project Management Team in a collaborative manner under an NEC contract. Mott MacDonald, Morgan Sindall UnPS & Bachy Soletanche are acting as designers.Some of the important advances in diaphragm walling made included:??Diaphragm wall design to both EC2 & EC7 taking into considering the assessment of chalk stiffness, high hoop stresses, large multiple openings and non-axisymmetric loadings.??Formation of shafts as a faceted circle from a series of overlapping panels, with primary panels up to 7.2m wide demanding concrete volumes up to 1300m3 be poured in one go. Overlapping secondary single bite panels cut into the grade C50/60 concrete.??Excavation of the full geological stratigraphy of London making bentonite management complex.??Panel verticality of 1:300 required over the full depth. The results achieved this and in many cases exceeded expectations with some panels coming in at up to 1 in 800 with the majority at 1 in 400 to 1 in 500. The project is also the first in the Soletanche Bachy Group to take data from the ultrasonic drilling monitor used to check the verticalty in electronic format in order to create 3D CAD as-built drawings.??Each diaphragm wall panel was reinforced over its full depth. Up to 18 separate pieces of reinforcing cage had to be installed in primary panels. Cages underwent a full range of temporary works designs to check that lifting, splicing and placing could all be undertaken safely. Fibreglass was used in the tunnel portals in the shafts to ease breakthroughs."

Jan 1, 2014

By Ihab Allam PE, Meeok Kim. PE. Ph. D

The wet weather equalization basin (EB) planned for Pacifica, CA is a 45 feet deep rectangular shaped underground water tank containing over 2.1 million gallons of water, and located only 500 feet away from the Pacific Ocean. The location and size of the water tank, and the geotechnical characteristics of the selected site presented many engineering and construction challenges. The engineering had to consider a structural system which can fit into the limited area of the site and yet need to meet the storage volume requirement. In addition, the system construction should meet the city’s tight budget and schedule.

By Guilherme L. M. G. Carvalho, Zachary T. Fleming

In a world of 2-dimensional design documents, envisioning and understanding 3-dimensional interferences for complex foundation construction scenarios can be challenging. Videos and computer models serve as 3-dimensional spatial aids but have drawbacks related to a fixed perspective. Augmented and virtual reality (AR/VR) provide new tools to communicate design challenges and improve construction planning. This paper provides a practical look at the basics of AR/VR systems and the tools available to the foundation design and construction industry by giving a high-level example of the technologies’ use in the design and delivery phases of a complex micropile installation project for the remediation of a dam foundation. Using these technologies, GEI was able to design and deliver a complex foundation remediation solution. AR/VR benefited regulators, and the client, to help understand the design concept, construction sequencing, and approach to overcoming installation challenges. Due to its user-friendly nature and less rigorous programming and hardware requirements, AR proved to be more useful than VR for this scenario. AR/VR will likely not replace videos and computer models; however, it can be a useful 3-dimensional visualization aid that complements the project delivery process and offers benefits that traditional methods cannot. INTRODUCTION Augmented and virtual reality is a promising and rapidly developing technology within the engineering and construction world. Like any rapidly developing new technology, the language describing it can be confusing and dynamic. To eliminate the confusion some definitions must be made. AR/ VR definitions The definitions of virtual reality (VR) and augmented reality (AR) for the purposes of this paper are as follows: VR is a computer-generated immersive environment that the user experiences within a digital 3- dimensional space (Satava, 1993)AR is a composite view created by superimposing digital objects into the user’s real-world view (Azuma, 1997). Often, VR is used in an office environment and allows the user to “visit” the digital site to review site planning, construction sequences, and interference geometry. AR can be utilized in both the office and onsite environments. Like VR, the in-office application for AR is commonly site planning. AR also can be utilized in the field for applications such as seeing through the ground to locate known existing obstructions like utilities, gas tanks, etc.

Jan 1, 2019

By D Mcleod, S Brindley, S Green

The design and engineering of flotation circuits is driven by numerous inputs, including (in no particular order) testwork outcomes, site considerations, type of separation required, energy sensitivity of the flotation response, personal experience and preference for flotation machines, maintenance access requirements, operability, level of automation and capital constraints.This paper discusses these and other issues in the Australian context and covers the flotation of copper/gold ores and polymetallic (copper/lead/zinc) ores. The paper discusses aspects of the following: how should testwork be done and what are the important inputs and outcomes? how should testwork results be interpreted and how does this impact on equipment selection? what processes can have a critical impact on flotation circuit performance, eg thickening and regrind? what options are available with the typical æflatÆ Australia site? how do you minimise capital cost and what impact can this have on flotation circuit operation and maintenance? how should circuits be controlled and operated? Particular focus is placed on some practical aspects of process design and engineering and the potential impact that engineering decisions can have on flotation plant operation.

Jan 1, 2005

By V. A. Marple, K. L. Rubow, Y. Tao

"A personal diesel exhaust aerosol sampler has been designed and evaluated in both laboratory and field settings. The sampler uses size selective sampling for the determination of the respirable mass concentrations of mineral dust and diesel exhaust particulate matter found in underground coal mines. This design is based on the premise that diesel exhaust particulate matter is predominantly less than 0.8 um while mineral dust is greater than 0.8 gm. Operating at a flow rate of 2 L/min, the sampler consists of a 10 mm Dorr-Oliver respirable dust cyclone followed by an 0.8 gm cutpoint impactor and an afterfilter. Field evaluations consisted of sampling at 6 different locations in these underground coal mines. Measured aerosol concentration less than and greater than 0.8 um have been compared with a well characterized cascade impactor.Techniques must be developed for measuring the mass concentration of diesel exhaust particulate matter found in underground coal mines due to the health concerns associated with worker exposure to diesel exhaust particulate matter. Diesel exhaust particles are in the respirable size range and have been regarded as a potential occupational carcinogen by NIOSH (1988). Furthermore, a 1988 MSHA advisory committee directed MSHA to develop a sampling protocol for assessing worker exposure to diesel exhaust particles.The University of Minnesota and the Bureau of Mines, over the past 4 years have measured the size distribution of diesel exhaust particles and mineral dust, both in the laboratory and underground mines (Cantrell, 1987; Cantrell et al., 1987; Cantrell and Rubow. 1988; Marple et al, 1986; Rubow et al., 1988: and Watts et al., 1989). To date, measurements have been made in nine coal mines. Seven mines utilized diesel-powered equipment at the mine face while two used electric-powered equipment. The results of these field tests indicate that mineral dust and diesel exhaust particles can be differentiated on the basis of particle size. The measured particle size distributions have been found to be bimodal with a saddle point at 0.8 um. This has led to the hypothesis that one method for measuring worker exposure to diesel exhaust particles would be to collect size fractionated particle samples separated at 0.8 um with the diesel particles being less than 0.8 um and the mineral dust particles greater than 0.8 um.Aerosol size distribution measurements, using a micro-orifice uniform deposit impactor (MOUDI), have been conducted in the mine intake air portal, intake entry to the working section, haulageway, and section return entry. The MOUDI is a ten stage cascade impactor with particle cutpoints ranging from 0.1 to 15 um aerodynamic diameter (Marple and Rubow. 1984b; Marple et al., 1989). The sampling flow rate is 30 L/min."

Mar 1, 1992

By Kanchan Mondal, Gopi Bylapudi, Anand Bhagwat, A. J. S. (Sam) Spearing

Corrosion of steel roof support systems can cause potential premature failure of the support, thus adversely affecting the excavation stability and rock-related safety. An in-house corrosion test system was designed and developed to test full-length roof bolts for material performance based on tensile load capacity and strength under different corrosive conditions found underground. Initially, ASTM A615 grade 60 steel roof bolts, which are the most commonly used bolt material in the United States, were tested with and without stresses in a simulated underground coal-mining environment for approximately six months. This paper mainly discusses the test system, protocol and system shortcomings, and makes recommendations based on the observations and results.