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By CADEN VITTI, Barbara J. Arnold

Mine tailings, the byproduct of mining and mineral processing, are increasingly mass-produced as a result of increased demand for metals and minerals as well as the advancement in technology that allows for the exploitation of lower-grade ores. Lower grades can increase the volume of tailings that may contain new gangue minerals that should be evaluated for the presence of critical minerals and other valuable metals. The practice of reprocessing, while relatively new, is crucial to reducing environmental damages, obtaining valuable critical minerals from waste, and contributing to more sustainable repurposing and disposal methods. With the increase in tailings dam failures in recent years, there is a large motivating factor in remining and removing the potential hazard to benefit the safety of potentially impacted communities. In analyzing the perspectives of various domestic and international studies, this literature review will determine the feasibility of reprocessing and reutilizing mine tailings waste for a more sustainable future while exploring current practices that have benefitted ecosystems and communities.

In the late 1980s and into the 1990s, the Mountain Pass Mine in California produced about 40 percent of the world?s rare earth elements. At the height of this production, the facility produced up to 54 L/s (850 gpm) of saltwater that was piped to offshore holding ponds where the water was evaporated. In 1998, following a series of waste water pipeline breaches, separations activities were suspended, reducing the Mountain Pass site to just the openpit mine and mill. The environmental concerns were addressed and the affected areas have since been remediated. However, in the years following the breaches, 97 percent of the world?s production of rare earth elements moved to China. By 2011, Molycorp, and the Mountain Pass Mine, had rebounded from the difficult times and were once again in a position to become a significant player in the rare earth industry.

Jan 1, 2011

By Rodolfo Lagos, Nicos Pfeiffer, Ben Harding, Clayton V. Deutsch

This paper outlines a cutting-edge probabilistic resource modeling workflow tailored to the Round Mountain epithermal gold deposit. The primary goal is to craft a robust and modern simulation process that enables the quantification and comprehension of anticipated discrepancies during mining reconciliation, offering a more precise gauge of expected gold quantities compared to conventional estimation models.

Dec 1, 2023

By John Dean

"Pumping backfilling medium used to fill in holes and caverns in mines is challenging. The often viscous, high solids materials are extremely abrasive and can destroy pumping systems in a matter of days. While a number of options are available, using a progressing cavity pump can often be the best solution. High pressure and capacity capabilities, coupled with low wear rates, ensures reliable cost effective operation.Thickened slurry backfilling for underground/excavation mining applicationsVoids and caverns develop as a result of mining operations penetrating deep into the earth seeking natural resources. After extracting all the ore from a mine, operators need to fill in these voids to preserve the integrity of the mine structure. They do this by pumping in a backfill medium. Each mine uses a different mix of components for backfilling, depending upon the mine’s specific structural requirements and environmental concerns, particularly water requirements. Most backfill mixes contain cement, or another cement-like substance, that acts as a binder to hold the backfill medium together. This is combined with tailings (unused rocks and waste from processing and/or extraction), and may also include chemicals or other binders to increase the material’s strength.Backfill pumping challengesPumping the backfilling medium can be a significant undertaking. This process involves transporting very viscous and high solid materials; the mix may contain 60-80 percent solids. These backfill slurries are extremely abrasive and the viscous material can wreak havoc with pumping systems. The material’s paste-like consistency presents problems for standard centrifugal pumps often used in other mining applications.Added complexity is posed when trying to achieve the required pressure, which depends upon how far away the material has to be pumped. It is not difficult to meet the pressure requirements if mixing the backfill material close to the area to be filled. However, pumping from extreme distances can be problematic — a great deal of pressure is required to transport the material from the mixing area to a distant backfilling site. Ideally, operators should be as close as possible to where they are filling, so they can use a smaller pump with lower power requirements."

Dec 1, 2018

By Todd Loudin

A majority of the chemical process industry uses lime in either a powder or liquid form. Engineering and maintenance personnel often face a long and potentially expensive trial-and-error period in order to find the best process equipment to handle lime. Limestone is mined from a quarry in the form of calcium carbonate (CaCO3). Then, it is crushed and fed into a kiln at approximately 1,093° C (2,000° F), where the carbon dioxide is burned off (calcining) to make calcium oxide (CaO).

Jan 1, 2010

Choosing the right valve for corrosive, abrasive slurry applications requires exacting analysis and a comprehensive understanding of the complete slurry process. Within the realm of flow control in abrasive and corrosive slurry applications, there is no room for a one-size-fits-all approach. To ensure minimal maintenance, maximum uptime and the lowest overall cost of ownership, the slurry processing toolbox must contain countless alloy and elastomeric pairings ? each carefully targeted to the particular process medium and conditions. This materials selection process is best tackled by turning to expert slurry application engineers and valve product managers who work closely with customers to specify the optimal valve for the given parameters. ?When plant operators and design engineers apply conventional valves in abrasive applications or use metal seated valves or simply apply the wrong valve for a particular flow control situation, it typically leads to rapid valve failure, the potential for hazardous leakage, unexpected shutdowns and costly downtime,? said Cal Cobb, valve products manager for Weir Minerals North America, manufacturer of Isogate slurry valves for service in mining, minerals processing and metallurgical environments.

Jan 1, 2011

By Robert Klug, Nils Engelke

"In order to extract proportionately small quantities of valuable minerals, mining companies move large amounts of earth. A resulting waste product of this process has traditionally been stored in a semi-liquid phase known as tailings, typically stored in a large pond created by an earthen dam at the low end of a drainage basin. It is generally expected that these dams are stable enough to withstand the pressure of the stored material. Unfortunately, history shows us that this is not always the case. The Baia Mare dam in Romania failed in 2000, causing tragic and prolonged environmental damage to several major European rivers. The Bento Rodrigues dam in Brazil failed on Nov. 5, 2015, and that event resulted in the loss of 16 lives.In hard rock mining, many minerals are imbedded within the ore. As part of the mining process, valuable minerals are extracted from the ore; often, the mineral content is only a fraction of the total ore volume processed. To extract the minerals, the ore is typically crushed and pulverized into very fine particles, then wetted to form slurries. The minerals are extracted from the slurries through a series of flotation and/or sedimentation steps with the aid of water-soluble separation chemicals typically known as reagents. Following the mineral extraction, the resulting residual wetted ore cuttings are labeled as tailings. At the end of the extraction process, the tailings are in a thick semi-fluid sludge state, often with trace elements of the extraction reagents.Historically, these tailings are deposited in giant basins or sludge ponds, where they pose a great threat to the environment while binding large volumes of waste process water.Process water recovery and achievingdry tailingsCurrent generation engineering studies, trials and successful field implementation have shown that an alternate process known as dry stacking is practical. The dry stacking process deposits dewatered tailings into containment areas that are smaller in overall footprint and significantly safer by reducing the transfer of reagents into the tailings storage area. In addition to achieving the dry tailing benefits mentioned, it is possible to recover valuable process water while dewatering the tailings sludge utilizing modern separation technology."

Jan 4, 2018

By Mustafa Kumral, Yuksel Asli Sari

Economic evaluations of underground mining operations are made based on the estimated or simulated grades of the block model as the actual values are not known. Depending on how the planning decisions are made, the risk of the operation can be managed and decreased. This research introduces a mixed-integer linear programming (MILP) model for stope sequencing optimization that considers the uncertainty associated with net present value (NPV) using chance-constrained programming (CCP). The introduced method permits achieving a balance between maximizing NPV and reducing the associated operational risk through transforming the problem into a multiobjective problem, where the objectives are maximizing the NPV and minimizing the risk. This risk is expressed in terms of the standard deviation of project outcomes, taking into account multiple possible scenarios. In a case study, the efficiency of the method was demonstrated as a decision-making tool capable of translating a specified risk or reliability level into a stope sequencing plan.

Jan 1, 2024

Automated drilling in surface mines is here, it?s successful, and it?s already at work in mines around the globe. Coal, copper, iron and gold mines in large mining countries such as Canada, Australia, South Africa, the United States and Chile are meeting mining objectives previously ruled out as unattainable. Pit Viper automation enables operators to accomplish more objectives safely. Operator assist functions like AutoLevel, AutoDrill, Auto Rod Changer and multi-rig teleremote control are a few of the features mines are using to gain consistent, sustainable productivity.

By William Gleason

"Government support for Canada’s mineral industry was on full display during the Prospectors & Developers Association of Canada (PDAC) conference in Toronto, ON, Canada on March 3-6. First, there was the announcement of the five-year extension of Canada’s Mineral Exploration Tax Credit (METC), the first multi-year extension of the METC since its inception in 2000. Canada’s Minister of Natural Resources, Amarjeet Sohi, added to that support when he spoke at the opening keynote session and announced the Canadian Minerals and Metals Plan (CMMP), a plan that aims to map out the future of the industry in Canada. Finally, the support for the mining industry was buttoned up with a visit to the conference by Canadian Prime Minister Justin Trudeau.More than 25,000 people from 135 countries attended the annual conference that features a robust trade floor, technical sessions and an investors’ exchange that aims to put mining companies in touch with potential investors. Mining companies and ambassadors from nations around the world are given the opportunity to present to small audiences throughout the conference and this year PDAC was able to sway the Prime Minister to speak on its behalf.Trudeau sat down with PDAC President Glenn Mullan on March 5 to talk about the METC extension and a host of other issues important to the Canadian and global mining industry, giving the home country a bit of a profile advantage when it came to making a pitch to investors.Trudeau entered the week of the conference in the midst of the most serious political scandal of his career and was defending himself against accusations of political interference with the top prosecutor in the land over a criminal case involving one of Canada’s largest companies, SNC-Lavalin. During the question-and-answer session at the Metro Toronto Convention Center, Trudeau seemed more than happy to keep to the discussion about mining. He spoke favorably about the industry during the half hour conversation and praised the industry for its work with Indigenous people as well as its efforts to advance technology and innovation. He made a case that Canada is a safe and reliable place for investment in the minerals sector.“We are at a time of change right now, of transformation with new technologies and global supply chains, and everyone is trying to adjust to the new realities that have accelerated so much these past years,” Trudeau said. “What we are trying to do as a country and what you have done as an industry is to try to look at where things are going – go to where the puck is going to be, not where it is. You, as an industry, know that investments in innovation, research, science — investment in technology and partnerships with Indigenous communities are all things that are going to give you opportunities to be competitive in the coming years.”"

Apr 1, 2019

By Florian Festge

It has been said that good things come in threes. In the case of screening for mining and quarry operations, profit comes in three distinct phases: layered, basic and sharp screening. But how good they are ? whether they maximize efficiency and improve the potential for success ? depends on having the right screen media on the deck for each of the three phases. A relatively new method for achieving that goal is a blended screen media approach that incorporates the ideal screen media for each phase and the ideal mix of media for the process overall. The goal in implementing a blended solution is to find the optimal combination of open area and durability. If this combination is found, maximum product quality and profits will be realized by increasing efficiency of classification while minimizing downtime and maintenance costs.

Jan 1, 2012

By C. L. Wilsey, K. M. Oakes, W. J. Reich, M. J. Protani

The time frame required to complete the National Environmental Policy Act (NEPA) process for a new mine or the expansion of an existing mine can range from nine to 24 months, or even longer. The time frame will vary depending on whether an environmental assessment (EA) or an environmental impact statement (EIS) will be completed Completing properly designed baseline studies to collect natural resource data to support the EA or EIS prior to the start of the NEPA process can shorten this time frame. In this paper, a two-year natural resource baseline study by Homestake Mining for the Ruby Hill Mine, Eureka County, NV, is used as a case study to describe how a properly designed and executed natural resource baseline study streamlined the NEPA process.

Jan 1, 2003

By J. W. Markham, M. Atiemo, K. Yoshida

INTRODUCTION In open-pit mining of high grade ores, operators of mining equipment in a pressurized cab are protected from inhaling radioactive aerosols by the use of filtered air through a pre-impactor and a HEPA (high efficiency particulate air) filter. At present, a limited amount of scientific information is available on the worker exposure to airborne alpha emitters in the mining of high-grade ores. (Miller, 1977, Nielson, et al, 1979). Factors affecting the worker exposure to alpha radiation are: the grade of uranium containing ores, the environmental conditions inside the mine pit, the protection factor of the cab filter system, the workers' attitude towards the hazards of radioactivity and the adopted contamination control in the cabs. Four series of field samplings were conducted during the fall of 1980 and the summer of 1981 at a mining site in northern Saskatchewan to investigate the extent of protection an equipment operator has against cab internal exposure to airborne alpha emitters with short and long half-life radionuclides. The variation in the breathing zone concentrationnof aerosols as a result of resuspension is discussed, however no attempt was made to isolate and investigate the factors and the associated parameters of the aerosol resuspension phenomenon. AEROSOL RESUSPENSION IN A CAB Mechanisms of Resuspension [Sources]: The presence of radioactive aerosols inside a cab and in the breathing zone of an operator may be due to initial concentration inside [(CO)], concentration in the filtered (HEPA) air (CC, at the flow rate [QC]), the concentration of the aerosol through resuspension ([CR]), the aerosol concentration in the air outside the cab ([CE]) and the concentration of the aerosol in the leaking air [(CL)], at the flow rate of [(QL)]. [Volumetric Equilibrium]: Assuming a uniform concentration of the aerosol in the cab, the aerosol concentration in the breathing zone[ (CBZ)] may be expressed as, [CBZ+CO+CC+CR-CL] If [QC] remains greater than [QL], there is pressurization in the cab. There is particle loss as a result of the leaking air from the tight cab, however the condition of adequate pressurization ensures that [CL ~ CC]. Also for dust particles filtered through HEPA [CC – 0] thus [CBZ + CO + CR] For the radioactive gases, [CBZ - CO + CC] Over long periods,[ CBZ – CE] but if [CBZ] exceeds the value of CE then the aerosol build-up in the cab has, occurred. [Resuspension]: Turbulent bursts are generated within the core region of a cab confinement, such that the down sweeps and the up sweeps of the air bursts cause resuspension of dust from the surfaces. Particles initiate resuspension by four major modes: namely, sliding, rocking, rolling, bouncing or sudden ejection or by combinations of these. Nevertheless the adhesion force between the particles and the surface must be overcome by ejection forces before ejection takes place (Kline et al, 1967, Corino and Bradkey 1969, Kim et al 1971). The phenomenon of particle resuspension from a surface may be expressed in a generalized form as: CR =f (Uz . R . D . H) where CR = Rate of particle resuspension UZ = Surface shear velocity R = Surface roughness parameter D = Aerodynamic diameter of particle H = Frequency of surface airburst A detailed discussion of the individual parameters was attempted for the case of farm tractor cabs by Atiemo (1981), such a treatment is out of the scope of this study. Only the effects of the properties of surface roughness will be discussed. Effect of Surface Properties The roughness of the surface from which dust particles are ejected plays a significant role in the deposition and resuspension of the dust. The roughness or the amount of protrusions greatly influence the intensity of air turbulence in the immediate vicinity of the surface (Schmel 1976). For most roughened surfaces therefore, larger particles may be dislodged in greater quantities than smaller particles. The deposition and the resuspension of dust particles from different surface materials of glass, cloth, metal and rubber have been studied in a wind tunnel (Atiemo, 1981). Field Conditions Mining equipments used are: a backhoe, a bulldozer with ripper attachment and two dumptrucks for high-grade ore operations; a payloader and two dumptrucks for waste handling; and a jumbo drill which drills dynamite holes for ore blasting. All this

Jan 1, 1981

By G. Robert Ganis

The folded Appalachians are a physiographic province of eastern North America extending from Nova Scotia to Alabama. The province strikes through the state of Pennsylvania (see Fig. 1) comprising roughly 20 percent of the state and it is here that the focus of this paper will attend. The province is a thick sedimentary sequence which was compressed into a folded mountain belt by the Appalachian Orogeny which terminated at the end of the Permian. The stratigraphy contains both carbonate and non-carbonate rocks as a reflection of the depositional environment at any specific time and place during the Paleozoic geosynclinal accumulation. Although a great deal of variety and difference exists in the geology from one end to another, a common thread of structural and stratigraphic style exists. Carbonate rocks, limestones and dolomites, comprise a substantial percentage of the total Appalachian stratigraphy and are interbedded with clastic materials such as sandstones, siltstones, and shales. The carbonate rocks are extensively mined and collectively represent a vast economic resource.

Jan 1, 1983

By P. Schilizzi

The increased impact of mining subsidence in the U.S. coalfields and the recent regulatory constraints legislated by government and state agencies have provoked an intense research effort on this topic by government agencies, coal companies and academic institutions. Subsidence and horizontal strain predictions are a basic requirement if subsidence and its associated effects are to be controlled and contained within acceptable environmental levels. As a result, several such prediction techniques have been proposed or are currently under development to assist coal operators in minimizing the detrimental effects of these surface deformations. VPI&SU has been actively involved in this research effort in the past few years, with particular emphasis on the Appalachian coalfield. During the initial stages of this research a large number of subsidence case studies were collected from the literature, the coal industry and government agencies. In total, data from 32 longwall panels and 60 room and pillar panels were collected. This data bank was used to determine relationships between the basic mining and subsidence parameters, in order to allow the evaluation of the various prediction methods for the Appalachian coal region. Based on this data two subsidence prediction techniques, one based on profile functions and the other on influence functions have been developed. Profile function methods provide a tool for a fast calculation of subsidence on a line across a mine panel. Influence function methods, on the other hand, allow for a more detailed calculation of ground movements, in any mode and at any depth, on a grid or at any specific point. The limitations of the data of the collected case studies, i.e. accuracy of surveys, frequency of monitoring, lack of horizontal movement measurements, etc, led VPI&SU to the initiation of a detailed subsidence and strain monitoring program above a number of active mines, located in three major coal producing counties of Virginia. The aim of this program was to enhance the data base with accurate and complete measurements of surface movements and to allow, therefore, the refinement of the prediction techniques. This paper presents this monitoring program, discusses in detail the results obtained from three specific case studies and provides recommendations for the implementation of the field data in the general prediction methods.

Jan 1, 1986

By D. Sinha

Mine investment decisions involve both objective and subjective criteria. The subjective criteria are efficiently decided by interaction with company experts. The Expert System approach can incorporate knowledge of experts and interact with conventional computer programs on mine evaluation. Artificial intelligence offers considerable opportunities in comprehensive mine investment decision making process.

Jan 1, 1998

By Hamid Maleki

Mine seismicity is influenced by the mechanical properties of both near-seam strata and overburden/underburden and the prudent selection of mining methods and mine layout designs, utilizing sitespecific structural setting of the mines. The importance of adequate data collection, monitoring, and prudent structural designs has long been recognized and utilized in many U.S. operations with adequate engineering resources. In this paper, two case studies of historic seismic events and contributing factors, in deep coal and trona mines with overburden thickness exceeding 1,500 ft, are reviewed using observations and analysis. By back analyzing the overburden response in a historic room-and-pillar coal mine, the overburden collapse mechanism associated with a 3.3 magnitude seismic event is reviewed as well as the need for improvements in designs including panel and barrier pillar widths. Similar high-order seismic events were also experienced in trona mines of the Green River Basin during 1990s, interrupting room-and-pillar mining and creating ground control concerns. Efforts to improve structural mine designs are described in this paper leading to stable and productive operations for decades following the high-order seismic events in both coal and trona case studies. These efforts included improving room-and-pillar extraction layouts and utilizing properly designed longwall mining techniques that were verified using long-term geotechnical instrumentation. The study mines are located on the Wasatch Plateau (WP), Utah and in the Green River Basin (GRB), Wyoming. More recently, in Utah’s East Mountain alone, Energy West Mining Company (EWMC) has extracted some 165 million tons of coal without any significant incidents. Overall, favorable geologic conditions and prudent mine layout designs are key elements to this successful experience in both single- and two-seam layouts. Utilization of conservatively designed longwall mining technique in the GRB has been geotechnically stable, using reported experience in 15 panels and monitoring results in the Northwest (NW) District with measurable longwallinduced seismicity being rare. These studies demonstrate a considerable amount of progress that has been made within the last four decades in the application of longwall mining technique, integrated monitoring, and analyses for the verification of structural designs in mines in the United States.

Jul 1, 2023

By S. Peng, N. Vayenas, A. Farah

"While genetic algorithms have been widely adopted in ore grade estimation and optimization, mine design, and production scheduling in the mining engineering field, reliability and maintainability analysis of mining equipment using genetic algorithms has been a relatively new research area in recent years. This paper presents an application of genetic algorithms using case studies with seven underground scoop trams whose maintenance records have been collected over a period of 12 months from an underground mine in the Sudbury mining area. Based on the assumption that various factors that contribute to machine failures resemble the biological evolution process, the authors have developed an in-house PC software application called GenRel which adopts genetic algorithms in its programming. In this study, the authors feed the historical maintenance data into GenRel in order to predict future maintenance characteristics of mining equipment in a time period of three months. Then the predicted maintenance characteristics are compared to the actual maintenance records in the same time period. A statistical study is then used to examine the similarity between the predicted data and the recorded data.INTRODUCTION Today maintenance costs of sophisticated engineering systems are so high that maintainability draws great attention from scientific researchers to operations managers. For instance, a study by [1] shows that American manufacturers spend more than 300 billion U.S. dollars on plant maintenance and operations. Therefore it is understandable that the main objectives of applying maintainability principles to engineering systems are to reduce projected maintenance costs, to use maintainability data to estimate system or equipment availability/unavailability and to determine labor-hours and other related resources needed to perform the projected maintenance. A system with better maintainability would inherently provide the benefit of lower maintenance costs, less time to recover with lower breakdown frequency (design for simplicity), less complexity of maintenance tasks and relatively reduced man-hours [2]. Most maintainability functions use the Time To Repair (TTR) as the independent variable. It is common to use probabilistic or statistical concepts to define a maintainability function, for example, the probability density function. Let t denote the time. Assuming a repair starts at t=0 and completes at time T, the maintainability can be mathematically defined [3] as in Equation (1)."

Jan 1, 2015

By William H. Langer

U.S. Geological Survey (USGS) recently initiated the Front Range Infrastructure Resources Project. This is a multidisciplinary study along the Rocky Mountain Front Range from Pueblo, Colorado, to Cheyenne, Wyoming, and is designed to collect, compile, and analyze new and existing data on natural aggregate (stone, sand, and gravel), as well as water, and energy resources. To identify aggregate resources in the Front Range, a 1:500,000-scale reconnaissance map showing locations and quality of both bedrock and surficial sources of natural aggregate in the Front Range urban corridor was prepared by processing the digital geologic maps of Colorado and Wyoming. The first step of the process was to identify map units as either bedrock or unconsolidated material. Bedrock was classified according to type (i.e., limestone, granite, gneiss, etc.), which in turn was classified based on the suitability of the bedrock for use as crushed stone. Unconsolidated materials were classified according to relative age, with the older, more weathered materials being defined as less suitable for use as aggregate than younger materials. As a spin-off from the Front Range Project, the techniques developed for analyzing the Front Range geology have been modified and expanded to include all of Colorado and New Mexico. More detailed digital aggregate maps (1:24,000 scale) are being prepared in collaboration with the Colorado Geological Survey (CGS). Maps from the CGS "Atlas of Sand, Gravel and Quarry Aggregate Resources, Colorado Front Range Counties" show the distribution of potential resources of sand and gravel and provide general information about the physical properties of the resources. These maps are being digitized and merged into a single Geographic Information System (GIS) data base. In addition, the project is adding more specific information to the maps about deposit thickness, volume, and quality. This additional information is being obtained through field-characterization studies and modeling activities. The GIs data base can be displayed and queried using off-the-shelf software such as ArcInfo?, ArcView?, and Map Professional?. In addition, the USGS is developing a decision-support system to assist users in analyzing various land-use options on resource availability.

Jan 1, 1999

By Faruk Oksuz, Dave Schiemann, Matt Trotter, Mike Padilla, Miguel Sanchez, Carmen Scalise

"Chicago’s Tunnel and Reservoir Plan (TARP) is a nearly $4.0 billion and over 30 years long program and arguably the largest and longest combined sewer tunnel and reservoir system in the world. Recently, a massive tunnel construction is underway for connection of the McCook Reservoir to the existing TARP tunnel system. Once completed in two stages in 2017 and 2019, the reservoir will hold 38 billion-liters (10 billion-gallons) of combined sewer overflows (CSO) and flood waters from the city of Chicago and over 20 communities in Cook County, Illinois. McCook Main Tunnel will connect Chicago TARP’s Mainstream Tunnel to the McCook Reservoir. Connecting two 10-meter (33-ft) diameter tunnels at 92 meters (300 feet) underground has not been a simple task for the McCook Tunnel Project participants, the project owner U.S. Army Corps of Engineers (USACE), local sponsor Metropolitan Water Reclamation District (MWRD) of Greater Chicago, designer Black & Veatch, and the contractor, Kiewit Infrastructure Company (Kiewit). Yet alone excavating and lining massive size tunnels, the team is also challenged with live tunnel conditions in TARP Mainstream Tunnel that carries CSO and flood flows from city of Chicago which runs full during rain events and must remain in service at all times. The project is a noteworthy feat for engineering and construction with the upcoming installation of world’s largest underground wheel gates for flow control within the tunnel. In this paper, we describe one of its kind elements of this major tunnel system along with key design and construction considerations, specifically for the live tunnel connection which is a rare occurrence in the tunneling industry. INTRODUCTION The McCook Main Tunnel system consists of a 10 m (33 ft) finished diameter and 490 m (1,600 ft) long hard rock tunnel constructed from a 27.5 m (90 ft) diameter and 92 m (300 ft) deep main gate and tunnel construction access shaft. The gate shaft houses six high head 4.4 m by 9 m (14.5 ft by 29.5 ft) wheel gates to be installed in the bifurcated and steel lined section of the tunnel. The tunnel also includes portal and energy dissipation structures as it daylights into the reservoir."

Jan 1, 2016