Article

RepairUndergroundPark Avenue Tunnel Rehabilitation

Ashley Cruz

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The Park Avenue Tunnel, formerly known as the Murray Hill Tunnel, is a 1,393-foot-long (425 m), 16-foot-wide (5 m), 9-foot-tall (3 m) thoroughfare traversing six New York City blocks. The tunnel was originally constructed in 1837 as an open rock-cut, with a brick arch constructed over the cut in 1854 to create the tunnel profile. For the next 150 years, the tunnel would be plagued with issues ranging from mechanical system failures to liner wall leakage due to the soil volume above, which is where the idea of shotcrete stabilization was introduced within the project scope.

Article

UndergroundPoe Tunnel

Jason Myers

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When you are faced with a project with limited access, material delivery by helicopter, the nearest personnel access is 5 miles (8 km) away, and the closest outside access to the shotcrete placement location is a half mile away, the only solution to handle all of these issues is shotcrete. The Poe Tunnel is a 15 mile (24 km) long tunnel in the foothills of the Sierra Nevada Mountains and is in an area of steep canyons. The tunnel transports water from a forebay on the North Fork of the American River to the Poe Powerhouse where electrical power is generated. The tunnel is almost 20 ft (6 m) in diameter and was constructed in the 1950's.

Article

UndergroundGeneralThe Value of VR Training for Today’s Shotcrete Nozzlemen

Matthew Wallace

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Recruiting, training, and retaining skilled shotcrete nozzlemen is mission-critical for a company’s success. Virtual, immersive training offers an effective, engaging mode of learning that supports the modern trainee. For beginning nozzlemen, virtual reality training gives them a safe, repeatable experience that can be completed in a classroom, free of job costs. Practice without cost or risk also helps improve job performance and satisfaction. These disruptive virtual reality (VR) technologies can provide safe, hands-on learning experiences without the field costs associated with hands-on training. Virtual learning is also valuable in today’s socially distanced world with its shifting remote learning requirements. Interactive digital tools will deliver meaningful, adaptive training for skilled trades now and in the future. Though some level of hand nozzling experience is still needed the best nozzlemen will be trained, in part, using virtual reality.

Article

UndergroundEncapsulation of Reinforcement in Tunnel Shotcrete Final Linings

Position Statement #3 ASA Underground Committee

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Using shotcrete for the placement of concrete for tunnel final linings is becoming more common. In the past the use of shotcrete final linings was typically limited to non-public or emergency egress areas, however, shotcrete is being used more and more in public areas. The use of shotcrete is typically an attractive alternative to form-and-pour final lining installation where formwork costs are high or technically challenging, pose a scheduling issue, or where labor rates are very high. Typical examples for successful use of shotcrete final linings are complex lining geometries, intersecting or merging tunnels, widenings, short tunnels without sufficient repeating utilization of the forms, or underground systems where formwork would block passing traffic.

Article

UndergroundMechanical Application of Shotcrete in Underground Construction

Position Statement #4 ASA Underground Committee

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The manual hand application of shotcrete began over 100 years ago and continues today in a wide range of applications and projects. To provide a proper distance of the shotcrete nozzle tip to the underground surface wall, surface receiving shotcrete or ‘substrate,’ the hand application of shotcrete in larger diameter underground structures required the nozzlemen to operate from a man-lift or similar equipment. Working from elevated platforms and the close proximity of the nozzleman to the substrate added safety challenges to projects. Thus, as more underground projects started to use the wetmix shotcrete process, spraying shotcrete with mechanical arms began to address these safety concerns.

Article

UndergroundSite-Specific Mine Site Safety in North America

Mike Ballou

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Show me a person who tells you that safety on a mine site is just plain common sense, and I’ll show you someone who doesn’t understand mine safety completely. Mine safety is not simply common sense. It is that, and a whole lot more. Most mines have their own set of mine-specific regulations and rules. Nearly all mines, in Canada, the USA, and Mexico, are required by law, to follow government-mandated requirements such as U.S. Department of Labor- Mining Health & Safety Administration (MSHA) and/or the Occupational Safety & Health Administration (OSHA). Canada and Mexico have their government agencies governing mining as well. Even with strict government regulations, most mines have safety regulations specific to each individual mine. Anyone who desires to visit a mine site needs to accept one thing- whatever the rules and regulations are for a particular mine- these regulations are serious business and are meant to be enforced.

Article

UndergroundSafety in Shotcrete Application in Underground Construction

Raul Bracamontes

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Because of its durability, strength, and flexibility in application, shotcrete is often used for the construction and stabilization of tunnels and other underground structures. The fact that tunneling involves general construction risks as well as tunnel specific environmental risks, makes this type of application potentially quite dangerous, and must be treated with caution. Risks cannot be eliminated, but we can implement measures to lower the risk.

Article

UndergroundGeneralASA Real-Time In-Situ Article

Benny Chen, Christian Reich, Peter Ayres, and Nicholas Carter

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Construction of sprayed concrete lining (SCL) ground support across the world utilizes the construct, verify and rework cycle. This methodology typically requires survey verification of the as-built result against design for each stage of the ground support installation. However, processing and analyzing the measurement data

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RepairArchitecturalUndergroundStructuralGeneralShotcrete Incorporated into ACI 318-19 Building Code

Charles Hanskat, Terence C. Holland, and Bruce A. Suprenant

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Since the shotcrete process originated well over 100 years ago, improvements in materials, equipment, and placement techniques have enabled it to become a well-proven method for structural concrete placement. The efficiency and flexibility of shotcrete have been used to great advantage in sizable structural projects, as

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UndergroundGeneralPerformance of Synthetic Sheet Waterproofing Membranes Sprayed with Steel Fiber-Reinforced Shotcrete

Antoine Gagnon, Marc Jolin, and Jean-Daniel Lemay

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The recent Position Statement #2, “Spraying Shotcrete on Synthetic Sheet Waterproofing Membranes,” published by the ASA Underground Committee, pointed out many aspects critical to successful performance and raised some potential issues affecting the placement.1 In the position statement, specific techniques are presented to prevent problems