This article examines the range of codes and standards applicable to the design of permanent shotcrete (sprayed concrete) linings, for underground construction. The relevance of these codes and standards to the designer will be dictated to some degree by the location of the project. There is no single approach to the design of such linings…
Advances in Silicate Accelerators for Shotcrete
Sodium silicate has long history of use in construction and geotechnical applications due to its versatility and reliable performance. In shotcrete placement, sodium silicate solutions were widely used as…
Automated Shotcrete Application in Tunnelling
The tunnelling industry has again been working toward the automation of shotcrete application for some years now, after research and development stalled around 2005. Robots had been developed with the capability of…
Outstanding Underground Project
2025 Carl E. Akeley Award: “Shotcrete as Final Liner – Design Considerations”
The 20th annual Carl E. Akeley Award was presented to Andy Thompson for his article, “Shotcrete as Final Liner — Design Considerations,” which was published in Shotcrete magazine, Volume 27, Number 3, 3rd Quarter 2025. The article discusses how shotcrete (often called sprayed concrete) is increasingly used worldwide as…
Humber College Station Shotcrete Construction: Design, Sustainability, and Execution – 2025 Outstanding Infrastructure Project
Humber College Station is located at the west end of the 6.4 mi (10.3 km) Finch West LRT, which includes 16 stops and two below-grade terminal stations. The Humber College Station is constructed below grade, however open to daylight, which presented unique logistical, structural, and architectural challenges…
New York City Grand Central Station New Passageway – 2025 Outstanding Underground Project
The prestigious Grand Central Station is located in a major hub center of New York City bound by East 42nd Street (south), Lexington Avenue (east), East 51st Street (north), and Madison Avenue (west). As one of the major hub centers…
Winter 2025 Follow up on Early Strength Testing
In my last column, I discussed the need for early strength testing in underground shotcrete…
How Do You Recruit for an Invisible Job?
You can be working on a large-scale, technically challenging, resource-consuming project … and if it goes well, people will not even know you’re there. Herein lies one of the struggles the tunneling industry faces: If people aren’t aware the projects exist, they also don’t know there are jobs available…
Traffic Repairs Using Low-Dust Shotcrete Material: Monitor-Merrimac Tunnel Project
Historically, the dust associated with dry-mix shotcreting caused hesitation in projects in urban or live traffic environments; however, recent innovations in low-dust materials have significantly changed planning considerations…