A once-in-a-generation investment in Montréal’s public transit, the Réseau Express Métropolitain (REM) is a new 42mi (67km), fully automated light rail network with 26 stations. A significant component of the infrastructure works for the REM system is a major renovation of the historic Mont Royal Tunnel, including extensive underground construction for the new Édouard-Montpetit station (EMP).
To build EMP Station, the contractor needed to excavate within Mont Royal’s double rail track and to enlarge the existing tunnel to create the side platforms. Traditional double shell construction methods—a waterproof membrane between the temporary shotcrete and the permanent cast in-place concrete lining—can be a significant contributor to embodied carbon in tunnel and station construction. Replacing conventional reinforcement in the permanent sprayed concrete lining with steel fibers can lower the embodied carbon and reduce the concrete required. It also saves labor and time by avoiding formwork and rebar fabrication.
For EMP Station, the design utilized a single shell sprayed concrete lining that will achieve a 125-year service life. The lining comprises an initial layer of 2in (5cm) thick shotcrete with Dramix® steel fiber for support and safety, followed by rock bolts as needed, and a spray-applied waterproofing membrane. A final 2in (5cm) layer of steel fiber reinforced shotcrete is applied. With the spray-on waterproofing membrane, the designed support system represents both the initial and the final liner. EMP Station marks the first time this single shell approach has used for a major transit station in North America and has been dubbed “NMTM” for “New Montreal Tunneling Method”.
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