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2014FallShotcreteEMag

Goin’ Underground Pedestrian Tunnel at Billy Bishop Toronto City Airport By Matt Croutch In early 2012, construction began on an under- become the unique arched-crown design of the-“Dale,” were launched to bore the seven interlocking “tunnel drifts,” forming what wouldwater pedestrian tunnel that will link BillyBishop Toronto City Airport to the mainland in Toronto, ON, Canada. The project will provide main tunnel. The TBMs were designed and a predictable, efficient, and convenient access manufactured by Technicore Underground (Fig. 2). route for the airport’s users. Tunnel construction Three of the tunnel drifts were built to include will be complete by Winter 2014/2015 (Fig. 1). new city of Toronto sanitary and water mains, The pedestrian tunnel will feature a modern, which will help save Toronto taxpayers an mechanized, underground walkway and will be estimated $10 million in duplicate construction powered by 100% green energy. To provide access efforts. Excavation of the tunnel was completed to the pedestrian tunnel, a new pavilion will be in October 2013, and shotcrete, waterproofing, constructed on the mainland, while an extension and reinforcing steel layers were installed. will be added to the airport terminal building on Original plans called for the use of wet-mix the island side. shotcrete, supplied from an on-site batch plant, to Technicore Underground, a leading tunneling provide initial support during the tunneling contractor, began excavation on the mainland and process. A steel fiber-reinforced mixture with a island shafts in May 2012. Once the shafts were specified fiber type and dosage was required in dug, two purpose-built, Canadian-made tunnel- the original shotcrete specification. A number of boring machines (TBMs), dubbed “Chip” and factors led Technicore’s project management team to investigate the use of dry-mix shotcrete. The ability to stop and restart the shotcrete process as required, without significant cleanup, was one of the key factors in choosing the dry process. Tech- nicore turned to King Shotcrete Solutions to design a dry-process shotcrete mixture that met the hardened property requirements outlined in the specification. King’s Technical Services Team offered the option of both steel and macrosynthetic fiber- reinforced versions of its MS-D3 Accelerated Shotcrete. To meet the requirements of the specification, flexural toughness testing was mandated. Testing according to ASTM C1550, “Standard Test Method for Flexural Toughness of Fiber Reinforced Concrete (Using Centrally Loaded Round Panel),” was performed at Laval University, Québec, QC, Canada. Three panels were shot on site and after 24 hours were trans- ported to the university, where they were tested for energy absorption at 7 days. The average corrected 7-day energy absorption value was 280 joules (0.27 BTUs). Fig. 1: In early 2012, construction began on an underwater pedestrian After receiving the test results, Technicore tunnel that will link Billy Bishop Toronto City Airport to the mainland submitted the macrosynthetic fiber-reinforced 38 Shotcrete • Fall 2014


2014FallShotcreteEMag
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