Following an official ground breaking held last month to mark the start of construction for Mizrahi DevelopmentsThe One, shoring work has begun at the Yonge and Bloor site of the supertall tower by Foster + Partners and Core Architects. Before excavation down to a depth of four storeys can begin, crews from GFL's Anchor Shoring division are working to build an earth retention system around the site's perimeter. 

Aerial view of The One site at Yonge and Bloor, image by Forum contributor Benito

Like at the nearby projects Uptown Residences to the west and One Bloor East to the east, because of the water table height here, shoring for The One is will be a watertight caisson wall system. Views of the site reveal that a series of hollow steel cylindrical piles have been driven vertically into the earth along the site's northern edge. An auger is then inserted to drill out the earth within the piles. Next, steel and concrete are added to create a vertical reinforced column. The cylindrical steel collar is then removed, and the process is then repeated dozens of times, until an underground concrete "bathtub" has been formed around the site.

Aerial view of The One site at Yonge and Bloor, image by Forum contributor Benito

With vertical walls secured with steel tiebacks into the ground behind them, the caisson will both hold back the surrounding soil and divert water around the site, creating the necessary conditions to allow a safe excavation of the building’s four-level underground parking garage.

Shoring for The One, image by Forum contributor skycandy

Construction activity is set to grow more interesting in the future, when work begins on the eight "super columns" that will form the base of the building's hybrid exoskeleton system, transferring the tower's load across its exterior and down to the foundations below. These columns—measuring up to 15 feet wide—will be installed using a large specialized drilling rig, which is currently en route from Europe.

Positioning of super columns within P4 level (black dashed rectangles), image retrieved from submission to City of Toronto

The super columns will mark the building's exterior aesthetics, with the hybrid exoskeleton serving as the tower's main design statement, while the lack of interior columns allowing for wide, open floorplans on the retail levels, and more flexibility for condominium suites above. Despite the lack of interior structural elements, the One's structural system has been engineered to be six times as strong as a typical high-rise.

The One, image courtesy of Mizrahi Developments

Additional information and images can be found in our database file for the project, linked below. Want to get involved in the discussion? Check out the associated Forum threads, or leave a comment in the field provided at the bottom of this page.

Related Companies:  A&H Tuned Mass Dampers, Aercoustics Engineering Ltd, Core Architects, Doka Canada Ltd./Ltee, McIntosh Perry, Mizrahi Developments, NEEZO Studios, Rebar Enterprises Inc, RWDI Consulting Engineers and Scientists, Terraprobe Inc, The Planning Partnership, VDF Vertical, Walters Group