Activity continues at Toronto's tallest active construction project on the southwest corner of Yonge and Bloor streets, where complex below-grade work is being carried out for Mizrahi Developments' The One. We've been keeping a close eye on the early stages of work for the 'supertall' tower designed by Foster + Partners and Core Architects since construction began in mid-2017. Our most recent update from early December covered the imminent start of drilling for the "mega caissons" that will act as footings for the tower's hybrid exoskeleton, a task which is now well underway.
There was a gradual buildup of heavy machinery in the months leading up to the mega caisson drilling, with a heavy-duty Link-Belt TG2300B crane arriving in November, and a Bauer BG 55 (BS 115) drilling rig appearing a few weeks later. Since the arrival of these two specialized pieces of equipment, crews have been busy working on the massive underground columns that will support the building's unique structural system.
The BG 55 rig has been working away at drilling caissons 3.65m in diameter and extending 30m into the earth below the base of the excavated pit. Once the boreholes are drilled, massive rebar cages weighing 40 metric tonnes are lowered in, and then filled with 378 cubic metres of concrete to form the caissons. The image below shows the red arm of a concrete pump feeding concrete into one of the boreholes. To its left, a yellow "deadman" is being lowered into the pit. This large steel piece is used when lifting the steel cages, keeping them from deforming when turning them from horizontal to vertical to lower them into the boreholes.
Installation of footings will be followed by forming of the lowest level of the garage. Upon eventually reaching its 306-metre height, The One will temporarily hold the title of Canada's tallest building, exceeding the roof height of First Canadian Place, the current title-holder, by 8 metres.
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 thread, or leave a comment in the field provided at the bottom of this page.
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