On 23/06/2021 Metrolinx officially broke ground on the Scarborough Subway Extension, though work is already well underway. At the northeast corner of Sheppard and McCowan, crews are building the launch shaft for the TBM. Fences are up, drill rigs are on site and crews are working hard to keep up the momentum Metrolinx has set over the past year.
The new extension will bring 7.8 km of subway service further into Scarborough and provide one reliable, smooth ride to and from downtown Toronto and within the city’s growing east end. Since the release of the preliminary design business case in February 2020, teams at Metrolinx and Infrastructure Ontario have moved rapidly to advance planning and procurement so that tunnelling can begin on the project. Just a few weeks ago, Strabag was awarded the tunnelling contract for the project and even before then, crews have been hard at work at the launch shaft site, where the tunnel boring machine will eventually be lowered into the ground.
Large drill rigs - over 33 m tall - will be used to create a watertight, foundational wall around the 28 m wide, 80 m long and 30 m deep launch shaft, before excavation can begin.
The installation of a secant pile shoring system, using a series of concrete columns with steel reinforcements, called piles, will create a strong, water-tight barrier that holds soil and water in place and out of the excavated area.
To begin installing this shoring system, crews dig up a path around the perimeter of the launch shaft where the piles need to be installed. Circular forms are placed along this path to identify where the piles need to be inserted into the ground. The drill rigs have augers, a giant drill bit, that drills into each circular formation and inserts piles deep into the ground, around the perimeter of the future excavation.
Although the launch shaft only needs to be excavated about 30 metres deep, the piles go much deeper than the base of the launch shaft. This is a critical requirement to extend support below the base of the launch shaft so that water doesn’t get into the shaft.
Strabag will be drilling over 300 of these secant piles into the ground over the next few weeks to create a water-tight wall around this excavation. After the secant piles are drilled and the shoring system is fully installed, crews will begin excavating the area to prepare for the arrival of the TBM in early 2022.
Later this year a community contest will be launched to crowd source names for the new TBM. Click here and ca/36 for the tunnelbuilder archive. Also visit https://www.infrastructureontario.ca and http://www.metrolinx.com/en/. 25/21.
