The Madison Group’s flagship high-rise mixed use condominium project is located in midtown Toronto, near Yonge and Eglinton. Anchor Shoring’s scope of work at this site involved the installation of a caisson wall soil retention system to allow for the construction of a five level underground parking garage.
The Madison presented many site conditions that complicated the shoring work: the deep excavation, saturated sand layers at depths below 14 metres, hydro ducts located very close to the North and West caisson walls and an existing shoring system that interfered with the proposed South caisson wall. Beyond the site conditions, logistical requirements added a facet of complexity: the work would need to coordinate the Madison design with the future Eglinton Crosstown LRT construction along the North caisson wall. Anchor collaborated with Madison and the Construction Manager, Tucker Hi Rise from the initial budget stages through site construction to ensure that each of these challenges were addressed in a proactive manner to ensure the work would be completely in a safe, high quality and productive manner.
Drilling of the caisson wall drill holes presented many challenges to be overcome due to their close proximity to live utilities and the requirement to terminate the holes in saturated sand. To provide the necessary precision and the need to install sectional casing to address the soil conditions, Anchor provided three Bauer BG-40 drill rigs for the installation of the piles and fillers in the caisson wall. 357 holes were drilled with depths up to 70 feet (21.3 m), totalling over 23,000 feet (7 kilometres) of vertical drilling. Over 6,500 m3 of concrete and 320,000 kg of steel soldier piles were placed by Anchor in the vertical holes.
The original design required drilling of the caisson wall holes below the base of the future Eglinton Crosstown LRT tunnel. Through value engineering Anchor was able to obtain approval to eliminate this requirement resulting in a savings to Madison of $400,000.00.
Three rows of regroutable tieback anchors were required to brace the 58 foot deep (17.5 m) excavation. The saturated sands which complicated the vertical drilling also brought challenges to the installation of the tiebacks. There were 260 tiebacks installed for a total of over 13,000 feet (4 kilometers) of drilling. Anchor worked with the client to sequence the excavation in a manner that allowed two tieback drill rigs to work simultaneously for the majority of project.
Through value engineering, dedication of resources and proactive planning Anchor was able to save more than a month off the project schedule.
“Anchor’s approach to the project from our initial discussions through the tender phase, the contract award and finally the physical installation of the shoring system, was nothing less than world class. They worked together with our project planning and consulting teams to come up with the best possible shoring design, involving the least possible risk to Madison. I would highly recommend Anchor Shoring to anyone who wants to work with one of the industry’s leaders in this field. You will not be disappointed.”