The Anchor Shoring Group of Companies was awarded the contract to install caisson walls and structural caissons for the North York General Hospital expansion.
An interlocking caisson wall was required to protect the existing hospital during the excavation for the proposed expansion. 50 piles 55 feet long and 112 fillers were installed for the caisson wall. The shoring was braced by regroutable tiebacks with a drilled length of 120 feet per tieback.
There were 169-36″ diameter caissons specified for this project. A combination of caissons founded in the till at 50 feet below grade and rock socketted caissons founded 115 feet below grade were required for the hospital expansion. 1,800 cubic metres of concrete was placed in the caissons.
The Anchor Shoring Group of Companies elected to drill the structural caissons from the existing grade surface to avoid working from the soft clay at the base of the final excavation. Temporary steel liners were vibrated through the soft clay and sealed in the till using a vibratory hammer mounted on a service crane. Drilling of the caissons was completed by crane mounted drill rigs. Full length reinforcing cages were installed in the rock socketted caissons using a service crane. Concrete was placed in each caisson and the liner extracted using a vibratory hammer.