TTC Steels Launch Shaft
The TTC tendered the Steeles Launch Shaft project as part of the much needed Shepherd subway extension into Vaughan. HCM undertook this project as a general contractor: self-performing the shoring, excavation, dewatering, and precision monitoring of the shoring system.
The shaft was 20 meters in depth and required removal of 20,000 cubic meters of material. RWH Engineering Inc. (RWH), an HC Group company, working together with T.H. O’Rourke Engineering, designed a three level strutted system of 460mm – 610mm diameter pre-loaded struts to brace the shoring walls. This design made the shoring system more durable as necessitated by the project due to the extended exposure to heat, cold and frost penetration as the excavated area was to remain open for a minimum of two years. The shoring was initially designed as piles and lagging with a portion of caisson wall, but was redesigned by RWH to a complete caisson wall as a result of these factors. RWH completed all monitoring which involved inclinometers, strain gauges, total stations, and piezometers. Final movement of the shaft showed less than 0.5% of the height. This project shows how HCM and RWH can perform a combination of construction activities, and provide the additional benefit of engineering and precision monitoring services, saving owners money while providing a safe shoring solution.
Client: Toronto Transit Commission
Location: North York, Ontario
