Press Release
Reprint free of charge. Copy requested.
Schöck Bauteile GmbH
Rosa Weimer
Vimbucher Straße 2
76534 Baden-Baden
Germany
Tel.: +49 (0) 7223 967-410
E-mail:
GFRP reinforcement used for subway construction
Schöck ComBAR installed at the Steeles West Station of the Toronto-York Spadina Subway Extension
The Toronto-York Spadina Subway Extension (TYSSE) will be a significant extension of the Toronto Transit Commission’s (TTC) metro system when it opens in 2015. The new 8.6 kilometres long rail line will run from Toronto north to York. The segment from Downsview Station to Steeles West station lies within the Toronto city limits. It is 6.2 kilometres long. The remaining 2.4 kilometres from Steeles West to Vaughan Corporate Center Station are located in York. The glass fibre-reinforced polymer (GFRP) rebar Schöck ComBAR – which is used for the subway construction – allows the saving of costs and time during the construction period. In contrast to steel-reinforced concrete GFRP bars can be broken down into small segments by the cutter head of the Tunnel Boring Machine (TBM). Therefore, a manual removal of the steel reinforcement in the path of the TBM and a stoppage of the machine are not necessary.
The Canadian company Lovat has been awarded the CAD$ 60 million contract to deliver four TBMs for the project. This is about two percent of the total project cost of CAD$ 2.6 billion. The first two TBMs were delivered at the end of 2010. The other two followed in early 2011. Tunnelling will commence shortly after the first two TBMs have been delivered.
The Toronto-York Spadina Subway Extension Project is financed by the Canadian government (approximately 29 percent), the province of Ontario (approximately 36 percent), the city of Toronto (approximately 21 percent) and the community of York (approximately 14 percent). The Toronto Transit Commission is responsible for the planning and construction of the TYSSE project. The Commission will operate the new subway line.
TBMs for inner-city subway tunnels
Nowadays, Tunnel Boring Machines are commonly used in the construction of inner-city subway tunnels as their usage minimizes the disturbances to surface traffic during the construction phase. Only the future stations are built in open construction pits. The tunnels between these shafts are excavated by the TBMs below ground, virtually unnoticed on the surface.
TBMs can not cut through steel-reinforced concrete drilled shaft walls as the steel bars get caught in the shovels of their shield. In addition, the steel bars can not be cut into pieces small enough to allow their transport by the TBM’s conveyor belt system. As a result, the conventional construction method with steel-reinforced drilled shaft walls necessitated the manual removal of the steel reinforcement in the path of the TBM. Not only was this time-consuming and expensive in itself, it also required the stoppage and retraction of the TBM in front of each shaft wall. Finally, to ensure that neither the soil nor potential groundwater outside the shaft wall would collapse into the opened hole, complex and expensive soil stabilization measures were required outside the wall.
Reinforced walls
All these time-consuming and costly measures are not required when the areas of the launch shaft head walls to be penetrated by the TBM are reinforced with glass fibre-reinforced polymer (GFRP). Even though these bars have a much higher tensile strength than steel rebars, they are easily machined and can be broken down into small bar segments by the cutter head of the TBM. These segments can then be transported by the machine's conveyor system together with the excavated soil. The TBM does not have to be stopped, and soil stabilization measures are not required, as the soil is always stabilized by the TBM. The resulting savings in the overall construction time and cost are substantial, and disturbances to the surface bound traffic during construction are limited to an absolute minimum.
Schöck Canada delivers GFRP reinforcement
Initial discussions between Schöck Canada Inc., producer of the GFRP reinforcement Schöck ComBAR, and the Toronto Transit Commission on the possible installation of GFRP rebar in the TYSSE project began in the summer of 2009. The design engineering office Hatch Mott MacDonald was involved in these discussions from the beginning. Both TTC and Hatch Mott MacDonald were quickly convinced of the benefits of installing GFRP reinforcement in the soft-eyes in the twin tunnel lines of the TYSSE project.
Construction of the first two launch shafts for the project, at Steeles West and Sheppard West stations, was opened for bids in February 2010. In both cases, GFRP reinforcement was specified in the bid documents. In early July, Schöck Canada Inc. was awarded the contract to deliver its GFRP rebar Schöck ComBAR for the shaft walls of Steeles West Station. The contract was awarded by HC Matcon Inc., a young family-run company located in Ayr, ON. HC Matcon was founded in 2001 and has been focusing successfully on providing full project service for civil engineering and foundation projects ever since. Ayr is not far from Kitchener, home of Schöck Canada Inc.
The contiguous caisson wall for the Steeles West station was built as a secant drilled pile wall. Six of the drilled piles of the excavation support system at Steeles West contain ComBAR bars. Each of the two soft-eyes contains three cages with ComBAR bars. Rebar cages with a diameter of 1050 mm were installed in the drilled shafts. The longitudinal ComBAR bars within the soft-eye had a core diameter of 32 millimetres. Double headed ComBAR bars, also with a core diameter of 32 millimetres, were used as shear reinforcement in the piles. 8 millimetres ComBAR bars were bent into rings at the site to serve as horizontal reinforcement / stirrups within the cages. A total of 3.5 tonnes of ComBAR were installed at Steeles West. Wire rope grips were delivered by Schöck for the connection of the ComBAR and the steel cage segments. Installation of the reinforcement began in July 2010.
The rebar cages at Steeles West were installed by C&T Reinforcing Steel, a renowned steel supplier in the Toronto metro area. The six cages containing ComBAR bars were assembled within just three days. The reinforcement drawings and detailing of the GFRP reinforcement within the soft-eyes was provided by Schöck engineers. Included in this package were detailed handling and installation instructions as well as the conceptual details for the lifting, installation and connection of the finished rebar cage segments.
“This project was a challenging deep excavation”, says Mark Montgomery of HC Matcon. “The project was based on efficient engineering and co-operation from both the shoring designer and Schöck. Their help in putting together the required glass fibre reinforcement and the co-ordination with the conventional steel rebar installs was tremendous.”
In the meantime Schöck has also received the contract for the installation of ComBAR at the Sheppard West Station.
approx. 6,900 characters
Project data
owner: Toronto Transit Commission (TTC)
contractor: HC Matcon Inc.
engineer: Hatch Mott MacDonald Group Inc.
designing engineer: T.H. O’Rourke Structural Consultants Inc.
installation: C&T Reinforcing Steel Co. Ltd.
This text is available online at:
www.schoeck-canada.com (“News & Media” section)
www.dako-pr.de (“Service” section).
Captions
[11-03 ComBAR cage_tunnel]
Installation of rebar cage in pile: The weight of a Schöck ComBAR bar is only a fourth of its steel counterpart. Combined with the flexibility of the bars this allows an easy installation.
Source: Schöck Canada Inc.
[11-03 ComBAR cage_lifted]
Rebar cage being lifted into position for installation in the piles: Six cages containing ComBAR bars were assembled within just three days.
Source: Schöck Canada Inc.
[11-03 ComBAR cage_close]
Detail rebar cage for drilled concrete piles with headed studs as shear reinforcement: The longitudinal bars within the soft-eye had a core diameter of 32 millimetres. 8 millimetres bars were bent into rings at the site to serve as horizontal stirrups within the cages.
Source: Schöck Canada Inc.
Please address any queries to
Schöck Bauteile GmbH dako pr corporate communications
Rosa Weimer Johannes Eisenberg
Tel.: +49 (0)7223 967-410 Tel.: +49 (0)214 20691-0
Fax: +49 (0)7223 9677-410 Fax: +49 (0)214 20691-50
E-mail: E-mail:
www.schoeck-canada.com www.dako-pr.de
Schöck – Steels West Station Page 2 of 6