Foundations for the new Champlain Bridge will soon be installed
Prefabrication of footings
Since mid-December, concreting for 16 of the new bridge’s 38 marine footings has been completed. Built in the middle of the L’Île-des-Sœurs west jetty, each footing is 11 metres by 2 metres (or 9 X 9 X 2 metres) and comes with a pier starter, giving the overall assembly a height of up to 14 metres. The footings are moved to the end of the jetty to the loading dock, using our supertransporter, « Thor the ant, » and will soon be installed on the riverbed, with the help of our floating foundation installer (FFI), a blue vessel that bears the name of its company, SARENS. Each specific location is excavated in advance.
Marine excavation to prepare the riverbed
Since fall, a power shovel on a marine excavation barge has been digging the riverbed to prepare it for the installation of the footings. Based on the geotechnical studies and drilling programs, it was recommended that workers dig until they hit designed rock. Each excavation is 4-5 metres deep within 4-5 metres of water. When installed, the 12 to 14 metres footings will be very visible above water.
Steps for installing the footings:
- First, the supertransporter must move the footing to the FFI, moored to the loading dock at the very tip of the west jetty.
- The footing assembly is then tied laterally on the FFI with steel cables.
- Once the assembly is secured, the FFI heads off to the designated location in the river.
- The FFI is then stabilized with a very powerful anchoring system.
- An advanced GPS system is used to position the FFI and the footing accurately.
- Additional adjustments are made using the FFI’s turntable, which allows workers to rotate the part when necessary.
- The part is lowered and put into place with a hydraulic cable and pulley system and hydraulic jacks.
- Final positioning checks are made with the GPS and precision prisms, located on each footing.
- The FFI returns to the dock and repeats the entire operation with the next footing.
- Concrete is poured to solidify the installation.
- Finishing work completes the process, depending on the setting of the concrete.
Footing Installation in numbers
- Number of footings to be installed in the river: 38 (plus 36 on land, for a total of 74 footings)
- Number of footings prefabricated to date: 16
- Weight of each footing and base assembly: 900 tons (on average)
- Number of locations excavated to date: 20
- Excavation depth: 4 to 5 metres
- Installation time: 2 to 3 days (on average)
- Number of people assigned to the operation: 30