I made a visit on Thursday the 16th to the John James Audubon Bridge site on the St. Francisville side (east side) of the river. A trial shaft foundation was being constructed. The contractor had drilled a shaft excavation approximately 30 feet below the ground surface. A complete reinforcing cage was placed in the excavation and concrete was then placed. The purpose of the trial shaft was to give the contractor’s team a practice run at building a shaft on dry land before moving out into the river. The contractor is using a casing oscillator to install the temporary casing at the shaft locations. The oscillator requires a large template frame as you can see in a couple of the photos below.
Of primary interest during the trial shaft installation was the concrete mix design and how it would perform during placement - would it retain its workability, would there be problems with segregation,etc. The exercise went relatively smoothly, providing confidence in the selected methods and installation plan as well as providing opportunities to see what kind of issues or delays may occur during production shaft installation, including scheduling concrete delivery efficiently. The concrete mix appeared to perform as intended. Everyone on the team will evaluate the events of the day and begin planning for the first shaft to be installed at the bridge piers in mid to late December. The first shaft in each pier will be a test shaft that will be tested using an O-Cell load test device.
The bridge site from the east bank looking west.
A view of the template frame with concrete truck in the foreground in front of the concrete pump.
The installation template frame with the casing oscillator (red) on top and the temporary shaft casing in the middle of the frame.
Concrete being placed by tremie inside the shaft.
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