Every major construction project has its unique challenges as no two jobs are the same. When dealing with bridge work, there are usually more complexities than meet the eye. The Virginia Department of Transportation's Gilmerton Bridge Replacement project in Chesapeake, Virginia, is one such example.
The project itself sounds straightforward, including the phased removal of an existing and active four-lane road bridge (circa 1938) and construction of a new six-lane vertical lift bridge complete with 18 approach spans.
Normally, the 12-foot diameter posts, or caissons, that support the bridge would be driven, or drilled, into the riverbed. However, the project is being built adjacent to a rail bridge and spans an active transportation waterway. Anything that could cause large vibrations was prohibited due to the age and proximity of the existing adjacent structures.
For this reason, drilling was eliminated as an option. An alternative process to embed the caissons was required.
A solution had to be found. PCL teams reviewed the situation to determine how they could meet the client’s requirements and get the job done. The team chose to proceed with an oscillating method, which cores the caisson into the underlying soil.
It was a method that had rarely been attempted before at this scope. PCL was confident in the solution, though, and purchased one of the largest oscillating drilling devices in the world to install the caissons. While this method wasn’t traditional, the innovative approach met the client’s needs. PCL’s clients’ goals always come first, and the company prides itself on being able to provide creative solutions to successfully complete every job.