By rosebell
With a 4.1m diameter, the Herrenknecht EPB shield machine completed two drives and an extension for the project in Columbus, Ohio.
Considering that sand and gravel, silty sand, cohesionless silt and clay, and a small bedrock section with boulders, cobbles, and water were challenging geology of the alignment, for tackling these conditions, Herrenknecht equipped the TBM with features including a copy cutter, anti-roll fins, an inflatable emergency seal in the tailskin, and a bentonite lubrication system.
While the launch shaft of both drives was the same, the TBM was dismantled and returned to the launch shaft to bore the north tunnel in the opposite direction, following completing the south tunnel, which logistically required the teams to adapt their launch plan to accommodate the figure eight style shaft with launch angles separated by 120 degrees.
Herrenknecht said: “We praised Granite Construction’s outstanding inventiveness and ingenuity in mastering the challenge of the umbilicals and the layout of crucial launch machinery.”
The new tunnel is going to help to decreasing combined sewer overflows into the lower portion of the Olentangy River.
