Paralleling a pair of existing two-lane tunnels, the new tubes are part of Virginia DOT’s largest-ever highway construction project
The $3.9-billion expansion of the Hampton Roads Bridge-Tunnel in Virginia reached another milestone on Sept. 24, as its tunnel boring machine broke through a retaining wall to complete a second 46-ft-diameter, 7,900-ft-long tube that will eventually add much-needed capacity for the congested crossing.
According to the Virginia Dept. of Transportation, the TBM moved a total of more than 1 million cu yd of highly compressed sand and clay on a 3-mile round-trip route that extended more than 100 ft below the riverbed, and up to 173 ft below the mean surface level. The agency said the machine set a world productivity record for its TBM class/size, boring 366 ft in a single week.
