By Lynda Myer
Following that the TBM broke through on Virginia’s first bored road tunnel in 17 April, the Hampton Roads Bridge-Tunnel (HRBT) Expansion Project marked a major landmark.
The intended TBM, which’s name is Mary, arrived at the North Island reception pit and currently is due to be repositioned for the return trip, while the process of turning her around and positioning for relaunch, it will take up to six months. The machine’s next purpose will be building a parallel tunnel back to the South Island.
With 131m length and a diameter of 14m, this variable density TBM, has been designed for the soft soils of the Hampton Roads region in Virginia.
The commissioning location of this TBM was the South Island (Norfolk side) in April last year. The distance that Mary excavated was 2.4km, whereas it caused to digging almost 685,800m3 of soil, and installing 1,191 concrete rings. The daily maximum advance of this machine was 34.4m, with 17 rings installed.
As the largest highway construction project in Virginia’s history, the HRBT Expansion’s value is US$3.9bn (£3.13bn) and it involves widening the current four-lane sections along nearly 16km of the I-64 corridor in Norfolk and Hampton, with new twin tunnels across the harbour.
Considering that this new tunnel is around 15m deeper than the existing tunnels, its deepest point 52.8m beneath the water surface. All other tunnels in Hampton Roads are immersed tubes.
In addition to being Virginia’s first bored road tunnel, it is only the third in the US.
According to said Virginia Department of Transportation (VDOT) commissioner Stephen Brich: “The Hampton Roads Bridge-Tunnel made history in 1957 as the world’s first tunnel constructed between two man-made islands. Today, the HRBT makes history again as Virginia’s first bored tunnel. With the breakout of the TBM, we are one step closer to the completion of this transformative project that will increase capacity at one of the region’s most congested corridors.”
TBM Mary was named after NASA engineer Mary Winston Jackson.
