NORTH AMERICA | PROJECTS
Above left: TBM’s first breakthrough on HRBT project. Adjacent ‘eye’ is for relaunch and return drive PHOTO CREDIT: HRBT Above right: Construction at advanced stage on LA metro’s D Line Subway Extension PHOTO CREDIT: LA METRO
The extension project connects Downtown LA with
West LA. The underground works required not only tunnelling through one of the most densely populated urban corridors but also dealing with challenging geological conditions. A 21ft (6.4m)-diameter closed face TBM was used to
build the 9 miles (14.5km)-long tunnel, and recorded an average daily advance of 39.4ft - 59.0ft (12m-18m). It is the longest tunnelling project through tar sands
in southern California and during the five years of excavation it faced many technical challenges, including gassy ground and abandoned oil wells. With the completion of tunnelling, the project owner,
LA Metro, will continue to work with its two contractors as a part of a JV with Skanska-Traylor-Shea and Tutor-Perini/O&G to complete seven new underground stations: Section 1 between Wilshire/Western and Wilshire/La Cienega; Section 2 between Wilshire/ La Cienega and Century City; and, Section 3 between Century City and Westwood. Section 1 is scheduled to open in 2025, Section 2 in 2026, and Section 3 in 2027.
US: VIRGINIA The Hampton Roads Bridge-Tunnel (HRBT) Expansion Project recently marked a major milestone when the single TBM on the twin-tube project recently broke through. HRBT is Virginia’s first bored road tunnel. The 46ft (14m)-diameter variable density TBM has
been designed for the soft soils of the Hampton Roads region. It was launched in April 2023 to bore a 1.5 miles (2.4km)-long tube from the South Island (Norfolk side) to the North Island, holing through into the reception pit. The TBM is 143yd (131m)-long and installed 1,191
precast concrete rings. It excavated approx. 897,000 yd3
(685,800m3 (34.4m), with 17 rings installed. ) of soil. Best daily advance was 37.6yd
On North Island the machine is being repositioned for
the return trip, boring the parallel tube back to the initial launch point on South Island. The turnaround for relaunch is expected to take up
to six months, allowing for relaunch in late Fall/early Winter. The US$3.9bn HRBT Expansion is the largest ever
highway construction project in Virginia. The project involves widening the current four-lane sections along nearly 10 miles (16km) of the I-64 corridor in Norfolk and Hampton, with the new twin tunnels across the harbour – which has existing tunnels. The new tunnels run approx. 16.4yd (15m) deeper
than the existing tunnels, with the deepest point 57.8yd (52.8m) below the water surface. All other tunnels in Hampton Roads are immersed
tubes.
CANADA In Toronto, one of two twin TBMs digging the western underground segment of Eglinton Crosstown West Extension recently achieved final breakthrough on its drives. The 750-tons, 143yd (131m)-long TBM – ‘Rexy’ –
completed the journey at the Scarlett Road extraction shaft, where it - and sister TBM ‘Renny’, following close behind - will be disassembled and removed from the ground. TBM Rexy spent the past two years digging one of
two 3.9 miles (6.3km)-long tunnels that stretch from Renforth Drive to Scarlett Road, where the future line will come to the surface and transition to an above ground section. The Eglinton Crosstown West Extension is 5.7 miles
(9.2km) in length and will bring the future Eglinton Crosstown LRT service farther west through York, Etobicoke, and into Mississauga. The project includes seven new stations.
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