West London station will likely be initial terminus of high-speed scheme
HS2 has completed its five-mile tunnelling drive into London.
A tunnel boring machine (TBM) named Sushila broke through at the Green Park Way vent shaft in Ealing in the west of the capital at the end of last week.
The drive has been part of the construction of the 8.4-mile Northolt Tunnel, which will eventually take high-speed trains from West Ruislip on the outskirts of London to the new station at Old Oak Common.
The west London station is expected to be the line鈥檚 southern terminus when services first begin, due to continuing delays in developing the new station project at Euston.
Sushila, which was named after a local school teacher, broke through into a reception can filled with foam concrete, an 鈥渋nnovative method鈥� which HS2 Ltd says was used due to high water pressure in the ground on the site.
It allows the TBM to maintain its pressure while sealant can be applied from the tunnel lining to prevent water ingress. Once depressurised, the reception can will be opened and the TBM lifted out.
The twin-bored Northolt Tunnel is being constructed by a quartet of TBMs, all of which will finish their journeys at Green Park Way.
A joint venture of Skanska, Costain and Strabag (SCS) are building the tunnel. The group is also constructing the Euston Tunnel eastward from Old Oak Common.
鈥淭he arrival of Sushila at the Green Park Way ventilation shaft marks a huge step in the delivery of the Northolt Tunnel and the new railway,鈥� said James Richardson, managing director of SCS JV.
鈥淭his achievement reflects the tremendous efforts of the entire team, which has drawn together global capability to deliver this incredibly complex section of work.
鈥淲e are making great progress on the remaining tunnelling, with three further TBMs in operation on the Northolt Tunnel and the two Euston Tunnel TBMs currently being prepared for launch.鈥�
The TBM used for the excavation, which is built by the German firm Herrenknecht, is 160m in length and weighs approximately 2,050 tonnes.
Last week, HS2 bosses were given a grilling from MPs over ever-rising costs on the scheme. New chief executive Mark Wild told a parliamentary committee that the organisation was undertaking a wholesale reset.
A recent departmental update to parliament revealed that the predicted cost of the scheme at completion had risen to stand at between 拢54bn and 拢66bn, although the Department for Transport is confident that this will come down after the planned reset.
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