The first of 38 cross-passages between the north and south bores of the 10-mile-long Chiltern Tunnel on High Speed 2 (HS2) have been completed.
Tunnel Boring Machines Florence and Cecilia are now more than four miles into their drives, meaning engineers from contractor Align – a joint venture of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick could turn their attention to the passages, which are designed to help evacuate trains inside the tunnels.
A remotely-controlled excavator was used to break out of the running bore, remove material and then break into the adjacent tunnel. While the excavations were taking place, sprayed concrete was used to line and stabilise the passage, before waterproof membranes and secondary lining were installed. Each cross-passage is between 15 and 20 metres long. KVJV was responsible for the ground treatment, while Euro Diamond Drilling and waterproofing specialist Rennesco are also working on the project.
After the cross-passages are complete, safety doors supplied by Bolton-based Booth Industries will be installed at both ends. The company is supplying more than 300 doors for all of the tunnels on Phase 1 between London and Birmingham. The HS2 contracts have enabled it to establish a new facility in the town and create up to 50 jobs over the next decade.