The build time for the Chiltern Hill tunnel has been reduced by 8 months, meaning it should only take a year to complete now
The extensions on each end of HS2’s longest tunnel are known as ‘porous portals’, which are created to prevent a sonic boom from full-speed trains.
HS2 trains are set to enter and exit the tunnel at 200mph.
These portals are identical to a pair built last year
The conclusion of these portals is a massive step forward for this part of the project, allowing them to bring the project build time down to 12 months.
The design of the portals has been engineered to dampen energy pulses that would otherwise roll along the tunnel. This would cause a release on the other side, and the trains would push the air out so quickly that they would cause a very audible boom at the end.
Mark Clapp, HS2 Ltd’s head of civils, said: “I am extremely proud of the team because they rose to the challenge of constructing these unique porous portals at the Chiltern Tunnel’s southern end – and then built on the experience to do even better by delivering identical structures 10 miles to the north in a little over half the time.
“They have clearly demonstrated the benefits that flow from retaining skilled people by providing a steady stream of work because this helps drive efficient project delivery – in short, they haven’t had to reinvent the wheel.”
The last tunnel for HS2 is underway
The last tunnel for HS2, the Euston tunnel, has begun its dig from Old Oak Common, to complete the last 4.5 miles on the 140-mile long route.
Two tunnel-boring machines are needed for the dig, with the second set to begin its dig when the first has completed its own. The machine weighs 1,624 tonnes.
Rail minister Lord Peter Hendy and secretary to the PM Darren Jones were both invited to a small ceremony, launching the machine to begin the tunnel dig.
Lord Hendy said: “It was brilliant to switch on the tunnel boring machine at Old Oak Common today – not just because it’s an engineering marvel – but because it brings HS2’s journey to Euston another step closer to reality.
“We’re putting HS2 back on track, and taking the railway into central London is crucial to unlocking its full potential to deliver more jobs, more homes, and a long-term boost to the whole British economy.”
The post Portal extensions completed on HS2’s longest tunnel appeared first on Planning, Building & Construction Today.
