First cross tunnel completed for HS2.

A new milestone has been reached for HS2 as the first tunnel cross passage was competed between the Chiltern tunnels.

This is the first of 38 underground connections between the northbound and southbound tunnels.

Milestone

The milestone was announced as tunnelling machines Florence and Cecilia under the Chilterns have reached the four-mile mark.

A remotely controlled excavator was used by the miners’ expert team to break out of and excavate from one running tunnel to the adjacent tunnel.

The Chiltern tunnels will enable operations of high-speed trains between London and the North with maximum speeds of 320km/h. The trains will run through two parallel tunnels connected by short passages for use in emergencies.

Lining

On completion, a water-proof membrane has been deployed followed by a secondary concrete lining built by putting concrete behind formwork installed in the cross passage.

HS2 tunnel engineering head Martyn Noak said: “HS2 is making huge progress, with 25,000 jobs supported by the project, construction in full swing between London and Birmingham and now the start of this new phase of tunnelling work under the Chilterns.”

Last month, HS2 completed a one-mile dig under Long Itchington Wood in Warwickshire utilising a 2,000t custom-made tunnel boring machine known as Dorothy.

Good progress

Align project director Daniel Altier said that preparation work has began for several other cross passages and that the team is “making good progress”.

Tunnelling works for the creation of the tunnels have been underway since June 2021. The company anticipates tunnelling through the Chilterns to be complete in March 2024.

 HS2 tunnel engineering head Martyn Noak said:

“HS2 is making huge progress, with 25,000 jobs supported by the project, construction in full swing between London and Birmingham and now the start of this new phase of tunnelling work under the Chilterns.”