By rosebell
While construction of the 13.5km tunnel that is due to carry high-speed trains between HS2’s super-hub station at Old Oak Common, west London, and the outskirts of the capital at West Ruislip, is undergoing by four TBMs, the tunneling process on HS2’s Northolt Tunnel beneath London has reached the halfway mark.
As the second longest tunnel on the new railway after one recently excavated beneath the Chiltern Hills, digging 27km of tunnel will be up to these machines that includes two bores over the 13.5km length.
The launching site of first machine, TBM Sushila, was eastwards from West Ruislip in October 2022, whereas TBM Caroline followed it one month later boring the adjacent tunnel.
The Green Park Way vent shaft in Greenford will be the final destination of both of these machines after completing 8km of the route and reaching where they will be lifted out.
The date of commencing TBM Emily’s journey to west from HS2’s Victoria Road Crossover Box site near Old Oak Common towards Greenford was February this year, while she was joined by TBM Anne in May and they are both going to complete 5.47km of the tunnel.
The quantity of combined travel by the four machines is over 13.1km, that is half of the total distance for the twin-bored tunnel. The completion of each tunnel drive will be staggered as they reach the final destination at Green Park Way, with the first TBM, Sushila, arriving later this year.
With average advance of 16m per day, the TBMs have dug almost 2 million tonnes of material.
Constrcution of Northolt Tunnel, which comprises of five shafts and headhouses, is up to the Skanska, Costain and Strabag (SCS) joint venture, which are also slated to build the Euston Tunnel eastward from Old Oak Common to central London.
According to SCS managing director James Richardson:”Reaching the halfway point of our tunneling program for the Northolt Tunnel demonstrates the huge progress achieved to date on one of the most complex and ambitious programmes embarked upon in the UK. Alongside the tunnelling operations we are now moving into the fit-out stage of the works in readiness for track and rail systems to be installed. At Old Oak Common, we are gearing up to assemble and install our final two TBMs, ready to take the high-speed line into central London.”
The scheduled date for arrival of TBMs in the UK is the current summer and they will be assembled in the underground box at the station site. Government is confirming timings and funding for the construction of the Euston Tunnel.
Additionally, according to HS2 ‘s May announcement, across the route between London and the West Midlands, tunneling on half of all the twin bored tunnels had been completed.
At the present, the 16km Chiltern Hills tunnel and a 1.6km beneath Long Itchington Wood in Warwickshire have been completed and two others remain under construction that are the Northolt Tunnel in London and the 5.6km Bromford Tunnel in the West Midlands taking the line into central Birmingham.
Considering that at the West Ruislip portal the Copthall Green Tunnel’s nearby golf course has been impacted by HS2’s tunneling, the excavated material from HS2’s tunnels is being reused to remodel this course and also to create green spaces in the Hillingdon area surrounding the new railway.
In order to being reused in sites of Rugby, Kent and Cambridgeshire, London clay removed from the Victoria Road Crossover Box side of the tunnel is being taken to the London Logistics hub via a spoil conveyor. The logistics hub has now transported over 2 million tonnes of materials to these sites, which are being used to backfill quarries to support housing developments and wildlife areas for birds.
