HS2’s Northolt Tunnel under the capital is 50% complete

HS2’s tunnelling team are celebrating completing half of the 8.4-mile twin bored Northolt Tunnel underneath London.

Four tunnel boring machines (TBM) are being used the complete the tunnel that will 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.

The machines will excavate 16.8 miles of tunnel overall – two bores over the 8.4-mile length – making it the second longest tunnel on the new railway after one recently excavated beneath the Chiltern Hills.

The first machine, named Sushila after a local teacher, was launched eastwards from West Ruislip in October 2022. This was followed one month later by TBM Caroline, named after astronomer Caroline Herschel, which is used to excavate the adjacent tunnel.

Both will complete 5 miles of the route, finishing their journeys at the Green Park Way vent shaft in Greenford – just over half way – where they will be lifted out.

Earlier this year, TBM Emily, which is named after Emily Sophia Taylor, began its journey west from HS2’s Victoria Road Crossover Box site near Old Oak Common towards Greenford. She was joined by the fourth machine, named Anne, after Lady Anne Byron, in May. They will both complete 3.4 miles of the tunnel.

Combined, the four machines have now travelled over 8.4 miles – 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.

Between them, the quartet of machines have excavated nearly 2 million tonnes of earth.

The excavated material is being put to beneficial reuse. Around the West Ruislip portal, it is being used around the Copthall Green Tunnel, to remodel a nearby golf course that has been impacted by HS2’s tunnelling and is being used sustainably to create new green spaces in the Hillingdon area surrounding the new railway.

London Clay removed from the Victoria Road Crossover Box side of the tunnel, is being taken to the London Logistics hub using a spoil conveyor. From there it is taken by rail to beneficial reuse sites across the UK in Rugby, Kent and Cambridgeshire. 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 build wildlife areas for birds.

The Northolt Tunnel is being built by a joint venture formed of the companies Skanska, Costain and STRABAG (SCS). The same JV will also construct the Euston Tunnel eastward from Old Oak Common to the centre of London.
When complete, HS2 will improve connections between London and the West Midlands, with trains running further north on existing lines.

The new high speed railway will create quicker and more reliable journeys, driving economic growth while crucially freeing up space for more local trains on the most congested part of the existing West Coast Main Line.

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0:00 Introduction
0:11 Walking around Victoria Road Crossover box
1:34 On TBM Caroline
3:20 Inside Victoria Road Ancillary Shaft
4:58 At Westgate Ventilation Shaft
6:09 Progress at South Ruislip Ventilation Shaft
6:58 Exploring Mandeville Road Ventilation Shaft
8:55 The purpose of the Green Park Way Ventilation Shaft
9:38 Outro

#HS2 #Construction #engineering #tunnel #london

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