Anyone who has been past West Ruislip, Breakspear Road South or Harvil Road in the last few months will have seen the huge destruction of our countryside due to the construction of the HS2 railway.
One of the West Ruislip TBMs
The next stage of the project will have started by the time you read this – the launch of the two Tunnel Boring Machines (TBMs) at West Ruislip digging the two tunnels heading into London. These machines are simply huge. Some key statistics:
◆ Each TBM is about 170m long and weighs 1,900 tonnes
◆ 15 people work in the machine at a time
◆ Operates 24 hours a day, 7 days a week
◆ Two tunnels 8.4 miles long from West Ruislip to Ealing
◆ Digging up to 15 metres a day
◆ Each exposed part of the tunnel is lined with 7 concrete segments (2m x 4m) fitted in a ring
◆ Each segment weighs around 8.5 tonnes
◆ The tunnel inner diameter is 8.7 m
◆ Boring through the Lambeth group (a set of geological rock strata), chalk and London clay
Delivering these huge TBMs to Ruislip was an enormous logistical challenge involving 260 deliveries, including 110 abnormal loads. It included removing street furniture (railings, traffic lights, street lights etc).
The cutting head of a TBM arriving in West Ruislip
The 4,220 concrete lining segments for each tunnel are initially due to be delivered by road, but will in time get to the site by rail. They are made at a factory in Kent – a big win for local campaigners as HS2 had originally insisted they had to be made on site by two new concrete factories on the edge of Ickenham / Ruislip.
The concrete segment factory in Kent
The lining segments are moved into the tunnel and TBM by special vehicles designed to carry loads in a tight space. They travel through the middle of the TBMs and the segments are lifted into place by cranes.
The spoil that the TBMs dig out of the ground comes out on conveyor belts and is carried over the river Pinn and Breakspear Road South. A lot of spoil will be dumped on land near the Dogs’ Trust, whilst the rest will be carried over the Chiltern line and dumped in the land between Breakspear Road South and Harvil Road.
The launch site from West Ruislip Bridg
The TBMs are expected to run for about 22 months until they reach Greenpark Way in Ealing. They are then expected to be recovered and recycled, but whether this is done by reversing them out of the tunnels, or by digging an access shaft and lifting them out, remains to be decided.
The specialist tunnelers are so superstitious that they will not start using a TBM without it being blessed by a priest first.
At the time of writing, it is not sure how much noise and other disturbance the residents will suffer from the 24 / 7 working. However, the local residents’ team of campaigners are continually holding HS2 to account, and in some cases elevating serious problems through to HS2 Director and Ministerial levels.
The launch site from the air, looking east
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