At Millcroft, we’re continuing to make our mark on the HS2 project, particularly in the assembly and preparation of Tunnel Boring Machines (TBMs). We are currently engaged in a critical phase at Old Oak Common, where our dedicated team is erecting the first two of four ‘dry enclosures,’ essential for pre-assembly of the TBMs.
Our enclosures are crucial stages in the TBM assembly process. Inside them, two cutterheads and two tailskins will be welded together before being removed to the ‘East Box’ excavation site. Here, the TBMs will undergo further assembly in preparation for their tunnelling mission. This marks the sixth and seventh TBMs Millcroft has worked with this year.
Millcroft’s track record with TBMs is impressive. Each machine is named after a local female icon. Previously, we have worked on TBMs Florence and Cecilia, which completed a 16km journey through the Chilterns on the Align Framework at Rickmansworth. Emily and Anne have also started their journey from North Acton to Greenpark Way in Greenwich, and TBM Lydia has completed a maintenance tunnel between Atlas Road and Old Oak Common East Box. Once each of the TBMs completes their section of work, the main body is put under temporary roof structures designed by Millcroft and dismantled.
The sheer scale of these TBMs is staggering. Each rotating cutterhead measures 10.26 metres in diameter, which is approximately the height of two giraffes standing on top of each other. The TBMs themselves are 170 metres long, equivalent to 1.5 football pitches, and weigh around 2,000 tonnes, roughly the weight of 340 African bush elephants. The cutterhead alone weighs over 110 tonnes and cuts away the earth in the TBM’s path. In addition to digging thetunnel, the TBM builds the wall with tunnel segments as it moves along.
Millcroft's expertise in this niche area has led to us working on 10 TBMs over the past four years, reflecting the high-quality delivery and specialist skills we bring to such complex projects. Our HS2 client, Skanska Costain Strabag JV, has contracted Millcroft for a variety of diverse and dynamic tasks, including edge protection handrails on the back of gantries, temporary roofs/dry structures and bird cages for workers to weld the TBMs together.
With a team of 40 scaffolders, most of whom have been part of the HS2 framework for a couple of years, we ensure rigorous training and safety measures. Workers undergo tunnel and confined space training, standard scaffolding qualifications and safety critical medicals. The nature of the work is demanding and involves 12-hour shifts across 7-day/7-night rotations, so we have implemented fatigue management measures to ensure the well-being of our team.
Millcroft’s work at Old Oak Common is just one part of our contribution to this transformative infrastructure development. Our expertise in designing and providing safe structures for constructing and dismantling of these enormous machines is helping to drive forward one of the UK’s most significant railway projects in decades.
