NAMED after 18th century astronomer Caroline Herschel, tunnel boring machine (TBM) Caroline began a journey under West London on October 27 that is estimated to take 22 months.
Excavating the southbound bore of the HS2’s five-milelong Northolt Tunnel between West Ruislip and Greenpark Way in Greenford, Caroline was launched three weeks after sister TBM Sushila (working in the same direction to create the northbound bore), which had by this time travelled 70 metres towards Greenford.
Construction
Caroline is expected to move an average of 14 metres per day. On its journey, it will install 4207 concrete tunnel segment rings, each consisting of seven segments, which have been manufactured by Pacadar at its factory at the Isle of Grain in Kent.