Buried Tideway TBM allows milestone breakthrough

29 July 2021

Tideway has announced that TBM Millicent, which had been due to complete her drive toward the shaft at Carnwath Road Riverside Site in Fulham, London, has instead been turned and buried to allow the construction of a short connection tunnel.

The decision to turn the TBM was taken by Tideway in conjunction with its West section JV comprising Balfour Beatty, Morgan Sindall and BAM Nuttall. Rather than allow Millicent to hole through at the Carnwath Rd shaft as originally planned, the team felt that turning her would allow operations at the busy shaft to run more efficiently. This detour paved the way for the final 75m to the shaft to be mined manually, with breakthrough occurring in mid-July following six months of work.

The final connection between the sprayed concrete-lined tunnel and the segmental tunnel involved the West section team breaking out the precast tunnel segments and forming an enlargement around the segmental interface ring. Prior to the works starting, the team carried out a full-scale trial of the connection to ensure that the they could achieve the quality required.

Currently, around 20km of the 25-km 'super sewer' have been constructed with secondary lining now underway.