Northern Line extension tunnelling completed

摘要

Tunnelling on London Underground's Northern Line extension was completed on November 8, when tunnel boring machine Amy broke through at Kennington. Amy began tunnelling in May, following sister machine Helen the previous month. Both TBMs had been supplied by NFM Technologies. The twin 5.2 m diameter tunnels have been bored at a depth of up to 26 m, and are lined with nearly 20000 precast concrete segments.