London Underground contractor Tube Lines last month completed main civil engineering work for a new platform at Stanmore station at the end of the Jubilee line.
The third platform is needed to meet rising demand for train turnaround ahead of a 2009 signalling upgrade.
Space was made for the new platform by removing 15,000t of soil from a neighbouring embankment and installing a bored pile retaining wall with a sprayed concrete finish.
Nearly 300, 600mm diameter reinforced concrete piles were placed 300mm apart and between 10m and 14m deep for the wall. Raking piles 12m long and 310mm diameter were also installed as wall anchors.
The new platform required around 150, 300mm diameter piles to be installed. During piling, the Jubilee line track had to be monitored for movement. Work began in October 2004 and is due to be complete in April 2007.