CONTRACTOR HOCHTIEF was this week poised to begin jacking a reinforced concrete box tunnel through a Surrey railway embankment after a seven month delay.
The tunnel, through an embankment beneath Smitham Station, is part of the £25M, A23 Coulsdon bypass being built for Transport for London (TfL).
The 9,000t box jack was meant to take place last July.
But the project was knocked off schedule when Hochtief hit unforeseen ground while installing temporary tubes to support the overlying station and railway track.
Hochtief has had to auger its way through obstructions to install the 46 contiguous steel tubes, said TfL project director Mike Jackson.
These obstructions were not picked up during the site investigation, Jackson added.
Hochtief has also had to redesign the excavation method to avoid possible face collapse during excavation. The contractor will use a mining shield to support the face as excavation advances, said Jackson.
Jacking is anticipated to take two weeks.