TGP was retained by the Balfour Beatty Amec Joint Venture to redesign and detail reinforcement cages for two of the three diaphragm wall phases during the construction of the new underground railway station adjacent to the Houses of Parliament.  The walls were up to 39 metres deep and consequently it was necessary for the cages to be fabricated off site in three sections.  These were brought to site during the night and coupled together as they were lowered into the excavated panels. 

The numerous floors and other elements of the structure which are connected into the wall necessitated extensive use of couplers and shear connectors. Part of the wall was constructed beneath the District and Circle Line.  This section required a maximum cage length of only four metres due to vertical clearance limitations.  The original design of the wall and detailed cages were too large for diaphragm wall construction and could not be fabricated or installed within the confines of the congested site.  However, by redetailing the reinforcement to accommodate the Contractor’s construction method, some of the most complex diaphragm walls ever constructed were completed on programme.