Phase 1 of this project, carried out in 2007, required the construction of a triple basement with a retained height of 13.5 metres. Over most of the site the rock level within the basement was 3 to 4 metres above formation level.
Our proposed solution was to provide a secant pile wall with 900mm CFA stiff piles and 640mm ODEX hard piles at 1.0 metre centres.
The 900mm diameter CFA piles were nominally socketed into rock and the ODEX 640mm piles were drilled 4 to 8 metres into intact rock. The pile wall was restrained by two levels of tie-back anchors.
Phase 2 works were carried out in 2010. The scope of works was considerably smaller than Phase 1 and included: secant piles as described above and 450mm & 600mm diameter CFA bearing piles with SWL’s of 1400 & 2200kN respectively. Both phases included the construction of guide walls, capping beams and both permanent and temporary tie-back anchors.