Horseferry Road Magistrates Court is being redeveloped by Barratt West London. The basement scheme reuses the existing diaphragm wall and replaces the existing basement structure with a new deeper structure.
The original scheme relied on providing a new piled basement structure within the existing diaphragm wall, which was to be propped at three levels. We proposed an alternative scheme using two levels of propping and a change of the basement structure to a raft slab. These proposals saved significant time and cost for the scheme.
The propping for the scheme was a mix of fabricated steelwork for the upper level with substantial tubular props and walings. For the lower level we proposed using part of the permanent works waling beam as temporary works and supporting this back to posts cast into the central raft slab with proprietary props. The use of proprietary props for the low level was driven by the short duration that they would be in place.
A major part of the work was in assessing the capacity of the existing diaphragm wall from investigation works and an assessment of the geotechnical capacity of the wall compared with the loads imposed on it from the revised dig levels. We demonstrated to Westminster that the proposed scheme was sound through their Technical Approval scheme.