Wood Wharf in London is the first residential scheme to be developed in Canary Wharf. The 136,000sq.m area is comprised of 3,500 homes, businesses and retail spaces, as well as a school and NHS facility. The site required the reclamation of 8,500m2 of existing dock. ByrneLooby was appointed to design a combi-wall cofferdam to allow dewatering of the area, to be followed by foundation construction for the new buildings.
The construction methodology of the combi-wall piles was unusual due to restricted impact driving and the presence of a hard caltite layer within the underlying strata. Oversized holes were drilled, the tubes forming the combi-wall dropped into the bores and the annulus between the bore and the tube filled with sand. This led to difficulties analysing the combi-wall, particularly assessing the level of movement of the wall once the dock was dewatered.
In the original tender proposal, the dock silt was to be removed. Considering the potential environmental benefits and financial saving that could be achieved by leaving this stratum in place, ByrneLooby produced a novel cofferdam design that did not require the silt to be removed. This design provided a solution where the clay was consolidated on site and a piling platform constructed above it. Advanced Finite Element analysis allowed ByrneLooby designers to be confident that the subgrade would allow the rigs to operate safely.