Underground Car Park, Cheshire

ClientHillcrest Homes
LocationKnutsford, Cheshire
CategoryLabour, Plant and Materials

DWM Plant Limited have recently completed a Labour, Plant and Materials package for the design and installation of a sheet piled basement to form a cark park area for a prestigious development in Knutsford for Hillcrest Homes.

The development has taken over ten years to come to fruition with Hillcrest’s initial proposals for apartments halted due to a moratorium. DWM Plant Limited looked at the project originally in 2011 with structural engineers Brian Clancy Higby Partnership. Over the course of the next few years DWM helped to develop the scheme using their expertise in sub-structure construction.

The site was to be constructed adjacent to the River Lily: the location of the project found the ground conditions to be medium dense sands over lying clay, with ground water under artesian head. The first stage of construction focussed on the creation of a secure underground car park that will provide parking for the development. This was looked at originally as a secant/contiguous piled wall V’s sheet piled cofferdam but given the restrictive planning and geotechnical issues, careful considerations were made and then the decision was made to use the sheet piled option.

During the design stages careful attention was made not to offer a solution that would puncture the clay strata preventing any issues with the ground water. The length of sheet pile was also required to be considered in the permanent condition, ensuring the pile length did not affect the flow net of the natural ground water. With the pile length being kept to a minimum, two levels of propping were required during excavation works until the base slab is constructed. The modular format of a proprietary system was adopted for the flexibility of installation over a traditional welded option.