Piling Works for Cardiff Central Square Development

Central Square is a five-hectare development in Cardiff city centre, comprising of six new buildings ranging from 5 to 25 storeys for a total of around 90,000m² of new mixed-use space. Arup has been serving as main engineering designer for the development. Balfour Beatty Ground Engineering undertook the piling works for the foundations and basement walls of the four buildings completed to date. The site lies between Cardiff Central station, the River Taff and the Millennium Stadium, in an area of reclaimed tidal flats and infilled channel of a river tributary. The new buildings are supported on CFA piles transferring the structural loads into the Mercia Mudstone bedrock below made ground and fluvioglacial deposits. The complex site history and ground conditions presented challenges to the pile design and construction works, including low strength bands in the mudstone, ‘artificial refusals’ from ‘plugging’ of the auger, and loss of pressure and slumping presented in various areas of the site. The paper presents the key site-specific challenges and solutions in the piling design and construction works for the Central Square development.