Case history: ground treatment of the sandfill at the new airport at Chek Lap Kok, Hong Kong

70Mm(3) of marine dredged sandfill was used in the construction of the reclamation for the new Hong Kong airport at Chek Lap Kok. The as-placed sandfill was in a relatively loose state below the water table with a relative density of 20-40%. To minimise future settlement caused by piling activities or possible seismic effects, vibrocompaction was carried out to densify the sand and produce a more uniform fill. The paper presents the results of vibrocompaction in one area and the use of CPT as the quality control test method. In this area CPT testing was carried out at four separate times; two before and two after vibrocompaction. The information collected over a four year period has also enabled the effects of ageing of the sandfill to be quantified.