Geotechnical Investigations Offshore Hong Kong

A comprehensive site investigation was performed offshore the island of Chek Lap Kok as part of the civil engineering design studies for the proposed replacement airport at Hong Kong, The program included conventional drilling and sampling carried out from floating craft, as well as extensive in situ testing, including piezocone penetration, field vane shear, and permeability tests. The laboratory testing program incorporated Ko‐consolidated, undrained, triaxial compression, extension, and direct simple shear tests, as well as numerous more conventional tests. The thrust of the investigation was the determination of engineering characteristics for two extensive marine clay deposits that are considered critical to the performance of the proposed airport reclamation. One of these deposits, referred to as the upper marine clay, covers the entire offshore portion of the site. It is extremely soft and sensitive, with undrained shear strengths ranging from 3–12 kPa and sensitivities of about 10. The other deposit, referred to as lower marine clay, is medium stiff and overconsolidated, with in situ shear strengths in the range of 40–90 kPa. The results of the field and laboratory tests are synthesized to develop engineering properties appropriate for reclamation design. Correlations between the piezocone data and field vane shear tests are presented, as well as correlations of compressibility parameters with index properties. Normalized strength parameters for the two marine clays are also presented.