An Assessment of the British Code of Practice for Site Investigations for Hong Kong Conditions

Abstract The Geotechnical Control Office has undertaken the preparation of two separate, complementary guides on “Rock and Soil Description ” and “Site Investigation ”, as companion documents to BS 5930:1981 for use in Hong Kong. This paper examines the need for a separate guidance document on site investigation for Hong Kong conditions. The predominance of heterogeneous weathered soil profiles and colluvium in Hong Kong presents particular problems, both in their description and investigation, which are not covered adequately by BS 5930:1981. Emphasis in this paper is placed on highlighting the shortcomings or inappropriateness of some of the BS 5930:1981 site investigation techniques when applied to Hong Kong conditions. For example, the British Code of Practice discusses techniques which are not used in Hong Kong, such as light cable percussive drilling; techniques and good practice associated with rotary core drilling are amplified instead. Similar treatment is given to the commonly installed open hydraulic (Casagrande) piezometers. Particular problems and interpretation of frequently performed field tests such as dynamic probing, the standard penetration test, in-situ vane shear test and impression packer surveys are also discussed.