Environmental installation of piles in Hong Kong and Macau

Abstract

Most infrastructures and high-rise buildings are supported by deep foundations founded in competent geologic strata. Piles are the most common type of deep foundations in practice in Hong Kong and Macau. Piles can be cast in-situ, such as large-diameter bored piles, or pre-fabricated, such as steel H-piles or precast prestressed concrete piles. Pre-fabricated piles are usually installed by percussion. Due to the growing environmental awareness of the public, problems of air pollution, noise and vibration induced by the percussion piling process are becoming unacceptable to the public. The problem is further aggravated by the extremely populous and congested living environments of Hong Kong and Macau. The banning of the use of diesel hammers in Hong Kong has eased the air pollution problem. However, problems of noise and vibration remain. The techniques of jacking pile and preboring precast prestressed piles will be presented in this seminar. These techniques of pile installation are more environmentally friendly in many aspects. For pile jacking, piles are jacked into the ground hydraulically to eliminate any air pollution, noise and vibration problems. The pile can be steel H-pile or precast prestressed concrete pile. Every pile is load-tested during the installation process and the reliability of the piles installed is thus greatly improved. Installation of precast prestressed concrete piles by preboring was initially developed in Japan. The soil in the vicinity of the pile is liquefied and improved by the introduction of cement-bentonite slurry through augering by specially designed equipment prior to installation of the precast prestressed concrete pile. The method of installation does not only eliminate the problems of air pollution, noise and vibration. It also eliminates the uncertainty of pile damage by percussion which is a common problem of driving of concrete piles. The method of pile installation was introduced to Macau recently and the first trial pile program was successfully performed in March 2012. These environmentally friendly pile installation techniques will be presented in the keynote lecture. Moreover, the construction problems and solutions associated with the installation techniques will be discussed.