An engineering solution for a hillside project in Hong Kong

Abstract

With the increasing land demand in Hong Kong, some developments encroach into existing hill slopes or even natural terrain, which presents a big challenge to geotechnical engineers to produce cost-effective site formation and foundation designs. This paper showcases an example of a large-scale site formation work with the use of a 3 m dia. permanent contiguous bored pile wall supported by permanent tie-backs to facilitate a 38 m deep excavation against a sloping terrain. With the use of the tie-back system, the movement of the adjacent ground was substantially reduced. This paper discusses the exceptional constraints and the construction challenges in this project, which include the limited site access, the difficult terrain with lack of suitable working platforms or flat grounds within the site, exposure to natural terrain hazards and the highly unbalanced excavation across the site. These constraints result in extensive temporary steel and earth platforms for facilitating the foundation construction and the excavation and lateral support works with a complex construction sequence. In addition, the findings of the back-analyses are presented to compare the predicted and the actual ground deformations using different soil models.