A Systematic Approach to Construction Risk Assessment for the Drainage Tunnel of Kai Tak Transfer Scheme of Hong Kong

INTRODUCTION The issue of increasing population is a problem prevailing in all urban cities in the world. Urban congestion in Hong Kong is particularly amplified by its hilly terrain. A clear trend can be seen in recent decades all over the world with networks of transportation as well as provisions of utilities services seeking underground solutions, which in some cases is the only feasible option. The demand of methods to minimise the environmental impact during the execution of these underground projects is also overwhelming. Compared to open type excavation methods such as cut and cover, tunnelling has much lower environmental impact to be public. With the development of sophisticated tunnel boring machine (TBM), the underground solutions appeared to be easily achievable with greatly improved construction safety. This is, however, not entirely risk free. Numerous problems and incidents have been seen from precedented tunnelling projects worldwide, affecting public life and/or properties, alarming the construction insurance industry. This is particularly important when tunnelling in an aged built up urban area such as the drainage tunnel for Kai Tak Transfer Scheme discussed in this paper.