Tunnelling in Hong Kong towards the millenium

Hong Kong continues to display a remarkable enthusiasm for undertaking ambitious tunnelling schemes despite apparent recessions in the Asian economy. This paper provides an outline of tunnel projects currently under construction, those recently tendered and a glimse of the extent of forthcoming projects which, according to Government sources, carry a price tag of HK$ 200B. Committed works will cost about HK$ 15B and involve a variety of TBM and drill and blast tunnels. These include the recently tendered works for KCRC's West Rail and MTRC's Tseung Kwan O railway extension, together with 5 no retendered TBM drives for the Strategic Sewage Disposal Scheme (SSDS) following forfeiture of the works by the Campenon Bernard-Maeda JV in mid-1997. The JV claimed unreasonable specifications leading to unacceptable levels of water inflow and dangerous working conditions. Key technical issues that are now arising in Hong Kong are: 1. the general use of design and build contracts for bored tunnel contracts; 2. a trend to accept TBM options for relatively short drives in urban areas; 3. the use of 'fixed-price' contracts which in the current competative market, can encourage tenderers to take contractors to take very high risks; and 4. the difficulty of predicting and managing water inflows in rock tunnels. This paper also includes a new empirical method of predicting water inflows in rock tunnels, and makes recommendations for managing these on-site.