A Review of Conventional and Innovative Permanent Support Systems for Rock Cavern Development in Hong Kong

In recent years, the HKSAR government departments have been playing a leading role to study the feasibility of rock cavern development in Hong Kong. These studies include the relocation of existing surface sewage treatment works, service reservoirs, refuse transfer stations, archive centre and laboratory to rock caverns. After completion of the relocation, the previously occupied surface land can be released for other developments beneficial to the communities. Conventional permanent support systems comprise the cast-in-situ concrete lining with sheet waterproofing membrane. These have been applied in most of the highway and railway tunnels in Hong Kong. However, it involves the use of bulky steel shutter, heavy rebar fixing and an extra set of redundant temporary supports, which leads to very expensive and time-consuming construction. With the advance development in construction technologies, permanent rock reinforcements with sprayed waterproofing membrane could be a cost-effective engineering solution. With the integration of temporary and permanent supports, the tight daily drill-and-blast cycle and timely permanent support installation is greatly enhanced. This paper provides a general review of different conventional and innovative permanent support systems for rock cavern development with the purpose of achieving more efficient design and construction. It also discusses the application according to the unique requirements for various cavern facilities.