Design Optimization of Permanent Systematic Rock Bolts and Shotcrete Lining for Large-Span Caverns in Hard Rock

The hilly terrain in Hong Kong is underlain by hard and massive igneous rocks. This brings favorable conditions to develop underground space including rock caverns as an alternative source of land supply. In recent years, the 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 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. For an underground excavation in competent rock, the use of empirical design approaches is usually fast and straightforward to assess the rock mass conditions and determine the rock support systems. However, there are a number of limitations that empirical approaches cannot adequately address regarding the design of rock caverns, in particular the appropriateness for large-span excavation and influence of multiple parallel excavations.