Underground Development - Pipe Curtain with Jack-in-place Rectangular Tunnel Boring Machine Technology

With the recent successful application of Rectangular Tunnel Boring Machine (RTBM) Jack-in place technology in Hong Kong, more interest is put into its wider use. However, the application of RTBM is restrained by geological limitations, such as shallow overburden depth, limited span depth ratio of the tunnel (< 2), etc.  Advanced underground construction technology – the adoption of systematic pipe curtain with Jack-in place RTBM methodology- was introduced recently in China and Overseas to construct underground railway tunnels, stations, pedestrian subways, and underpass in challenging congested urban areas. This advanced methodology focuses on underground structures construction in which stringent settlement control with shallow overburden cover is required.  It also possesses the flexibility to adapt to different sizes of cross-sections, which makes wide span (>20m) underground structures can be constructed by the trenchless method.  Given the future of Hong Kong infrastructure development, this paper is aimed to explore the potential for developing underground space based on this advanced solution to resolving problems in an old and congested urban area.  Taking past successful project experiences in Mainland China as examples, this paper has discussed the geological requirements, construction method, sequence, ground settlement performance, etc.  It also provides consideration that should be aware of the adoption of technology in typical Hong Kong geological conditions. The RTBM technology offers a new solution to the infrastructure development projects in Hong Kong with better buildability, safety and productivity.