Geotechnical Design and Performance of a Jacked-in-Place Subway in the First Application of the Rectangular Tunnel Boring Machine Technology in Hong Kong

The construction of a 140 m long subway at the Kai Tak Development was faced with aggravated constraints of urban settings –including congested utilities, lack of space, traffic concerns, proximity to structural foundations and existing facilities, etc.  Combined use of the rectangular tunnel boring machine (RTBM) technology and segmental jacking techniques provided an innovative solution.  This paper gives an overview of the design and construction process, the geotechnical challenges encountered and the measures to tackle them.  Specifically, earth pressure balance (EPB) underlying the technology and jacking force assessment will be discussed.  The successful completion of this project demonstrated the feasibility of the RTBM technology in typical geological conditions of Hong Kong, and the potential for routine applications for tunnel-type underground facilities particularly in congested urban areas.