Construction Techniques of Horizontal Ground Freezing Pre-excavation Support of Gongbei Port Tunnel

The Gongbei Port tunnel is a critical component of the Hong Kong-Zhuhai-Macau Bridge, currently the largest ongoing construction project in China, connecting Hong Kong, Zhuhai and Macao with a series of bridges and tunnels. It is designed to be excavated using conventional methods with a pipe roof in combination with the horizontal artificial ground freezing as an excavation support. The pipe roof consists of 36 pieces of 1620-mm-diameter steel pipes jacked using slurry shield machines. The freezing pipes are installed inside the roof pipes and are called as in-pipe ground freezing. The combination of a pipe roofing system with in-pipe ground freezing is the first attempt of such techniques in China. This paper presents a detailed description of the design, major construction challenges, and construction techniques for the horizontal ground freezing used in the Gongbei Port tunnel excavation. The construction of the Gongbei Port tunnel provides valuable case history experience to similar projects worldwide.