Abstract:

The pipe curtain retaining method of curved pipe jacking is applied to the construction of mined section of Gongbei Tunnel, which is a significant part of Hong KongZhuhaiMacao Bridge Connecting Project. The estimation of total jacking force in curved alignment still remains its necessity and difficulty especially when driving in complex ground. A total of 37 steel pipelines with diameter of 1 620 mm and average length of 255 m are installed around the tunnel section as an advance support. Two different calculation methods, including an empirical formula and a theoretical formula are used to estimate the jacking force and compare with the insite driving force. The results indicate that: 1) The friction force calculated by empirical formula coincides with actual friction force in deep buried condition; however, it is larger than actual friction force in shallow silty ground. 2) Compared with the measured penetration load, the calculated passive earth pressure is more conservative. 3) The slurry shows a significant influence on the jacking force, but not so obvious in the initial stage of jacking; however, when a continuous and complete slurry jacket is formed, the friction force reduces (lower than 1 kN/m2).

Key words: Hong KongZhuhaiMacao Bridge, Gongbei Tunnel, curved pipe jacking, jacking force, penetration load, frictional resistance