Abstract: Pipe jacking always results in the disturbance of the surrounding soft soil. Therefore, the pipe group jacking sequence in Wenlinshan Tunnel (Fuzhou) with a shallow soil cover, a large cross section, and high environmental protection requirements is optimized using a numerical simulation software FLAC3D. Initially, the stress release ratio is calibrated according to the onsitemeasured surface displacement to improve the reliability of the numerical simulation. Herein, a series of modeling experiments is performed using different jacking sequences. Further, the disturbance degrees of these jacking sequences with respect to the surrounding soil are comparatively analyzed. Analytical results show that the soil stress release ratio becomes 8% after pipe jacking, and the surface settlement can be effectively controlled during pipe jacking from the tunnel sidewalls to the crown. Finally, a prediction method is established based on the random medium theory for the surface settlement induced by pipe group jacking when considering ground loss. The field test results are in good agreement with the prediction results.

Key words: shallowburied highway tunnel, soft soil, piperoof method, jacking sequence, settlement prediction