Key Construction Technologies for Large River-Crossing Slurry Shield Tunnel: Case Study

With the rapid urbanization and unprecedented development of urban traffic, there is an increasing need for river crossings with large-diameter tunnels in short spans, such as in the Yangtze River Delta, China. In order to satisfy the slope requirement of the road during the river crossing, the thickness of the overburden beneath rivers is inevitably very shallow. Meanwhile, the slurry pressure of a shield tunnel during construction is difficult to control when crossing under the river embankment, usually built with roller-compacted soil rock, where the thickness of the overburden varies widely. The structure stiffness of such an embankment is low and the integrality is poor. In this scenario, there will, without doubt, be an increase in risks and difficulties for river-crossing shield tunnel construction. In this paper, key construction technologies adopted to overcome the difficulties in large river-crossing slurry shield tunnel construction are put forward based on the Jiangyin West Chengjiang Road Tunnel project. A test of advance was conducted for the length of 100 m (67 rings) to optimize the shield excavation parameters and make shield operators skilled through continuous tests and explorations. Then supplementary countermeasures were carried out to ensure the safety of the shield tunneling. Multiple countermeasures provided a powerful guarantee for successfully tunneling under the rivers.