Influences of Underwater Shield Tunnelling on River Embankment Seepage Stability Considering Various Overburden Thickness

Abstract

Underwater shield tunneling will disturb the soil near the river, especially in water-rich soft ground. This may cause a groundwater infiltration hydraulic gradient to exceed the critical value, leading to calamities, such as unexpected flooding or submerged erosion. To ensure the security of construction and the stability of river embankment seepage, it is crucial to assess the safety of the underwater tunnel cover thickness. A shield tunnel project under a river in Hefei is used as an example. The numerical model established by the finite element method is used for calculating and analyzing the changes in the groundwater flow field and the stability state of embankment seepage induced by underwater shield tunneling under different overburden thickness conditions. The results show that the construction disturbance of the shield tunnel through the river is increased, the internal force environment of the embankment slope is destroyed, and the maximum seepage hydraulic gradient is increased. In the case study, the embankment keeps in a stable state of seepage when the cover thickness of the shield tunnel has 2.9 times its outer diameter. The findings of this study can serve as a scientific guide to assure seepage stability in an underwater shield tunneling project and to stop river embankment erosion.

Keywords

• river-crossing tunnel
• cover thickness
• seepage stability
• numerical simulation