Seepage-stress coupling response of cofferdam under storm surge attack in Yangtze estuary

The cofferdam of the tidal flats behind Changxing Island was studied to explore the seepage-stress coupling properties of the cofferdam on a soft clay foundation under a storm surge attack. A numerical model coupling multiple influencing factors was established, which included tidal changes, wave loading, surges, soil strength degradation, and seepage effects. In addition, the dam global stability was investigated. The results showed that the permeability coefficient of the dam determined the magnitude and distribution of the seepage field during tidal level fluctuations. The tidal flood and ebb changed the periodic displacement of the dam body. When accounting for the wave loading applied on the cofferdam, the strength-weakening effect of the soil foundation induced by the wave cyclic load could produce additional displacement in the static and dynamic analysis of the dam. A stress-concentrated area was evident at the slope foot and hillslope in the coupled-field dam model that included the seepage force. The influence factors played important roles on the stress field, displacement field, and global stability. By comparing the calculated results and data, the established model and calculation method were validated, and the results are of theoretical and practical interest for predicting cofferdam resistance to storm surges.

Automated summary

The permeability coefficient of the cofferdam determines the magnitude and distribution of the seepage field during tidal level fluctuations, while wave loading can induce additional displacement by weakening the soil foundation strength.