Abstract:

To investigate the influence of the internal pumping process on the seepage field and stability of the cofferdam body after the closure of the artificial island cofferdam, a case study is conducted on the island cofferdam project of the largescale marine traffic hub on the east artificial island of the ShenzhenZhongshan link. Then, the finite element analysis software Geostudio is applied to establish the internal precipitation construction model of the cofferdam under different pumping conditions, and the stability analysis of cofferdam seepage field and slope is carried out during the pumping process to provide reference for the actual construction. The results show that: (1) The cofferdam body tends to be more unstable when the seepage concentrated at the foot of the slope on the backwater side at a higher pumping speed with higher wetting line. (2) The deformation of the cofferdam mainly occurs in softbase silt layer with slight displacement of the cofferdam itself, and the pumping speed has little effect on the displacement of the cofferdam, which indicates that additional reinforcement measures, such as replacement and highpressure jet grouting, are needed for the seabed foundation silt layer at the early stage of cofferdam filling. Furthermore, the analysis of the cofferdam slope stability with the limit equilibrium show that the safety factor of the cofferdam slope first decreases and then increases with the decreasing inner water level. In addition, a smaller minimum safety factor is obtained for a higher pumping speed. Considering the limitation of site construction progress, it is recommended to select the pumping speed of 1 m/d on the premise of meeting the stability of weir slope.

Key words: artificial island, earthrock cofferdam, seepage characteristics, stability analysis, numerical simulation