Performance Assessment and Optimization of an Earth–Rock Cofferdam Considering Seepage Effect

A cofferdam is planned to be built on the Yigong Zangbu River. Due to the complex geological conditions of the river valley at the construction site, the thickness of the overburden layer is large, and the permeability is high, hence the structural form of the cofferdam needs to be considered comprehensively. Combined with Biot consolidation theory, the analysis method of cofferdam consolidation based on stress and seepage coupling is established. Through the Morgenstern–Price limit equilibrium method and the FEM, the performance of the seepage control system designed by the cofferdam structure is systematically studied. Special attention is paid to the overall seepage flow of the cofferdam, the stress state of the cofferdam and the cutoff wall, and the stability change of the cofferdam caused by the change of water level. The results show that the change of cofferdam structure has a significant influence on the seepage field, stress field, and stability of the cofferdam. The optimal design parameters of the cutoff wall are proposed, and it is suggested that the composite geomembrane-inclined core wall cofferdam can be well adapted to the complex terrain characteristics. The method proposed in this study is helpful to understand the performance of the seepage control system widely used in cofferdam engineering.