Initial Sinking Method for Large Open Caisson in a Highway Bridge Project

Abstract

Open caisson foundation has been widely used as anchor foundation for cable-stayed bridge in recent years. Large scale open caisson displays different mechanical characters compared with small and medium-sized open caisson in both construction process control and spatial mechanical performance. Generally, the drainage sinking of a large open caisson is more dangerous than the non-drainage sinking. At the beginning of caisson subsidence, the blade foots tend to deviate outwards because there is no buoyancy force or lateral constraint at the blade edge, which may lead to larger tensional force at the bottom of the caisson structure. Therefore, proper design of the first sinking scheme is particularly important for large-scale open caisson. A three dimensional soil- structure interaction finite element modeling, which is based on a large-scale open caisson for anchor foundation of a highway bridge project, is carried out to analyze the influence of the caisson structure diameter on the internal force in condition of first sinking. Numerical results indicate for large-scale open caisson the initial sinking method has a great influence on the tensional force generated in the caisson structure. It is also revealed the model of structure on Winkler foundation may lead to significant error in calculating the deformation pattern and internal force of the caisson structure. The numerical results and conclusion will provide reference for properly design of initial sinking method of similar large-scale open caisson projects.