Automatic monitoring and structural stress analysis during ultra-large onshore caisson sinking construction

Abstract

During the sinking process of ultra-large onshore caisson, the structural stress of caisson will change significantly due to the changes of earth pressure, end resistance, water level in caisson and attitude of caisson. Based on the south anchoring onshore caisson project of Nanjing Longtan Yangtze River Bridge, the structural stress analyses were carried out based on the automated caisson monitoring data. The results show that the automated monitoring system can acquire the key data of caisson in real time and efficiently, and the monitoring results reflect the structural stress and displacement characteristics in different construction stages. The vertical earth pressure at the bottom four corners of the caisson is significantly greater than the other positions, indicating that there is an obvious stress concentration phenomenon at the four corners. The stress at the bottom of the horizontal earth pressure monitoring is smaller than that at the middle and bottom of caisson, which verifies the existence of stress disturbance area around the cutting. Steel shell concrete at the bottom of partition wall is the weakest position of caisson structure, and the structural safety risk is higher from the first casting to the second sinking. If the risk of tensile cracking occurs in the process of casting, each diagonal can be carried out several times to make full use of the structure's own resistance to reduce the development of tensile stress. The conclusion can be used for reference in the design and construction of similar projects.