Study On The Displacement Character Of The Open Caisson Under Long-term Horizontal Load

The open caisson is common among gravity type foundations of suspension bridges, which was always built on the hard rock or soil before, used to resist the tremendous force from the main cable with the friction on the bottom of foundation. However, many suspension bridges were built in the area with deep water and soft soil in recent years. Because of the low strength and the time-variant effect of soft soil, the displacement distribution of the open caisson changes over time under the long-term horizontal load. So far there is no perfect theoretical method for the analysis of load-bearing performance of open caissons built in soft soil yet, and the structural design is in lack of reliable basis, therefore the research is particularly necessary. The main contents of this paper are as follows:Firstly, a experimental program was developed based on the research proposal and indoor scale model experiments were done. Experiments were divided into four groups, including one short-term experiment, two long-term full model experiments and one long-term half model experiment. Horizontal bear capacity of the caisson modle was measured and the long-term experimental scheme was designed based on the short-term experiment.Besides, the distribution regularities of the earth pressure around the open caisson, the deflection of the open caisson and the horizontal displacement of the soil surface in front of the open caisson were analyzed according to the results of long-term full model experiments. In addition, the PIV flow measurement technology was applied in the half model experiment to research the rheological properties of soil before the open caisson.At last, a p-y curve model considering about burial depth, time and loading levels was presented based on the elastic-plastic p-y curve model, and corresponding calculation formula was put forward. The results of experiments and ABAQUS are in good agreement with the theoretical computation results. Besides, the calculation formula was used to analyzed project cases, and the calculation accuracy can meet the need of engineering, which means the research can provide useful references for engineering application and designing.