Consolidation Characteristics and Bearing Behavior of Sand Pile Composite Foundation in Caisson Heightening

To study the influence of consolidation on the bearing capacity of the composite foundation in the process of caisson heightening, the consolidation characteristics of the sand pile composite foundation in the process of caisson heightening are discussed based on the sand pile composite foundation engineering of a large-scale onshore caisson foundation. The influence of loading duration and replacement rate of the sand pile are analyzed. Based on the area ratio method of pile-soil and the pile-soil stress ratio method, the formula of the ultimate bearing capacity of the sand pile composite foundation considering the consolidation effect is derived, which is compared with the measured value of the ultimate bearing capacity of the foundation. The results show that the time history curves of the bearing capacity of the composite foundation based on the two methods are close, and the initial bearing capacity is less than the measured value of bearing capacity, while the bearing capacity after consolidation is 68% and 80% higher than the natural strength of the composite foundation. This method considers the influence of consolidation on the bearing capacity of the foundation in the process of caisson heightening. It can avoid the problem of stagnant sinking of open caisson as it underestimates the actual bearing capacity of the foundation, and provides suggestions for calculation of ultimate bearing capacity of the composite foundation considering the influence of consolidation and formulating the reasonable construction scheme of open caisson.