Vertical Load Transfer Behavior of Composite Foundation and Its Responses to Adjacent Excavation: Centrifuge Model Test

In urban construction, more and more foundation pit excavations are adjacent to existing buildings with composite foundations. Therefore, it is necessary to study the interaction between foundation piles and supporting structures. In this article, a centrifuge model test has been carried out to study the vertical load transfer behavior of composite foundation with rigid piles and its responses to adjacent excavation. The test model was designed based on a real excavation project adjacent to an existing composite foundation. The sand pluviation method was used to build the foundation model. An in-flight excavation method and a loading device for multilevel uniform surface load were used in the test. Finally, the variations of induced axial force, pile skin friction, and pile-soil stress ratio along with the depth were investigated. Some useful conclusions can be drawn as follows: (1) the negative skin friction in the upper part of piles, induced by the overlaying load, increases first and then decreases along with the depth; (2) pile-soil stress ratio decreases along with the depth under initial loads, while it increases first and then decreases when the load is larger; (3) pile-soil stress ratio always increases with loads in the same depth, indicating that mobilized skin friction of piles is continuously developed; and (4) more significant changes of the axial force, skin friction, and pile-soil stress ratio of composite foundation piles are observed in the shallow soil and for the later excavation stage. Therefore, the deformation of the foundation pit should be strictly controlled during the later excavation stages.