Performance of composite caisson-pile foundation (CCPF) under axial and monotonic lateral loading

ABSTRACT: Composite Caisson-Pile Foundation (CCPF) is a novel type of hybrid foundation developed from the combination of the caisson and piles foundation to take advantage of both foundation types. CCPF minimizes construction time and cost and offers innovative solutions to challenging site circumstances in deep water. The CCPF may decrease the length and embedment depth of the caisson and pile foundation compared to traditional foundations. However, there are still a few crucial hurdles to fully accepting CCPF foundations as primary foundations in deep water with complex geology. Comprehensive research is required to evaluate the performance of the CCPF and to increase the confidence level in the use of CCPF, despite the lack of research in the direct performance analysis of the CCPF under various loading and soil conditions. A series of reduced-scale tests were performed on CCPF. The load settlement, load improvement ratio (LIR), settlement reduction ratio (SRR), and load sharing characteristics of the CCPF were investigated at varying relative sand densities and pile configurations to comprehend the effect of various influencing factors on the behavior of CCPF. The test results indicate that adding piles under the caisson can effectively increase load capacity and decrease the settlement of the foundation system. A three-dimensional finite element model of CCPF was prepared in PLAXIS 3D and calibrated using the reduced-scale laboratory test results.