Three Dimensional Finite Element Analysis and Back-analysis of CFA Standard Pile Groups and Piled Rafts Founded on Tropical Soil

Abstract

This paper deals with Plaxis 3D finite element simulations of the mechanical response of deep foundations founded in a collapsible tropical soil. Main attention is initially paid to differences between single continuous flight auger (CFA) pile behavior and the behavior of CFA piles in standard groups. The numerically computed load-settlement curves are compared to field load test data obtained at the experimental research site of the University of Brasília (UnB), leading to conclusions about the appropriateness of adopting laboratory, in situ or back calculated parameters as input of numerical programs that simulate 3D foundation systems. Further, the contribution of the contact surficial soil/top raft is numerically examined by simulating the behavior of identical “piled raft” systems founded in the same site. The numerical simulated results of “piled raft” and standard pile group systems are then compared in terms of load capacity, system stiffness, load share between pile tip, shaft and raft, and mean developed lateral pile shaft friction. Having the results at distinct loading stages, as at working and failure levels, the analyses show the differential behavior, and design obtained responses, one may expect from conventional pile groups and “piled rafts” of CFA floating piles when founded in tropical soils. It is a mixed theoretical/experimental paper with practical interest for foundation designers and constructors.