Evaluation of Piled Raft Performance Using a Verified 3D Nonlinear Numerical Model

The piled raft foundation system presents a feasible foundation option for high rise buildings. Piled raft foundations have a complex three-dimensional soil-structure interaction scheme including the pile-soil interaction, pile–pile interaction, raft-soil interaction, and finally the piles-raft interaction. Consequently, comprehensive 3D numerical models are sought to investigate this complex interaction. In this paper, a 3D finite element model was verified using published geotechnical centrifuge test results to further enhance the accuracy of the model. The study considered piled rafts installed in sand with stiffness that varies linearly with depth. A comprehensive parametric study was conducted to evaluate the effect of different foundation parameters including: pile diameter, pile spacing, raft width, and raft thickness on the overall behavior of the piled raft. The load carrying capacity of the piled raft and the load sharing mechanism between the raft and piles are evaluated. It was found that the load carried by piles is higher for rigid rafts (K_f > 600) due to the minimal interaction between the raft and subsoil compared to the relatively flexible rafts (K_f < 150). Moreover, the load transmitted by the raft increased by about 75% as the raft width increased from 4 to 7 m.