3D numerical analysis of piled raft interaction in drained soft clay conditions

Abstract

Raft and pile foundations are combined with the twofold aim of increasing the overall bearing capacity and reduce the average/differential settlements. This results in a complex system and gives rise to significant soil–structure interaction mechanisms. In the last years, both bearing capacity and settlements of piled raft have been usually expected on the basis of empirical formulas, analytical relationships, and numerical analyses. The conventional design methods currently used in practice are based upon relatively conservative assumptions of raft–soil–pile interaction; as a result, they are in many cases inaccurate and unlikely to result in optimum design. Thus, resorting to numerical analyses seems to be the most reliable method, mainly because of the multiple interactions and the three-dimensional geometry that must be considered in most cases. In this context, 3D finite difference analyses were performed to investigate the behavior of piled raft foundation system in drained conditions of soft clays. The overall objective of the present paper focuses on the load response and effects of multiple interactions of piled raft subjected to vertical loading. For this purpose, several types of foundations were considered including piled raft, group of piles and unpiled raft. For optimization purposes, the behavior of the piled raft was also investigated by varying some parameters as pile number and piling configuration. The concluded observations from the parametric study provide further insight into the mechanical response of piled raft and aim at helping the engineers in taking a logical path in an iterative design process for a piled raft foundation.