Settlement and load sharing behavior of piled raft foundation: a review

Piled rafts are increasingly being used to support different heavy infrastructure facilities. The total resistance of piled raft is cumulative of shallow component, i.e., raft and deep component, i.e., pile accounting for different interactions among component elements. The paper discusses the mechanism of load transfer in unpiled raft, pile groups, and piled raft foundation systems. Large variability in stiffness and geometry and different interactions among piled raft components, i.e., pile, raft, and soil, establish it as a unique and complex foundation system. A large number of methods have been developed idealizing different in situ conditions to estimate the settlement and load sharing of the piled raft foundation system. This paper presents a detailed review of different available methods to estimate settlement and load sharing of piled raft systems. Different simplified methods, computer programs, approximate numerical methods and analytical approaches are useful to evaluate approximate settlement and load sharing of piled raft systems for the initial design stage; however, a rigorous three-dimensional finite element analyses approach capable of capturing complex soil-pile-raft interaction considering more number of governing parameters is useful for the final design of the piled raft foundation. Favorable conditions, the mechanism of the piled raft, and factors affecting piled raft performance are discussed here. Details of different settlement and load sharing estimation methods are presented here. Different micro-details, i.e., observed settlement, load sharing ratio, and pile and raft details of successful published cases of piled raft foundation worldwide, are also listed here. Design recommendations are made based on the available information, and different aspects of piled raft foundation that need further attention are also highlighted. The paper is useful to practicing geotechnical engineers and researchers working in the area of piled raft foundations.