Performance of piled raft foundation supported by either connected or unconnected piles

Abstract

Piled raft is commonly used as foundation for high rise buildings. The design concept of piled raft foundation is to minimize the number of piles, and to utilize the entire bearing capacity. High axial stresses are therefore, concentrated at the region of connection between the piles and raft. Recently, an alternative technique is proposed to disconnect the piles from the raft in a so called unconnected piled raft foundation UCPR, in which a compacted soil layer (cushion) beneath the raft, is usually introduced. The piles of the new system are considered as reinforcement members for the subsoil. In the current study, the behavior of both connected and unconnected piled rafts systems has been studied experimentally. The effects of different factors, such as; the piles number and configuration, on the load settlement behaviour and pile load sharing are also investigated. The results indicate that when unconnected piles are used, the total settlement of the piled raft system is significantly reduced, and the pile load sharing considerably decrease, e.g., for piled raft with nine piles the total settlement has decreased by 35.6% and pile load sharing has decreased by 20.9%.