Piled Raft Foundation System for Tall Buildings

Abstract

Design of a safe and economical foundation system is an important task in tall build-ing design. Deep foundations such as piled foundations are generally adopted to transfer heavy loads from superstructure to the bearing stratum. Providing adequate geotechnical capacity and limiting the deferential settlement are two important design considerations in the design of piled foundations. The foundation design becomes economical when both the criteria of bearing capacity and settlement are satisfied in an optimum way. A piled raft foundation is an advanced concept in which the total load coming from the superstructure is partly shared by the raft through bearing from soil and the remaining load is shared by piles through skin friction and end bearing. Consequently, piled raft system is generally adopted when pile foundations for tall buildings become uneconomical or unsatisfactory. Due to the three dimensional nature of the load transfer, piled raft foundations are regarded as very complex systems involving many interaction factors such as pile-to-raft, raft-to-soil, and pile-to-soil. This paper intended to present a detailed discussion on the analysis of piled raft system addressing available analytical methods to analysis piled raft system. Considering of deferent factors influencing the pile raft behaviour are summarized in this paper. A detailed numerical analysis approach for the analysis of piled raft foundation is discussed. Further, a case study investigating the performance of piled raft system for an eighty-one storied tall building is presented.