Establishing a Graphical Method for Calculation of Raft Thickness in Piled Raft, Pile Group and Raft Foundation

Based on the rafts observation of 26 high-rise buildings in Vietnam and around the world, it is recorded that they are very thick. So, the questions is, what is the role of raft (and its thickness) in a foundation system individually, and the interactions between raft-soil and pile in the whole upper structure in general? And why do rafts in some buildings seem to be very thick? For example, MesseTurm Tower is 256 meters tall with raft's thickness of 6.0 meters while the others are relatively thinner such as Dubai Tower is 400 meters tall with raft's thickness of 2.5 meters. A literary review and a parametric study on the factors affecting raft thickness shows that it depends on the number of floors, pile system's properties and Young modulus of soil. Based on the mentioned observation, a graphical method is, therefore developed. The method is then verified and calibrated into six case studies equivalent to six buildings constructed in Vietnam and around the world. The estimated raft thicknesses from the 26 mentioned cases using the graphical method are reasonable in comparison with designed ones. Thanks to that, they can explain the cases of thick or thin rafts.