Study On Optimal Design Of Raft Thickness In Piled-raft Foundation

Piled-raft foundation is widely used in high-rise buildings due its good integrity, high bearing capacity and the ability of controlling differential settlement. Study of analysis method for piled-raft foundation has always been very important in geotechnical engineering, and the determination of raft thickness is the most crucial problem in the design of piled-raft foundation. Up to now, empirical approach is most frequently used in designing institute. However, it has some limitation and poor economy. Because of this, research on determination of raft thickness in piled-raft foundation is carried out.In this paper, research status both at home and abroad is firstly reviewed about the vertical stress and settlement of foundation, pile-raft interaction and raft analysis. The design principal of software POGAP produced by Zhejiang University is introduced. Using POGAP, the piled-raft foundation of a practical project in Hangzhou is analyzed, the effect of raft thickness on foundation settlement, pile reaction, and raft internal force is investigated, and optimal analysis on raft thickness is carried out. In the end, three kinds of methods of calculating raft thickness in China is introduced and evaluated, based on which a new method of determining raft thickness is proposed. Three practical projects is quoted to verified the new method, proving that the method is able to be applied to practical engineering.