ANALYSIS OF PILED-RAFT FOUNDATION BY THE FINITE ELEMENT METHOD

Abstract

The piled raft is a geotechnical composite construction consisting of three elements: piles,raft and soil. It is suitable as a foundation for large buildings. This paper presents an analysis of piled raft foundation, included material nonlinearity and soil structure interaction. An efficient computer program in FORTRAN 9Ois developed for this analysis. A 20 node disoparametric brick element has been used to model pile, raft, soil and interface materials. Thin layer interface element has been used to model the contact zone between the pile and soil, and between raft and soil. The behavior of the piled raft material is simulated by using a linear elastic model. However, the behavior of soil and interface materials is simulated by an elasto-plastic model by the use of Mohr Coulomb failure criterion. Some of the variables of piled-raft system, related to settlement and differential settlement in sandy soil, have been studied, where the length of piles and distance between piles an effective role in reducing both settlement and differential settlement of foundation system. Also increasing the thickness of raft foundation reduces the effectiveness of additional piles for the purpose of reducing differential settlement.