3-D Finite Element Analysis Of Shear Wall-Piled Raft-Soils Interaction

With the rapid development of economics and technology, there are more and more high-rise buildings constructed on pile foundation. Piled raft foundation, in which both the piles and the soils under the raft carry the loads from superstructure, is an important foundation form of high-rise buildings. With the development of interaction theory and the improvement of computing technique, the mechanisms of load transfer for piled raft foundation has began to be studied. However, piled raft foundation is a very complicated system and is related to many factors. Therefore, it is necessary and important to study thoroughly on the interaction of superstructure, piled raft and soils.In this paper, a 3-D finite element model based on a 15-floors high-rise building case in Hangzhou is proposed by ABAQUS to analyze the interaction of shear wall structure, piled raft and soils. The effects of superstructure rigidity, soil deformation modulus, raft thickness and pile length are analyzed. Meanwhile, the constitutive behavior of soil is assumed to be elastic and elasto-plastic. The main conclusions are obtained as follows:(1) With the increment of superstructure rigidity, specially after reaching 9th floor, the differential settlement and the moment of the raft per unit load increase slowly. This shows the effects of superstructure rigidity are limited.(2) The foundation reaction presents a more obvious shape of saddle when the superstructure rigidity is considered. The loads carried by the piles in the corner and on the edge of the base are more than that in the center. The proportion of the loads carried by soils is about 10%~20%.(3) When the soil is one layered and uniform, with the increment of deformation modulus of soil, the proportion of the loads carried by soils increases, and the differential and maximal settlement as well as the moment of the raft decrease. If there's a overlying crust just under the raft, the proportion of the loads carried by soils will increase slightly.(4) With the increment of raft thickness, the differential settlement decreases, the proportion of the loads carried by soils increases, and the moment of the raft increases greatly.(5) The differential settlement and moment of raft can be controlled by adjusting the length of local piles. In order to make full use of piles and save the cost, the reasonable ratio of long and short pile length is suggested to be 1.75~2.0.