Behaviour Of Piled Rafts With Piles Of Different Lengths And Diameters Under Vertical Loading

With the vigorous development of construction projects in China, the piled raft foundation has been widely used in high-rise buildings and ultra-high buildings.Today many significant results have been achieved on the pile-raft-soil interaction,but most of these achievements were achieved on the condition of the traditional even cloth pile way which have the same length, have the same diameter and have the same spacing, even there are various assumptions and formulas, so far the achievements of the pile-raft-soil interaction have not provided consultation for the practical designing.So it is an important subject for seeking a design method of practical, economic and reasonable, safe and reliable in the domain of piled-raft studying.On the basis of having reading the predecessors's research achievements in the field of the pile raft foundation, I have obtained some rules about the characters of the pile raft foundation. At present the research about the pile raft foundation which have different pile-diameter and pile-length is rarely. Establishing 3-D finite element analysis thinking over piled rafts construction process, the characters of settlement,raft-force, pile-head-counterforce and pile-surface-friction of piled rafts which have different pile-diameter and pile-length were studied by finite-element analysis software MIDAS/GTS under the action of the even and uneven vertical load base on the interaction of pile and soil,also the characters differences of the piled rafts which have the same pile-diameter but the different pile-length in several different cloth pile way were analyzed and compared. The results indicate that it is right very helpful for decreaseing settlement and adjusting raft-force when the long piles or the big-diameter piles were seted where the vertical load and the interaction is powerful, but the effect no longer apparent by increasing the pile-length when it over a certain value. The settlement of foundation can be decreased effectively when the ratio of pile-raft area were increased based on the even cloth pile way.This paper analyses some success cases at home and abroad about decorating design of the stiffness of piled raft foundation, it verify that setting long pile or increasing pile diameter in the overload zone, setting short pile in the shallowly bearing stratum can be reducing the differential settlement and raft slabs, also can be making full use of support layer of foundation bearing capacity.