Analysis Of Holistic Design Of Pile-Raft Foundation With Applications

With the appearance of more and more the high-rise and the super high-rise buildings,the pile-raft foundations have been widely used in the practical engineering. At present,some achievements have been gained on this topic. Based on the research work of the others,some supplementary analyses are presented in this paper.The working performance of single pile among pile group and the stress distribution of pile-group foundation are analyzed,and calculation methods for the settlement and the vertical bearing capacity of pile group foundation are studied.The 16-node degenerated iso-parametric element is proposed for the analysis of raft foundation with mid-thick plate. The stiffness matrix of single pile among the pile group can be founded assuming the total contact between the plate and the foundation. And the results of stress and deformation of plate,the force on pile and the settlement of pile bottom can be solved after the finite element disperse for the plate and the establishment of balance equation of pile-raft interaction.Based on the previous theoretical analysis,two practical projects of pile-raft foundation of high-rise building on soft ground are studied by using the software of pile-raft foundation interaction analysis program POGAP. The choice of standing layer for pile,the rational compression modulus of soil under pile,the place of pile and the space between piles,and the reasonable thickness of plate are analyzed,some well-regulated conclusions can be achieved. An experiential equation for choosing the optimal thickness of plate is also given. Meanwhile,the key research topics are focused on how to reduce the differential settlement between the main tall building and the anex on soft ground,where to set the post-cast strip,and what cause the smart change of the internal force of plate under the core canister of tall building. An experiential equation for estimating the maximum moment of plate is advanced. A method for calculating the range and the thickness of the local enganced plate and another experiential equation for estimating the increment of maximum moment of the local plate are also suggested. It will be helpful for designing the same type of high-rise buildings.