Settlement Analysis And Numerical Simulation Of Rigid Pile Composite Subgrade Under Oil Tank Flexible Foundation

Composite subgrades under rigid and flexible foundations are different in the load transferring mechanism, the characteristic of bearing capacity and the deformation model. For rigid foundations, the deformations of pile and surrounding soil are compatible, whereas the deformations are incompatible for the flexible foundations as a result of the puncture of pile. The mostly used calculation methods for the deformation of composite subgrade under flexible foundation are based on the theories used for the rigid foundations, which brings about great inaccuracies, especially for such subgrade that are settlement-control designed.Based on the assumption of pile side friction resistance and soil shear stress distribution models, and compatibility of interaction shear stress of pile and soil for each element of the pile-soil system, a new theoretical approach to predict the deformation behavior of soft ground reinforced by rigid piles under oil tank flexible foundation is presented in this paper. The proposed method is compared with other methods, and verified with finite element analysis method, and a reasonable agreement is obtained. Modified Geddes method is used to calculate the additional stress of underlying soil, and layerwise summation method is used for the deformation calculation.For the single pile composite subgrade, finite element analysis is performed using ANSYS software. By imposing contact elements between the pile-soil interfaces, the pile-soil interaction is considered. Numerical evaluations are made for a range of parameters to illustrate the influences of various parameters, such as pile length, replacement ratio, footing modulus, pile modulus etc. Finally a project example is used to verify the finite element analysis results with those actually tested. A series of useful conclusions are obtained...