A Method for Estimating Immediate Settlement of Piles and Pile Groups

Abstract

In this study we examine a method based on Mindlin’s solution in order to estimate the load-settlement behavior of piles and pile groups for rational design of pile foundations. First, the theoretical aspects of the previous method proposed by Poulos and other investigators are briefly presented. Some modifications are made to the method so as to consider additional factors such as soil non-linearity and multi-layering. Next, in order to evaluate the numerical accuracy, vertical displacements and axial forces of pile groups or single piles embedded in non-homogeneous soil calculated by the previous method and by the modified method are compared with values calculated by more sophisticated methods such as the boundary element method and the finite element method. As a result, we conclude that, from a practical point of view, the modified method based on elasticity is sufficiently accurate in regard to axial force distribution as well as settlement. We also propose tentative input soil constants for immediate settlement using solely the results of SPT. Finally, the values of pile top settlement calculated by the modified method are compared with the results of 26 field vertical load tests on cast-in-place concrete piles. The results show that the calculated values coincide approximately with the measured values, meaning that the proposed modified method of calculation and the proposed input soil constants seem to be adequate for the preliminary estimation of immediate settlement of cast-in-place concrete piles.