Experimental and Numerical Study of Pile-to-Pile Interaction Factor in Sandy Soil

Abstract

In structures to support large vertical and horizontal loads, piles are usually used in the form of closely spaced group. The piles in a group are not only affected by their individual loads transmitted from the pile cap, but also by additional loads transferred through the soil from the interference of neighboring piles. This group interaction influences the group stiffness, load-transfer mechanism and group settlement. In order to predict the response characteristics of pile groups, the interaction factors calculated using Mindlin's solution based on the theory of elasticity has been widely applied. The pile-to-pile interaction factor is defined as the ratio of displacements or rotations of an unloaded receiver pile to those of neighboring loaded source pile due to soil deformation. In this paper, a series of centrifuge model tests were carried out to examine the effect of soil relative density and pile spacing and pile tip condition on the interaction factor between two adjacent piles. Based on the results, soil relative density has a significant effect on the interaction between piles and thus it must be considered in the calculation of interaction factor. For this purpose, a correction to the Randolph and Wroth equation based on the test results was proposed in which the effect of soil relative density is contemplated. With an increase in the pile spacing, the value of interaction factor for all cases decreased. Compared to the effect of pile shaft, pile tip condition has a little effect on the interaction factor. The obtained results were also compared with those from a three-dimensional finite element analysis and a good agreement between the measured and the calculated results was observed.