Dynamic Response of Laterally Excited Pile Groups

Abstract

Lateral dynamic experiments were performed on small-scale pile groups at two different sites, one with stiff soil and the other with soft soil. The pile diameters and spacings were varied to create spacing to diameter (\Is/d\N) ratios of between 2.25 and 15.0. The results showed the group interaction effects to be negligible at \is/\id ratios greater than 12 for the stiff site, and greater than 16 for the soft site. The experiments are the first to alter both the pile diameter and the pile spacing and confirm that the spacing-to-diameter ratio is an important parameter when calculating group interaction effects. The dynamic testing was found to cause a permanent nonlinear response in the groups. A simple linear elastic theoretical analysis was then developed to predict the dynamic response of the groups. The analysis produced good estimates of the experimental results for a constant value of Young’s modulus for each site. The values of Young’s modulus used in the modeling were found to be typical of those for lateral loads on pile foundations.