Lateral Pile-Group Interaction Factors for Free-Headed Pile Groups in Sand from Full-Scale Experiments: Fid-Bau Portal

Lateral Pile-Group Interaction Factors for Free-Headed Pile Groups in Sand from Full-Scale Experiments

M. Ochoa / M. W. O'Neill

In order to analyze foundations supported by groups of vertical, pin-headed, laterally loaded piles, it is necessary to include in some rational way the effect of pile-soil-pile interaction, or the increase in pile-head flexibility that occurs in each pile in a group in comparison with an isolated pile. A study was undertaken to measure experimentally pile-head flexibility reduction (interaction) factors in a full-scale pile group in sand. The measurements were accomplished by testing individual piles within a pile group of nine piles cyclically at varying magnitudes of applied ground line shear, two-pile subgroups and three-pile subgroups. The response of certain unloaded piles was also monitored during these individual-pile and small-group tests. Analysis of the results indicated a significant effect of position on flexibility reduction in a two-pile group (leading or trailing) for piles spaced 3 diameters on center and loaded in line and a lesser effect for piles loaded side-by-side. A consistent set of interaction factors was developed from the experiments and applied to the analysis of deflection and shear load distribution in the full nine-pile group, which had been tested earlier on the same test site, through the use of simple matrix techniques. (aw)