Static and dynamic lateral response of a 15 pile group

摘要

To improve our understanding of the lateral resistance of pile groups, we have performed a series of static and dynamic lateral load tests on a full-scale pile group. The pile group consisted of 0.324 m-diameter steel pipe piles driven closed-ended into cohesive soil with an undrained shear strength of about 45 kPa. The test piles were driven in a 3x5 arrangement at a normalized spacing of 3.92 pile diameters in the direction of loading. A single pile test was also performed for comparison purposes. Lateral resistance was found to be a function of row position with piles in the first row carrying about the same average load as a single pile. The average load decreased for the second and third row piles but then remained about the same for subsequent rows. P-multipliers were determined for each row and were found to decrease as deflection increased. After 15 cycles of loading, the peak static resistance decreased by about 17%. Following static loading, dynamic loads were applied using a statnamic device. The dynamic load-displacement curves were stiffer and had larger hysteretic loops than the static curves. Analyses using an equivalent single degree of freedom model indicate that the damping ratio was between 30 and 40%.