Lateral Load Behavior of Full-Scale Pile Group in Clay

A static lateral load test was performed on a full-scale pile group to determine the resulting pile-soil-pile interaction effects. The 3 × 3 pile group at three-diameter spacing was driven into a profile consisting of soft to medium-stiff clays and silts underlain by sand. The piles were instrumented with inclinometers and strain gages. The load carried by each pile was measured. A single pile test was conducted for comparison. The pile group deflected over two times more than the single pile under the same average load. Group effects significantly reduced load capacity for all rows relative to single pile behavior. Trailing rows carried less than the leading row, and middle row piles carried the lowest loads. Maximum moments in the group piles were 50–100% higher than in the single pile. P-multipliers were 0.6, 0.38, and 0.43 for the front, middle, and back row piles, respectively. Good agreement between the measured and computed pile group responses was obtained using the p-multiplier approach. Design curves are presented to estimate p-multipliers over a range of pile spacings.