Influence of orientation angle on the lateral behavior and efficiency of 2x2 and 3x3 pile groups based on 1-g physical model tests

The efficiency and performance of pile groups under lateral loading are influenced by their arrangement and orientation relative to the direction of the applied load. This study explores the effects of different orientation angles (θ 0, 15°, 30°, and 45°) on the lateral behavior of 2 × 2 and 3 × 3 pile groups via 1-g physical model tests and analytical evaluations. The findings reveal that for θ 0, significant shadowing effects result in lower group efficiency (Ge), whereas θ 45° results in less shadowing and higher Ge values, indicating more effective load transfer and reduced interaction among piles. The independence ratio (IR) correlates with Ge, increasing with less interaction among piles. The soil reaction (p)–pile deflection
(y) curves for pile group members are less mobilized than those for single piles, with leading row piles more mobilized than trailing rows, highlighting the impact of overlapping zones of influence. The p-multiplier (pm) varies with pile location and θ, with higher values for leading rows at θ 0, and significantly increases with θ 45°. For 3 × 3 pile groups, edge columns exhibit higher pm values with increasing θ,whereas center columns display varied trends due to changes in pile positioning and reduced shadowing. These findings underscore the importance of considering pile group orientation in practice to optimize design and improve performance under lateral loads, with practical implications for geotechnical engineering applications.