Effect of Loading Direction on the Response of Laterally Loaded Pile Groups in Sand

Previous experimental studies on laterally loaded pile groups usually applied loading along the direction parallel to the edge of the pile cap. This study aims to determine the effects of the loading direction on the response of laterally loaded pile groups through a comprehensive experimental investigation. Model pile groups with different configurations embedded in sand were subjected to lateral loads along various horizontal directions. The results show that the loading direction has a predominant effect on the evolution and eventual distribution of force among piles in the pile group, the bending responses along the piles, and the total lateral resistance of the pile group. These results can be attributed to different group-interaction effects under different loading directions. For both square and rectangular configurations, the pile groups provide the largest total lateral resistance along the diagonal direction. The effect of the loading direction on the response of the pile group is affected by the configuration of the group. The pile group at medium spacing ($5D$) is more sensitive to changes in the loading direction. Back-calculated $p\text{-multipliers}$ indicate a substantial difference in $p\text{-multipliers}$ of individual piles when the pile groups are loaded along different directions. The $p\text{-multipliers}$ of the front-row pile can be approximately 67% larger when loaded along the diagonal direction than when loaded along the direction parallel to the edge of the pile cap. The effects of both the pile group configuration and the loading direction on the values of $p\text{-multipliers}$ should be considered in analyzing the responses of pile groups under lateral loads.