Evaluation of Dynamic Group Pile Effect in Dry Sand by Centrifuge Model Tests

Abstract

It is well known that the average load for a pile in a closely spaced group is substantially less than that for a single isolated pile at the same deflection. Therefore, the p-multiplier has been used to determine p–y curves for groups of piles. The p-multiplier under seismic loading is yet to be determined. In this study, a series of centrifuge shaking-table tests for a 3  3 group pile was performed for various pile spacings, ranging from three to seven times the pile diameter. Test results confirm that the p-multiplier increases with increasing pile spacing. The p-multiplier of the piles in rows 1 and 3 within a group is smaller than that of the center pile in row 2. Therefore, under seismic loading conditions, the group pile effect in rows 1 and 3 piles is greater than that in row 2 piles. In addition, the behavior of piles in same row is different according to the location of each pile within group piles.