In this research, the behavior of pile group models under uplift load has been investigated. The tests were done in two methods, laboratory (an experimental model) and numerical (by ABAQUS). In both methods, the loading procedure is strain-controlled. The goal is to evaluate pile groups' net final uplift force and efficiency. Values of embedment length to the diameter of the pile (l/d) are 5, 15, and 25. Besides, pile groups are surveyed in three arrangements: linear (2×1), square (2×2), and rectangular (2×3). It is found that the effect of the variables on uplift capacity and pile group efficiency is not the same. Based on the results, the net final uplift capacity and pile group efficiency do not vary linearly. By increasing the embedment length, the net final uplift capacity increases remarkably while the relevant efficiencies increase slightly at first and then tend to be constant. Although the changes in pile arrangements from linear to rectangular conclude greater net final uplift capacities, the pile group efficiencies decrease. The maximum efficiency is allocated to the linear pile group (2×1) with l/d of 25.

Keywords: Pile group, efficiency, uplift load, compact sand, pile length.