A series of 45 tests were performed on piles to investigate the influences of soil density and different pile configurations on the ultimate lateral resistance and pile group efficiency. The pile groups were loaded in an incremental manner. The nonlinear load versus lateral displacement and vertical settlement of the pile cap could be adequately defined.
The soil density effects on single pile against the average pile deflection are presented in Figure 4. From the figure it is seen that the load-deflection curves were nonlinear and a similar trend was observed in loose and dense conditions. Vertical displacements were negligible compared to horizontal deflections and it is in agreement with previous studies which stated that soil-pile interaction could be determined separately under lateral and vertical loads. The differences of the lateral deflection increased when the relative density increased from 30% to 75% under the same moment of load. Therefore, a higher relative density will provide a stiffer resistance for pile subjected to lateral loading. This is owing to the increasing of shear strength of sand as it becomes denser. In other words, pile behavior subjected to lateral loads depends on the interaction between the surrounding soil and pile material.