Evaluation of the behavior of screw pile groups in clay soils under compressive and uplift forces

Screw piles, which is one of the ground improvement methods, are finding more place in practice day by day. For this reason, there is a need for studies to investigate the behavior of screw piles under compressive and uplift loads. In this context, the behavior of screw piles with different number of helixes in groups was investigated with different number of screws and group patterns. To evaluate behavior of screw piles, settlement ratios, group efficiency and helix number efficiency values were calculated by using finite element method. Based on an experimental study from the literature, modelling was performed on PLAXIS 3D, which works with the finite element method, and the results were matched. As a result of this study, it was observed that increasing the number of helixes increased the bearing capacity under both compressive and uplift forces. In addition, it was determined that group efficacy values changed in different patterns and different number of pile groups. Optimum screw pile type for group patterns also differs for different load conditions. The modelling results were visualized and were found to match with the failure surfaces reported in the literature. It was suggested that optimum helix number and group pattern for screw pile applications can be achieved with evaluating settlement and efficiency values together.