Investigation of bearing capacity of screw piles in weak soils by experimental and numerical studies

In this study, experimental and numerical analyses were carried out to investigate the behavior of screw piles under tensile and compressive forces. Two different soils, cohesive and cohesionless soils, were selected and the experiments were carried out with these soils. Within the scope of the experimental studies, cohesive and cohesionless soil deposits were prepared and the behavior of the piles in these soils was investigated by model loading tests. In this context, four different piles, namely traditional pile, three, five and seven helix screw piles, were used in the experiments and modelled in numerical analyses. Parameters such as the effect of the number of helixes in screw piles, their performance in cohesive and cohesionless soils, failure surfaces, helix efficiency were analyzed. Then, experiments were carried out with geotextile to improve the performance of screw piles under tensile force. In addition, geopolymer coated geotextile was formed by coating on geotextile with binder formed by using sodium hydroxide, sodium silicate and fly ash and used in experiments to increase the performance under tensile force. After the model created with PLAXIS 3D was verified with the experimental results, parametric studies were carried out. As a result, the bearing capacity increased for both compressive and tensile forces as the number of helixes increased in cohesive soil, while in cohesionless soil, this effect was the same under compressive force but decreased under tensile force. The use of geotextile and geotextile coated with geopolymer caused an increase in bearing capacity in cohesionless soils but not in cohesive soils. While the increase in auger diameter increased the bearing capacity, the increase in embedment depth increased the bearing capacity under tensile force mostly in cohesionless soil.