Experimental and numerical analysis of uplift (tensile) strength in pile foundations

In foundation engineering, significant progress has been achieved in construction techniques in parallel with recent technological advancements. These developments have created a need to reassess certain foundation systems from different perspectives. This issue is particularly relevant for special structures such as high-voltage transmission lines, radio and television towers, wind energy turbines, GSM operator base stations, tall industrial chimneys, offshore platforms, viaduct crossings, and pipeline systems. In this study, a laboratory-scale model test setup was developed to investigate the tensile forces occurring in such foundation systems, taking into account previously established theories as well as recent experimental studies, and to explore scenarios that have not yet been addressed. The experimental setup employed a model pile with a shaft diameter of 25 mm and a bell diameter of 75 mm, and the effects of soil density, embedment ratio, and bell configuration were examined. The behavior of bell-shaped single piles embedded in loose and dense sand was investigated both experimentally and numerically using the three-dimensional finite element method in the PLAXIS 3D software, with and without geogrid reinforcement. The results demonstrated a good agreement between the experimental and numerical findings. At the conclusion of the study, it was determined that the uplift capacity of bell-shaped piles increased compared to straight piles as the embedment ratio increased. Furthermore, the geometric configuration of the bell-shaped pile was found to optimize soil–pile interaction and significantly enhance load transfer efficiency. In addition, the placement of geogrid reinforcement was shown to substantially influence the uplift capacity of the pile, with an optimal reinforcement distance of u/D = 0.25 from the bell head being recommende