Investigation of plate size effect in multi-helical piles with model tests

Helical piles are a type of pile commonly used in many areas of geotechnical engineering. They are steel foundation systems placed into the ground by rotating motion to safely transfer all dead and live loads from the structure to the soil. In this study, the behavior of helical piles placed in loose sand under axial compressive load was investigated through laboratory model tests. In the tests, the embedded pile length (L) and shaft diameter (d) were kept constant, while the number of helical plates (N), the spacing between helices (s), and the diameter of the helical plates (D) were taken as variable parameters. The effects of these parameters were examined using load–displacement curves. Then, the test results were compared with collapsing criteria methods found in the literature. As a result of the tests, it was observed that increasing the number and diameter of helices also increased the bearing capacity. It was determined that the highest bearing capacity values were obtained when the helix spacing / helix diameter ratio (s/D) was between 1.5 and 2.5. However, when this ratio increased further, the bearing capacity began to decrease.