Experimental study on the vertical bearing performance of precast screw pile using transparent soil

Abstract

In recent years, screw piles have been increasingly utilized in geotechnical engineering practice to enhance the bearing capacity of soft foundations. In this study, the vertical bearing characteristics of screw piles and the displacement field of the surrounding soils were analyzed using the transparent soil model tests. Comparative studies between the screw piles and the smooth surface piles were carried out, and several influential factors are considered, such as the tapered pile, the screw spacing, screw height and screw thickness. Results showed that the bearing capacity of screw piles was higher compared with the smooth surface piles, and the screw pile with a constant diameter along its whole length improved the bearing capacity. A larger inclination and an optimal screw spacing were essential for the screw piles. However, the screw thickness was found to have minimal impact on the bearing capacity and soil displacements. A larger screw height and the tapered pile angle caused larger horizontal deformations. The influence range of the screw pile on the surrounding soil was wider compared with the smooth surface pile. In addition, three movement stages of soil particles between the screw structures were identified, including the soils around the screw dragged closer to the pile surface, the soils within the ‘screw’ structure moving vertically downward and the soil particles that were extruded out of the screws. It is hoped that this study can provide some guidelines for understanding the bearing–deformation mechanism of screw piles during the penetration process.