Screw piles are widely used because of their several advantages, such as easy installation, minimal required equipment, removability and reusability, minimum produced noise, and vibration during installation and cost-effective. Furthermore, helical piles are installed mostly by the use of mechanical torque, which reduces the damage to adjacent structures, and can be constructed without excavation or pouring concrete.
This study investigates the load transfer mechanism that includes the effect of helix bending deflection on end-bearing capacity, distribution of ground pressure under the helix and soil deformation around the screw pile. The helix to shaft diameter ratio of 2.5 and 2.8 with a strong helix and a weak helix were used. The model ground was prepared with fine sand at 80% of relative density.To investigate the load transfer mechanism, the experimental tests were modelled in a 3D finite element code (PLAXIS 3D). A good agreement between the experimental and numerical approaches was found. The numerical analyses showed that a large influence zone exists under the screw pile with a strong helix, which resulted in higher mobilized soil shear strength that contributed to higher end-bearing capacity. In the case of a strong helix, a uniform pattern of pressure distribution was observed under the central shaft and the helix. A similar pattern of pressure distribution under the central shaft was observed in the weak helix case but the pattern of pressure distribution under the helix changed from uniform to triangular to trapezoidal at various stages during the load test. The normalized end-bearing capacity decreased linearly with the increase in normalized helix bending deflection in both approaches, i.e. experimental and numerical.
Figure 7. Load-settlement curves (a) Helix diameter, Dh, = 55 mm (b) Dh = 60 mm
This article was published in Soils and Foundations, 2021, and available as open access here:doi: https://doi.org/10.1016/j.sandf.2021.04.001 ( https://www.sciencedirect.com/science/article/pii/S0038080621000524)
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.