Influence of helix bending deflection on the load transfer mechanism of screw piles in sand: Experimental and numerical investigations

Abstract

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. A good agreement between the experimental and numerical approaches was found. The numerical analyses showed that large influence zone exists under screw pile with strong helix, which resulted in higher mobilized soil shear strength that contributed to higher end-bearing capacity. In the case of strong helix, uniform pattern of pressure distribution was observed under the central shaft and the helix. Similar pattern of pressure distribution under the central shaft was observed in 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.