Advancement ratio effect on screw pile performance in the bearing layer

Abstract

The advantages of using screw piles are quite evident nowadays, which enhances its importance in the field of deep foundations. Moreover, the current environmental challenges direct the construction industry towards sustainability, creating more opportunities for such type of piling techniques to be used in the future. Therefore, more investigation is required to optimise screw pile performance in terms of ultimate bearing capacity associated with installation efforts. To explore further, the current study focused on the effect of the advancement ratio on ultimate bearing capacity and work done due to installation load and torque. The model scale of testing is adopted, and two kinds of ground (using Toyoura sand), i.e., scenario I: loose sand over dense sand and scenario II: loose sand, are prepared to install the single helix screw pile. In the case of scenario I, the screw is installed up to 1 times the helix diameter into the dense bearing layer. Based on the experimental results, it was observed that as the advancement ratio (from 0.25 to 1.25) increased, the installation load also increased. On the other hand, the installation torque decreased with the increase in advancement ratio. This was due to the increase in the number of rotations per pitch penetration and the resultant movement of sand particles. The change in the state of the ground around the screw pile is strongly related to the advancement ratio and initial density. The ideal advancement ratio (1.0) is difficult to attain in the field due to high pressing load demand; empirical equations are developed, which can be used to estimate the increase/decrease of ultimate bearing capacity and associated installation requirements in terms of work done for the initial design stage.