NUMERICAL ANALYSIS OF SCREW PILES IN COHESIONLESS SOIL

Abstract

Screw piles are hollow steel tubes with one or more helix welded to the shaft, which are inserted into ground by applying torque at head of pile. Use of Screw piles in deep foundation has increased in past few years due to their advantages over other alternatives. Because it takes shorter time to install, it is removable and reusable also, can be installed at any inclination. From performance point of view, it provide greater compressive and uplift capacity than that of traditional driven steel piles with same shaft diameter and length. Due to its many advantages it can be a good option in deep foundation. In this project, numerical modeling of screw pile is carried out with the help of a 3D finite-element software, Plaxis 3D.Then the results of our numerical modeling are verified by comparing it with the real field test data reported by EIsherbiny and ElNaggar (2013). Laboratory test has been done to find out the soil properties required for parametric study. And the effect of different parameters like depth, diameter of shaft and helix & helical bade pitch was analysed. The investigation shows that relative density plays a important role in deciding ultimate axial capacities towards different parameters like depth , diameter of shaft and helix & helical bade pitch. In addition to that, helical blades of screw pile and its embedment ratio (H/ Dh ) plays significant role in axial capacity. When considering ultimate axial load capacity, an increase in diameter of helix is significantly more important than an increase in shaft diameter. Increase in the pitch of screw pile has no such significant effect on ultimate axial load- capacity.