THE EFFECT OF THE PRESENCE OF INFILLING CONCRETE ON FLEXURAL PERFORMANCE OF SPUN PILE – AN EXPERIMENTAL STUDY

This research investigates the effect of the presence of infilling concrete inside of the middle void of the spun pile on its flexural behavior. The flexural monotonic load without axial load testing was conducted on the full-scale of two spun piles with infilling concrete. The dimensions of the pile were 400 mm in diameter, 75 mm in wall thickness, and 6,000 mm in length. The compressive strength of the concrete of the spun pile and infilling concrete was 58.4 MPa and 26.9 MPa, respectively. The observed flexural behaviors were the moment capacity, displacement ductility factor, and failure modes. Comparing with the previous research result about the testing of the spun pile without infilling concrete, the present testing results show that the presence of infilling concrete as the core of the spun pile’s section did not have a significant effect on the flexural performances of tested spun pile. Low compressive stress on compression fiber, due to no axial load, caused no concrete crushing occurred and the confinement mechanism of spiral reinforcement did not work. The fracture of the PC bar on extreme tensile fiber become the trigger of the failure of the pile. All piles had a ductility factor around µ ∆ = 4 in all cases. According to the seismic design code requirement, the spun piles were appropriate to be applied to a moderate seismic risk area. In application, due to seismic load, the piles should be designed remaining in the elastic state.