Investigation of soil plug formation in hollow piles using PIV technique

ABSTRACT The foundation systems for bridges and marine structures demand deep foundations like hollow driven open-ended piles, where hard-bearing strata exist on deep soil underneath loose inland and oceanic sea floors. During this driving process, a soil plug is formed near the hollow pile tip region, resulting in soil crushing and compression at the pile tip. The conventional methods fail to predict such volume changes and densification of the embedded soil. The present study utilised Particle Image Velocimetry (PIV) technique to assess the plugging at the pile tip and compare the penetration rate under different infill densities. The PIV results indicated that at a specific energy, pile geometric parameters and infill conditions strongly influenced pile drivability in a granular medium. Due to disturbance caused by pile driving at the base, high compressive strains are observed for large diameter piles, while large dilative strains developed soil plug during the penetration stage for small diameter piles. The plug surface profile was concave for larger diameter piles due to active arching mechanism, while it was convex for small diameter piles due to passive arching generated by lateral soil confinement within the pile wall surface.