Physical Modelling of Pile Tip Damage Arising from Impact Driving-Paper

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The study investigates how impact driving can damage the tips of large, thin-walled offshore piles and trigger extrusion buckling, which increases driving resistance and may cause premature refusal. Damage is a growing concern as pile diameters increase relative to wall thickness and installations encounter boulders, dense soils, and weak rock.<br /><br />Researchers conducted nine centrifuge tests at 80g using model steel piles with a diameter-to-thickness ratio of 100. The piles were driven into dense sand, either alone or through thin layers of cemented sand or gravel representing embedded boulders. Some tests produced initial dents or severe tip crumpling. A pile with a small dent caused by a gravel layer subsequently developed pronounced extrusion buckling when driven into dense sand: the dent grew to 9 mm and extended 55 mm up the pile. Further distortion began where cone resistance exceeded approximately 25 MPa. Gravel caused more severe damage than the cemented layers, likely because angular stones applied concentrated loads to the pile tip.<br /><br />The results show that hard inclusions can initiate tip damage and that even a modest dent can grow during continued driving in sufficiently strong, stiff soil. The resulting distortion can substantially increase driving resistance. The tests demonstrate the importance of accounting for local soil heterogeneity and pre-existing pile imperfections when assessing installation risk, while also indicating the need for further research to quantify conditions leading to buckling.

Keywords

impact driving

offshore piles

extrusion buckling

tip damage

driving resistance

centrifuge tests

dense sand

gravel layer

pile denting

soil heterogeneity