Behaviour of thin-walled open-ended piles during driving

This paper investigates the driving of thin-walled open-ended piles using numerical simulation of the wave propagation inside the soil plug and the pile. Using an axisymmetric finite element model, stress wave propagation in the vicinity of the pile toe is studied. It is found that at the bottom of the soil plug the interaction between the waves travelling in radial and vertical directions is important. When the pile wall is thin, the majority of the axial stress wave reaching the pile toe is reflected with the opposite sign, as at a free edge. Consequently, pile penetration can be considered as a penetration of a knife edge into the soil. The capability of several simplified numerical models to reproduce the driving response given by the finite element model is studied. It is seen that when the pile is unplugged, an accurate response cannot be obtained, without modelling the radial wave propagation and the interaction between the soil above and below the base of the soil plug. However, when the base of the soil plug fails, a simple one-dimensional pile-in-pile model can be used to achieve results with an adequate accuracy.