Common Pitfalls of Pile Driving Resistance Analysis – A Case Study of the Wikinger Offshore Windfarm

Pile driving resistance analyses are often performed to provide indicative information on potential axial static capacity. This involves a well-established approach, commonly known as signal matching, in which dynamic measurements made during impact driving are related to estimates of shaft and base resistance through wave propagation theory. The dynamic traces can theoretically be matched by more than one distribution of shaft and base resistance. As the solution process is not unique, the estimated capacity is inherently more subjective and less reliable than capacities obtained from static testing. The effects of time (set-up) and loading style must also be considered. This paper focuses on the sensitivity of signal matching predictions considering the effect of various shaft and base soil resistance models, as well as more practical aspects concerning the operator and software dependency of the predictions. The response, at the end of driving and at the beginning of restrike, of two hollow steel piles driven in two distinct ground profiles is analysed with three software codes (CAPWAP, Allwave-DLT & IMPACT), considering simple and more advanced soil resistance models. The results highlight the uncertainty in signal matching simulations, and the requirement for confirmation with static testing.