The influence of stress wave phenomena during statnamic load testing

Because of its advantages compared to static and dynamic load testing, especially for bored piles, the application of Statnamic load testing has increased considerably. The Unloading Point Method (UPM) has become a standard tool for the analysis of Stat-namic (STN) load testing signals. The method is based on the assumption that the pile can be modelled as a concentrated mass and springs. Modelling is only valid when stress waves phenomena are minimal. In case of long piles or short duration STN testing, stress wave phenomena are not negligible. The sensitivity of STN to stress wave phenomena can be characterised by the wave number which is determined by the duration of the STN load, the stress wave velocity and the pile length. With the stress wave program TNOWAVE simulations have been made for piles with the same ulti-mate capacity but different wave numbers. Conclusions are drawn from these results as to what wave number UPM can be applied reliably to predict ultimate load capacity. Some measures to correct for stress wave phenomena, when they occur, are discussed