Ground response during offshore pile driving in a sandy slope

This paper presents an analysis of field measurements obtained during pile installation tests in a submerged sandy slope. The field test was performed in 2016 as part of the construction of a new sea lock in the Netherlands. Ground vibrations and excess pore pressures were to be limited in order to prevent damage to neighbouring locks and maintain slope stability. Geophones and piezometers were installed in the slope, at depth, and at various lateral distances from the pile axis. In the analysis, focus is placed on the installation of a tubular steel pile, which was subjected to both vibratory and impact driving. An assessment is made of some factors, such as driving equipment and pile tip penetration depth, affecting both the magnitude of ground vibration and its spatial and temporal characteristics. A similar analysis is conducted of the pore pressure measurements, with particular attention paid to the part of driving carried out in a homogeneous sand layer. Measured vibrations and excess pore pressures are compared to established attenuation relationships and published data, respectively. An approach is suggested in which the test results and interpretation may be used in assessing the potential implications of excess pore pressure development in the sand layer for slope stability.