A039 Z-99 Time-lapse shear-wave seismic to define the lateral extent of impact due to sheet piling Summary 1 It has not been possible so far to measure in the field in a laterally continuous manner the impact of sheet piling on subsoil structures and hence potentially on adjacent buildings. We propose the idea of time-lapse shear-wave seismic reflection surveys for this purpose. Result on field data shows that despite the usual difficulty to achieve sufficient reproducibility in seismic field data acquisition the impact of sheet piling on the soil boundaries can still be distinctly recognized in the time-lapse shearwave data.