Detection of geological structures using impact-driven piling as a seismic source

Seismic imaging during piling may reduce construction costs in sensitive areas, and combined with technology to look ahead of the pile tip, the risk of stopping the piling before reaching the bedrock may be reduced. Seismic images obtained during piling can give vital information about the subsurface structure in the vicinity of the pile. In this paper, we discuss how to produce seismic images as a part of the piling procedure without using any external seismic sources. Using surface and borehole synthetic data examples, we show that it is possible to use pressure waves emitted from the pile tip for imaging purposes. A pilot field study was carried out to test the feasibility of this method. The field study revealed that high-frequency pressure (P) waves are emitted from the pile tip. However, they are masked by strong surface and shear waves, especially at the nearer offsets. The data processing approach allowed us to achieve reasonable signal-to-noise ratio for pressure waves at the further offsets while the signal was not as well recovered at the nearer offsets. This study demonstrates that it is possible to acquire fair quality signals without using any seismic source other than the impact on the pile itself. More field data are needed, and some acquisition procedures need to be optimized before the method can be applied for practical imaging.