Effective Vs and Vp characterization from Surface Waves streamer data along river embankments

Abstract

River embankments are linearly extended earth structures built for river flood protection. Their continuity and uniformity are fundamental prerequisites to ensure and maintain their protection efficiency. Weakness points usually develop in localized areas where geotechnical variability is present in the embankment body or in the underlying subsoil. Given their significant length, and the localized nature of weakness points, the characterization of river embankments cannot rely on local geotechnical investigations but requires the application of efficient and economically affordable methods, able to investigate relevant lengths in a profitable way. This is even more essential when the investigations are conducted near, or in foresee of, significant flood events, when timing of the surveys is essential. In this paper the application of a procedure (W/D procedure) for the seismic characterization of river embankments, specifically designed for surface waves streamer data, is presented. The W/D procedure allows the combined definition of 2D shear (Vs) and compressional (Vp) wave velocity models and can be developed in order to be automated as a fast imaging tool. Its application to the characterization of a test site (Bormida river embankment, Piedmont Region, Italy) is presented. It is also shown that the obtained results are comparable to standard seismic processing approaches with the advantage of reduced survey time and increased efficiency, giving preliminary results directly in the field.