A Surface Wave Tomography Tool in Geotechnical Applications - A 3D Experiment at a Controlled Test Site

Summary In this study a specific methodology for the application of Surface Wave Tomography at geotechnical scale is proposed and evaluated with its implementation at a Test site of known conditions for the location of an underground tunnel. The main target of the proposed methodology is the construction of high resolution frequency dependent group and phase Rayleigh velocity maps. It can be implemented in 2D or even in 3D active seismic acquisition schemes, on uniform or even arbitrary layouts, on the condition that the seismic geophones are installed on a dense grid or line. Common refraction and MASW equipment can be used or even more advanced equipment like wireless geophones or 3C-stand alone nodes depending on the needs of the survey. The application of the specific automated workflow on a 3D acquisition experiment of real conditions concludes that 3D frequency dependent phase and group velocity maps can detect lateral variations very efficiently. Both group and phase velocity maps delineated the presence of the tunnel and the subsurface condition in general with high precision. The individual or even the joint inversion of the derived 3D phase and group velocity maps can lead to a high resolution pseudo 3D Vs estimation