A geotechnical site investigation by surface waves

Recent advances in non-invasive in situ surface wave techniques have heightened interests in application of these techniques for near surface geotechnical site investigations. It is apparent that these techniques cannot offer the same level of accuracy as mechanical techniques, but do however, provide a more time and cost effective approach. A limitation of geophysical techniques is the necessity of providing a constraint to prevent the misinterpretation of measured data. Hence, a combination of both mechanical (to constrain) and geophysical techniques, benefits from the advantages while limiting the disadvantages of both. However, in order to reduce the necessity of mechanical testing to provide constraining information, the paper proposes a novel approach by combining the passive Horizontal toVertical Spectral Ratio (HVSR) technique and an array based active surface wave technique. This proposed technique relies on the notion of the phase velocity dispersion curve, array based technique providing constraining information to the HVSR technique. Results so far suggest that this two-step procedure of combining these surface wave techniques (HVSRplus), allows for very reasonable estimation of the near surface shear wave velocity (V_s) profile, in the absence of constraining information from mechanically measured data. Of course, care must be taken when not calibrating or verifying against reliable mechanical data. Results produced by this technique have been verified against invasive mechanical (boreholes, SPT) data.