Improved data interpretation method for SASW tests at complex geotechnical sites

The Spectral-Analysis-of-Surface-Waves (SASW) method is a nonintrusive seismic method for evaluation of shear stiffness profiles at geotechnical sites from surface wave measurements. Recent field experience has demonstrated the complexity of interpreting surface wave data at sites with large and abrupt stiffness changes. Geotechnical sites in polar environments as well as offshore sites containing gas hydrates have the potential to exhibit such strong stiffness contrasts which create multiple wave groups and result in complex phase spectra that can be easily misinterpreted. To aid in the correct interpretation of SASSY data collected at such complex sites, a new phase interpretation scheme, called ''impulse Response Filtration'' (IRF), is proposed. This filtered impulse response leads to a clearer interpretation of the phase differences between receivers. The IRF method is explained and demonstrated using experimental results from a pavement site which closely simulates frozen over unfrozen geotechnical sites representative of polar environments.