Use Of Masw For Geotechnical Site Characterization Using Corrected Triaxial Geophones

A comparison of 3-component surface wave data to uncorrected vertical geophone records at a soft soil site on the flood plain of the Tennessee River is presented. The data is collected using 10 Hz vertical and 4.5 Hz horizontal geophones, which are calibrated against a reference piezoelectric accelerometer and servo-hydraulic testing system. The records from the field associated with MASW survey are corrected for the mechanical response of the geophones using experimentally-determined transfer functions. MASW data are obtained using 1 m geophone spacing with a 22 kg weight dropped from a height of 1.5 m. It is expected that the vertical and radial (horizontal toward the source) geophones will record Rayleigh waves, but the horizontal transverse geophones should not record a Love wave, because it is not generated efficiently by a vertical impact on laterally homogeneous strata. Contrary to expectations, both Rayleigh and Love wave dispersion curves are observed. Rayleigh waves appeared on the vertical and radial geophones, but their dispersion curve cutoff at frequencies lower than approximately 27 Hz. Love wave dispersion was observed on the transverse horizontal geophones at frequencies below 27 Hz. Hypothetically, the Love waves could have been caused by scattering related to small scale in heterogeneities in the soil.