Identification of the shear velocities of near surface soils using fundamental leaky torsional guided waves

A technique is presented that uses a circular pipe for the measurement of the bulk shear (S-wave) velocities of unconsolidated, saturated media, with particular application to near surface soils. The technique requires the measurement of the attenuation characteristics of the fundamental leaky T(0,1) mode that propagates along an embedded pipe, from which the acoustic properties of the surrounding medium are inferred. From dispersion curve analysis, the feasibility of using the T(0,1) mode, which is non-dispersive and has constant attenuation over the all frequency range, is discussed. The principles behind the technique are discussed, and the results of an experimental laboratory validation are presented. The experimental data are best-fitted for the different depths of wetted sand, and the shear velocities as a function of depth are formulated, using power law.