Ultrasonic wave dispersion and attenuation in models of porous ground and sediment

Ultrasonic wave transmission of models for ground and sediments, as a function of ultrasonic wave frequency and vertical and horizontal incidence directions, was investigated both theoretically and experimentally. The aim of this investigation was to determine the optimal wave frequency and wave direction of the most penetrating ultrasonic radiation, for a given ground and sediment particle size distribution. The results can be applied towards the detection of underground objects, in particular the detection of underground non-metallic objects such as fossils and mines, which are currently undetectable with metal detectors. Special, computer software was used to determine the dispersion characteristics of ultrasonic waves in fluid saturated media consisting of packed spherules in 50 to 3000 μm range. The software included Fast fourier Transforms of the transmitted signals, both in the frequency and phase space. The results showed that previous theories could not be used to explain the observations without significant modification. Good agreement between theory and experiment could finally be obtained with the new model.