High frequency p-wave attenuation dispersion in water-saturated granular medium with bimodal grain size distribution

Abstract

Compressional wave attenuation in water-saturated granular medium depends on both the frequency and grain size. In recent series of high frequency measurements on porous medium, such as water-saturated glass beads and marine sediments, the effect of grain size distribution on attenuation has been investigated, and a variety of grain size dependence on attenuation has been reported. Particularly, dispersion relation in the granular medium with bimodal grain size distribution is significantly different from that in the medium with unimodal grain size distribution. In this study, two sets of glass beads experiments employing unimodal and bimodal grain size distributions are performed. In order to examine wave propagation phenomenon in the bimodal grains, the attenuation dispersion is represented as a function of three parameters; porosity, volume fraction of scatterers, and Rayleigh parameter kd. Heuristic dispersion model considering scattering phenomenon will also be discussed for comparison with measurements.