Experimental study and model prediction of acoustic wave dispersion and attenuation in medium-coarse sandy sediments

Abstract

A comparable joint dataset of compressional-wave (P-wave) and shear-wave (S-wave) speed and attenuation for saturated Ottawa sand under consistent sample conditions was obtained, using a dual-probe acoustic measurement method (DPAMM) for P-waves (20–150 kHz) and bender element (BE) testing for S-waves (8–22 kHz). The dataset was used to evaluate whether Biot, BS, and BICSQS models can simultaneously reproduce both wave types and to identify the dominant dissipation mechanisms over the measured frequency ranges. The results reveal that P-wave and S-wave attenuation increase positively with frequency, with S-wave attenuation being significantly higher and more frequency-dependent than wave speeds. Among the models evaluated, the BICSQS model exhibits greater consistency with measured data, as it accounts for multiple dissipation mechanisms within the sediment. Specifically, P-wave speed and attenuation were respectively governed by contact squirt flow and Biot fluid loss dissipation, while S-wave behaviour was influenced primarily by shear drag loss, with attenuation additionally affected by Biot flow. Based on the BICSQS model, the frequency-dependent trends of the P-wave to S-wave speed ratio and attenuation ratio were further analysed, and cross-validation at their overlapping frequency of 20 kHz confirmed the reliability of both methods for characterising frequency-dependent acoustic behaviour in medium-coarse sediments.