The Effect Of Pressure On Acoustic (1-20 Khz) Velocity And Attenuation During The Melting Of Ice-Bearing Sand

ABSTRACT Acoustic velocity and attenuation in ice-bearing sediments are strongly influenced by ice and water saturations and can vary with frequency, but the mechanisms linking acoustic response to ice content and morphology remain poorly understood. We measured velocity and attenuation in ice-bearing sand using an acoustic pulse tube, which allowed multifrequency analysis, under effective pressures of 2.5, 5.0, and 7.5 megapascals. Our experiments simulated thawing permafrost conditions at depths of up to 450 meters. As the ice melted, acoustic velocity decreased and attenuation increased, with the most pronounced changes observed at lower pressures. These changes also varied with frequency, especially at higher frequencies. Comparisons with three-phase Biot models suggest that velocity is mainly affected by ice saturation, while attenuation is also influenced by ice morphology (i.e., whether it is pore-filling or cementing) and by the permeability of the sediment frame. These results demonstrate that low-frequency acoustic measurements under controlled conditions can provide insights into the effects of ice saturation, distribution, and morphology on acoustic behavior in ice-bearing sediments that are relevant to field experiments. Our work supports more effective use of acoustic data for permafrost monitoring and highlights the importance of considering both ice saturation and microstructural characteristics when assessing the acoustic properties of ice-bearing sediment.