Parameter estimation of sediment in the Yellow River based on the porous medium acoustic theory

Presently, the use of sub-bottom profiler sonar signals is limited to inversing the physical parameters of the sediment in the surface layer (first layer). In this study, based on the acoustic theory of porous medium, the acoustic inversion of the physical parameters of the lower layer (second layer) sediment is studied. When acoustic waves propagate in water and sediment media, interlayer reflection and transmission, intralayer attenuation, and other processes change the energy. The reflection and transmission coefficients of acoustic waves incident perpendicularly to the water—sediment and sediment—sediment interfaces are derived, and the effects of the reflection and transmission process of acoustic waves on the amplitude are quantified. The relationship between the frequency shift and relaxation time of the transmitted signal in different particle size sediments is established to estimate the corresponding attenuation coefficient using the frequency shift of each layer signal. On this basis, combined with the diffusion process of acoustic waves, the equation for extracting the acoustic wave reflection and transmission coefficients of each layer at the interface is derived from the measured sonar signal. Further calculations show that the sediment parameters have a greater influence on the reflection coefficient, and the feasibility of calculating the physical parameters of the lower sediment using the reflection coefficient has been proved. Under the premise of obtaining the physical parameters of surface sediment, this study provides specific methods and steps for inverting the physical parameters of the lower sediment. The on-site detection in the Xiaolangdi reservoir area of the Yellow River, combined with the sediment sampling test results, proved that the proposed method of inversion of the lower sediment parameters based on the porous medium acoustic theory is feasible.