Wave Propagation Theory of Multi-Scale Wave Induced Flow in Unsaturated Porous Medium

When elastic waves propagate in an unsaturated porous medium, the macro Biot flow, micro squirt flow, and meso flow will occur. The unsaturated porous medium is equivalent to the inclusion of gas phase porous fluid embedded in the background medium containing liquid phase porous fluid. Based on the unsaturated dual porous medium model, the micro squirt flow is introduced, and the wave propagation equation of unsaturated porous medium including macro, micro and mesoscopic scale wave introduced flow is established. The numerical analysis indicates that the model in this paper can better predict the wave velocity dispersion and attenuation in a wider frequency band.