Suction cup effect coupling shear waves across unconsolidated smooth wet solids

Accurate modeling of the propagation of sound waves in unconsolidated marine sediments depends on understanding the interparticle contacts and coupling mechanisms of compressional and shear waves. The theory of elastic waves in unconsolidated marine sediments [M. J. Buckingham, J. Acoust. Soc. Am. 103, 288–299 (1998)] depends on the grain roughness, where the shear speed goes to zero as the losses vanish. The current paper examines shear wave coupling phenomena between unconsolidated solids in the absence of roughness. Fundamental experimental results are presented, demonstrating the transmission of shear waves across smooth glass plates coupled with a localized capillary thin water film hermetically sealed between the plates with the suction cup effect. The glass plates were pressed against each other while immersed in distilled water until they became slip resistant. The diffraction pattern of Newton fringes was observed surrounding the water film. Results from experiments using seawater, microbubbles, and curved surfaces are discussed leading to acoustic characterization of saturated and partially saturated marine sediments. [Work supported by ONR.]