Transversal waves velocity evaluation in sand bottoms

Abstract

This paper presents the evaluation of the transversal wave sound propagation velocity in a wet mixture of sand, when the grazing angle is lower than the limit. This evaluation is made by means of getting the frequencies at which the amplitude of reflected echo reaches a minimum. We started from the theoretical model giving the plane waves reflection characteristics when the target is made of a series of dioptrics; in our study the dioptric was formed by two parallel perpex wall, 0.01 m thick, making a receptacle filled with the sand-water mixture of thickness several times greater than 0.01 m; this special container was then immersed in a water tank. It was possible for us to separate very clearly all the minima of the reflection coefficient corresponding to the perpex walls from those produced by the sand-water mixture, as well as to locate all the series of minima in function of the acoustic impedance presented by the mixture. By comparing these results with those obtained by straight measure of the delayed time suffered by the transversal wave traveling through the sandy layer, we are able to confirm the behavior of the sand medium, for transversal waves propagation, in function of porosity.