Observation of a second bulk compressional wave in a porous medium at ultrasonic frequencies

摘要

A second bulk compressional wave has been observed in a waterhyphen;saturated porous solid composed of sintered glass spheres using an ultrasonic mode conversion technique. The speed of this second compressional wave was measured to be 1040 m/sec in a sample with 18.5percnt; porosity. The theory of Biot, which predicts two bulk compressional waves in porous media, provides a qualitative explanation of the observations. To the authorrsquo;s knowledge, this type of bulk wave has not been observed at ultrasonic frequencies.