Dennis J. Yelton
Nicholas P. Chotiros
Appl. Res. Labs., Univ. of Texas, Austin, TX 78713-8029
Reflection, transmission, and scattering properties of an inhomogeneous
Biot medium were studied via numerical simulation. The inhomogeneous medium was
bounded by a semi-infinite water medium on the source side, and a semi-infinite
Biot medium of equivalent average properties on the other side. The
inhomogeneous medium was simulated as a randomly layered Biot material. Each
layer represented a granular material of particular grain size. By setting the
thickness of each layer equal to a random grain size, a randomly stratified
granular medium was simulated. Lateral variations in grain size were simulated
by performing a coherent ensemble average of results from several realizations
of the randomly stratified medium. The free parameters were the grain size mean
and standard deviation. Other parameters were chosen to represent
water-saturated sand. Reflected and transmitted signals were computed for a
1-MHz normally incident plane wave. Coherent and random components of the
reflected signal were calculated. The random component was related to the
scattering strength of the medium. It was found to increase with both the mean
and the standard deviation of the grain-size distribution. The results are
consistent with previous experimental results [Nolle,