Seiji Nakagawa
Neville G. W. Cook
Dept. of Mater. Sci. & Mineral Eng., Univ. of California, Berkeley, CA 94720
K. T. Nihei
L. R. Myer
Lawrence Berkeley Laboratory, Berkeley, CA 94720
Two-phase particulate composite samples with inclusions of varying size and concentration were made with cement and sand or pebbles. The velocities of P-wave (60-kHz) and S-wave (150-kHz) pulses and the attenuation of S-wave pulses were examined. The results of the tests suggested that the velocities were consistent with the results of effective media models which were inclusion size independent. However, the frequency-dependent attenuation of the S wave was strongly affected by the size of the inclusions. For inclusions sized on the order of 1/10 of the wavelength, the waves showed decreasing attenuation with increasing concentration, while for the sizes of about 1/4 and 1/1 of the wavelength, the waves showed maximum attenuation at volumetric concentrations of about 30% and 70%, respectively. Many aspects of the observed wave behavior for moderate concentrations were similar to numerical simulations of 1-D wave propagation in a layered media, where the matrix and inclusions were represented by alternating layers with different seismic properties and stochastically varied thicknesses. [Work supported by NSF.]