NONLINEAR ACOUSTOELASTIC PROPERTIES OF GRANULAR MEDIA

The nonlinear properties of a medium consisting of randomly packed sph erical granules are investigated, where the interstitial pore space ca n be occupied by a fluid. The equation of state of the medium is deriv ed, and the dependence of nonlinearity parameters on the properties of the granule material, the characteristics of the fluid, and the initi al static strain is analyzed. It is shown that granular media have an anomalously high nonlinearity in comparison with homogeneous materials . Experimental data obtained for model samples of granular media are i n good quantitative agreement with the theoretical conclusions. Publis hed results full-scale experiments to determine the nonlinear characte ristics of loose rock are also in good agreement with the theoretical estimates.