The Effect of Voids and Inclusions on Wave Propagation in Granular Materials

Abstract

Theoretical and experimental studies have been conducted on the dynamic response of granular materials containing local discontinuities of voids and inhomogeneous inclusions. The granular medium was simulated by a specific assembly of circular disks which were subjected to explosive loadings of short duration. Voids were created by removing particular disks from the assembly, while inclusions were constructed by replacing certain disks with those of a higher impedance material. The computational simulation was accomplished through the use of the distinct element method in which the intergranular contact forces and displacements of the assembly disks are determined through a series of calculations tracing the movements of each of the individual disks. The experimental study employed the use of photoelasticity in conjunction with high-speed photography to collect photographic data of the propagation of waves in transparent assemblies of model granular media. Comparisons were made between the computational results and the experimental data for the local intergranular contact forces around each void or inclusion. Both voids and inclusions produce local wave scattering through various reflection mechanisms, and the results seem to indicate that the inclusions produced higher local wave attenuation.