A DISCRETE ELEMENT STUDY OF THE RELATIONSHIP OF FABRIC TO WAVE PROPAGATIONAL BEHAVIORS IN GRANULAR-MATERIALS

Wave propagation in granular materials is numerically studied through discrete element simulation. Two-dimensional (2-D) model material syst ems composed of large numbers of circular particles were numerically g enerated. The particles in these model materials were randomly distrib uted with a biasing algorithm to produce fabric anisotropy so as to cr eate preferred directions within the material. Wave motion is introduc ed through dynamic loadings to appropriate boundary particles to produ ce horizontal and vertical plane wave propagation within each model ma terial. Discrete element simulation with a non-linear hysteretic inter particle contact law is used to model the dynamic behaviour of the mod el granular systems, and this yields information on the wave speed and amplitude attenuation. Through the investigation of several model sys tems, relationships are established between wave propagational charact eristics and granular microstructure or fabric. Specific fabric measur es which were used included branch vectors, path microstructures and v oid characteristics. Distributions of these fabric descriptors were de termined, and comparisons and correlations were made with the discrete element wave propagation results. Conclusions of this study indicated that while all three fabric measures provided some degree of correlat ion with the wave motion behaviours, the void fabric descriptor produc ed the best correlation for the assemblies under investigation. (C) 19 97 by John Wiley & Sons, Ltd.