SCALE EFFECTS ON DYNAMIC WAVE-PROPAGATION IN HETEROGENEOUS MEDIA

To study scale-effects on wave propagation in 3-D heterogeneous media, we conducted dynamic and static laboratory experiments on seven sampl es of glass beads cast with epoxy. We measured P and S wave velocities and frequency dispersion by the pulse-transmission method, and static elastic Young's modulus by a uniaxial stress test. We changed the sca le of the heterogeneity by varying the diameter of the glass beads in each sample, and obtained wavelength to scale ratios varying from 0.2 to 20. We observed about 22% P-wave velocity dispsersion and 15% S-wav e velocity dispersion within this range of wavelength to scale ratios. We observed no scale effects on the static Young's modulus of the sam e seven samples. It is clear that strong wave velocity dispersion in t he experiment is due to the dynamic wavelength-scale effects caused by scattering.