ELASTIC-WAVE PROPAGATION IN A MEDIUM CONTAINING ORIENTED INCLUSIONS WITH A CHANGING ASPECT RATIO - A PHYSICAL MODEL STUDY

Velocities of shear waves with different polarizations, as well as com pressional-wave velocities, have been measured using a pulse transmiss ion method in a series of physical models. The observations were made in a composite material filed with rubber inclusions, of variable aspe ct ratio, simulating cracks filled with a 'weak' material. The inclusi ons were oriented in a plane but distributed randomly in position. At a crack density of 5 per cent the experimentally measured velocities o f shear and compressional waves are compared with results predicted by a theoretical model of Hudson (1981), Good agreement between the Huds on theory and the experiment is obtained for shear waves at all aspect ratios, but the agreement between theory and experiment for compressi onal waves is observed only for an aspect ration of 0.012. For dispers ion analysis, velocities were obtained at different frequencies using a multiple-filtering technique, Results of dispersion analysis indicat e that the maximum velocity dispersion for both shear waves (S1, S2) o ccurs at a 0 degrees angle of incidence and the minumum velocity dispe rsion occurs at a 90 degrees angle of incidence. The variation of anis otropy as a function of aspect ratio and crack density can be related to Thomsen's (1986) anisotropy parameter gamma = (V-s2/1/V-s2/2-1)/2. This variation suggests that the crack density is more important than the effect of the aspect ratio. Finally, we show that the ratio V-p/V- s is anisotropic. The present paper is a continuation of the elastic w ave propagation discussed by Ass'ad et al. 1993.