Vibrational Characteristics of Soil Deposits with Variable Wave Velocity

The paper studies certain dynamic characteristics of soil deposits with wave velocities increasing with depth according to (l+pz)'", where m = 1, 2/3, 1/2, 1/4 and 0. Analytical solutions are presented for the fundamental periods, mode shapes and amplification functions due to vertically propagating shear waves and the effects of type (m) and rate ( p ) of heterogeneity are systematically investigated. Then analyticalnumerical techniques are used to study the attenuation with depth in a deposit of the vertical and horizontal displacements due to travelling of Rayleigh waves. Differences attributed to different heterogeneities are discussed in connection with the machine isolation problem and the steady-state vibration technique for soil exploration. Finally, the dependence on soil heterogeneity of the time-distance response curves, obtained during seismic refraction surveys, is graphically illustrated.