Numerical prediction of wave reaction of the layered elastic half-space

Abstract

This paper presents the results of numerical analysis obtained for layered elastic half-space loaded dynamically. The main problem was to study the dynamic response of the medium in conditions of multiple refl ections and refractions of waves on the borders of layers. The subject of this study was the dynamic behaviour of heterogeneous, isotropic, horizontally – layered, elastic half-space. The numerical calculations program included variations of the foundation. The foundation was composed of two layers, wherein the fi rst layer’s thickness was 2, 4 or 6 m. Wave propagation modelling was performed using the method of fi nite differences. The decline of the amplitude of vertical vibrations along with the distance in uniform media generally is supported by the standardized prediction. The standardized prediction for the decline of amplitudes of the horizontal vibration along with the distance may lead to understating. Local fading and strengthening of amplitude of vertical and horizontal displacements occur. This effect should not necessarily be connected with ground medium stratifi cation, even though such effects in case of stratifi ed medium have increased. If a vulnerable layer is on top of the rigid one, larger amplitude of vertical displacement is obtained at the surface rather than in a uniform, weak medium. In the case of inverse layout of the layers, i.e. if the rigid layer is lying on top of a thick, vulnerable layer, the amplitude of vertical displacements on the surface are smaller compared to the amplitude obtained in a uniform, rigid medium.