Surface waves in a stratified half space with enhanced continuum properties. Part 1: Formulation of the boundary value problem

This paper discusses the propagation of surface waves in an elastic stratif ied half space, which consists of a granular elastic upper layer resting on a classic elastic substratum. We will consider both the case of an upper l ayer with second-gradient continuum properties, and an upper layer with Cos serat continuum properties. These enhanced continuum formulations are able to describe micro-scale effects as governed by the individual particle disp lacements and particle rotations. The micro-scale effects become important when the length of the surface waves is of the same order of magnitude as t he particle size, which may occur in a high-speed railway track that consis ts of an upper layer of ballast particles. In an accompanying paper we will therefore analyse the critical structural response of the stratified half space when it is subjected to a moving, harmonically vibrating load. This m odel is representative for a high-speed railway system. (C) 1999 Editions s cientifiques et medicales Elsevier SAS.