Introduction

The static behaviour of a medium consisting of infinite horizontal layers can be described by an equivalent homogeneous medium (Schoenberg and Muir, 1989). In this article we give a simplified notation for the calculation of the equivalent medium and discuss the question of how an equivalent medium should be defined. If stress is applied on the top boundary of a stack of layers and the homogeneous equivalent medium, both media show identical changes in elastic deformation energy within the medium and the same exterior displacements and average forces on the boundaries.