Behaviour of Railway Ballast Under Cycling Loading

Abstract

Ballast is widely employed for the construction of railway track because of its mechanical properties and its flexibility from the point of view of construction and maintenance. This granular material, produced by crushing of hard rocks, is confined between concrete sleepers supporting the rails and the platform. The ballast layer needs to be raised from time to time because of its cumulative settlement under repeated loading [1, 2]. The increasing of cost of such operations with the advent of high speed trains has motivated a number of studies on physical origins of settlements. The ballast layer is a thin granular interface with a thickness that is below the correlation length of contact forces. These correlations are expected to be long ranged because ballast grains are faceted and angular, and there is strong wall effect due to the confinement of ballast between the sleepers and the sublayer. In this paper we investigate the mechanical behaviour of a model portion of railway track submitted to 60000 loading cycles. The aim of this study is to characterize the stabilisation phase and to propose a settlement model.