Year

2019

Degree Name

Doctor of Philosophy

Department

School of Civil, Mining and Environmental Engineering

Abstract

Modern day demand for faster and heavier transport in Australia has made the railways to increase the train speeds and axle loads. This advancement poses serious geotechnical challenges with traditional ballasted railway tracks. A consequence of increasing train speeds is the generation of elevated ground borne vibrations and the associated stress amplification in the track layers. Under such conditions, railway ballast, being the important load bearing component of these railway tracks, may experience excessive deformation and degradation and could result in more frequent and increasingly expensive track maintenance. In this sense, it is important to assess the influence of train speeds on the stress-strain and degradation behaviour of ballast under train movement. A number of analytical models have been developed to compute the critical train speed based on the elasto-dynamic response of the track, however, the long-term performance of ballast layer involving elasto-plastic deformations and degradation needs to be incorporated to optimize maintenance costs for high speed railway tracks.

An analytical model of a railway track has been developed based on the elastic wave propagation in track layers, to predict the elasto-dynamic response of the track including amplification of instantaneous displacements and dynamic stresses, as a function of train speeds and axle loads. The analytical model could also predict the complex stress paths in the ballast layer involving cyclic rotation of principal stress axes, at different train speeds and the resonating train speed has been derived.

FoR codes (2008)

0905 CIVIL ENGINEERING

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.