Thesis_Radampola_Senanie_Sujeewa_Redacted.pdf (5.37 MB)

Evaluation and modelling performance of capping layer in rail track substructure

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posted on 2023-11-03, 04:00 authored by Senanie Radampola
"In the design of rail track structures where the subgrade cannot achieve the desired capacity, enabling the required standard of track geometry to be maintained for the speed, axle load and tonnage to be hauled, a capping layer of granular material is placed between the natural ground or the embankment fill material and the ballast to protect the underlying weaker layers. In spite of the important role played by the capping layer, very little research has been carried out on its performance. The current practice of design of the capping layer, therefore, is based on working stress philosophy where reduced levels of stresses are assumed not to degrade the subgrade. Even on tracks containing a thick ballast layer that ensures allowable levels of working stress the subgrade has been found to have permanently deformed. Design of capping layers based on plastic deformation, therefore, appears appropriate. This thesis aims at determining the load levels that cause detrimental plastic deformation in the capping layer. The suite of material properties that characterise plastic deformations of capping layer is neither readily available nor easily determined. This thesis proposes a cheaper method of evaluating a range of capping layer material properties using penetration tests on specimens contained in California Bearing Ratio (CBR) test moulds coupled with a finite element modelling based back calculation technique. The suite of material properties thus determined are used for the simulation of the behaviour of capping layers under the boundary and loading conditions similar to those in practice. The predicted results are validated using laboratory experiments on large size capping layer specimens." -- abstract



Central Queensland University

Additional Rights

I hereby grant to Central Queensland University or its agents the right to archive and to make available my thesis or dissertation in whole or in part through Central Queensland University’s Institutional Repository, ACQUIRE, in all forms of media, now or hereafter known. I retain all copyright, including the right to use future works (such as articles or books), all or part of this thesis or dissertation.

Open Access

  • Yes

External Author Affiliations

Centre for Railway Engineering; James Goldston Faculty of Engineering and Physical Systems;

Era Eligible

  • No


Associate Professor Manicka Dhanasekar ; Mr Tim McSweeney ; Dr Netra Gurung

Thesis Type

  • Doctoral Thesis