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Experimental investigation of static and cyclic behaviour of scaled railway ballast and the effect of stress reversal

Experimental investigation of static and cyclic behaviour of scaled railway ballast and the effect of stress reversal
Experimental investigation of static and cyclic behaviour of scaled railway ballast and the effect of stress reversal
The aim of the research was to improve the fundamental understanding of mechanical behaviour of ballast and study the effect of tamping on ballast. The experiments were carried out on scaled railway ballast to eliminate the difficulties associated with testing large particle granular materials. Consideration was given to the gradation, mineralogy and shape during scaling.
Particle characterisation work was carried out on scaled and full size ballast using imaging techniques to examine the validity of the use of scaled ballast. Detailed analysis of results is used to quantitatively measure the changes in shape with particle size. The results show measurable differences in particle shape between different particle size intervals. As the differences are small in magnitude, they do not invalidate the use of scaled ballast.
Monotonic, cyclic experiments were carried out as part of a laboratory testing programme. Scaled ballast shows generally similar stress strain behaviour to larger granular materials. The friction angle of 40o to 50o for the confining pressure range of 15 kPa to 200 kPa falls within the range of friction angle obtained for full size ballast in the literature. The effect of changing confining pressure during train loading was examined. The results show that the settlement increases and the stiffness reduces when the confining pressure cycles. The effect of principal stress reversal during tamping was examined by an extension stage after the cyclic loading. It is shown that massive settlement occurs after the extension stage during initial cycles and settlement returns back to the pre-extension stage soon under loading. The results evidence the disruption of ballast structure and loss of stiffness due to tamping. Specimens were resin stabilised within the triaxial cell after specific stress paths had been followed. The changes in structure during a specific stress path can be studied by CT examination.
Aingaran, S.
65bf7144-632a-4f95-a983-a3e3a6d7d27e
Aingaran, S.
65bf7144-632a-4f95-a983-a3e3a6d7d27e
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Zervos, Antonios
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Aingaran, S. (2014) Experimental investigation of static and cyclic behaviour of scaled railway ballast and the effect of stress reversal. University of Southampton, Engineering and the Environment, Doctoral Thesis, 285pp.

Record type: Thesis (Doctoral)

Abstract

The aim of the research was to improve the fundamental understanding of mechanical behaviour of ballast and study the effect of tamping on ballast. The experiments were carried out on scaled railway ballast to eliminate the difficulties associated with testing large particle granular materials. Consideration was given to the gradation, mineralogy and shape during scaling.
Particle characterisation work was carried out on scaled and full size ballast using imaging techniques to examine the validity of the use of scaled ballast. Detailed analysis of results is used to quantitatively measure the changes in shape with particle size. The results show measurable differences in particle shape between different particle size intervals. As the differences are small in magnitude, they do not invalidate the use of scaled ballast.
Monotonic, cyclic experiments were carried out as part of a laboratory testing programme. Scaled ballast shows generally similar stress strain behaviour to larger granular materials. The friction angle of 40o to 50o for the confining pressure range of 15 kPa to 200 kPa falls within the range of friction angle obtained for full size ballast in the literature. The effect of changing confining pressure during train loading was examined. The results show that the settlement increases and the stiffness reduces when the confining pressure cycles. The effect of principal stress reversal during tamping was examined by an extension stage after the cyclic loading. It is shown that massive settlement occurs after the extension stage during initial cycles and settlement returns back to the pre-extension stage soon under loading. The results evidence the disruption of ballast structure and loss of stiffness due to tamping. Specimens were resin stabilised within the triaxial cell after specific stress paths had been followed. The changes in structure during a specific stress path can be studied by CT examination.

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More information

Published date: February 2014
Organisations: University of Southampton, Civil Maritime & Env. Eng & Sci Unit

Identifiers

Local EPrints ID: 366814
URI: http://eprints.soton.ac.uk/id/eprint/366814
PURE UUID: f3c49552-0d5b-4166-ba78-724c560592b7
ORCID for William Powrie: ORCID iD orcid.org/0000-0002-2271-0826
ORCID for Antonios Zervos: ORCID iD orcid.org/0000-0002-2662-9320

Catalogue record

Date deposited: 20 Oct 2014 12:39
Last modified: 06 Jun 2018 13:06

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