Numerical simulation of the effect of moving loads on saturated subgrade soil

Zhao, HY; Indraratna, B; Ngo, T

Numerical simulation of the effect of moving loads on saturated subgrade soil

Zhao, HY Indraratna, B

Ngo, T

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Publisher:: Elsevier BV
Publication Type:: Journal Article
Citation:: Computers and Geotechnics, 2021, 131, pp. 103930-103930
Issue Date:: 2021-03-01

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Field	Value	Language
dc.contributor.author	Zhao, HY
dc.contributor.author	Indraratna, B https://orcid.org/0000-0002-9057-1514
dc.contributor.author	Ngo, T
dc.date.accessioned	2021-01-13T22:58:49Z
dc.date.available	2021-01-13T22:58:49Z
dc.date.issued	2021-03-01
dc.identifier.citation	Computers and Geotechnics, 2021, 131, pp. 103930-103930
dc.identifier.issn	0266-352X
dc.identifier.issn	1873-7633
dc.identifier.uri	http://hdl.handle.net/10453/145404
dc.description.abstract	© 2020 Elsevier Ltd The substantial increase in excess pore pressure and plastic strain in subgrade soil due to faster and heavier trains is a major cause of track instability. Stresses that occur in track substructure during the passage of trains have not often been captured accurately due to insufficient rigour in dynamic analysis. This paper presents a numerical investigation into the plastic/dynamic characteristics of a saturated porous medium (capping and subgrade) subjected to moving axle loads. In this study, a detailed numerical analysis is described, whereby a coupled fluid-dynamic framework is developed for the saturated porous medium in conjunction with a generalized plasticity model, in order to examine the cyclic loading response of a soft subgrade soil. The constitutive model is calibrated by undrained cyclic triaxial testing carried out on a soft foundation soil retrieved from a coastal railroad site having a historical record of mud pumping. Kelvin elements are attached to the transmitting boundary to absorb wave energy and to prevent any back-propagation of waves into the saturated subgrade domain. This approach is then validated against a semi-analytical solution and wayside measurements. The results show that the stress path corresponding to the applied moving load exhibits a series of heart-shaped envelopes along which the deviator stress and mean effective stress gradually decrease with the successive loading cycles. The build-up of pore water pressure and the associated soil deformation (e.g. accumulated settlement) are exacerbated when the train speed approaches a critical velocity of the saturated subgrade. A relationship between the train speed, track settlement and drainage capacity of a sub-ballast (capping) layer is also established. As a practical guide, the influence of permeability of the capping layer is highlighted in relation to controlling track settlement for a given operational train speed.
dc.language	en
dc.publisher	Elsevier BV
dc.relation	http://purl.org/au-research/grants/arc/IC170100006
dc.relation.ispartof	Computers and Geotechnics
dc.relation.isbasedon	10.1016/j.compgeo.2020.103930
dc.rights	info:eu-repo/semantics/restrictedAccess
dc.subject	0905 Civil Engineering, 0914 Resources Engineering and Extractive Metallurgy, 0915 Interdisciplinary Engineering
dc.subject.classification	Geological & Geomatics Engineering
dc.title	Numerical simulation of the effect of moving loads on saturated subgrade soil
dc.type	Journal Article
utslib.citation.volume	131
utslib.for	0905 Civil Engineering
utslib.for	0914 Resources Engineering and Extractive Metallurgy
utslib.for	0915 Interdisciplinary Engineering
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology/School of Civil and Environmental Engineering
pubs.organisational-group	/University of Technology Sydney
utslib.copyright.status	closed_access	*
dc.date.updated	2021-01-13T22:57:10Z
pubs.publication-status	Accepted
pubs.volume	131

Abstract:

© 2020 Elsevier Ltd The substantial increase in excess pore pressure and plastic strain in subgrade soil due to faster and heavier trains is a major cause of track instability. Stresses that occur in track substructure during the passage of trains have not often been captured accurately due to insufficient rigour in dynamic analysis. This paper presents a numerical investigation into the plastic/dynamic characteristics of a saturated porous medium (capping and subgrade) subjected to moving axle loads. In this study, a detailed numerical analysis is described, whereby a coupled fluid-dynamic framework is developed for the saturated porous medium in conjunction with a generalized plasticity model, in order to examine the cyclic loading response of a soft subgrade soil. The constitutive model is calibrated by undrained cyclic triaxial testing carried out on a soft foundation soil retrieved from a coastal railroad site having a historical record of mud pumping. Kelvin elements are attached to the transmitting boundary to absorb wave energy and to prevent any back-propagation of waves into the saturated subgrade domain. This approach is then validated against a semi-analytical solution and wayside measurements. The results show that the stress path corresponding to the applied moving load exhibits a series of heart-shaped envelopes along which the deviator stress and mean effective stress gradually decrease with the successive loading cycles. The build-up of pore water pressure and the associated soil deformation (e.g. accumulated settlement) are exacerbated when the train speed approaches a critical velocity of the saturated subgrade. A relationship between the train speed, track settlement and drainage capacity of a sub-ballast (capping) layer is also established. As a practical guide, the influence of permeability of the capping layer is highlighted in relation to controlling track settlement for a given operational train speed.

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http://hdl.handle.net/10453/145404