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Modelling old railway embankments under different traffic conditions

Modelling old railway embankments under different traffic conditions
Modelling old railway embankments under different traffic conditions
Most UK railway embankments were rapidly built in the Victorian era using soil excavated from a cutting nearby, loosely tipped to full height without systematic compaction. This resulted in material heterogeneity with irregular clay fill slopes. The clay fill could be characterised as relatively dense and overconsolidated clay clods in a soft and remoulded clay matrix mixed with foreign material. The clay fill embankments have deteriorated due to cycles of both train and environmental loading. Triaxial test results confirmed the inherent variability of intact Lias Clay fill regarding the undrained shear strength, small-strain stiffness, pore pressure response and soil structure. The shearing response was governed by the soft clay matrix. The cyclic threshold stress of the clay fill was determined by a normalised stress ratio at 𝑞𝑐𝑦𝑐/𝑀𝑝′ = 0.8 that was valid for all sample types of Lias Clay.
The mechanical behaviour of typical old railway embankments under different traffic and track conditions was investigated using a validated, advanced constitutive model fully coupled with pore water interaction as saturated porous media. A mixed finite element was developed through ABAQUS, which can effectively replicate the transient behaviour of an elastoplastic material under dynamic loading and partially drained conditions regardless of loading frequency and soil permeability. The developed algorithm is numerically stable, which enables short- and long-term simulations on a range of geotechnical applications. Finite element analyses of track-embankment-ground system with validated parameters indicated complex transient and residual behaviours of stresses, pore pressure and deformations under passages of a single wheel, a whole train and 100 trains. The effects of vehicle geometry, axle load, rest period, track support system modulus, soil permeability and slope gradient on plastic slope deformations and residual pore pressure were carefully investigated and discussed.
Old railway embankments, Lias Clay, Train loading, Finite Element Analysis, Pore water pressure
University of Southampton
Sang-Iam, Jeerapat
92029628-1058-4de7-8ac7-35af29e99a53
Sang-Iam, Jeerapat
92029628-1058-4de7-8ac7-35af29e99a53
Smethurst, Joel
8f30880b-af07-4cc5-a0fe-a73f3dc30ab5
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c

Sang-Iam, Jeerapat (2023) Modelling old railway embankments under different traffic conditions. University of Southampton, Doctoral Thesis, 355pp.

Record type: Thesis (Doctoral)

Abstract

Most UK railway embankments were rapidly built in the Victorian era using soil excavated from a cutting nearby, loosely tipped to full height without systematic compaction. This resulted in material heterogeneity with irregular clay fill slopes. The clay fill could be characterised as relatively dense and overconsolidated clay clods in a soft and remoulded clay matrix mixed with foreign material. The clay fill embankments have deteriorated due to cycles of both train and environmental loading. Triaxial test results confirmed the inherent variability of intact Lias Clay fill regarding the undrained shear strength, small-strain stiffness, pore pressure response and soil structure. The shearing response was governed by the soft clay matrix. The cyclic threshold stress of the clay fill was determined by a normalised stress ratio at 𝑞𝑐𝑦𝑐/𝑀𝑝′ = 0.8 that was valid for all sample types of Lias Clay.
The mechanical behaviour of typical old railway embankments under different traffic and track conditions was investigated using a validated, advanced constitutive model fully coupled with pore water interaction as saturated porous media. A mixed finite element was developed through ABAQUS, which can effectively replicate the transient behaviour of an elastoplastic material under dynamic loading and partially drained conditions regardless of loading frequency and soil permeability. The developed algorithm is numerically stable, which enables short- and long-term simulations on a range of geotechnical applications. Finite element analyses of track-embankment-ground system with validated parameters indicated complex transient and residual behaviours of stresses, pore pressure and deformations under passages of a single wheel, a whole train and 100 trains. The effects of vehicle geometry, axle load, rest period, track support system modulus, soil permeability and slope gradient on plastic slope deformations and residual pore pressure were carefully investigated and discussed.

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More information

Published date: 20 March 2023
Keywords: Old railway embankments, Lias Clay, Train loading, Finite Element Analysis, Pore water pressure

Identifiers

Local EPrints ID: 475720
URI: http://eprints.soton.ac.uk/id/eprint/475720
PURE UUID: eb444410-e7e6-475c-8f04-0130aea20b1c
ORCID for Jeerapat Sang-Iam: ORCID iD orcid.org/0000-0002-8716-3616
ORCID for William Powrie: ORCID iD orcid.org/0000-0002-2271-0826

Catalogue record

Date deposited: 27 Mar 2023 16:31
Last modified: 17 Mar 2024 02:41

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Contributors

Author: Jeerapat Sang-Iam ORCID iD
Thesis advisor: Joel Smethurst
Thesis advisor: William Powrie ORCID iD

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