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Pore pressure generation in a poro-elastic soil under moving train loads

Pore pressure generation in a poro-elastic soil under moving train loads
Pore pressure generation in a poro-elastic soil under moving train loads
During the passage of a train along a railway track, the underlying soil experiences repeated loading. If the soil is saturated, pore pressures will increase as the load passes, and these may or may not start to dissipate before each load is removed. To investigate the dynamic response and excess pore pressures generated in a saturated ground below the track, this study uses a 2.5D finite element model (FEM) of a coupled track-embankment-ground system. The saturated soil is modelled using Biot’s theory of elastic wave propagation. The implementation of the method is verified by comparison with semi-analytical solutions for both single-phase elastic and poro-elastic media. It is then used to investigate the influence of load speed c, soil Darcy permeability kD and stiffness on the excess pore water pressures generated. It is found that the ratio c/kD determines the extent to which excess pore pressures build up during passage of the load, at any given depth. For a saturated soil of a particular stiffness, if c/kD is less than 104, the soil can be viewed as highly permeable in relation to the load speed and almost no excess pore pressure is developed. For a single moving load, there is a critical value of c/kD, above which the maximum pore pressure reaches a constant value; this critical value depends on the depth. Below the critical value, the pore pressure accumulated during the passage of a train depends on c/kD but is otherwise independent of the load speed. The pore pressure accumulated during the passage of a bogie pair is greatest for intermediate values of c/kD. For small values of c/kD (high permeability), the pore pressure build-up is small, whereas for large values of c/kD (low permeability) the pore pressure does not dissipate during the loading cycle. The variation in the maximum stress ratio, (/)max, with permeability depends on the depth under consideration. The depth to which pore pressures are generated and the effects of soil stiffness are also discussed in this paper.
0267-7261
1-15
Bian, Xuecheng
b0dbeeda-cee0-4870-ab0b-be795d7e045c
Hu, Jing
915d2ade-ccec-4366-a6d3-7deb0cb21682
Thompson, David
bca37fd3-d692-4779-b663-5916b01edae5
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Bian, Xuecheng
b0dbeeda-cee0-4870-ab0b-be795d7e045c
Hu, Jing
915d2ade-ccec-4366-a6d3-7deb0cb21682
Thompson, David
bca37fd3-d692-4779-b663-5916b01edae5
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c

Bian, Xuecheng, Hu, Jing, Thompson, David and Powrie, William (2019) Pore pressure generation in a poro-elastic soil under moving train loads. Soil Dynamics and Earthquake Engineering, 125, 1-15, [105711]. (doi:10.1016/j.soildyn.2019.105711).

Record type: Article

Abstract

During the passage of a train along a railway track, the underlying soil experiences repeated loading. If the soil is saturated, pore pressures will increase as the load passes, and these may or may not start to dissipate before each load is removed. To investigate the dynamic response and excess pore pressures generated in a saturated ground below the track, this study uses a 2.5D finite element model (FEM) of a coupled track-embankment-ground system. The saturated soil is modelled using Biot’s theory of elastic wave propagation. The implementation of the method is verified by comparison with semi-analytical solutions for both single-phase elastic and poro-elastic media. It is then used to investigate the influence of load speed c, soil Darcy permeability kD and stiffness on the excess pore water pressures generated. It is found that the ratio c/kD determines the extent to which excess pore pressures build up during passage of the load, at any given depth. For a saturated soil of a particular stiffness, if c/kD is less than 104, the soil can be viewed as highly permeable in relation to the load speed and almost no excess pore pressure is developed. For a single moving load, there is a critical value of c/kD, above which the maximum pore pressure reaches a constant value; this critical value depends on the depth. Below the critical value, the pore pressure accumulated during the passage of a train depends on c/kD but is otherwise independent of the load speed. The pore pressure accumulated during the passage of a bogie pair is greatest for intermediate values of c/kD. For small values of c/kD (high permeability), the pore pressure build-up is small, whereas for large values of c/kD (low permeability) the pore pressure does not dissipate during the loading cycle. The variation in the maximum stress ratio, (/)max, with permeability depends on the depth under consideration. The depth to which pore pressures are generated and the effects of soil stiffness are also discussed in this paper.

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Jing Hu manuscript - final - Accepted Manuscript
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Accepted/In Press date: 3 June 2019
e-pub ahead of print date: 15 June 2019
Published date: October 2019

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Local EPrints ID: 431812
URI: http://eprints.soton.ac.uk/id/eprint/431812
ISSN: 0267-7261
PURE UUID: 5e715ec1-a9e3-4ec0-9953-d12bf200a323
ORCID for David Thompson: ORCID iD orcid.org/0000-0002-7964-5906
ORCID for William Powrie: ORCID iD orcid.org/0000-0002-2271-0826

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Date deposited: 18 Jun 2019 16:30
Last modified: 18 Feb 2021 16:47

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Author: Xuecheng Bian
Author: Jing Hu
Author: David Thompson ORCID iD
Author: William Powrie ORCID iD

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