The geomechanical behaviour of peat foundations below rail-track structures

This thesis presents the results of research conducted to define the response of peat foundations underlying railway embankments to heavy axle loads. Three field sites were investigated, two in Northern Alberta on Canadian National Railway’s Edson and Lac-La-Biche subdivisions, and one on the Lévis...

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Bibliographic Details
Main Author: Hendry, Michael
Other Authors: Barbour, Lee, Martin, Derek, Sharma, Jitendra, Haug, Moir, Kells, James, Dolovich, Allan
Format: Thesis
Language:English
Published: University of Saskatchewan 2011
Subjects:
Online Access:http://hdl.handle.net/10388/ETD-2011-12-237
id ftusaskatchewan:oai:harvest.usask.ca:10388/ETD-2011-12-237
record_format openpolar
institution Open Polar
collection University of Saskatchewan: eCommons@USASK
op_collection_id ftusaskatchewan
language English
topic Peat
railroad
railway
geotechnical
laboratory
instrumentation
spellingShingle Peat
railroad
railway
geotechnical
laboratory
instrumentation
Hendry, Michael
The geomechanical behaviour of peat foundations below rail-track structures
topic_facet Peat
railroad
railway
geotechnical
laboratory
instrumentation
description This thesis presents the results of research conducted to define the response of peat foundations underlying railway embankments to heavy axle loads. Three field sites were investigated, two in Northern Alberta on Canadian National Railway’s Edson and Lac-La-Biche subdivisions, and one on the Lévis subdivision in southern Quebec. The scope of this thesis is fourfold: the development and installation of instrumentation; the laboratory testing of peat specimens retrieved from each site; the development of a conceptual model for the behaviour of peat beneath an embankment subjected to heavy axle loads; and finally, the modelling of the strength of the peat foundations relative to the applied loads. The first component of this research included the development and installation of instrumentation to measure in situ the distribution and magnitude of strain and pore pressure generation. The development included the assembly of instrumentation systems to measure all of the required parameters, and the development of the ShapeAccelArrayTM (SAA) from Measurand Inc. to measure horizontal cyclic motion under train loading. It was found the SAA, as provided by the manufacturer, was not able to provide accurate measurements of displacement. A method for determining the magnitude of cyclic displacement from the output of the MEMS accelerometers was developed from the laboratory testing data done as part of this study. This resulted in the ability to obtain a profile of cyclic displacement with depth. The second component of the research was the laboratory testing of peat specimens retrieved from the sites. Consolidated undrained triaxial tests and direct shear tests were conducted on remoulded peat, remoulded peat fibre and Shelby specimens of peat to investigate the fundamental mechanisms which control the strength of peat. The results were analyzed within the frameworks of elastic behaviour of cross-anisotropic materials and shear strength of fibre-reinforced soil. The test results from samples collected at all three sites were compared and the influence of peat fibres on the undrained strength was explored. The third component was the development of conceptual models for the undrained behaviour of peat, and peat foundations subjected to moving axle loads. A model for peat was developed from the cross-anisotropic response observed during the laboratory testing and correlations to fibre reinforced soil literature. This material model was then applied to the spatial distribution of stresses and orientation of principal stresses below embankments. The final component of the project was an analysis of the field data collected from all three sites to provide the magnitude and distribution of strain and pore pressure generation developed within the peat foundations. Further analysis of the measured response was conducted with both with calculations of effective stress paths and finite element modelling to determine the distribution of stress, the locations of potential yielding within the foundations and to determine how close to yielding the peat is under the maximum applied stresses. The results of this thesis provide new tools for the railway industry to evaluate the response and stability of railway embankments over peat foundations. The development of the SAA allows for the in situ measurement of the magnitude and distribution of displacement, and from this the strain, within soft soils under heavy axle loading. The conceptual models developed and applied to the undrained response of peat foundations provide a framework to evaluate the stability of railway embankments over soft foundations. The results of the application of this framework to the study sites included in this thesis provide context for further investigations.
author2 Barbour, Lee
Martin, Derek
Sharma, Jitendra
Haug, Moir
Kells, James
Dolovich, Allan
format Thesis
author Hendry, Michael
author_facet Hendry, Michael
author_sort Hendry, Michael
title The geomechanical behaviour of peat foundations below rail-track structures
title_short The geomechanical behaviour of peat foundations below rail-track structures
title_full The geomechanical behaviour of peat foundations below rail-track structures
title_fullStr The geomechanical behaviour of peat foundations below rail-track structures
title_full_unstemmed The geomechanical behaviour of peat foundations below rail-track structures
title_sort geomechanical behaviour of peat foundations below rail-track structures
publisher University of Saskatchewan
publishDate 2011
url http://hdl.handle.net/10388/ETD-2011-12-237
long_lat ENVELOPE(-65.815,-65.815,-68.134,-68.134)
geographic Shelby
geographic_facet Shelby
genre Lac la Biche
genre_facet Lac la Biche
op_relation http://hdl.handle.net/10388/ETD-2011-12-237
TC-SSU-201112237
_version_ 1766061379315302400
spelling ftusaskatchewan:oai:harvest.usask.ca:10388/ETD-2011-12-237 2023-05-15T17:06:17+02:00 The geomechanical behaviour of peat foundations below rail-track structures Hendry, Michael Barbour, Lee Martin, Derek Sharma, Jitendra Haug, Moir Kells, James Dolovich, Allan December 2011 http://hdl.handle.net/10388/ETD-2011-12-237 eng eng University of Saskatchewan http://hdl.handle.net/10388/ETD-2011-12-237 TC-SSU-201112237 Peat railroad railway geotechnical laboratory instrumentation text Thesis 2011 ftusaskatchewan 2022-01-17T11:54:57Z This thesis presents the results of research conducted to define the response of peat foundations underlying railway embankments to heavy axle loads. Three field sites were investigated, two in Northern Alberta on Canadian National Railway’s Edson and Lac-La-Biche subdivisions, and one on the Lévis subdivision in southern Quebec. The scope of this thesis is fourfold: the development and installation of instrumentation; the laboratory testing of peat specimens retrieved from each site; the development of a conceptual model for the behaviour of peat beneath an embankment subjected to heavy axle loads; and finally, the modelling of the strength of the peat foundations relative to the applied loads. The first component of this research included the development and installation of instrumentation to measure in situ the distribution and magnitude of strain and pore pressure generation. The development included the assembly of instrumentation systems to measure all of the required parameters, and the development of the ShapeAccelArrayTM (SAA) from Measurand Inc. to measure horizontal cyclic motion under train loading. It was found the SAA, as provided by the manufacturer, was not able to provide accurate measurements of displacement. A method for determining the magnitude of cyclic displacement from the output of the MEMS accelerometers was developed from the laboratory testing data done as part of this study. This resulted in the ability to obtain a profile of cyclic displacement with depth. The second component of the research was the laboratory testing of peat specimens retrieved from the sites. Consolidated undrained triaxial tests and direct shear tests were conducted on remoulded peat, remoulded peat fibre and Shelby specimens of peat to investigate the fundamental mechanisms which control the strength of peat. The results were analyzed within the frameworks of elastic behaviour of cross-anisotropic materials and shear strength of fibre-reinforced soil. The test results from samples collected at all three sites were compared and the influence of peat fibres on the undrained strength was explored. The third component was the development of conceptual models for the undrained behaviour of peat, and peat foundations subjected to moving axle loads. A model for peat was developed from the cross-anisotropic response observed during the laboratory testing and correlations to fibre reinforced soil literature. This material model was then applied to the spatial distribution of stresses and orientation of principal stresses below embankments. The final component of the project was an analysis of the field data collected from all three sites to provide the magnitude and distribution of strain and pore pressure generation developed within the peat foundations. Further analysis of the measured response was conducted with both with calculations of effective stress paths and finite element modelling to determine the distribution of stress, the locations of potential yielding within the foundations and to determine how close to yielding the peat is under the maximum applied stresses. The results of this thesis provide new tools for the railway industry to evaluate the response and stability of railway embankments over peat foundations. The development of the SAA allows for the in situ measurement of the magnitude and distribution of displacement, and from this the strain, within soft soils under heavy axle loading. The conceptual models developed and applied to the undrained response of peat foundations provide a framework to evaluate the stability of railway embankments over soft foundations. The results of the application of this framework to the study sites included in this thesis provide context for further investigations. Thesis Lac la Biche University of Saskatchewan: eCommons@USASK Shelby ENVELOPE(-65.815,-65.815,-68.134,-68.134)