Track substructure inclusions forreducing the risk of mud pumpingin heavy haul tracks

Arivalagan, Joseph

Track substructure inclusions forreducing the risk of mud pumpingin heavy haul tracks

Arivalagan, Joseph

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Publication Type:: Thesis
Issue Date:: 2022

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Field	Value	Language
dc.contributor.author	Arivalagan, Joseph
dc.date.accessioned	2023-03-28T21:42:02Z
dc.date.available	2023-03-28T21:42:02Z
dc.date.issued	2022
dc.identifier.uri	http://hdl.handle.net/10453/168758
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US.UTF-8
dc.description.abstract	In recent times the demand for railway transportation has increased rapidly all over the world because a sustainable mode of transportation is needed to convey passengers and other commodities. However, subgrade soil with low bearing capacity is susceptible to instability under unfavourable drainage conditions. Subgrade soils with low/medium plasticity characteristics that undergo high cyclic stress levels are prone to fluidisation due to the rapid increase in excess pore water pressure (EPWP). Subsequently, subgrade can become unstable which leads to fines being pumped into the ballast/subballast layer (mud pumping). Excessive fine content, EPWPs, applied cyclic stress and frequency are the primary factors that induce particle migration and associated mud pumping. However, the actual mechanisms and cost-effective solutions to prevent subgrade fluidisation were not thoroughly understood due to its complexity and limitations. In this study, a series of laboratory experiments were carried out to examine the following aspects of mud pumping: (1) the occurrence of subgrade fluidisation by simulating various drainage conditions, (2) the role geotextiles play in stabilising subgrade/ballast interface, and (3) the effectiveness of a prefabricated vertical drain (PVD) and geocomposite system in reducing the fluidisation potential using dynamic filtration apparatus (DFA). Soil specimens were tested at loading frequencies ranging from 1.0 to 5.0 Hz and cyclic deviator stresses from 40 to 70 kPa, simulates a maximum axle load of 35 tonnes. The axial strain (εₐ), EPWPs, and time-dependent excess pore pressure gradient (EPPG) that developed under undrained (impermeable) and free drained (no capping) conditions were used to define the failure criteria. The results showed that geocomposite with an effective filter membrane could prevent the migration of particles under typical train loading (25 tonnes). However, when the cyclic deviatoric stress increased (up to 35-40 tonnes of axle loading), the ability of geocomposites to alleviate the EPWP diminished. The effectiveness of PVDs was also assessed under various loading conditions. The combined PVD-geocomposite system could reduce the accumulation of EPWPs and continuously dissipate them as the number of cycles increases, thereby providing a viable solution for mitigating the effects of subgrade fluidisation. Design guides were introduced with the field applications at Chullora, NSW. Finally, a numerical study was carried out to evaluate the use of geosynthetics under typical rail track conditions. The predictions revealed the efficiency of geosynthetics at regulating and dissipating the generation of EPWPs under train loading.	en_US.UTF-8
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US.UTF-8
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/168758/2/02whole.pdf
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	© 2022 Joseph Arivalagan
dc.rights	au.edu.uts.lib/ppc
dc.title	Track substructure inclusions forreducing the risk of mud pumpingin heavy haul tracks	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

In recent times the demand for railway transportation has increased rapidly all over the world because a sustainable mode of transportation is needed to convey passengers and other commodities. However, subgrade soil with low bearing capacity is susceptible to instability under unfavourable drainage conditions. Subgrade soils with low/medium plasticity characteristics that undergo high cyclic stress levels are prone to fluidisation due to the rapid increase in excess pore water pressure (EPWP). Subsequently, subgrade can become unstable which leads to fines being pumped into the ballast/subballast layer (mud pumping). Excessive fine content, EPWPs, applied cyclic stress and frequency are the primary factors that induce particle migration and associated mud pumping. However, the actual mechanisms and cost-effective solutions to prevent subgrade fluidisation were not thoroughly understood due to its complexity and limitations. In this study, a series of laboratory experiments were carried out to examine the following aspects of mud pumping: (1) the occurrence of subgrade fluidisation by simulating various drainage conditions, (2) the role geotextiles play in stabilising subgrade/ballast interface, and (3) the effectiveness of a prefabricated vertical drain (PVD) and geocomposite system in reducing the fluidisation potential using dynamic filtration apparatus (DFA). Soil specimens were tested at loading frequencies ranging from 1.0 to 5.0 Hz and cyclic deviator stresses from 40 to 70 kPa, simulates a maximum axle load of 35 tonnes. The axial strain (εₐ), EPWPs, and time-dependent excess pore pressure gradient (EPPG) that developed under undrained (impermeable) and free drained (no capping) conditions were used to define the failure criteria. The results showed that geocomposite with an effective filter membrane could prevent the migration of particles under typical train loading (25 tonnes). However, when the cyclic deviatoric stress increased (up to 35-40 tonnes of axle loading), the ability of geocomposites to alleviate the EPWP diminished. The effectiveness of PVDs was also assessed under various loading conditions. The combined PVD-geocomposite system could reduce the accumulation of EPWPs and continuously dissipate them as the number of cycles increases, thereby providing a viable solution for mitigating the effects of subgrade fluidisation. Design guides were introduced with the field applications at Chullora, NSW. Finally, a numerical study was carried out to evaluate the use of geosynthetics under typical rail track conditions. The predictions revealed the efficiency of geosynthetics at regulating and dissipating the generation of EPWPs under train loading.

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