Performance assessment of peat rail subgrade before and after mass stabilization

Abstract

Abstract:Railway tracks over peat subgrades can experience large ground deformations, increased pore-water pressures, formation of pumping holes, and pumping of fines during the passage of trains, which can lead to accelerated track deterioration and risk of derailment. One approach to mitigate these issues is to improve the subgrade stiffness using mass stabilization, which involves mixing a binding agent, such as cement, into a soil to improve its physical properties. This paper describes the development and use of a method to calculate trackbed modulus to quantify the improvement due to mass stabilization at a site with peat subgrade. Track modulus was calculated using in-service freight trains by measuring track displacements using digital image correlation and wheel loads from a nearby wheel impact load detector. Because of the voids that existed between the rail, sleepers, and ballast it was found that using displacements of the ballast crib to calculate the trackbed modulus, instead of the overall track modulus using rail or sleeper displacements, provided a way to quantify the improvement of the subgrade that was not affected by the presence of voids. The results indicate the post-rehabilitation trackbed modulus was double the original baseline value for the track section, indicating that mass stabilization can be an effective rehabilitation strategy to improve the stiffness of problematic peat subgrades.Key words: railway, track modulus, mass stabilization, peat, digital image correlation.Résumé : Les voies de chemin de fer par-dessus des fondations de tourbe peuvent subir de grandes déformations du sol, l'augmentation de pressions interstitielles, la formation d'orifices de pompage, et le pompage de fines pendant le passage des trains, ce qui peut conduire à l'accélération de la détérioration de la voie et le risque de déraillement. Une façon d'atténuer ces problèmes est d'améliorer la rigidité de la plate-forme en utilisant la stabilisation, qui implique le mélange d'un liant, comme le ciment, dans un sol pour améliorer ses propriétés physiques. Cet article décrit le développement et l'utilisation d'une méthode de calcul du module du tracé afin de quantifier l'amélioration due à la stabilisation de masse à un site avec des fondations de tourbe. Le module de la voie a été calculé à l'aide de trains de marchandises en service par la mesure de la corrélation d'images numériques à l'aide de déplacements et des charges de roues à proximité d'un détecteur de charge d'impact de roues. En raison des vides qui existent entre les rails, les traverses, et les ballasts, il a été constaté que l'utilisation des déplacements de la case de ballast pour calculer le module du tracé, au lieu de l'ensemble des modules des voies en utilisant les déplacements de traverses ou des voies, a fourni un moyen de quantifier l'amélioration de la fondation qui n'est pas affectée par la présence d'espaces vides. Les résultats indiquent que le module de la tracée suite à la réhabilitation était double de la valeur de référence initia...

Laboratory study on subgrade fluidization under undrained cyclic triaxial loading

“…Liquefaction being a deep-seated phenomenon occurring under the action of dynamic accelerations with the effective stresses dropping to zero, whereas mud pumping occurs at shallow depths (i.e. low confining pressure) due to the repetitive (cyclic) loading applied over a considerable period of time at the subgrade-ballast interface as a result of long freight or heavy haul trains (Duong et al 2013;Hudson et al 2016;Wheeler et al 2017). Additionally, the heavy haul train loading frequency range adopted to examine the cyclic behaviour of a subgrade soil (> 1.0 Hz) is significantly larger than that used for investigating liquefaction under seismic loads (Muramoto et al 2006;Indraratna et al 2010;Trinh et al 2012;Duong et al 2014;Yang and Pan 2017).…”

An Evaluation Model of Subgrade Stability Based on Artificial Neural Network

“…Abundant experimental evidences show that the subgrade fill is generally unsaturated even after compaction. Therefore, many efforts have been paid to analyze the slope stability under the rainfall infiltration of subgrade [18][19][20][21]. Based on the permeability comparison of unsaturated and saturated soils by Daud et al [22], Yadav et al [23] empirically determined the water permeability range of the subgrade slope fill, and obtained the soil-water characteristic curve by analyzing the time trend of water content of the slope fill.…”

The influence of variation in track level and support system stiffness over longer lengths of track for track performance and vehicle track interaction

“…A variety of technologies could be used for this, including high speed video recording of track-mounted targets for digital image correlation, deflectometers anchored at depth, position sensitive devices, lasers and inertial sensors such as geophones or accelerometers [20][21][22][23][24]37]. Track stiffness can be obtained from these types of measurements based on the load-deflection behaviour of the track [38][39][40][41], or by analysing the spectrum of low frequency vibrations without the need to know the load [42,43]. Absolute sleeper levels can be measured from the side of the track by conventional surveying.…”

“…The cost of equipment and potential volume of data have tended to limit the extent of previous deployments to a few sleepers (tens of metres), so most studies have tended to focus on a specific feature e.g. a transition [22,23,[44][45][46] or poor ground conditions [20,41]. Lower cost transducers and data acquisition systems, e.g.…”