Numerical and Physical Modelling of Road Embankments on Seasonally-Frozen Peat

Earl Marvin de Guzman, Marolo Alfaro

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Transportation Geotechnics

ABSTRACT: Test sections of road embankment on seasonally-frozen peat were instrumented to investigate their performance and to develop more economical method of construction. Test ‚Section A' was constructed with geotextile base layer while ‚Section B' was with geotextile and corduroy. Laboratory-scale physical modelling is undertaken to understand further the operating mechanisms involved in the performance of the two test sections under a more controlled environment. Artificial transparent clay that has similar deformation properties with most of the natural clays and peats was used as foundation material. It allows determination of spatial deformations beneath the embankment using Particle Image Velocimetry (PIV) technique. A commercially-available computer program is used in the numerical modelling to simulate the field performance of instrumented sections. The results from numerical modelling are reasonably close to the measured values in the field. The load-settlement behaviour in the field is reasonably simulated in the laboratory-scaled physical model. Deformation patterns from PIV indicate that embankment with geotextile layer and corduroy has smaller lateral movements in the foundation compared to that of the embankment with only geotextile layer. RÉSUMÉ Des sections d'essais de la levée de route sur de la tourbe saisonnière gelée ont été instrumenté pour examiner leur performance et pour développer une méthode de construction plus économique. La section d'essai ‚A' a été construite avec une base de géotextile tandis que la section ‚B' était avec du géotextile et des ondulations transversales. La modélisation physique à l'échelle laboratoire s'engage à mieux comprendre les mécanismes d'opération impliqués dans la performance des deux sections d'essais dans un environnement mieux contrôler. L'argile transparente artificielle, qui a des propriétés de déformation similaire à des argiles et des tourbes naturelles, a été utilisée comme le sol de fondation. Ceci permettre la détermination des déformations spatiales sous la levée en utilisant une technique de vélocimétrie par images de particules (PIV). Un programme d'ordinateur, disponible commercialement, est utilisé par la modélisation numérique pour simuler la performance en champ des sections instrumentées. Les résultats de la modélisation numérique sont suffisamment proches aux données mesurées dans le champ. Le comportement du charge-tassement dans le champ est simulé dans la modélisation physique à l'échelle laboratoire. Des patrons de déformation de la PIV indique que la levée avec des géotextiles et des ondulations transversales ont de plus petits mouvements dans la fondation comparer à celui avec seulement la base de géotextile. 1 INTRODUCTION In Northern Manitoba, hundreds of kilometers of roads are built over peat terrain Peat is a highly compressible material with very low shear strength, very high moisture content, and very high organic content. Past methods of highway embankment construction over peat deposits included excavation or displacement of peat that resulted in large fill quantities. In many cases fill materials are obtained from bedrock quarries at great distances from work area. A research partnership was established to improve the understanding of the performance of road embankments on peat terrain in Northern Manitoba. The partners are Manitoba Infrastructure and Transportation (MIT), AECOM Ltd., and the University of Manitoba. The research involved design, construction, and monitoring of a 2km stretch of new road along the Provincial Road (PR) 373, 200km southeast of Thompson, Manitoba. The emphasis on embankment construction for this project is the displacement method or without removal of peat. This can result to large settlements, which is a concern for both design and long term maintenance operations. Two test sections were instrumented for this study to improve embankment performance on peat deposits. Test Section A has geotextile wrap-around reinforcement placed at the base of the embankment (Figure 1). Test Section B has geotextile wrap-around reinforcement at the base and timber logs placed near the toe (Figure 2). Both sections have been constructed when the ground was still frozen for ease of construction and to minimize the negative impact to the environment. This paper is a continuation of the results presented by De Guzman & Alfaro (2013a, 2013b) and will focus on the numerical and physical modelling of the test sections. Figure 1. Schematic diagram of embankment with geotextile wrap-around reinforcement

RÉSUMÉ: ical and Physical Modelling of Road Embankments on Seasonally-Frozen Peat

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Earl Marvin de Guzman; Marolo Alfaro (2014) Numerical and Physical Modelling of Road Embankments on Seasonally-Frozen Peat in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper112,author = Earl Marvin de Guzman; Marolo Alfaro,title = Numerical and Physical Modelling of Road Embankments on Seasonally-Frozen Peat,year = 2014}