Geothermal Modelling of Ground Thermal Regime Beneath a Highway Embankment on Degrading Permafrost

David Flynn, Marolo Alfaro, Jim Graham

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

Session: Cold Regions Geotechnics

ABSTRACT: Changes in temperature can lead to thawing and degradation of permafrost and consequent issues related to the integrity of linear infrastructure such as highways. This paper presents thermal numerical modelling for an instrumented highway embankment on degrading permafrost. The instrumented site is located 18 km north of Thompson, Manitoba on Provincial Road (PR) 391. Thermistors were installed beneath the toe, mid-slope, shoulder and centerline of the embankment. Monitored ground temperatures were used to calibrate the thermal numerical model. RÉSUMÉ Les changements en température mènent à la dégel et à la dégradation du pergélisol et en conséquence il y a des issues relier à l'intégrité linéaire de l'infrastructure tel que des routes. Ce papier présent la modélisation thermique numérique de la dégradation du pergélisol pour une levée instrumentée d'autoroute. Le tel site est situé 18km au nord de Thompson, Manitoba sur la route provinciale 391. Des thermistances étaient installées en-dessous du front, de la mi-pente, de l'accotement et de la ligne médiane de la levée. Des températures du sol régulées ont été utilisées pour calibrer le modèle thermique numérique. 1 INTRODUCTION Development in northern Canada is important for the socio-economic well-being and protection of national sovereignty of the region. Northern Canada is sparsely populated and communities are often remotely connected. Transportation infrastructure is crucial to provide a link to promote development of these communities and the nearby natural resources such as petrocarbons, minerals, and hydro power. Nearly half of the land surface in Canada is underlain by permafrost, primarily in high altitude and northern regions. Permafrost thickness can vary from several hundred metres in the continuous permafrost regions in the Arctic to thin and sporadic thicknesses found in the southern discontinuous permafrost regions. Figure 1 shows the extent of permafrost in Manitoba. The project site, near Thompson, Manitoba, is located within a region of discontinuous permafrost. The permafrost becomes continuous to the north near Churchill, Manitoba on Hudson Bay. Construction in northern Manitoba follows similar practices to those used in the south. Thermal conductivities of fill materials and asphalt pavement are typically higher than the native soils they displace. Construction and maintenance practices involve vegetation removal, and changes to both the drainage patterns and snow removal. These factors contribute to increased heat transfer to previously frozen ground, disturbances to the existing thermal regime, and can lead to thawing and degradation of the embankment. Transport Canada, Manitoba Infrastructure and Transportation (MIT), and the University of Manitoba (UM) are working together to find improvements to the design, construction, and maintenance of highways in regions of permafrost. This collaborative effort includes providing support to projects that involve field instrumentation, monitoring, laboratory testing, and numerical modelling. This paper presents thermal modelling currently underway on a project site located 18 km north-west of Thompson, Manitoba on Provincial Road 391 as shown in Figure 1. The highway is located in discontinuous permafrost and is the only road that connects other remote northern communities, hydro generating stations and mines in north-western Manitoba Figure 1: Location of Test Site and Permafrost in Manitoba

RÉSUMÉ: ermal Modelling of Ground Thermal Regime

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Cite this article:
David Flynn; Marolo Alfaro; Jim Graham (2014) Geothermal Modelling of Ground Thermal Regime Beneath a Highway Embankment on Degrading Permafrost in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper248,author = David Flynn; Marolo Alfaro; Jim Graham,title = Geothermal Modelling of Ground Thermal Regime Beneath a Highway Embankment on Degrading Permafrost ,year = 2014}