There is a growing need to improve the understanding of the behaviour of infrastructure in permafrost regions. Permafrost affects nearly half of the land surface in Canada, especially in the north. Further development of natural resources in northern Canada will provide socio-economic benefits to the region and its residents. Linear infrastructure, such as highways, is an important part of that development. The integrity of infrastructure in northern regions is negatively impacted by thawing and degradation of the underlying permafrost initiated by changes in both air and ground temperatures. Subsequent deformations due to settlement and lateral spreading can lead to potentially hazardous driving on highways. The author’s research focused on a section of highway embankment on Provincial Road (PR) 391 located 18 km north of Thompson, Manitoba. The purpose of the research was to further understanding of the thermal and deformation behaviour of an embankment subjected to degrading permafrost conditions. The author’s research consisted of laboratory testing, instrumentation installation, data monitoring, and numerical modelling. Laboratory tests on four-inch (101.6 mm) diameter Shelby tube samples characterized the soil at the site. Data were collected remotely via satellite, and included ground temperatures, pore water pressures, and displacements both laterally and vertically. Ground temperatures indicated a frost bulb, a region of frozen ground, under the embankment. Thermal models using TEMP/W simulated the current ground thermal regime and projections of future thermal behaviour of the embankment. Deformation numerical models using SIGMA/W incorporated changes in the size of the frost bulb over a freeze-thaw cycle to simulate the deformation behaviour of the embankment. The numerical models were compared with the collected data.

In this research, two comprehensive numerical models were developed using ABAQUS/CAE Finite Element (FE) software: 1) geothermal model, and 2) coupled thermo-hydro-mechanical model. In the first model, a purely heat transfer analysis was performed to reproduce the conditions at the site and investigate the subsurface thermal regime beneath the road embankment. The existence of a frozen section (frost bulb) underneath the embankment and its size and location were investigated by the model. The second model concentrated on the mechanical behaviour of the road embankment. Temperature-dependent thermal and mechanical properties were used for all the materials. Model parameters were calibrated using the results of the triaxial and oedometer tests which have been conducted by previous researchers. A fully-coupled and a sequentially-coupled analysis were conducted. The results of the two analyses were compared to each other and to the field measurements. / February 2016