Permafrost refers to ground (soil or rock) that remains at or below 0 °C (32 oF) for at least two years. About half of Canada is underlain by permafrost and it exists extensively throughout the northern region. The exploitation of the non-renewable resources of this region requires the development of a transportation network including railway lines over the permafrost. The general understanding about permafrost is that it can provide adequate bearing capacity. However, the thermal stability of frozen ground is very sensitive. This balance is subjected to change due to various reasons such as construction activities and climate warming. The change in thermal equilibrium may initiate thawing and lead to permafrost degradation. The more rapid warming trend in the north has raised concerns regarding the development and maintenance of transportation infrastructure in this region.
The National Research Council Canada (NRC) in collaboration with the Transport Canada has conducted an extensive literature review to document the current state of knowledge regarding the design, construction and maintenance of transportation infrastructure, in particular railway tracks, on permafrost regions around the world. This review includes:
- an overview to the ground thermal regime and the effects of various parameters such as snow, vegetation, construction activity, etc. on the thermal stability of permafrost (section 1),
- different types of permafrost and their distributions in Canada (section 2).
- projected temperate in northern Canada under future climate and its economic impacts on the critical infrastructure of this region (section 3)
- the major challenges encountered during the construction and operation of railway lines in permafrost regions around the world along with a detailed historical description of the design, construction, and maintenance of the Hudson Bay railway line in Canada (section 4).
- the major considerations for the design and construction of transportation infrastructure in permafrost regions, recommended by various codes and standards in Canada (sections 5).
- an extensive review of the mitigation methods that are commonly used to preserve the stability of transportation infrastructure in permafrost regions, their cost, effectiveness, and long term performance in stabilizing railway embankments (section 6).
- the practical considerations for construction of railway embankment to minimize disturbance to the ground thermal stability during construction (section 7).
- introducing the proposed 110 km railway line to connect the Baffinland iron ore mine (located on Baffin Island, Nunavut) to Milne Inlet (section 8).
- the state of permafrost research in Canada and around the world based on analyzing the number of publications listed in Scopus (section 9)
- expert opinions concerning the most significant gap in the current state of knowledge regarding the construction of transportation infrastructure over permafrost regions in Canada (section 10).