What is permafrost?
Figure 1 Modified from Heginbottom et al. (1995). cartography by B. O’Neill. The National Atlas of Canada; Natural Resources Canada, Geomatics Canada, MCR Series no. 4177, 1995, 1 sheet, https://doi.org/10.4095/294672 (Open Access)
What is ground ice?
Figure 2 a) Example of ice wedge polygons (Copyright Government of Northwest Territories) b) Massive ice exposed in the headwall of a retrogressive thaw slump near Holmes Creek NWT (Photo by Trevor Lantz)
What is the active layer?
Figure 3 a) Trumpet curve of permafrost thermal profile. The maximum depth affected by the annual temperature variations is called the depth of zero annual amplitude; it varies with air temperature and the type of soil (ADAPT, http://www.cen.ulaval.ca/adapt/communications/permafrost101.php). b) Slump exposing the ice-free active layer sitting above a large ice wedge. Photo credit: Benjamin Jones, USGS, Public Domain (Modified by NASA)
What is a talik?
Figure 4 Changes in active layer thickness (ALT) in response to climate warming. ALT reaches a maximum prior to talik development. Figure from Connon et al., 2018
Why is permafrost changing?
Why is permafrost important?
Figure 5 Oblique overview of Dempster Highway km 27, NWT showing road embankment and permafrost thaw related disturbances (van der Sluijs et al., 2018).
Permafrost Engineering is the application of engineering principles in areas where permafrost may be present, and design conditions are affected by temperatures below 0°C. These conditions mostly exist in high northern and southern latitudes or at high elevations. In recent years, engineering projects and developments in cold environments has increased in importance due to access required to enable mining of natural resources, resource transportation (e.g., pipelines), or in improving infrastructure and accessibility (e.g., infrastructure corridors).
For engineering purposes, it is important to appreciate the physical differences in the materials that may be encountered and used as foundations or for construction such as snow, firn, and ice in special forms, including sea ice, glacier ice, pore ice, segregated ice, ground ice, ice shelves or icebergs. However, understanding the conditions that prevail in the cryosphere is also required for the design of conditions that are artificially induced, for example, artificial ground freezing used to increase the strength of the ground temporarily to build tunnels, caverns, or shafts (e.g. Thermosphyons)
Thermosyphons (Photo Courtesy of BGC Engineering Inc.)
In addition to challenges resulting from the complex material properties, other notable challenges are related to the logistics, such as the remoteness of a site, availability of site investigation equipment and construction material, or access in steep and mountain environments. Further the effects of the harsh climatic conditions, including cold temperatures, darkness at high latitude, or major diurnal air temperature variations and low oxygen levels in high mountain areas, are wearing on equipment and people. This often results in limited information for the design, such as site investigation or historical climate data. However, the latter is important in carrying out future projections and designing for potential effects from climate change. Since the cryosphere is often found in environments that are ecologically very sensitive, it is important to understand how a planned infrastructure affects the environment and it is essential to select an appropriate adaptation strategy.