Surface-coupled three-dimensional geothermal model for study of permafrost geothermal regime in a building environment

In many Canadian northern communities the stability of building foundation systems relies on the strength of the underlying permafrost. Building deterioration owing to the loss of this strength or stability would profoundly affect the economies and well-being of the surrounding communities. Although studies of permafrost geothermal regime in natural conditions have been conducted for a long time, studies of ground temperature and its spatial pattern and trend in a building environment are limited. The need for the study is more pressing with the projection of climate warming. Detailed information about the pattern and trend of ground temperature and active layer thickness dynamics under climate warming is essential for examination of potential permafrost degradation, as well as its impacts on buildings that are built on/in it. To quantify geothermal responses, and then permafrost degradation, to climatic change in different locations underneath a building, a surface-coupled three-dimensional geothermal model was developed. The model is physical process-based and couples heat and water processes at ground surface and subsurface with simulation of incoming solar radiation and precipitation distributions surrounding and underneath a building by accounting for the effect of the building's dimensions and orientation on the energy and water balance processes at the ground surface. This paper describes the theoretical basis upon which the model is built, the specific factors, and processes considered to represent the permafrost environment surrounding and below buildings, as well as the testing of the model with two different data sets and a theoretical model.