Thermal effects in permafrost

The role of climate and, in particular, air temperature in determining the geographical distribution of permafrost is discussed briefly for Canadian conditions. The thermal properties of permafrost materials and the climatic factors that make up the surface heat balance are discussed in general terms. The importance of surface materials in determining the ground thermal regime is illustrated by a number of theoretical calculations based on a one- dimensional finite-difference model. Using a simplified two- dimensional finite-difference model, theoretical calculations of thawing round a hot oil pipeline and freezing around a cold gas pipeline are presented and the settlement and stability problems that would result are discussed qualitatively. The importance of drainage and the effect of water bodies on permafrost is commented on. Finally, a brief review is given of current design and construction practice to minimize thermal disturbance when placing fills and foundations in permafrost regions.