Introduction

Frozen soil is defined as a soil where the soil moisture has turned totally or partially into ice. On the other hand, permafrost is defined solely on the basis of soil temperature. If the soil temperature remains below 0 °C for at least two years, the soil is considered permafrost. The upper layer of the permafrost undergoes a cyclic temperature change during the year from frozen in the winter to thawed in the summer. This layer is called the active layer or seasonally thawed layer. The active layer in a permafrost region can extend from as little as 20 cm to about 2 m (Shur et al. 2005) depending on climate, soil texture, and organic content above mineral soil. In areas without permafrost the layer of soil which is frozen in the winter is called the seasonally frozen layer. Most permafrost on earth is thousands of years old, but some can be quite new. In permafrost regions, contaminant impacts generally initiate at or near the soil surface and affect the active layer, suprapermafrost water, and uppermost permafrost (Chapter 3). It is this realm that most concerns environmental scientists and engineers tasked with environmental cleanup. A thorough understanding of properties of the active layer and the upper permafrost is necessary for planning and implementing effective remediation of cold media.

Review and recent advances

Thermal and physical properties of frozen ground

Thermal conductivity of soils

The thermal conductivity of soil is the measure of its ability to conduct heat. Soil thermal conductivity is a function of the thermal state of the ground (frozen or unfrozen), water content, dry density, gradation, and mineralogy.