Soil thermal properties for the design of underground structures in cold regions

A reliable method of measuring soil thermal resistivity using the thermal probe is presented. A field and laboratory survey of 100 Canadian soils was used to compile a thermal properties database. The soils were grouped according to the Unified Soil Classification System (modified) and the thermal dryout curve (thermal resistivity versus moisture content) envelopes defined. Although the thermal dryout curve for a given soil may be placed within a specified envelope, its exact shape and position are determined by other parameters (ie. dry density, organics, mineral composition, particle shape, fines content, etc.) and their complex inter-relationship. The influence of ambient temperature on the thermal resistivity was investigated. For wet soils above 0 degrees C, resistivity decreases as temperature increases; at 0 degrees C there is a dramatic reduction (20 to 40%) in the resistivity; below 0 degrees C resistivity decreases as temperature decreases.