The Thermal Probe—Measurement of the Thermal Conductivity and Drying Rate of Soil in the Field
The thermal probe is a metal rod with an internal heating element and temperature sensor. In the field it is pushed into a predrilled hole in otherwise undisturbed soil, and the thermal properties of the soil are estimated from the temperatures recorded at intervals after a constant power is supplied to the heating element. The following are discussed in this paper: the theory behind the methods for identifying the thermal properties, the design of the probe and auxiliary equipment, the results of laboratory trials, the field testing procedures, and the results of field trials. The probe, the theory, and the testing procedures extend the application of thermal probes from their traditional use for thermal conductivity measurement beyond their more recent use for the study of the thermal stability of soil near underground power cables to the measurement of native thermal conductivity, dry thermal conductivity, and the rate at which drying fronts move within the soil.