Development and Application of the Heat Pulse Method for Soil Physical Measurements

Accurate and continuous measurements of soil thermal and hydraulic properties are required for environmental, Earth and planetary science, and engineering applications, but they are not practically obtained by steady-state methods. The heat pulse (HP) method is a transient method for determination of soil thermal properties and a wide range of other physical properties in laboratory and field conditions. The HP method is based on the line-heat source solution of the radial heat flow equation. This literature review begins with a discussion of the evolution of the HP method and related applications, followed by the principal theories, data interpretation methods, and their differences. Important factors for HP probe construction are presented. The properties determined in unfrozen and frozen soils are discussed, followed by a discussion of limitations and perspectives for the application of this method. The paper closes with a brief overview of future needs and opportunities for further development and application of the HP method.