A New Apparatus for Measuring Thermal Properties of Soils and Rock in Situ

To interpret the results in thermal remote sensing and to study the problem of heat storage in the ground, it is necessary to be able to determine in situ two independent thermal properties of each layer. A former system, in which heating wire and two probes were inserted into the ground was not convenient for coarse soils containing gravels or pebbles and for rocks. The new apparatus necessitates only to be put in close contact with the surface of the material to measure. The sensor consists of a block of silastene containing heating wire and the two temperature probes. The temperature difference is measured at two or three intervals of time after the beginning of the heating. Master curves are used to deduce the conductivity and the diffusivity of the material. The calculation of the temperature difference is made by the finite element method.