Comparison of a Modified Transient Plane Source and Transient Line Source Techniques for Measuring the Thermal Conductivity of Two Sands

Experiments were conducted to compare two laboratory techniques for measuring thermal conductivity of unsaturated soils: ( 1) a modified transient plane source (MTPS) method for non-destructive measurements using a planar, interfacial heat reflectance sensor; and (2) a transient line source (TLS) method utilizing a single-probe heat source. Thermal conductivity and thermal conductivity dry out curves (TCDCs) were measured for two sands, including a poorly graded sand, and a well-graded sand with silt. The MTPS sensor resulted in larger thermal conductivity values than the TLS sensor for pore water saturations greater than 50%. At low pore water saturation, the MTPS sensor potentially underestimates thermal conductivity due to poor sensor-soil contact potentially resulting from the absence of water bridges between the sensor and soil surface.