Comparative assessment of transient- and steady-state soil thermal conductivity using a specially designed consolidometer

Precise estimation of soil thermal conductivity is crucial for reliable heat flow analysis in soil. Research indicates variations in soil thermal conductivity values estimated using transient-and steady-state temperature mea-surements. However, sources of such reported differences cannot be specified with certainty. This paper presents the development of a soil thermal conductivity measurement device that enables simulation of a specified stress condition on soil specimens and estimation of both transient-and steady-state soil thermal conductivity values from different segments of a single test. A series of thermal conductivity tests were performed on seven different soils using the specially-designed test setup. The difference in soil thermal conductivity values obtained from transient-and steady-state responses are compared to those reported in the literature. In contrast to steady-state soil thermal conductivity, results indicate an increase in transient-state soil thermal conductivity beyond a threshold value of the rate of soil temperature increment during the transient-state measurement. Furthermore, empirical relations are suggested to correlate soil thermal conductivity of fine-grained soils with plasticity index, hydraulic conductivity, and coefficient of consolidation.

Automated summary

This paper presents the development of a new soil thermal conductivity measurement device that can simulate soil under different stress conditions and estimate both transient and steady-state thermal conductivity. The results from tests on seven different soils show that the transient-state thermal conductivity increases beyond a certain threshold value of temperature increment rate.