Various factors, such as the volumetric fraction of constituents, mineralogy, and pore fluids, affect heat flow in granular materials. Although the stress applied on granular materials controls the formation of major pathways for heat flow, few studies have focused on a detailed investigation of its significance with regard to the thermal conductivity and anisotropy of the materials. This paper presents a numerical investigation of the stress-induced evolution of anisotropic thermal conductivity of dry granular materials with supplementary experimental results. Granular materials under a variety of stress conditions in element testing are analyzed by the three-dimensional discrete element method, and quantitative variations in their anisotropic effective thermal conductivity are calculated via the network model and conductivity tensor measurements. Results show that the directional development of contact area and fabric under anisotropic stress conditions leads to the evolution of anisotropy in thermal conductivity. The anisotropy induced in thermal conductivity by shear stress is higher than that induced by compressive stress because shear stress causes more significant changes in microstructural configurations and boundary conditions. The shear-stress-induced evolution of anisotropy between principal thermal conductivities depends on dilatancy as well as shearing mode, and the shear-driven discontinuity localizes the conductivity. Factors involved in the stress-induced evolution and their implications on the thermal conductivity characterization are discussed.
Bibliographical noteFunding Information:
Acknowledgments The authors are grateful to Dr. Eui-Ryong Jang at Seoul National University for his valuable comments on the DEM simulations. The expert opinion from the anonymous reviewers is greatly appreciated. Financial support for this work was provided by a grant from a Strategic Research Project Development of Extreme Cold Region Site Investigation and Monitoring System funded by the Korea Institute of Construction Technology (KICT), the basic science research program through National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 2011-0005593), and the Korea Institute of Geosciences and Mineral Resources (KIGAM).
All Science Journal Classification (ASJC) codes
- Geotechnical Engineering and Engineering Geology
- Earth and Planetary Sciences (miscellaneous)