Investigation on anisotropic thermal conductivity of compacted GMZ bentonite

Gaomiaozi (GMZ) bentonite has been considered as a potential material for construction of engineering barrier in Chinese deep geological repository for disposal of high-level nuclear wastes. In the present work, thermal conductivity tests were conducted on statically compacted GMZ bentonite specimens using the needle probe method. Cubic specimens with different initial saturation degrees and dry densities were prepared and the thermal conductivity tests were conducted along the directions both parallel and perpendicular to the bedding plane of the specimen. Results show that the thermal conductivity nonlinearly increases with increasing saturation degree with a transition point that proximately corresponding to the air entry value. Meanwhile, the thermal conductivity along the parallel direction is much higher than that along the perpendicular direction. The anisotropy coefficient decreases with increasing saturation. However, the anisotropy coefficient increases with increasing dry density and the influence depends on saturation degree.