Thermal conductivity of GMZ bentonite pellet mixtures with different grain-size distributions

ZHANG Zhao; YE Weimin; LI Yuwan; HE Yong; WANG Qiong; CHEN Yonggui

doi:10.11779/CJGE20231186

Volume 47 Issue 7

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Chinese Journal of Geotechnical Engineering > 2025 > 47(7): 1527-1535. > DOI: 10.11779/CJGE20231186

ZHANG Zhao, YE Weimin, LI Yuwan, HE Yong, WANG Qiong, CHEN Yonggui. Thermal conductivity of GMZ bentonite pellet mixtures with different grain-size distributions[J]. Chinese Journal of Geotechnical Engineering, 2025, 47(7): 1527-1535. DOI: 10.11779/CJGE20231186

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Thermal conductivity of GMZ bentonite pellet mixtures with different grain-size distributions

ZHANG Zhao^{1, 2,},
YE Weimin^1, ,,
LI Yuwan^{1, 3},
HE Yong^{1, 2},
WANG Qiong¹,
CHEN Yonggui¹

1.
Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education, Tongji University, Shanghai 200092, China
2.
School of Geosciences and Info-Physics, Central South University, Changsha 410083, China
3.
CSSN Institute of the Engineering Investigation & Design Co., Ltd, Shanghai 200063, China

Funds:

the National Key Research and Development Program of China 2019YFC1509900

the National Natural Science Foundation of China 42207227

the Natural Science Foundation of Hunan Province 2022JJ40586

More Information

Received Date: December 03, 2023
Revised Date: November 04, 2024
Accepted Date: November 18, 2024
Available Online: December 18, 2024
Published Date: November 19, 2024

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Abstract

Abstract

The bentonite pellet mixture has been proposed as a candidate backfilling material for technological gaps in deep geological repositories for disposal of high-level radioactive waste. Its thermal conductivity plays an important role in the safety assessment of the repository. In this study, a series of thermal conductivity tests are conducted on the GMZ bentonite pellet mixtures with different grain-size distributions. The results demonstrate that as the pellet size increases, the thermal conductivity of the mixtures firstly increases and then decreases for the specimens freely filled. However, the thermal conductivity monotonically decreases with the increase of the pellet size for the specimens packed at a given dry density. During the hydration process, the time-history curves of thermal conductivity for the pellet mixtures with different grain-size distributions can be approximately divided into a rapidly increasing stage and a stable stage. Meanwhile, the evolution and the stable time of thermal conductivity are both influenced by the particle composition. The bentonite pellets are swelled to fill the inter-pellet pores upon hydration, and the infiltration frontier gradually moves from the top/bottom part to the middle one, which is accompanied by a gradually structural transformation from a granular structure into a continuously homogeneous one. After approaching to the saturated state, the relationship between the thermal conductivity and the dry density for the bentonite pellet mixtures shows a good consistency to that of the compacted bentonite blocks.
- deep geological disposal,
- bentonite pellet,
- thermal conductivity,
- grain-size distribution

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References (25)

References

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