ZENG Z T, CAO S S, LIN M Y,et al.Evolution of water retention performance and its micromechanism in compacted bentonite buffer materials under alkali-thermal conditions[J].Journal of Henan Polytechnic University(Natural Science) ,2026,45(4):180-189.

doi:10.16186/j.cnki.1673-9787.2024110058

Received:2024/10/27

Revised:2024/12/31

Published:2026/06/17

Evolution of water retention performance and its micromechanism in compacted bentonite buffer materials under alkali-thermal conditions

Zeng Zhaotian1, Cao Shanshan1, Lin Mingyu1, Li Gongyan1, Liang Zhen1,2

1.Guangxi Key Laboratory of Geotechnical Mechanics and Engineering， Guilin University of Technology，Guilin  541004，Guangxi， China;2.Xinjiang Transportation Planning Survey and Design Institute Co.， Ltd.， Urumqi  830006， Xinjiang， China

Abstract: Objectives During the continuous operation of a deep geological repository， groundwater in the surrounding rock continuously erodes the lining concrete， causing it to gradually age and decompose， producing highly alkaline solutions. Meanwhile， the nuclear waste in the repository continuously decays and generates heat， steadily raising the temperature inside the repository environment. Under these alkali-thermal conditions， the water retention performance of the bentonite buffer layer material will change. To ensure the effectiveness of the buffer barrier performance， an in-depth investigation into its water retention performance was conducted.  Methods The saturated salt solution method was employed to determine the water retention performance curves （degree of saturation S_r vs. suction s） of compacted MX80 bentonite specimens under alkali-thermal conditions. The effects of alkali solution concentration （C_NaOH=0， 0.1， 0.3， 1.0mol/L） and temperature （T=20， 60， 90℃） on the water retention performance were investigated. Combined with previous XRD and MIP test results from the research group， the mechanisms by which alkali concentration and temperature affect water retention performance were analyzed. Results The results indicate that under alkali-thermal conditions， the water retention performance of compacted bentonite specimens decreases with increasing alkali concentration and temperature. The higher the alkali concentration and temperature， the more significantly the water retention performance degrades. The change in water retention performance of bentonite under alkali-thermal conditions is caused by the alteration of montmorillonite content. Temperature accelerates the alkali-induced dissolution of montmorillonite， indirectly leading to a decline in water retention performance. The water retention performance of bentonite decreases with the reduction of montmorillonite content， and there is a clear linear relationship between the two. Conclusions The evolution of water retention performance of bentonite under alkali-thermal conditions was thoroughly discussed. The research results can provide scientific data support for the prediction of hydraulic conductivity and the performance evaluation of engineering barriers.

Key words:MX-80 bentonite;alkali-thermal condition;water retention performance;mineral composition;micromechanism