Effect of drying cracks on swelling and self-healing of bentonite-sand blocks used as engineered barriers for radioactive waste disposal

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外文摘要：Experiments were conducted to evaluate the healing of drying cracks in air-dried bentonite-sand blocks after hydration and swelling in groundwater,providing justifications to simplify the protection of blocks prior to installation in a high-level radioactive waste repository.Synthetic groundwater was prepared to represent the geochemistry of Beishan groundwater,and was used to hydrate the blocks during the swelling pressure and swelling strain measurements,as Beishan is the most promising site for China's repository.Healing of the surface cracks was recorded by photography,and healing of the internal cracks was visualized by CT images and hydraulic conductivity of air-dried blocks.The results indicate that the maximum swelling pressure and swelling strain are primarily affected by the geochemistry of Beishan groundwater,but not affected by the drying cracks.The maximum swelling pressure and swelling strain of air-dried blocks are comparable to or even higher than the pressure and strain of fresh blocks.The maximum swelling pressure measured in strong(i.e.high ion strength)Beishan groundwater was 44％of the pressure measured in deionized(DI)water,and the maximum swelling strain was reduced to 23％of the strain measured in DI water.Nevertheless,the remained swelling of the blocks hydrated in strong Beishan groundwater was sufficient to heal the surface and internal drying cracks,as demonstrated by the pictures of surface cracks and CT images.The hydraulic conductivity of the air-dried block permeated with strong groundwater was comparable(3.7 x higher)to the hydraulic conductivity of the fresh block,indicating the self-healing of drying cracks after hydration and swelling in groundwater.A simplified method of protecting the block with plastic wraps before installation is recommended,since the remained swelling of the block hydrated in Beishan groundwater is sufficient to heal the drying cracks.

外文关键词：

Beishan groundwater chemistryBentonite bufferDrying cracksHigh-level radioactive waste(HLW)Self-healingSwelling

作者：

Yu Tan、Guangping Zhou、Huyuan Zhang、Xiaoya Li、Ping Liu

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作者单位：

School of Civil Engineering and Mechanics,Lanzhou University,Lanzhou,730000,China

Key Laboratory of Mechanics on Disaster and Environment in Western China(Lanzhou University),Ministry of Education,Lanzhou,730000,China

Civil and Environmental Engineering,University of Wisconsin-Madison,WI,53706,USA

基金：

国家自然科学基金中央高校基本科研业务费专项Gansu Province Science FoundationEnvironmental Research and Education Foundation

项目编号：

41972265lzujbky-2021-5720JR10RA492

出版年：

2024

DOI：

10.1016/j.jrmge.2023.07.025

岩石力学与岩土工程学报(英文版)

中国科学院武汉岩土力学所中国岩石力学与工程学会武汉大学

岩石力学与岩土工程学报(英文版)

CSTPCD

影响因子：0.404

ISSN：1674-7755

年,卷(期)：2024.16(5)

参考文献量86