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Cracking and sealing behavior of the compacted bentonite upon technological voids filling
Abstract The technological voids, which are inevitably formed during the construction of the deep geological repository for high-level radioactive nuclear waste, have negative influence on the hydro-mechanical properties of the engineered barrier. In this study, hydration tests along with image acquisition were carried out on compacted GMZ bentonite samples with simulated technological voids to investigate the self-sealing behavior and research emphasis was placed on the cracks appearing during the hydration. Results showed that with the presence of technological voids, the self-sealing process of the hydrating sample can be visually divided into cracking and closing stages, both of which were affected by the sample preparation process, the void width, and the sample height. The hydration cracks occurred at the early phase was considered as tensile cracks induced by the failure of tensile strength against the tensile stress induced by the difference of swelling strain. At the end of hydration, though the cracks were closed with the sealing of technologicalvoids, the distributions of water content and dry density along the sample diameter were found in a decreasing and an increasing trend with the increasing distance from the technological voids, respectively. By applying the image processing method, the cracking and sealing behaviors were further studied with the reciprocal verification of digital images and grey scale profiles. A good agreement between the grey scale profiles and digital images was found and the quantifiable grey values could accurately reflect the color difference on the samples which was difficult to be distinguished by the naked eye, showing the applicability and superiority of image processing technology.
Highlights Hydration cracks were found on the compacted bentonite during the self-sealing process. Two stages can be identified in the self-sealing process: a cracking stage and a closing stage. The digital images could be quantified by the grey scale values accurately. Heterogeneous distributions of water content and dry density existed due to the effect of technological voids.
Cracking and sealing behavior of the compacted bentonite upon technological voids filling
Abstract The technological voids, which are inevitably formed during the construction of the deep geological repository for high-level radioactive nuclear waste, have negative influence on the hydro-mechanical properties of the engineered barrier. In this study, hydration tests along with image acquisition were carried out on compacted GMZ bentonite samples with simulated technological voids to investigate the self-sealing behavior and research emphasis was placed on the cracks appearing during the hydration. Results showed that with the presence of technological voids, the self-sealing process of the hydrating sample can be visually divided into cracking and closing stages, both of which were affected by the sample preparation process, the void width, and the sample height. The hydration cracks occurred at the early phase was considered as tensile cracks induced by the failure of tensile strength against the tensile stress induced by the difference of swelling strain. At the end of hydration, though the cracks were closed with the sealing of technologicalvoids, the distributions of water content and dry density along the sample diameter were found in a decreasing and an increasing trend with the increasing distance from the technological voids, respectively. By applying the image processing method, the cracking and sealing behaviors were further studied with the reciprocal verification of digital images and grey scale profiles. A good agreement between the grey scale profiles and digital images was found and the quantifiable grey values could accurately reflect the color difference on the samples which was difficult to be distinguished by the naked eye, showing the applicability and superiority of image processing technology.
Highlights Hydration cracks were found on the compacted bentonite during the self-sealing process. Two stages can be identified in the self-sealing process: a cracking stage and a closing stage. The digital images could be quantified by the grey scale values accurately. Heterogeneous distributions of water content and dry density existed due to the effect of technological voids.
Cracking and sealing behavior of the compacted bentonite upon technological voids filling
Wang, Qiong (author) / Meng, Yuhong (author) / Su, Wei (author) / Ye, Weimin (author) / Chen, Yonggui (author)
Engineering Geology ; 292
2021-06-20
Article (Journal)
Electronic Resource
English
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