Thermomechanical Analysis of Fiber–Bentonite-Based Mixtures as Buffer Material in an Engineered Nuclear Barrier
Publication: Journal of Materials in Civil Engineering
Volume 33, Issue 2
Abstract
Buffer/backfill material is an important part of engineered barriers in deep geological repositories of high-level radioactive waste (HLRW). A good buffer material not only possesses good heat conductivity, expansion, and sealing characteristics, but also exhibits enough strength. Its thermomechanical performance can significantly influence the safety and stability of a HLRW repository. Polypropylene fibers were mixed with bentonite-based mixtures (bentonite–sand–graphite) to form a buffer material with high strength, good heat dissipation capacity, and strong isolation capacities. The effects of fiber content, fiber length, and sand particle size on the shear strength, swelling pressure, and thermal conductivity of fiber–bentonite-based (BSGF) mixtures were analyzed under given graphite and sand contents. Detailed analyses of the shear, expansion, and heat transfer mechanisms of BSGF mixtures were performed to understand the behavior. The results indicated that the strength of BSGF material improved significantly with the addition of fiber content, whereas swelling potential and thermal conductivity were reduced. With an increase in sand particle size, cohesion and maximum swelling pressure decreased, whereas internal friction angle and thermal conductivity increased. The optimum fiber content, fiber length, and sand particle size were determined based on the thermomechanical performance of BSGF mixtures. These findings help in the field application of buffer materials with different fiber contents, fiber lengths, and sand particle sizes.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
Acknowledgments
The financial support from the National Key R&D Program of China (No. 2016YFC0800200), the Scientific Research Foundation of the Graduate School of Southeast University (Grant No. YBPY1977), the Project of Jiangsu Province Transportation Engineering Construction Bureau (No. CX-2019GC02), and the National Natural Science Foundation of China (Nos. 41672294 and 41877231) are gratefully acknowledged.
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Journal of Materials in Civil Engineering
Volume 33 • Issue 2 • February 2021
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© 2020 American Society of Civil Engineers.
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Received: Mar 30, 2020
Accepted: Jun 24, 2020
Published online: Nov 30, 2020
Published in print: Feb 1, 2021
Discussion open until: Apr 30, 2021
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