Investigation of initial hydration and rehydration of geosynthetic clay liners from sandy subgrades via X-ray computed tomography images |
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| Affiliation: | 1. VNU Key Laboratory of Geo-environment and Climate Change Response, University of Science, Vietnam National University, Hanoi, Viet Nam;2. Faculty of Advanced Science and Technology, Kumamoto University, Japan;3. Vietnam Japan University, Vietnam National University, Hanoi, Viet Nam;4. Faculty of Geology, University of Science, Vietnam National University, Hanoi, Viet Nam;1. Department of Civil Engineering, National Central University, Jhongli, Taiwan, ROC;2. Department of Mass Rapid Transit, Sinotech Engineering Consultant, Ltd, Taipei, Taiwan, ROC;1. State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures, Shijiazhuang Tiedao University, Shijiazhuang, 050043, China;2. School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang, 050043, China;1. School of Civil Engineering, Central South University, Changsha, 410075, China;2. School of Mechanics and Engineering Science, Shanghai University, Shanghai, 200444, China;3. College of Civil Engineering, Henan University of Technology, Zhengzhou, 450001, China;4. School of Civil Engineering, Changsha University of Science & Technology, Changsha, 410114, China;1. State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu, 610059, China;2. MOE Key Laboratory of Deep Earth Science and Engineering, Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu, 610065, China |
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| Abstract: | The hydraulic conductivity of geosynthetic clay liners (GCLs) widely used as barrier systems considerably depends on their hydration status after the initial hydration of virgin GCLs and the rehydration of desiccated GCLs. Free hydration tests were performed on virgin and desiccated GCLs over sandy subgrades to compare their hydration level. In addition, high-resolution micro-X-ray computed tomography (CT) images of both GCLs and sandy subgrades with different gravimetric water content (i.e. 15%, 20%, and 25%) after the initial hydration were analyzed for better insights. The results show significant influences of subgrade water content on moisture content and thickness of virgin GCLs. Water loss of sandy subgrades and the time interval necessary for reaching a steady state of desiccated GCLs during rehydration was greater and longer than virgin GCLs during initial hydration. X-ray CT images verified a dense distribution of bentonite particles, macropores, and minor desiccation cracks that existed in poorly-hydrated GCLs over unsaturated sand. On the other hand, the completely saturated sandy subgrade facilitated the hydration of GCLs, leaving a lot of macropores in the sand. The relationship between water distribution and the frequency of macropore generation observed in the upper contact zone of sandy subgrades was also indicated via these X-ray CT images. |
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| Keywords: | Initial hydration Rehydration Pore structures Geosynthetic clay liners Sandy subgrades X-ray CT images |
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