Stress-dependent temperature effect on the swelling behavior of compacted GMZ bentonite
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ORIGINAL PAPER
Stress-dependent temperature effect on the swelling behavior of compacted GMZ bentonite Wei-Min Ye 1,2 & Yang Wang 1 & Qiong Wang 1 & Yong-Gui Chen 1 & Bao Chen 1 Received: 22 July 2019 / Accepted: 8 April 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A series of temperature-controlled swelling pressure and swelling strain tests were performed on Gaomiaozi (GMZ) bentonite to study the temperature effects on the swelling behavior. The influence of sample dry densities (for swelling pressure tests) and applied various vertical stresses (for swelling strain tests) were taken into account. Emphasis was put on the stress-dependent properties of temperature effects. Results show that at a certain temperature, there is a unique relationship between the stress level and the void ratio of saturated bentonite specimens for either the swelling pressure or swelling strain tests. This relationship could be defined as “swelling stable line” (SSL), which was bilinear shaped and reflects a stress-dependent swelling behavior of compacted bentonite. This stress-dependent swelling behavior is attributed to the different hydration mechanisms under lower and higher stresses. A comparison of SSLs at different temperatures shows an obvious stress-dependent behavior of temperature effects on swelling properties. These stress-dependent temperature effects on swelling behavior of GMZ bentonite are further confirmed by data collected from literatures on various types (i.e., Ca- or Na-bentonite) of bentonites: regardless of the predominant cations, the elevation of temperature increased the swelling potential in the lower stresses part of SSL, whereas it reduced the swelling potential in the higher stresses part. This phenomenon is related to the influences of temperature on the swelling processes (i.e., hydration, diffuse double-layer repulsion, and separation of elementary layers) under different stress levels. Keywords Compacted GMZ bentonite . Swelling pressure . Swelling strain . Swelling stable line . Stress-dependent temperature effects
Introduction Compacted bentonite has been selected as buffer/backfill materials for high-level radioactive waste (HLW) disposal in many countries (Pusch 1983; Komine and Ogata 1996; Villar 2006; Siddiqua et al. 2011; Wen 2006; Ye et al. 2009). Thanks to its high swelling capacity and self-healing property, compacted bentonite is expected to swell and fill in various gaps and cracks in buffer/backfill materials and surrounding rocks in the repository to form barriers that could effectively prevent the intrusion of groundwater from the surrounding
* Qiong Wang [email protected] 1
Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China
2
United Research Center for Urban Environment and Sustainable Development, The Ministry of Education, Shanghai 200092, China
geological formations and the possible release of radioactive waste from the canister. Meanwhile, during this swelling pr
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