Self-sealing behavior of compacted bentonite–sand mixtures containing technological voids

Watanabe, Yoshitomo; Yokoyama, Shiyoshi

doi:10.1016/j.gete.2020.100213

Cited by 20 publications

(2 citation statements)

References 16 publications

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“…Nevertheless, no completely homogeneous density or water content distribution was observed in any of the tests, and the bentonite that was closer to the gap had final higher water content and lower dry density. This was also observed in similar tests with axial gaps performed by Watanabe and Yokoyama [37] in bentonite/sand mixtures and by Dueck et al [10], Harrington et al [15] and Daniels et al [6] in bentonite, even though the axial and radial pressures measured had attained equilibrium.…”

Section: Discussionsupporting

confidence: 83%

Bentonite swelling into a void under suction or water flow

2022

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In the context of the deep geological disposal of nuclear waste and to improve the understanding of the homogenisation process of bentonite barriers, in particular with regard to the filling of technological voids, tests were performed with compacted FEBEX bentonite samples hydrated under limited axial swelling conditions. The samples were saturated from the top surface using the vapour transfer technique (imposing suctions of 6 and 0.5 MPa), or with deionised water injected at a low flow rate either from the bottom surface or from the gap on top. The final water content of the samples saturated via vapour transfer was related to the suction imposed during the tests according to the water retention curve. Thus, the final water content of the samples tested under suction 6 MPa was lower and not enough to allow sufficient bentonite swelling to close the gap. In contrast, the samples saturated under suction 0.5 MPa reached higher water contents and were able to fill the gap before the equilibrium water content had been reached. In the tests performed with liquid water supplied through the gap, the samples were able to swell easily into the open void and the gap closed earlier than when hydration took place from the opposite end. In all the tests, the final water content of the bentonite was higher and the dry density lower towards the hydration surface. These gradients were more remarkable and persistent as the initial strain was larger. No completely homogeneous density or water content distribution was observed in any of the tests. These changes were also reflected in the pore size distribution. The pores of size larger than the upper limit of mercury intrusion porosimetry (~ 550 µm) were also quantified, which allowed a better representation of the pore size distribution of the more swollen samples. Although the void ratio corresponding to pores smaller than 200 nm (em) was initially higher, over time the volume of macropores (eM) increased more, giving place to an overall decrease in the em/eM ratio, which tended to be constant along the samples in the longest tests. In the first stages of hydration, the macropore void ratio and size considerably increased close to the gap in the tests with saturation from it.

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Section: Discussionsupporting

confidence: 83%

Bentonite swelling into a void under suction or water flow

2022

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“…In the 1970s, sixty percent of the 250,000 new homes built on expansive soils each year in the U.S. experienced minor loss and BACKGROUND Modern, scientific, soil swelling measurements and characterization date back for over a half century, when Seed et al (1962) evaluated the utility of the plasticity index ["liquid limit" percentage minus "plastic limit" percentage (Coleman and Douglas 2008)] for such purposes, but the plasticity index was later shown to be impractical in humid environments (Jones 2012). Tripathy et al (2004) characterized swelling of clays, such as bentonites (Bharat and Gapak, 2018) used as barrier materials for storing radioactive waste, and Watanabe and Yokoyama (2021) did similar work with clay/sand mixtures. Rao et al (2004) suggested that free swell index, identified experimentally using the ratio of the difference between the oven-dried soil volume in water vs. in kerosene to the final volume of soil in kerosene (Holtz and Gibbs, 1954), can circumvent the need for considering the many other soil properties when estimating swelling potential.…”

Section: Introductionmentioning

confidence: 99%

Property Risk Assessment for Expansive Soils in Louisiana

Mostafiz

Friedland

Rohli

et al. 2021

Front. Built Environ.

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The physical properties of soil can affect the stability of construction. In particular, soil swelling potential (a term which includes swelling/shrinking) is often overlooked as a natural hazard. Similar to risk assessment for other hazards, assessing risk for soil swelling can be defined as the product of the probability of the hazard and the value of property subjected to the hazard. This research utilizes past engineering and geological assessments of soil swelling potential, along with economic data from the U.S. Census, to assess the risk for soil swelling at the census-block level in Louisiana, a U.S. state with a relatively dense population that is vulnerable to expansive soils. Results suggest that the coastal parts of the state face the highest risk, particularly in the areas of greater population concentrations, but that all developed parts of the state have some risk. The annual historical property loss, per capita property loss, and per building property loss are all concentrated in southeastern Louisiana and extreme southwestern Louisiana, but the concentration of wealth in cities increases the historical property loss in most of the urban areas. Projections of loss by 2050 show a similar pattern, but with increased per building loss in and around a swath of cities across southwestern and south-central Louisiana. These results may assist engineers, architects, and developers as they strive to enhance the resilience of buildings and infrastructure to the multitude of environmental hazards in Louisiana.

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Gas migration at the granite–bentonite interface under semirigid boundary conditions in the context of high‐level radioactive waste disposal

Liu,

Wang,

Guo

et al. 2024

Deep Underground Science and Engineering

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The corrosion of waste canisters in the deep geological disposal facilities (GDFs) for high‐level radioactive waste (HLRW) can generate gas, which escapes from the engineered barrier system through the interfaces between the bentonite buffer blocks and the host rock and those between the bentonite blocks. In this study, a series of water infiltration and gas breakthrough experiments were conducted on granite and on granite–bentonite specimens with smooth and grooved interfaces. On this basis, this study presents new insights and a quantitative assessment of the impact of the interface between clay and host rock on gas transport. As the results show, the water permeability values from water infiltration tests on granite and granite–bentonite samples (10−19–10−20 m2) are found to be slightly higher than that of bentonite. The gas permeability of the mock‐up samples with smooth interfaces is one order of magnitude larger than that of the mock‐up with grooved interfaces. The gas results of breakthrough pressures for the granite and the granite–bentonite mock‐up samples are significantly lower than that of bentonite. The results highlight the potential existence of preferential gas migration channels between the rock and bentonite buffer that require further considerations in safety assessment.

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Self-sealing behavior of compacted bentonite–sand mixtures containing technological voids

Cited by 20 publications

References 16 publications

Bentonite swelling into a void under suction or water flow

Bentonite swelling into a void under suction or water flow

Property Risk Assessment for Expansive Soils in Louisiana

Gas migration at the granite–bentonite interface under semirigid boundary conditions in the context of high‐level radioactive waste disposal

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