• Title, Summary, Keyword: Bentonite

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복합오염물질제거를 위한 현장반응층 이용에 관한 연구

  • 조현희;박재우
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.168-171
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    • 2003
  • This research was conducted to assess the performance of the mixed reactive materials with sand, iron filings, and HDTMA-bentonite for trichloroethylene (TCE) and chromate removal under controlled groundwater flow conditions. TCE and chromate removal rates with the mixtures of iron filing/HDTMA-bentonite were highest among four columns due to reduction by iron filings and sorption by HDTMA-bentonite. The greater capacity of the mixed iron filing/HDTMA-bentonite compared HDTMA-bentonite was due to an enhanced chromate reduction in addition to chromate sorption. The presence of chromate caused greater inhibition of TCE removal in the column with iron filings, while the presence of TCE caused less inhibition of TCE. Also, nitrate caused the decrease in TCE removal relative to chloride. Nitrate ions may also significantly affect TCE reduction rates by competing for electrons with the chlorinated compounds. The anion and co-existed contaminants competing effects should be considered when designed permeable reactive barriers (PRBs) composed of zero valent iron for field applications to remediate TCE and chromate.

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Strength and Permeability Characteristics of Soil-Bentonite Mixture (Soil-Bentonite 혼합토의 강도 및 투수 특성)

  • Jin, Guangri;Im, Eunsang;Kim, Kiyoung;Sin, Donghoon
    • Journal of the Korean Geoenvironmental Society
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    • v.11 no.4
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    • pp.5-12
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    • 2010
  • Soil mixture using bentonite as a cutoff material is used a lot for various structures such as landfills, banks and dams as cutoff materials. But seepage water is expected to seep since shear failure of filter layer occurs due to external load, embankment load when constructed. Generally, only coefficient of permeability of Soil Mixture is considered irrespective of the changes of intensity on amount of additives. This research is to study on how the changes of amount of bentonite affects permeability and strength of soil mixture. So successive experiments for measuring permeability and strength were conducted as the amount of bentonite changes from 0 to 4%, mixing with the bed material and then making specimens. Around construction site of B dam. As a result, 2.085E-07 cm/sec was shown when the amount of Soil Mixture was 4%. It is proved that unconfined compressive strength and tensile strength increase as the amount of bentonite increases, but saturation shear strength of bentonite soil mixture from the CD experiment is hardly influenced by the amount of bentonite.

A Study for Permeability as Mixing Ratio at Bentonite-mixed Soil (벤토나이트 혼합토의 혼합비에 따른 투수성 연구)

  • Ju Jae-Woo;Suh Kyeh-Won;Park Jong-Beom
    • Journal of the Korean Geotechnical Society
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    • v.22 no.1
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    • pp.45-52
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    • 2006
  • A theoretical equation, from which we can get a suitable ratio of bentonite at bentonite-mixed soil, was derived for desigri of the impermeable condition. Bentonite is a soil with great expansion property and it has the permeability lower than $1\times10^{-7}cm/sec$ in spite of its maximum expansion state. Accordingly if the void of soil is filled with the liquid of bentonite, water will flow only through the veid of bentonite liquid. And the permeability of bentonite-mixed soil will always satisfy the condition as impermeable zone. However, because it is very difficult to mix uniformly bentonite with soil, it is thought that the actual mixing ratio fur the impermeable zone will be grater than that by theoretical equation. Permeability tests were performed to check the equation and a modified equation was suggested from the experimental results.

Applicability of Electrical Conductivity Monitoring Technique for Soil-bentonite Barrier (흙-벤토나이트월에 대한 전기전도도 모니터링 기법의 적용성 평가)

  • Oh, Myoung-Hak;Yoo, Dong-Ju;Kim, Yong-Sung;Park, Jun-Boum
    • Journal of the Korean Geotechnical Society
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    • v.23 no.7
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    • pp.47-55
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    • 2007
  • In this study, applicability of electrical conductivity monitoring technique for containment barrier such as soil-bentonite wall was evaluated. Laboratory tests including permeability tests and column tests were performed to understand variations in electrical conductivity at different bentonite contents, hydraulic conductivities, and heavy metal concentrations. The electrical conductivity of compacted soil-bentonite mixtures was found to increase proportionally with bentonite content. Accordingly, the hydraulic conductivity of compacted soil-bentonite mixtures which decreases linearly with increasing bentonite content was found to have an inversely proportional relationship with the electrical conductivity. In column tests, electrical conductivity breakthrough curves and concentration breakthrough curves were simultaneously obtained. These results indicated that electrical conductivity measurement can be an effective means of detecting heavy metal transport at the desired locations within barriers and verifying possible contaminant leakage. Experimental results obtained from this study showed that the electrical conductivity measurement can be a promising tool for monitoring of containment barrier.

A Study on Unsaturated Permeable Properties of the Soil-Bentonite Mixtures (Soil-Bentonite 혼합토의 불포화 투수특성 연구)

  • Kim Man-il
    • The Journal of Engineering Geology
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    • v.15 no.2
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    • pp.123-132
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    • 2005
  • This study presents the results of a laboratory investigation performed to study physical properties of soil-bentonite mixtures through the vertical permeation test and dielectric measurement test using Frequency Domain Reflectometry system for the liner of waste landfill. For the laboratory experiments, geotechnical testing was conducted on pre-mixed soil-bentonite which is consisted of standard sand, weathered granite soil and bentonite for estimating physical parameters such as a volumetric water content, void ratio and dielectric constant. In experiment results, initial soil-bentonite mixing rate has an effect of change of volumetric water content. Also change of volumetric water content of a soil-bentonite mixture is clearly detected to measure a response of dielectric constant. In order to estimate an unsaturated permeable property of soil-bentonite mixtures, equations between volumetric water content and dielectric constant were derived from this study.

An Elastoplastic Analysis for Spent Nuclear Fuel Disposal Container and Its Bentonite Buffer: Asymmetric Rock Movement (고준위폐기물 처분장치 및 완충장치에 대한 탄소성해석 : 비대칭 암반력)

  • 권영주;최석호
    • Transactions of Materials Processing
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    • v.12 no.5
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    • pp.479-486
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    • 2003
  • This paper presents an elastoplastic analysis for spent nuclear fuel disposal container and its 50 cm thick bentonite buffer to predict the collapse of the container while the horizontal asymmetric sudden rock movement of 10 cm is applied on the composite structure. This sudden rock movement is anticipated by the earthquake etc. at a deep underground. Elastoplastic material model is adopted. Drucker-Prager yield criterion is used for the material yield prediction of the bentonite buffer and von-Mises yield criterion is used for the material yield prediction of the container. Analysis results show that even though very large deformations occur beyond the yield point in the bentonite buffer, the container structure still endures elastic small strains and stresses below the yield strength. Hence, the asymmetric 50 cm thick bentonite buffer can protect the container safely against the 10 cm sudden rock movement by earthquake etc.. Analysis results also show that bending deformations occur in the container structure due to the shear deformation of the bentonite buffer. The finite element analysis code, NISA, is used for the analysis.

A Study on the Nonlinear Structural Analysis for Spent Nuclear Fuel Disposal Container and Bentonite Buffer (고준위폐기물 처분장치와 이를 감싸고 있는 벤토나이트 버퍼에 대한 비선형 구조해석)

  • 권영주;최석호
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.19-26
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    • 2002
  • In this paper, the nonlinear structural analysis for the composite structure of the spent nuclear fuel disposal container and the 50cm thick bentonite buffer is carried out to predict the collapse of the container while the sudden rock movement of 10cm is applied on the composite structure. This sudden rock movement is anticipated by the earthquake etc. at a deep underground. Horizontal symmetric rock movement is assumed in this structural analysis. Elastoplastic material model is adopted. Drucker-Prager yield criterion is used for the material yield prediction of the bentonite buffer and von-Mises yield criterion is used for the material yield prediction of the container(cast iron insert, copper outer shell and lid and bottom). Analysis results show that even though very large deformations occur beyond the yield point in the bentonite buffer, the container structure still endures elastic small strains and stresses below the yield strength. Hence, the 50cm thick bentonite buffer can protect the container safely against the 10cm sudden rock movement by earthquake etc.. Analysis results also show that bending deformations occur in the container structure due to the shear deformation of the bentonite buffer. The elastoplastic nonlinear structural analysis for the composite structure of the container and the bentonite buffer is performed using the finite element analysis code, NISA.

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Study on physical characteristics of Graphite-added bentonite grout for backfilling closed-loop groud heat exchanger (수직 밀폐형 지중 열교환기용 뒤채움재로서 흑연(Graphite)을 첨가한 벤토나이트 그라우트재의 물리적 특성연구)

  • Lee, Kang-Ja;Gil, Hu-Jeong;Lee, Chul-Ho;Choi, Hang-Seok;Choi, Hyo-Pum
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.179-187
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    • 2009
  • Bentonite-based grouting has been popularly used to seal a borehole installed for a closed-loop vertical ground heat exchanger in a geothermal heat pump system (GHP) because of its high swelling potential and low hydraulic conductivity. The bentonite-based grout, however, has relatively lower thermal conductivity than that of ground formation. Accordingly, it is common to add some additives such as silica sand to the bentonite-based grout for enhancing thermal performance. In this study, graphite is adapted to substitute silica sand as an addictive because graphite has very high thermal conductivity. The effect of graphite on the thermal conductivity of bentonite-based grouts has been quantitatively evaluated for seven bentonite grouts from different product sources. In addition, comparisons of viscosity between applications of graphite and silica sand as additives has been carried out. In conclusion, using graphite has thermal conductivity about three times higher than that of silica sand.

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Strength Characteristics of Soil-Bentonite Mixture (Soil-Bentonite 혼합토의 강도 특성)

  • Jin, Guang-Ri;Shin, Dong-Hoon;Im, Eun-Sang;Kim, Ki-Young
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.844-851
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    • 2009
  • A soil mixture with low permeability and bentonite as an additive has been highly utilized as a cutoff material in landfills, banks, and dams. Even though it is anticipated that the water can seep through shear failures in the filter layer due to external loads and embankment loads during construction, usually only the coefficient of permeability of the soil mixture is considered rather than the changes of strength from the different amounts of additives. Therefore, the amount of bentonite was changed between 0%~4% in the soil mixture of the bed material to conduct a series of unconfined compressive strength, tensile strength, and shear strength tests on a specimen in order to study the characteristics of the strength. In the result, the unconfined compressive and tensile strength were increased along with the increased amount of bentonite in the low water content; however, the tensile strength in the consolidated-drained shear test generally showed similar values without significant changes.

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