• Title, Summary, Keyword: Bentonite

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Performance of Soil-Bentonite Cutoff Wall considering Defects and Formation of Bentonite Cake

  • Nguyen, The Bao;Lee, Chul-Ho;Lim, Jee-Hee;Jeoung, Jae-Hyeung;Choi, Hang-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.1264-1273
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    • 2010
  • Soil-bentonite cutoff walls are widely recognized to be the effective barrier for containment of wastes and groundwater. Bentonite cake is usually found remaining on the trench surface due to the use of bentonite slurry during the excavation for the cutoff wall construction. Defects also inevitably take place due to the inappropriate construction procedures or improperly mixed soil-bentonite backfill. The defects include insufficient keys and windows in the soilbentonite cutoff wall. In this study, the performance of the soil-bentonite cutoff wall is evaluated based on the flow rates through the wall. Three-dimensional numerical models were applied to simulate the groundwater flow through the soil-bentonite cutoff walls of typical geometries with consideration of the defects and bentonite cake. Results of the simulations showed that the bentonite cake has no effect in the insufficient key cases. In the keyed wall cases, the bentonite cake with very low hydraulic conductivity significantly impedes the flow of groundwater through the wall. The presence of the bentonite cake not only compromises the window defect but also renders the wall construction more effective in blocking the groundwater flow. These findings show the significance of the bentonite cake in a soil-bentonite cutoff wall construction.

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Fundamental Study on Geotechnical Properties of Sand-Bentonite Mixtures (모래-벤토나이트 혼합물의 지반 공학적특성에 관한 기초 연구)

  • 권무남;유택항
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.39 no.6
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    • pp.99-110
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    • 1997
  • The study was conducted in order to investigate the basic geotechnical properties of sand-bentonite mixtures with the various bentonite contents. The results obtained are as follows : 1. Optimum moisture content of sand-bentonite mixtures was approximately 17.10~18.52% corresponding to the maximum dry density of 1.58~1 .64gf/$cm^3$. As the bentonite contents and curing peroid increased, both the maximum dry density and optimum moisture content of sand-bentonite mixtures increased. 2. The unconfined compressive strength of sand-bentonite mixtures increased as the increase of bentonite content, but it did not change along the curing period. 3. The sand-bentonite mixtures ruptured at 8~15% of the axial strain and the maxi-mum shearing stress was about O.7Okgf/$cm^2$. 4. According to the increase of bentonite content, the cohesion intercept and internal friction of the sand-bentonite mixtures increased slightly in the shear test, while the cohesion intercept increased largely, and the internal friction angle decreased largely in the triaxial test. 5. Both the initial void ratio and swelling of the sand-bentonite mixtures were very low with respect to the consolidation pressure increase. 6. The swelling and shrinkage of sand-bentonite mixtures increased slightly according to the increment of bentonite content.

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Effect of Bentonite on the Mechanical Properties of ABS Resin (Bentonite가 ABS 수지의 기계적 물성에 미치는 영향)

  • Don, Yoon-Seung;Shim, Mi-Ja;Kim, Sang-Wook
    • Applied Chemistry for Engineering
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    • v.5 no.6
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    • pp.981-989
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    • 1994
  • For the development of new material used bentonite in ceramic/organic material composite, ABS(acrylonitrile-butadiene-styrene) material was used as a matrix polymer and a series of bentonite was blended together. This bentonite, filler like talc or mica for plastic material, was used since natural bentonite(Ca type) is easily obtainable in Korea, Na-bentonite changed from natural bentonite by $Na_2CO_3$ based on the specified compositions, changes in the static and dynamic mechanical properties. It was discovered that the increased content of natural and Na- bentonite results in higher modulus with reduced impact strength. And Rockwell hardness was constant. And Na- bentonite filled polymer showed improvement in impact strength and lower in modulus as the natural bentonite filled polymer. The storage modulus(E') of Na- bentonite filled ABS resin was higher than that of Ca- bentonite filled ABS resin, while higher temperature, storage modulus(E') decreased. At higher frequency, tan ${\delta}$ peak was shifted at high temperature.

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Solid-liquid Separation of Swine Wastewater using Bentonite (벤토나이트를 이용한 양돈 폐수의 고액분리)

  • Yim, Je-Hyun;Kang, Seon-Hong
    • Journal of Korean Society of Water and Wastewater
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    • v.18 no.6
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    • pp.742-747
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    • 2004
  • Solid-liquid separation of swine wastewater was conducted using bentonite as coagulant. During the separation experiment, coagulation efficiency was also investigated. To determine optimal bentonite dose, 0.1, 0.2, 0.4, 0.8, and 1.6% (w/v basis) of bentonite was dosed. Suspended solid removal efficiency was 87-98% at whole bentonite dosage. But sediment volume was increased, and settling velocity was decreased at excessive bentonite dosage. Therefore optimal bentonite dosage was evaluated around 0.2-0.4%. In the test to determine optimal pH, coagulation using bentonite was performed at pH 3, 4, 5, 6, and 7. At lower pH suspended solid removal efficiency was increased. However, sediment volume was also increased and phosphorus release was observed. Thereby optimal pH for bentonite coagulation might be appeared in the range of 6-7.

Rheological Studies on the Aqueous Suspension of Korean Bentonite (국산벤토나이트 현탁액의 유동학적 성질)

  • Kim, Eun-Hee;Rhee, Gye-Ju
    • YAKHAK HOEJI
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    • v.34 no.5
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    • pp.302-310
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    • 1990
  • A study has been made of the Korean bentonite aqueous suspension contrast with American bentonite by means of XRD IR swelling, gel formation and rheogram at various conditions such as concentration, temperature and pH. The Korean bentonite was identified as montmorillonite clay containig a small proprotion of crystoballite and mordenite, and its swelling power were acceptable for requirements of Korean pharmacopeia regulations though its values were not satisfied. Korean bentonite swelled to 10 times and American one did to 15 times compared to its bulkiness of powder. The rheogram of Korean bentonite suspension reveals bulged pseudoplatic flow with yield value at higher concentration and pseudoplastic flow without yield value at lower concentration. The higher the concentration, the greater were the apparent viscosity and hysteresis loop. Korean bentonite suspension showed insignificant temperature dependence on both apparent viscosity and hysteresis loop and it was more temperature dependent on viscosity but less on hysteresis loop than those of American sample. The pH dependence was so high on viscosity that apparent minimum value was near pH 7 and maximum value at pH 3 or 7. The hysteresis loop appeared minimum over the pH range 5-7 and maximum near pH 3 or 11. The Korean bentonite was inferior to the American bentonite in swelling volume, gel formation, thioxotropy, however, it would be possible to improve the quality of Korean bentonite by developing the method of purification for bentonite clay.

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Study on the development and application of slow releasing fertilizer using Korean natural clay minerals II. Synthesis and application of K-bentonite (점토광물을 이용한 완효성 비료(K비료)개발 및 응용에 관한 연구 II. 비료의 합성과 응용)

  • Park, Kuen-Woo;Choy, Jin-Ho
    • Korean Journal of Environmental Agriculture
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    • v.5 no.2
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    • pp.135-140
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    • 1986
  • K-bentonite was made by ion exchange reaction in $K^{\ast}$ ion saturated aqueous solution. K-bentonite had a slow releasing effect in different soils such as sand, sandy loam and clayey loam, but the effect was the best in sand. The growth of radish and lettuce was better in the plot fertilized with K-bentonite than with KCl in sand culture in field condition. There was no effects on the growth of radish grown in pot in glass house. Vitamin C, nitrate content, thiocyanate ion content and dry weight of radish were not affected by K-bentonite and KCl in both pot and field culture. The commercial production of K-bentonite was discussed.

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Effect of Exchangeable Cation on Radionuclide Diffusion In Compacted Bentonite

  • Park, Jong-Won;Park, Hyun-Soo;Dennis W. Oscarson
    • Nuclear Engineering and Technology
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    • v.28 no.3
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    • pp.274-279
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    • 1996
  • Diffusion coefficient is a critical parameter for predicting radiological source term(migration rate and flux of radionuclide) through given near field conditions in spent fuel or high level waste repository. The effect of exchangeable cation-$Na^+$ and $Ca^{2+} - on the diffusion of $I^- \;and^3H$ (as HTO) in compacted bentonite was examined using a through-diffusion method. Bentonite material used here was compacted to a density of 1.3 Mg/m$^3$, and Na-bentonite was saturated with a solution of 100 mol NaCl/m$^3$ and Ca-bentonite with 50 $mol\;CaCl_2$/m$^3$. The results show that effective diffusion coefficients are generally higher by a factor of two to five in Ca-than Na-clay. This is attributed to the larger particle size of Ca-compared to Na-bentonite; hence, Ca-bentonite has a greater proportion of relatively large pores, which make a greater contribution to mass transport than small pores. Although the nature of the exchangeable cation affects mass diffusion in compacted bentonite, the effect is small and not likely to influence performance assessment modeling of compacted bentonite-based barriers.

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An Experimental Study on the Erosion of a Compacted Calcium Bentonite Block (압축된 칼슘벤토나이트 블록의 침식에 대한 실험적 연구)

  • Baik Min-Hoon;Cho Won-Jin
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.3 no.4
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    • pp.341-348
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    • 2005
  • Bentonite has been considered as a candidate buffer material in the underground repository for the disposal of high-level radioactive waste because of its low permeability, high sorption capacity, self sealing characteristics, and durability in nature. In this study, the potential for separation of bentonite particles caused by the groundwater erosion was studied experimentally for a Korean Ca-bentonite under the relevant repository conditions. Results showed that bentonite particles can be generated at the bentonite/granite interface and mobilized by the water flow although the intrusion of bentonite into fracture by swelling pressure was observed to be small. Different processes of mobilization of theses colloids from the compacted bentonite block have been identified in this study. The concentration of particles eluted in water was increased as the flow rate increased. Thus the result reveals that the erosion of the bentonite surface due to the groundwater flow together with intrusion processes is the main mechanism that can mobilize bentonite colloids in the fracture of the granite.

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Factors Affecting the Electrical Properties of Bentonite Slurry (벤토나이트 슬러리의 전기적 특성에 대한 영향인자 분석)

  • Yoo, Dong-Ju;Oh, Myoung-Hak;Kim, Yong-Sung;Park, Jun-Boum
    • Journal of the Korean Geotechnical Society
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    • v.22 no.10
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    • pp.21-32
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    • 2006
  • Factors affecting the electrical properties of bentonite slurry were identified and electric conduction mechanism in slurry was examined. Electrical conductivity of bentonite and soil-bentonite slurry linearly increases with the bentonite content. Test result indicated that the change In electrical conductivity of slurry was mainly caused by dissolved cations from bentonite particles. The relationship between electrical conductivity and bentonite content was affected by the initial electrical conductivity of slurry solution and fine content in soil-bentonite mixture. Such influences were evaluated and the calibrated relationships were suggested. Based on the suggested relationship between electrical conductivity and bentonite content, bentonite content in various bentonite and soil-bentonite slurry can be quantitatively evaluated by using electrical conductivity measurement method.

The Permeability Characteristics of the Reactive Soil - Bentonite Landfill Liner (혼합반응 차수재의 투수특성 연구)

  • 이강원;황의석;안기봉;정하익;김학문
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.545-552
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    • 2002
  • The purpose of this paper is to investigate permeability characteristic of soil-bentonite landfill liner and development of desirable liner system. In this study, permeability tests for soil-bentonite, reactive soil-bentonite and apply bentomat and reactive mat are carried out under the low and high water pressure. According to test result, additional amount of bentonite decreases the coefficient of permeability up to the bentonite mixture ratio of 15%. Therefore, the permeability test for landfill liner's indicated that the use of general water would be in more safe side because the liner system show low permeability duet decrease effect of porous by suspended soild(SS). The permeability of leachate for Zeolite mixture ratio 0, 5, 10% with bentonite mixture ratio 15% showed negligible variation in the permeability with general water. Therefore, Zeolite could be used as a successful that is available purification material for the treatment of leachate, without changing the of landfill liners. Also odious smell could be removed by adding smell amount of Zeolite to the leachate. It was revealed that the bentomat and reactive mat installed in soil-bentonite layer effectively improved the permeability as well as purification of the leachate.

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