• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1090-1099
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• 2006

Tensile strength of soil is one of the important strength parameters in geotechnical engineering. The importance of the tensile strength of soil has been pointed out and given considerable attention in many highway pavements and earthfill dams. Recently, one of tensile strength problems, cracking failure of clay liners which is related to leakage of polluted water has been reported. Thus, the tensile strength of compacted sand-bentonite mixtures, which are used widely in the landfill construction site as clay liners was measured by Improved Unconfined Penetration (IUP) test. In addition, to find out the effects of contamination levels of water on the tensile strength and desiccation crack pattern, different pH levels of water were used for making specimens prepared with three different mixing contents of bentonite.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.453-460
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• 2004

To prevent penetration of rainwater into the landfill site is the main purpose of the final cover in landfill sites. Conventional designs of landfill covers uses geotextiles such as geomembrane and GCL, and clay liners to lower the permeability of final covers of landfill sites. However, differential settlement and the variation of temperature in landfill sites cause the development of cracks or structural damage inside the final cover and it is also difficult to obtain clay - the main material of the compacted clay liner in Korea. Thus the former final cover system that suggests geomembrane and GCL or compacted clay liner has several limitations. Therefore, an alternative method is necessary and one of them is the application of SRSL(self-Recovering Sustainable Liner) material. SRSL is two different layers consist of individual materials that react with each other and form precipitates, and with this process lowers the permeability of the landfill final cover. SRSL generally is made up of two layers, so that when a internal crack occurs the reactants of the two layers migrate towards the crack and heal it by forming another liner. In this study the applicability of SRSL material for landfill final cover was examined by performing; (1) jar test to verify the formation of precipitate in the mixture of each reactants, (2) falling head test considering the field stress in order to confirm the decrease of permeability or prove that the hydraulic condctivity is lower than the regulations, (3) compression tests to judge weather if the strength satisfies the restricts for landfills, (4) freeze/thaw test to check the applicability of SRSL for domestic climate. In addition, the application of waste materials in the environmental and economical aspect was inspected, and finally the possibility of secondary contamination due to the waste materials was examined by performing elution tests.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.79-89
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• 2002

Various geosynthetics used as liners or protection layers are installed in the solid waste landfills. The interface shear strength between geosynthetics installed at the slope of the landfill is a very important variable for the safe design of the bottom and cover systems in the solid waste landfills. The interface shear strength between Geomembrane and Geotexile is estimated by a large direct shear test in this study, The effects of normal stress, water existing between geosynthetics and surface condition of Geomembrae, i.e. smooth or textured, were investigated. The test results show that the effect varied depending on the level of normal stress and the type of geosynthetic combinations. The shear strength was evaluated by the Mohr-Coulomb failure criterion in this research. The shear strength parameters obtained from tests considering the site specific conditions such as normal stress, dry or wet, and surface condition of geosynthetic should be applied to the design of geosynthetics installed at the slope of the landfill to construct a safe solid waste landfill.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.483-490
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• 2005

At present around 50 companies have their own crushing plants, which manufacture rock into crushed sand, over around 350 different quarry throughout the nation. However, in most plants the stone dust sludge is left as it is in their plants so that they have difficulty to utilize. Furthermore, environmental pollution may be even caused due to dust generated when it is dried. Recycling is starting capturing the attention of the people working over the quarry due to the reasons described above. This research has studied in the quarters the usability as landfill liner of the stone dust sludge, which is industrial waste. We investigated what technological properties it would have after mixing the stone dust sludge with SM(sandy soil) first and then with blast furnace slag or reject ash, which is waste, and cement as the stabilizer. As the result of three tests; compacting test, strength test, and permeability test; to satisfy the regulatory guideline of the government that is the compress strength over 5 $kgf/cm^2$, the flexibility over 1 $kgf/cm^2$, and the permeability under $1.0{\times}10^{-7}cm/sec$ From this research, we could confirm that stone dust sludge would be used as waste landfill liner if it were mixed with other waste by the proper mixing ratio.

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.29-38
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• 2004

A finite element nonlinear stress-deformation model with multi-interface element is applied to the stability analysis of waste landfill slope. Strength parameters of waste and geosynthetic materials are obtained from the triaxial test of waste and the direct shear test of geosynthetics, respectively. The landfill models used for the numerical models are fit to regulations of the Korean waste management law. The results of the strength tests showed linear behavior for the waste and nonlinear behavior for the eosynthectic materials. The stability analysis with multi-interface element for the geosynthetic materials in the liner system showed large shear stress and slippage at the boundary of the foundation and the slope of the waste fill. This analysis verified the necessity of multi-interface analysis for waste landfills with composite liners.

• Journal of the Korean Geotechnical Society
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• v.27 no.12
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• pp.5-15
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• 2011

Conventional designs of landfill covers use geosynthetics such as geomembrane and GCL, and clay liners to lower the permeability of final covers of landfill sites. However, differential settlement and the variation of temperature or humidity in landfill sites cause the development of cracks or structural damage inside the final cover. This study examined the application of a Self Recovering Sustainable Liner (SRSL) as an alternative landfill final cover material. SRSL consists of double layers, which have chemicals, can generate precipitates filling the pores of the layers by chemical reaction. The interface material forms an impermeable layer and in case of internal cracks, the reactants of the two layers migrate towards the crack and heal it by forming another liner. In this study the applicability of SRSL material for landfill final cover was examined by performing flexible wall permeameter tests to prove that the hydraulic conductivity is lower than the regulations and unconfined compression tests to judge whether the strength satisfies the restriction for the landfill final cover. Furthermore, the environmental impacts on the permeability and strength were evaluated. The experimental results show that the SRSL has lower hydraulic conductivity and higher strength than the regulations and is little influenced by climatic changes such as wet/dry or freeze/thaw process.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1997.05a
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• pp.47-52
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• 1997

The experimental investigations considered in this paper are similar in many respects to those of Lee$^1$, with some key differences. First, there is no layering of the soils in a heterogeneous liner. The only soil investigated is the clay component of the cover liner. This ensures that the clay is exposed to freezing and that frost propagation in the clay can be investigated separate from other processes. Second, a closed system approach to the simulation was adopted. According to Jones$^2$, closed-system freezing occurs when there is no source of water available beyond that originally present in the soil voids. Freezing under such conditions results in very thin or non-existent ice lenses. One of tile objectives of the experiments described in this paper was the moisture migration and the changing of moisture contents of the compacted clay liner in landfill. The closed-system was used to limit tile variables in the experimental simulation to make these calculations more direct, although the final results could be applied to an open system also. As a result, the moisture content decreased about 45%-46% after two freeze/thaw cycles.

• Membrane and Water Treatment
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• v.6 no.5
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• pp.393-409
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• 2015

Zinc and lead pollution are public environmental issues that have attracted lots of attention for a long time. Landfill leachate contains heavy metals, such as Zn(II) and Pb(II), which are usually related to the pollution of groundwater, especially in developing countries. Bentonite has been proven to be effective in enhancing the membrane property of clay, by which landfill liners can have better barrier performance towards the migration of contaminants. In this study, 5% sodium bentonite amended with locally available Fukakusa clay was utilized to evaluate the membrane behavior towards the heavy metals zinc and lead. The chemico-osmotic efficiency coefficient, ${\omega}$, was obtained through Zn(II) and Pb(II) solutions with different concentrations of 0.5, 1, 5, 10, and 50 mM. According to the results, ${\omega}$ continually decreased as the Zn(II) and Pb(II) concentrations increased, which is consistent with the Gouy-Chapman theory. Compared to normal inorganic ions, the membrane behavior towards heavy metal ions was lower. The migration of heavy metal ions was not observed based on experimental results, which can be attributed to the adsorption or ion exchange reaction. The mechanisms of the membrane performance change were discussed with the assistance of XRD patterns, free swelling results, XRF results, and SEM images.

• Journal of the Korean GEO-environmental Society
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• v.9 no.6
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• pp.21-29
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• 2008

As household and industrial wastes continue to rapidly increase every year, the demands for landfill sites are also increasing. However, the construction of landfill sites causes many problems due to the high costs of liners, while the leachate from the landfills generates secondary contamination of surrounding lands and groundwater. The purpose of this study is to determine the proper mixing ratio to meet the liner conditions (must be less than $1{\times}10^{-7}cm/sec$), using the local soil as the main material and using fly ash, bentonite, and cement as the mixing materials. The possibility of using this mixture as the liner for landfill sites was examined. To determine the proper mixing ratio, this study conducted basic physical properties tests, compaction tests, consolidation tests, and uniaxial compression tests. It was found that the higher the ratio of bentonite, the lower the coefficient of permeability, and the higher the ratio of fly ash, the higher the coefficient of permeability. The reason for this is that, while bentonite expands and fills pores, fly ash cannot fill the pores because the particles have a round shape and do not have adhesion. In conclusion, the optimum coefficient of permeability that meets the landfill liner condition was obtained when the ratio of bentonite was 15% or higher. If fly ash was mixed, the landfill liner condition was met when the ratio of bentonite was 15% or higher and the ratio of fly ash was 20% or lower.

• Economic and Environmental Geology
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• v.34 no.3
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• pp.283-299
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• 2001

The middle cover soils and clay liners collected from the Kumheung landfill in Gongiu City were analysed for As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, Ti and Zn concentrations using 0.] N HCl digestion and total/sequential extraction experiments followed by ICP-AES determination. The uncontaminated soil and sediment samples were also analyzed for the comparison. The results of sequential extraction showed that Cu was dominant in the oxidizable fraction, and As, Ni, Sr, Ba, and Mn were in the exchangeable fraction. Zinc and Mn occurred mostly in association with reducible, residual and carbonate fractions. Most of Cd and Pb were bound to the reducible and oxidizable fractions. The main carrier of Co, Cr, Fe and 11 was the residual fraction and another important carrier was the reducible fraction. The percentage of the metals of organically-bound form in the middle cover soils and clay liner was in the order of Cu(48%) > Ti(42%) > Pb(27%) > As(25%) > Cd(20%). As deduced from sequential extraction analysis, potential order of metal mobility in the middle cover soils and clay liner from the landfill was proposed: Cd > Sr > As > Ni > Mn > Ba > Cu > Pb > Zn » Co > 11 > Fe > Cr. Based on the 'geoaccumulation index' and the 'enrichment factor' normalized to A], the level of contamination of Cu, Ni and C1' was significant in the samples from Kumheung landfill and surrounding farmland. Their enrichments were attributed partly to anthropogenic pollutions.