• Korean Journal of Soil Science and Fertilizer
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• v.49 no.5
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• pp.548-554
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• 2016

Optimal range of soil physical quality to enhance crop productivity or to improve environmental health is still in dispute for the upland soil. We hypothesized that the optimal range might be established by comparing soil physical parameters and their interactions inhibiting crop growth. The parameter identifying optimal range covered favorable conditions of aeration, permeability and root extension. To establish soil physical standard two experiments were conducted as follows; 1) investigating interactions of bulk density and aeration porosity in the laboratory test and 2) determining effects of soil compaction and deep & conventional tillage on physical properties and crop growth in the field test. The crops were Perilla frutescens, Zea mays L., Solanum tuberosum L. and Secale cereael. The saturated hydraulic conductivity, bulk density from the root depth, root growth and stem length were obtained. Higher bulk density showed lower aeration porosity and hydraulic conductivity, and finer texture had lower threshold bulk density at 10% aeration bulk density. Reduced crop growth by subsoil compaction was higher in silt clay loam compared to other textures. Loam soil had better physical improvement in deep rotary tillage plot. Combined with results of the present studies, the soil physical quality was possibly assessed by bulk density index. Threshold subsoil bulk density as the upper value were $1.55Mg\;m^{-3}$ in sandy loam, $1.50Mg\;m^{-3}$ in loam and $1.45Mg\;m^{-3}$ in silty clay loam for optimal soil physical quality in upland.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.2
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• pp.110-115
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• 1998

In this paper, the sensitivity of the leachate level is analyzed using the program HELP to reduce the high leachate level on the landfill. Hydraulic parameters analyzed were porosity, field capacity, wilting point and initial water content of cover soil and waste. Also, the influence of the difference between the initial water content and the field capacity on the leachate level in the landfill was analyzed. The results of the sensitivity analysis show that the increase of the porosity and the wilting point decreases the leachate level, while the increase of the field capacity and the hydraulic conductivity increases the leachate level. Major parameters to the change of the leachate level were the hydraulic conductivity in the case of cover soil and the porosity, the field capacity and the initial water content in the case of waste.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.394-397
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• 2006

Hydrogeologic and hydrochemlcat conditions of two uncontrolled landfills without reliable underlying liners, leachate collection and treatment systems were compared. With similar weather conditions, spatial distribution and temporal variations of contaminants of concern and redox parameters were different for the two landfills. These differences are highly associated with ages and hydrogeologic settings of the landfills. Groundwater flow diverges from the Cheonan landfill while it converges to downgradient area in the Wonju landfill. Less permeable clayey silt layer or silty soil in the subsurface limited dispersion of leachate plume in the former landfill but highly permeable sandy soil with good lateral extent facilitated rapid plume dispersion in the latter landfill. In addition, hydraulic properties of the cover soil played a role in the different development of redox conditions, which resulted in significantly different concentrations of nitrates. Most problematic contaminants at downgradient wells of the landfills are ammonia and nitrate.

• Geomechanics and Engineering
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• v.34 no.3
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• pp.221-231
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• 2023

Biopolymer stabilization is a sustainable alternative to traditional techniques that cause a lesser negative impact on the environment during production and application. The study aims to minimize the biopolymer dosages by sizing the bio-additives to the nanoscale. This study combines the advantages of bio and nanomaterials in geotechnical engineering applications and attempts to investigate the behaviour of a low viscous biopolymer, nano sodium carboxymethyl cellulose (nCMC), to treat organic soil. Soil is treated with 0.25%, 0.50%, 0.75% and 1.00% of nano-bio additive, and its effect on the plastic behaviour, compaction characteristics, strength, hydraulic conductivity (HC) and compressible nature are investigated. The strength increased by 1.68 times after 90 days of curing at a dosage of 0.5% nCMC through the formation of gel threads connecting the soil particles that stiffened the matrix. The viscosity of 1% nCMC increased exponentially, deterring fluid flow through the voids and reduced the HC by 0.85 times after curing for 90 days. Also, beyond the optimum dosage of 0.50%, the nCMC forms a film around the soil particles that inhibits the inter-particle cohesion causing a reduction in strength. Experimental results show that nCMC can effectively substitute conventional additives to stabilize the soil.

• Geomechanics and Engineering
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• v.7 no.6
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• pp.633-647
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• 2014

Biopolymers, polymers produced by living organisms, are used in various fields (e.g., medical, food, cosmetic, medicine) due to their beneficial properties. Recently, biopolymers have been used for control of soil erosion, stabilization of aggregate, and to enhance drilling. However, the inter-particle behavior of such polymers on soil behavior are poorly understood. In this study, an artificial biopolymer (${\beta}$-1,3/1,6-glucan) was used as an engineered soil additive for Korean residual soil (i.e., hwangtoh). The geotechnical behavior of the Korean residual soil, after treatment with ${\beta}$-1,3/1,6-glucan, were measured through a series of laboratory approaches and then analyzed. As the biopolymer content in soil increased, so did its compactibility, Atterberg limits, plasticity index, swelling index, and shear modulus. However, the treatment had no effect on the compressional stiffness of the residual soil, and the polymer induced bio-clogging of the soil's pore spaces while resulting in a decrease in hydraulic conductivity.

• Weed & Turfgrass Science
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• v.6 no.3
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• pp.262-271
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• 2017

This study was conducted to evaluate incorporation ratio of soil amendment 'Profile' to improve soil physicochemical properties and turfgrass growth. The soil amendment was added 0 (sand only), 3, 5, 7, and 10% to USGA Green-spec green sand soil. As incorporated with more 'Profile' amendment, soil electrical conductivity (EC), cation exchangeable capacity (CEC), capillary porosity and total porosity of root zone were increased than those of control, while bulk density and hydraulic conductivity decreased. Turfgrass index and clipping yield of creeping bentgrass grown in sand soil incorporated with 7% 'Profile' were improved than those of control. Correlation coefficient of turf color index and incorporation ratio of the soil amendment 'Profile' was found to show significantly positive correlation. These results indicated that application of the soil amendment 'Profile' to sand soil in golf course green improved turfgrass growth and quality by increasing CEC and porosity of root zone.

• Geomechanics and Engineering
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• v.12 no.5
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• pp.803-813
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• 2017

This study discussed the possible optimization of enzyme-mediated calcite precipitation (EMCP) as a soil-improvement technique. Magnesium chloride was added to the injection solution to delay the reaction rate and to improve the homogenous distribution of precipitated minerals within soil sample. Soil specimens were prepared in 1-m PVC cylinders and treated with the obtained solutions composed of urease, urea, calcium, and magnesium chloride, and the mineral distribution within the sand specimens was examined. The effects of the precipitated minerals on the mechanical and hydraulic properties were evaluated by unconfined compressive strength (UCS) and permeability tests, respectively. The addition of magnesium was found to be effective in delaying the reaction rate by more than one hour. The uniform distribution of the precipitated minerals within a 1-m sand column was obtained when 0.1 mol/L and 0.4 mol/L of magnesium and calcium, respectively, were injected. The strength increased gradually as the mineral content was further increased. The permeability test results showed that the hydraulic conductivity was approximately constant in the presence of a 6% mineral mass. Thus, it was revealed that it is possible to control the strength of treated sand by adjusting the amount of precipitated minerals.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.260-263
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• 2005

Uncontrolled landfills have been a threat to surrounding environment and human health. To examine the effect of hydrogeological properties on plume migration caused by landfill leachate, two representative landfills in Cheonan and Wonju were selected. In these landfills, seven and eight groundwater wells were installed respectively to monitor water quality and waterlevel, and to perform hydraulic and tracer tests. This study reports preliminary evaluation results including site characteristics, waterlevel measurement and slug tests.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.966-972
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• 2009

Soil-aggregate system in pavement foundations exist in unsaturated conditions. However, change in water content on foundation layers due to joint and structural cracks during rainfall may cause problems like layer deformations or partial settlements. Therefore, a need exist to evaluate the infiltration and drainage capacity of soil-aggregate foundation system under both saturated and unsaturated conditions. To do that, a laboratory soil-water characteristic curve and permeability under unsaturated conditions are assessed to establish hydraulic properties of geomaterials and limited numerical analysis are performed respectively. As a result, it was found that suction profiles and drainage process was greatly influenced by the initial suction of soil-aggregate system at the time of infiltration, soil water characteristics curves, and hysteresis effects.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.5-12
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• 2002

Hydraulic conductivity k is one of the most important engineering properties of soil. However, both field and laboratory procedures fur the determination of k are often tedious and expensive. This paper presents new models to predict k using statistical parameters from grain size distribution. A number of permeability tests far 36 types of sands mixed based on statistics were conducted to develop the regression-based models. Parameters used to estimate k are both the geometric mean and geometric standard deviation of the soil samples, or the particle-size distribution curve parameters such as D_{10},D_{50},D_{60}. Hydraulic conductivity predicted by this model is in good agreement with the laboratory measurements fir the soil samples obtained at 20 locations within the Korean Peninsula. The performances of the proposed models were also compared with those of existing models including Hazen's.