• 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.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.02a
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• pp.41-48
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• 2003

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.3
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• pp.69-78
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• 2003

The main purpose of this study was to verify the shore margin protection effect of the root system of Salix gracilistyla Miq. developed from direct sticking cuttings on wetland, focusing on the effect of the root system reducing soil particle dissociation rate in water. The soil dissociation rate was examined through slaking tests with cylindric pure soil column at maximum particle density and the same size column of root reinforced soil. The dry weight of remained soil was measured after 5, 10, 15, 30minutes and 1, 6, 12, 24, 48hours inundation. As results, the soil particles began to dissociate severely at 10 minutes and only 10% of soil particles were left after 25minutes inundation. The stable slope angle of pure soil was $36^{\circ}$after 24 hours. On the other hand, the columns of root reinforced soil were stable even after 24hours, being dissociated only 7.2% of soil particles. So, it was revealed that the root system was very effective materials protecting more than 80% of soil particle from dissociation in inundation.

• Structural Engineering and Mechanics
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• v.87 no.2
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• pp.173-189
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• 2023

For a given structural geometry, the stiffness and damping parameters of the soil and the dynamic response of the structure may change in the face of an equivalent linear soil behavior caused by a strong earthquake. Therefore, the influence of equivalent linear soil behavior on the impedance functions form and the seismic response of the soil-structure system has been investigated. Through the substructure method, the seismic response of the selected structure was obtained by an analytical formulation based on the dynamic equilibrium of the soil-structure system modeled by an analog model with three degrees of freedom. Also, the dynamic response of the soil-structure system for a nonlinear soil behavior and for the two types of impedance function forms was also analyzed by 2D finite element modeling using ABAQUS software. The numerical results were compared with those of the analytical solution. After the investigation, the effect of soil nonlinearity clearly showed the critical role of soil stiffness loss under strong shaking, which is more complex than the linear elastic soil behavior, where the energy dissipation depends on the seismic motion amplitude and its frequency, the impedance function types, the shear modulus reduction and the damping increase. Excellent agreement between finite element analysis and analytical results has been obtained due to the reasonable representation of the model.

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.3
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• pp.143-152
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• 2013

No-till farming system has been extensively studied all over the world as the effective method for maintaining the soil fertility. The general advantages of this system have been well known for reducing the labor, fuel, machinery, and irrigation cost as well as for increasing the soil quality through soil aggregation, water infiltration, microbial population and etc. Recently, it becomes more popular with the increase of interest on sustainable agriculture, especially because of its higher carbon sequestration potential compared to conventional tillage. Crop residue management should be essentially included to look forward to achieving the positive effect on reduction of greenhouse gas. Nonetheless, there are also negative opinions on effect of no-till farming system. For example, some researchers reported that soil physical properties were not improved by no-till under certain soil and climatic conditions. This means no-till farming systems were strongly affected by the soil characters and climatic conditions. Therefore, the researches to meet the specific-regional characters are greatly needed in order for no-till farming system to successfully settle in Korea. The objective of the review article is to present the future direction and perspective on no-till farming system in Korea. For this purpose, we summarized the results of domestic and foreign researches about no-till farming system until now. Specifically, the chapter on foreign research consisted of four parts: positive and negative effects, the effect in paddy soil, and latest research direction (2012-2013) of no-till farming systems. Whereas, review for domestic researches was divided into two main parts: paddy and upland soils. In the final chapter, the priorities for the optimum conservation tillage in Korea were discussed and proposed through the previous researches.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.521-528
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• 2003

In this study, a newly modified soil nailing technology called as the NDB(New Down and Board) soil nailing system is introduced. To improve the trafficability, workability, and economical efficiency, SMC(Sheet Molding Compound) board is adopted instead of using the concrete block facing. The SMC board has a distinct advantage of showing a fine view by directly coating with any kind of environmental photos. Composite material properties of the SMC board and cement grout are distinguished features of the NDB soil nailing system. In the present study, both laboratory tests(bending and punching failure tests) and field pull-out tests are carried out to analyze the behavior characteristics of the NDB soil nailing system, including the stress and strain distribution.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.6
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• pp.12-18
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• 2004

This study is to make plans for perpendicular greening with artificial ground of planter type to improve urban environment. The experiments of this study are performed to find out the suitable soil and irrigation method for artificial ground of planter greening. Thereupon, organic or inorganic soil improvement material is mixed with soil of each planter as experiment, In result, the plants in soil mixed organic soil improvement material thrive rather than that in soil mixed inorganic material, It is to be desired that the planter equip with the irrigation system, be wider than planter and be planted shrubs for positive plant growth. As for irrigation system, drip irrigation is effective on plant growth southern exposure but Ebb and Flow is effective eastern exposure. Therefore, irrigation system should consist of two types above plus keeping water on the bottom of planter to save water and store rainwater.

• Journal of Environmental Science International
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• v.19 no.9
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• pp.1137-1142
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• 2010

This study proposes a guideline of a green roof system suitable for the local environment by verifying the growth of Zoysia japonica in a shallow, extensive, green roof system under rainfed condition. The experimental soil substrates into which excellent drought tolerance and creeping Z. japonica was planted were made with different soil thicknesses(15cm, 25cm) and soil mixing ratios(SL, $P_7P_1L_2$, $P_6P_2L_2$, $P_5P_3L_2$, $P_4P_4L_2$). The plant height, green coverage ratio, fresh weight, dry weight and chlorophyll contents of Z. japonica were investigated. For the soil thickness of 15cm, the plant height of Z. japonica was significantly as affected by the soil mixing ratio and it was shown in the order SL= $P_4P_4L_2$ < $P_7P_1L_2$ = $P_5P_3L_2$ < $P_6P_2L_2$. For the soil thickness of 25cm, the plant height was increased in order to SL < $P_7P_1L_2$, $P_6P_2L_2$, $P_5P_3L_2$ < $P_4P_4L_2$. The green coverage ratio was not observed by soil the mixing ratio or soil thickness. However, the green coverage ratio was 86~90% with a good coverage rate overall. The chlorophyll contents of Z. japonica were not significantly affected by the soil mixing ratio in the soil thickness of 15cm, but were higher in the natural soil than in the artificial soil at 25cm soil thickness. The fresh weight and dry weight of Zoysia japonica were heavier in the 25cm thickness than in the 15cm thickness and in the artificial soil mixture than in the natural soil. The result indicated that the growth of Zoysia japonica was more effective in the 25cm soil thickness with artificial soil than in the 15cm soil thickness with natural soil in the green roof system under rainfed condition.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.4
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• pp.335-340
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• 2016

Soil organic carbon plays an important role on soil physico-chemical properties and crop yields in paddy soil. However, there is little information on the soil organic carbon under different forage cultivation during winter season in rice paddy. In this study, we investigated the soil organic carbon and physico-chemical properties in 87 fields of paddy soil cultivated with Barley, rye, and Italian ryegrass (IRG) as animal feedstock during winter season. Organic carbon was 12.9, 14.3, and $16.9g\;C\;kg^{-1}$ in soil with barley, rye, and IRG cultivation, respectively. Among rice-forage cultivation systems, the rice+IRG cropping system was 19.5% higher than in the mono-rice cultivation. Bulk density ranged from 1.17 to $1.28g\;cm^{-3}$ irrespective of cropping systems, and had strongly negative correlation with the soil organic carbon in the rice+IRG cropping system. Carbon storage in rice+IRG cropping systems was average $29.6Mg\;ha^{-1}$ at 15 cm of soil depth, which was 20.4 and 10.3% higher than those of barley and rye cultivation. Increasing carbon storage in paddy soil contributed to the fertility for following rice cultivation. This results indicated that IRG cultivation during winter season could be an alternative and promising way to enhance soil organic carbon content and fertility of paddy soil.

• Earthquakes and Structures
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• v.14 no.1
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• pp.85-94
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• 2018

The paper focuses on the seismic responses of a hyperbolic cooling tower resting on soil foundation represented by the three-parameter Vlasov elastic soil model. The three-parameter soil model eliminates the necessity of field testing to determine soil parameters such as reaction modulus and shear parameter. These parameters are calculated using an iterative procedure depending on the soil surface vertical deformation profile in the model. The soil and tower system are modeled in SAP2000 structural analysis program using a computing tool coded in MATLAB. The tool provides a two-way data transfer between SAP2000 and MATLAB with the help of Open Application Programming Interface (OAPI) feature of SAP2000. The response spectrum analyses of the tower system with circular V-shaped supporting columns and annular raft foundation on elastic soil are conducted thanks to the coded tool. The shell and column forces and displacements are presented for different soil conditions and fixed raft base condition to investigate the effects of soil-structure interaction. Numerical results indicate that the flexibility of soil foundation leads to an increase in displacements but a decrease in shell membrane and column forces. Therefore, it can be stated that the consideration of soil-structure interaction in the seismic response analysis of the cooling tower system provides an economical design process.