• Journal of Environmental Science International
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• v.4 no.5
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• pp.427-435
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• 1995

In order to discuss the differences among the SMP(Surface Moisture Availability Parameter), by previous researchers on the basis of their own theoretical and empirical background, we assessed the SMP according to the soil types and volumetric soil water contents. The results are as follows. There are differences among all the five SMAPs. There's a tendency that the larger grain size, the higher value of parameters. And they divided into two groups for their value: one group has parameters with exponential function and the other with cosine and linear function. The maximum difference between the two groups appears when the volumetric soil water contents are 0.07m3m-3 for sand, 0.l1m3m-3 for loam, 0.12 for clay, and 0.13m3m-3 for silt loam. So, these differences must be considered when we estimate the surface evaporation rate. From field data, the paddy field soil around Junam reservoir is classified as a silt has high wetness, 0.56. So, the parameter obtained from the field measurement is much higher than that of Clapp and Hornberger(1978)'s Table. This study treated the SMP for a certain point of time in winter season. But if we measured the soil water contents continuously, we could obtain better time-dependent parameter. Key words : SMAP(Surface Moisture Availability Parameter), Paddy field, Volumetric soil water content, Evaporation, Capillary potential.

• Geomechanics and Engineering
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• v.28 no.3
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• pp.239-253
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• 2022

Suitable techniques to stabilize organic soil and improve its engineering behaviour are in demand. Despite various alternatives, nano-additives proved to be an effective stabilizer owing to their strength enhancing properties. The study focuses on using nano-silica as a potential stabilizer to improve organic silt. Soil was treated with four dosages of nano-silica namely 0.2%, 0.4%, 0.6% and 0.8% of dry weight of the soil. Nano-silica treated soil showed a strength increase of nearly 25% at a dosage of 0.4% after curing for two hours. Strength of the treated soil improved with age. Strength improved by nearly 62.9% after 28 days of curing and 221.4% after 180 days of curing due to formation of Calcium - Silicate - Hydrate (CSH) gel in the soil matrix. Dosage of 0.6% nano-silica is observed to be the optimum dosage. Coefficient of permeability and compression index showed an increase by 13.32 and 5.5 times respectively owing to aggregation of particles and creation of void spaces as visualized from the scanning electron micrographs. Further model foundation study and numerical parametric studies using PLAXIS 2D indicate that optimized and economic results can be obtained by varying the additive dosage with depth.

• Journal of the Korean GEO-environmental Society
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• v.15 no.7
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• pp.31-38
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• 2014

For analysis of mechanics properties of soil cement, unconfined compressive strength has been proposed by existing case studies. In this study, mechanical changes with water content of silt, curing time and cement content were analyzed through unconfined compressive strength test. In addition, the changes for B factor by Abrams were compared with existing case studies after the prediction equations could be proposed about the unconfined compressive strength of admixed cement soil. Especially, the B constant factor was changed with soil characteristics and curing time. For analysis results of appropriateness status and unconfined compressive strength, consideration of variable form was titrated. The prediction equations at low plasticity silt admixed using the uniaxial compressive strength with applying Abrams's equation and considering cement content, curing time is proposed.

• Journal of Environmental Science International
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• v.4 no.5
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• pp.41-41
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• 1995

In order to discuss the differences among the SMP(Surface Moisture Availability Parameter), by previous researchers on the basis of their own theoretical and empirical background, we assessed the SMP according to the soil types and volumetric soil water contents. The results are as follows. There are differences among all the five SMAPs. There''s a tendency that the larger grain size, the higher value of parameters. And they divided into two groups for their value: one group has parameters with exponential function and the other with cosine and linear function. The maximum difference between the two groups appears when the volumetric soil water contents are 0.07$m^3m^{-3}$ for sand, 0.l1$m^3m^{-3}$ for loam, 0.12 for clay, and 0.13$m^3m^{-3}$ for silt loam. So, these differences must be considered when we estimate the surface evaporation rate. From field data, the paddy field soil around Junam reservoir is classified as a silt has high wetness, 0.56. So, the parameter obtained from the field measurement is much higher than that of Clapp and Hornberger(1978)''s Table. This study treated the SMP for a certain point of time in winter season. But if we measured the soil water contents continuously, we could obtain better time-dependent parameter.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.4
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• pp.373-377
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• 1985

This experiment was designed to find out the soil properties to control the soil erodibility. Two kinds of soil conditioners, hydrophilic Uresol and hydrophobic Bitumen were treated to sandy loam and silt loam. Soil erodibility was tested during a simulated rainfall in a soil pan which was covered with a 2cm layer of treated and untreated aggregates (< 5.36mm) on a soil layer. The runoff starting time was delayed 8-20 minutes by Uresol treatment and it was hasten 1-21 minutes by Bitumen treatment. Runoff rates were reduced by Uresol to 62.5% in sandy loam and 93.7% in silt loam, but it was increased by Bitumen treatment. Erosion from the Uresol treated soil was remarkably reduced to 1.7-23.6% of that in the untreated soil. In case of the Bitumen treatment, the soil loss from silt loam was reduced to 55.5% of the control, but it was increased in sandy loam soil by 52% over the control. The ratio of soil loss and runoff, sediment concentration in runoff, was noticeably increased when the soil structure was unstable. There was significant correlation between soil loss and logarithm of wetting angle-stability index. Soil loss was greatly increased when the index was less than 0.2.

• Journal of Forest and Environmental Science
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• v.37 no.2
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• pp.116-127
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• 2021

Predicting carbon distribution of soil aggregates is difficult due to complexity in organo-mineral formation. This limits global warming mitigation through soil carbon sequestration. Therefore, knowledge of land use effect on carbon stabilization requires quantification of soil mineral cations. The study was conducted to quantify carbon and base cations on soil mineral fractions in Natural Forest, Plantation Forest and Farm Land. Five 0.09 ha were demarcated alternately along 500 m long transect with an interval of 50 m in Natural Forest (NF), Plantation Forest (PF) and Farm Land (FL). Soil samples were collected with soil cores at 0-15, 15-30 and 30-45 cm depths in each plot. Soil core samples were oven-dried at 105℃ and soil bulk densities were computed. Sample (100 g) of each soil core was separated into >2.0, 2.0-1.0, 1.0-0.5, 0.5-0.05 and <0.05 mm aggregates using dry sieve procedure and proportion determined. Carbon concentration of soil aggregates was determined using Loss-on-ignition method. Mineral fractions of soil depths were obtained using dispersion, sequential extraction and sedimentation methods of composite soil samples and sieved into <0.05 and >0.05 mm fractions. Cation exchange capacity of two mineral fractions was measured using spectrophotometry method. Data collected were analysed using descriptive and ANOVA at α_0.05. Silt and sand particle size decreased while clay increased with increase in soil depth in NF and PF. Subsoil depth contained highest carbon stock in the PF. Carbon concentration increased with decrease in aggregate size in soil depths of NF and FL. Micro- (1-0.5, 0.5-0.05 and <0.05 mm) and macro-aggregates (>2.0 and 2-1.0 mm) were saturated with soil carbon in NF and FL, respectively. Cation exchange capacity of <0.05 mm was higher than >0.05 mm in soil depths of PF and FL. Fine silt (<0.05 mm) determine the cation exchange capacity in soil depths. Land use and mineral size influence the carbon and cation exchange capacity of Gambari Forest Reserve.

• Geotechnical Engineering
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• v.12 no.5
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• pp.17-26
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• 1996

The undrained behavior of Asan marine soil was investigated by using an automated triaxial testing device. The stress-strain behavior at the preand postfailure state of marine soil under undrained compression and eatension conditions was compared with the behavior of pure silt, pure clay and the overall behavior of Asan marine soil was predicted with the modified Camflay model and the bounding surface model. The marine soil sampled in Asan bay area was clayey silts with 70oA silt-30% clay content and the testing samples were prepared in both undisturbed and remolded conditions. All samples are normally consolidated with 400 kPa of effective mean confining pressure and each sample is unloaded to 200, 100, 67 kPa, respectively. And then the shear test was performed with different confining pressure. According to experimental results, there exists an unique failure line whose slope is lower than silt's and higher than clay's. It is identified that the undrained shear strength of normally consolidated samples increases after crossing the phase transformation line because of volume dilation tendency which is not seen in clay. Overconsolidated samples show different soil behavior compared with pure silt due to its tendency of change in volume. It is also found that the overall behavior of Asan marine soil cannot be predicted precisely with the modified Cam-clay model and the bounding surface model.

• Geomechanics and Engineering
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• v.32 no.3
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• pp.347-359
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• 2023

With the development of infrastructure, there is a critical shortage of filling materials all over the word. However, a large amount of silt accumulated in the lower reaches of the Yellow River is treated as waste every year, which will cause environmental pollution and waste of resources. Microbial induced calcium carbonate precipitation (MICP) technology, with the advantage of efficient, economical and environmentally friendly protection, is selected to solidify the abandoned Yellow River silt with poor mechanical properties into high-quality filling material in this paper. Based on unconfined compressive strength (UCS) test, determination of calcium carbonate (CaCO₃) content and scanning electron microscope (SEM) test, the effects of cementation solution concentration, treatment times and relative density on the solidification effect were studied. The results show that the loose silt particles can be effectively solidified together into filling material with excellent mechanical properties through MICP technology. The concentration of cementation solution have a significant impact on the solidification effect, and the reasonable concentration of cementation solution is 1.5 mol/L. With the increase of treatment times, the pores in the soil are filled with CaCO₃, and the UCS of the specimens after 10 times of treatment can reach 2.5 MPa with a relatively high CaCO₃ content of 26%. With the improvement of treatment degree, the influence of relative density on the UCS increases gradually. Microscopic analysis revealed that after MICP reinforcement, CaCO₃ adhered to the surface of soil particles and cemented with each other to form a dense structure.

• Korean Journal of Agricultural Science
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• v.38 no.4
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• pp.631-639
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• 2011

This research was conducted to investigate potential use of New Zealand spinach (Tetragonia tetragonoides) as a new vegetable crop which will be cultivating in salt-affected soils including reclaimed land. Traditionally New Zealand spinach has been studied to explore functional compound or salt removing potential. To cultivate the crop species in the salt-affected soil widely, it is essential to obtain salt and soil texture responses under the controlled environment. Fifty nine New Zealand spinach ecotypes native to Korean peninsula first collected over seashore areas, and primitive habitat soil environment was evaluated by analyzing soil chemical properties from 32 locations. Different textures of sandy, silt loam, and sandy loam soils were prepared from nearby sources of sea shore, upland and paddy soils, respectively. Target salinity levels of 16.0 dS/m, 27.5 dS/m, 39.9 dS/m, and 52.4 dS/m in electrical conductivity (ECw) were achieved by diluting of 25, 50, 75, 100% (v/v) sea water to tap water (control, 0.6 dS/m), respectively. Various measurements responding to soil texture and irrigation salinity included plant height, root length, fresh weight (FW), dry weight (DW), leaf parameters (leaf number, leaf length, leaf width), lateral branching, and inorganic ion content. was found to adapt to diverse habitats ranging various soil chemical properties including soil pH, organic matter, exchangeable bases, EC, and cation exchange capacity (CEC) in Korea. Responding to soil texture, New Zealand spinach grew better in silt loam and sandy loam soil than in sandy soil. Higher yield (FW and DW) seemed to be associated with branch number (r=0.99 and 0.99, respectively), followed by plant height (r=0.94 and 0.97, respectively) and leaf number (r=0.89 and 0.84, respectively). Plant height, FW, and DW of the New Zealand spinach accessions were decreased with increasing irrigation salinity, while root length was not significantly different compared to control. Based on previous report, more narrow spectrum of salinity range (up to 16 dS/m) needs to be further studied in order to obtain more accurate salinity responses of the plant. As expected, leaf Na content was increased significantly with increasing salinity, while K and Ca contents decreased. Growth responses to soil texture and irrigation salinity implied the potential use of New Zealand spinach as a leafy vegetable in salt-affected soil constructed with silt loam or sandy loam soils.

• Journal of Ecology and Environment
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• v.32 no.4
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• pp.295-304
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• 2009

To understand the properties of soil in Dokdo, we collected soil samples from 12 locations on Seodo and 23 locations on Dongdo, in Dokdo of Gyeongsangbuk-do Province in 2007-2008 and analyzed the soil's physical and chemical characteristics. Sand comprises the largest component (49.37%) of Dokdo soil, followed by silt (40.70%) and clay (9.93%). The soil structure consists mostly of sand loam, followed by loam and silt loam. The pH level of soils from Dokdo varied dramatically among sampling sites and seasons, ranging from 3.36 to 8.02. The total ion content of Dokdo soil also varies greatly among survey places and periods, but in general the total ion content was high in summer when vegetation develops, and low in spring. The exchangeable cation contents of the soil showed low levels in samples where the soil pH was low, including habitats dominated by Agropyron tsukushiense var. transiens and Echinochloa crus-galli, whereas the exchangeable cation contents were high where the organic contents were high, as in habitats dominated by Liriope platyphylla and Artemisia japonica subsp. littoricola. Soil N contents varied greatly among survey sites and higher N contents were found in soil inhabited by Chenopodiaceous plants than in habitats inhabited by other plants. The substantial differences in phosphorus contents among sites were related to excrement of black-tailed gulls. To understand the basic physical and chemical features of the soil on Dokdo, it will be necessary to conduct seasonal and long-term research on soil pH, ion contents, organic contents, N and P, as well as obtaining precise data from samples collected at different depths.