• Geomechanics and Engineering
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• v.31 no.4
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• pp.409-422
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• 2022

The use of calcium sulfoaluminate (CSA) cement as a rapid-hardening cement admixture or eco-friendly alternate for ordinary Portland cement (OPC) has been attempted over the years, but the cost of CSA cement and availability of suitable aluminium resource prevent its wide practical application. To propose an effective ground improvement design in sandy soil, this study aims at blending a certain percentage of CSA with OPC to find an optimum blend that would have fast-setting behavior with a lower carbon footprint than OPC without compromising the mechanical properties of the cemented sand. Compared to the 100% CSA case, initial speed of strength development of blended cement is relatively low as it is mixed with OPC. It is found that 80% OPC and 20% CSA blend has low initial strength but eventually produces equivalent ultimate strength (28 days curing) to that of CSA treated sand. The specific OPC-CSA blend (80:20) exhibits significantly higher strength gain than using pure OPC, thus allowing effective geotechnical designs for sustainable and controlled ground improvement. Further parametric studies were conducted for the blended cement under various curing conditions, cement contents, and curing times. Wet-cured cement treated sand had 33% lower strength than that of dry-cured samples, while the stiffness of wet-cured samples was 25% lower than that of dry-cured samples.

• Geomechanics and Engineering
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• v.36 no.4
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• pp.343-353
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• 2024

The hydraulic anisotropic behavior of unsaturated soil has not been fully explored in relation to the grain-size distribution. The present study conducted laboratory assessments to examine the hydraulic anisotropy condition of statically compacted specimens in various initial states. The investigation incorporated the concept of hydraulic anisotropy by employing two discrete forms of soil stratification: horizontal-layering (HL) and vertical-layering (VL). The examined soils comprised sandy silt and silty sand, exhibiting either unimodal or bimodal soil-water characteristic curve (SWCC). This study aimed to investigate the potential correlation between the hydraulic anisotropy ratio and soil properties. The present study established a correlation between the hydraulic anisotropy ratio and several soil parameters, including fine content, dry density, plastic limit, and liquid limit. The study results indicate a non-linear relationship between the percentage of fine and dry density in soils with unimodal and bimodal soil-water characteristic curve (SWCC) and hydraulic anisotropy ratio.

• Magazine of the Korean Society of Agricultural Engineers
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• v.14 no.2
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• pp.2661-2667
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• 1972

In the construction of earth dam, embankment, highway by filling, a compaction is to increase the density of applying pressure. By compaction interspaces between the soil graivos decrease so that density and adhesion increase but void and permeability decrease. Good compaction results in higher stablilty. The effect of the compaetion depends on a number of factors, of which the most important are soil charactesistics. Water content, and external force. In this study discussed is about sandy loam that since, with indentical force exerted and indentical compaction method, the effect of the compaction will be different due to the soil characteristics, the change of optimum moisture content and of maximum dry density by compaction yields difference in Compaction for a same sample.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.720-723
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• 2006

This study performed slope stability analysis by changing analysis methods and shear strength with the slope stability analysis program. The conclusions of the study are as follows. 1) The safe factor of clayey soil applied with Bishop's simple method turned out to be similar to or slightly higher than those of other methods, for both dry and saturated conditions. 2) The safe factor of sandy soil applied with GLE method turned out to be slightly higher than those of other methods. But when applied with Bishop's simple method, it appeared to be slightly higher than those of other methods. 3) The safe factor of ordinary soil applied with GLE method showed the highest result. 4) Janbu method showed the lowest safe factor among all the methods for the above three types of soils.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.975-978
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• 1997

This Paper presents a high impedance fault (HIF) detection algorithm of distribution systems using wavelet transform. Two HIFs on dry soil and sandy soil were simulated on various load conditions in 22.9 kV distribution systems using EMTP, and the current wavelets were decomposed by wavelet transform. The current root mean square(rms) change, the index change rate and the relative amplitude change were used as the multi-criteria for a HIF detection. The index change rate and the relative amplitude were made using the wavelet coefficients.

• Journal of Plant Biology
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• v.17 no.3
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• pp.107-112
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• 1974

Leaf temperature is complicated with the microclimate and the dry matter production in a plant community. But a daily change of leaf temperature varying by the locality in plant body or plant community is not yet clear. To resolve such a question, following experiment was designed; Helianthus tuberosus L., Glycine max L., Zea mays L., Impomoea batatas Lam., and Cucurbita moschata var. toonas Makino were planted in the different sandy loam, $2m{\times}2m-quadrat$, which has a eastern, southern, western and northern edge. In each plot 17-25 plants were planted and the distances between individuals spaced uniformly. And leaf temperature were measured by MR3-C type thermistor from 14th May through 20th August. It is seems that the upper leaf is affected by solar radiation, the lower leaf by released heat from the earth and the middle leaf by the conditions of both zones. Measuring the temperature of a leaf that is on terminal, central, left and right margins and base part, temperature of control plant in a leaf was sloped during about two hours from noon. It is noticeable as a "noon sleeping" phenomenon.henomenon.

• Journal of the Korean Institute of Landscape Architecture
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• v.18 no.3 s.39
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• pp.137-141
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• 1990

This study was carried out to investigate the propagation methods of the Rhododendron micranthum as a landscape plant The results obtained are as follows :　1. The optimum temperature for seed germination was $20^{\circ}C$, and the seed germination needs light. 2. GA and thiourea did not affect the seed germination under light, but GA gad substitutive effect. 3. 87% and over of germination rates were obtained in room temperature and $5^{\circ}C$ dry storages. 4. The rooting rate was high on sandy loam, vermiculite, and vermiculite 50%+sand 50%, at softwood and hardwood cutting(hardwood ; 45~48%, softwood ; 45~48%). 5. The significant effects on rooting were found with the treatment of NAA 500~2000ppm.

• The Korean Journal of Mycology
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• v.21 no.4
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• pp.316-322
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• 1993

Examination by scanning electron microscopy and potato-dextrose agar medium showed that the dry seeds of R. raetam were externally free of fungi. When planted in sandy loam soil, the seeds become colonized with eleven soilborne fungal species. The fungi were isolated on cellulose agar, pectin agar and lignin agar media. Aspergillus flavus, A. niger, Penicillium capsulatum and Fusarium oxysporum had broad occurrence and recovered on the three media. The production of hydrolytic enzymes by the isolated fungi depends on the substrate and species. P. capsulatum, P. spinulosum and A. niger had wide enzymatic amplitude and they were able to produce cellulolytic, pectolytic and lignolytic activities on corresponding substrates as well as on seed coat containing media. The lignolytic activities of the isolated species except Chaetomium bostrychods and Trichoderma viride were enhanced on applying the seed coat materials as C-source rather than using lignin. Soaking R. raetam seeds in culture filtrates of the most fungi grown on seed coat supplemented media induced pronounced and distinct stimulating effect on seed germination. The most effective filtrates were those of P. capsulatum, P. spinulosum and Sporotrichum pulverulentum.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.398-401
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• 2006

Two landfills of this study containing municipal wastes without any bottom liner and leachate treatment system have different landfill age, waste volume and most importantly different hydrogeologic settings. The one (Cheonan) is situated in an open flat area while the other (Wonju) is located in a valley. In the interior of the landfills, typical anaerobic conditions revealed by low DO and ${NO_3}^-$ concentrations, negative ORP values, high $NH_3$, alkalinity and $Cl^-$ concentrations were observed. Generally higher levels of contaminants were detected in the dry season while those were greatly lowered in the wet season. Significantly large decrease of Cl concentration in the wet season indicates that the dilution or mixing is one of dominant attenuation mechanisms of leachate. But detailed variation behaviors in the two landfills are largely different and they were most dependent on permeability of surface and subsurface layers. The intermediately permeable surface of 1.he landfills receives part of direct rainfall infiltration but most rainwater is lost to fast runoff. The practically impermeable surface of clayey silt (paddy field) at immediately adjacent to the Cheonan landfill boundary prevented direct rainwater infiltration and hence redox condition of the groundwaters were largely affected by that of the upper landfill and the less permeable materials beneath the paddy fields prohibited dispersion of the landfill leachate into downgradient area. In the Wonju landfill, there exist three different permeability divisions, the landfill region, the sandy open field and the paddy field. Roles of the landfill and paddy regions are very similar to those at the Cheonan. The very permeable sandy field receiving a large amount of rainwater infiltration plays a key role in controlling redox condition of the downgradient area and contaminant migration.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.1
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• pp.67-75
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• 1993

This study is to analyze both root growth and soil moisture extraction pattern during the growing period of upland crops with respect to soybean, redpepper, sesame. Field and lysimeter tests were conducted under 12 treatments of soil moisture level by the San Cristobal experimental design(1981) and 3 soil type(sand, sandy loam, silty loam) for 4 years('87-'90) at the experimental plot of Rural Development Administration located in Suwon. The results of this study are summarized as follows : 1.For soybean, redpepper and sesame, root growth in dry soil was better than that in wet soil and it could be expressed as a sin function in terms of time. Maximum root depth was about 55cm, 44cm, 40cm respectively. 2.The average soil moisture extraction pattern for soybean, redpepper and sesame were 61.4%, 62.8%, 79.5% for zone l(0-l5cm). 25.5%, 27.1%, 18.3%, for zone 2(15-30cm).11.4%, 9.8%, 2.3% for zone 3(30-45cm), 1.7%, 0.3%, 0.04% for zone 4(45-60cm) respectively. This means that Zone 1 would be the dominant zone in irrigation scheduling. 3.With respect to soybean, the soil moisture extraction pattern(SMEP) was varied somewhat according to the erent maintenance of soil moisture level. The average SMEP for high maintenance of soil moisture was 46%, 29%, 17%, 8%, for middle maintenance of soil moisture was 43%, 29%, 17%, 11 % and for low maintenance of soil moisture was 40%, 28%, 20%, 12%, respectively. 4.With respect to soybean, the soil moisture in the upper layer was distinctly consumed more than that in the lower layer for clay loam soil and the soil moisture of all layers was consumed evenly for sand soil. The SMEP for sandy loam soil showed a middle result compared with the above 2 soil types.