• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.69-78
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• 2022

Geotextile tubes are widely used to prevent erosion in coastal areas and to replace the backfill for shore slopes in the reclamation of land using dredged soil. In this study, The triaxial confining pressures were chosen as 10kPa, 50kPa, or 100kPa for the specimens reinforced with geotextile considering the condition in the site. The strain behavior under various compressive stresses was then identified. At strains 0% to 7%, the stress-strain behavior was the same due to the effect of initial strain hardening, in which the force was exerted according to the relaxation of the geotextile regardless of the confining pressure (≤100kPa). At strains of 7% or more, the specimen with the small confining pressure had smaller deformation under load, which increases the tensile resistance provided by the reinforcing geotextile. Brittle fracture was then observed due to strain softening and the deviator stress abruptly decreased. This is different from the phenomenon in which the shear strength increases as the confining pressure increases in general triaxial compression tests. In the geoxtile-confined tests, geotextiles are primarily subjected to tensile displacement. Thereafter, the modulus of elasticity increases rapidly, which exhibits the elastic behavior of the geotextile.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.6
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• pp.51-64
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• 2022

Along with the urbanization, the risk of urban flooding due to climate change is increasing. Flood regulation, one of the ecosystem services, is implemented in the different level of function of flood risk mitigation by the type of ecosystem such as forests, arable land, wetlands etc. Land use changes due to development pressures have become an important factor in increasing the vulnerability by flash flood. This study has conducted evaluating the urban flood regulation service using InVEST UFRM(Urban Flood Risk Model). As a result of the simulation, the potential water retention by ecosystem type in the event of a flash flood according to RCP 4.5(10 year frequency) scenario was 1,569,611 tons in urbanized/dried areas, 907,706 tons in agricultural areas, 1,496,105 tons in forested areas, 831,705 tons in grasslands, 1,021,742 tons in wetlands, and 206,709 tons in bare areas, the water bodies was estimated to be 38,087 tons. In the case of more severe 100-year rainfall, 1,808,376 tons in urbanized/dried areas, 1,172,505 tons in agricultural areas, 2,076,019 tons in forests, 1,021,742 tons in grasslands, 47,603 tons in wetlands, 238,363 tons in bare lands, and 52,985 tons in water bodies. The potential economic damage from flood runoff(100 years frequency) is 122,512,524 thousand won in residential areas, 512,382,410 thousand won in commercial areas, 50,414,646 thousand won in industrial areas, 2,927,508 thousand won in Infrastructure(road), 8,907 thousand won in agriculture, Total of assuming a runoff of 50 mm(100 year frequency) was estimated at 688,245,997 thousand won. In a conclusion. these results provided an overview of ecosystem functions and services in terms of flood control, and indirectly demonstrated the possibility of using the model as a tool for policy decision-making. Nevertheless, in future research, related issues such as application of models according to various spatial scales, verification of difference in result values due to differences in spatial resolution, improvement of CN(Curved Number) suitable for the research site conditions based on actual data, and development of flood damage factors suitable for domestic condition for the calculation of economic loss.

• Korean Journal of Organic Agriculture
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• v.30 no.2
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• pp.279-290
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• 2022

This study was conducted to find out that winter green manure crops could be efficient replacements of expeller cake fertilizers, which were mostly imported, on environment-friendly red pepper production. Four treatments were compared under the condition of plastic film house: 1) barley (B); 2) hairy vetch (HV); 3) mixtures of barley and hairy vetch (B/HV); 4) expeller cake (EC). Total nitrogen content in hariy vetch was 3.6%, which was higher than 1.5~1.8% in barley and mixtures of barley and hairy vetch. P₂O₅ and K₂O contents were similar in all green manures. Supplying amount of nitrogen from B, HV and B/HV plot, which were 172 kg ha^-1, 193 kg ha^-1, and 198 kg ha^-1, were higher than amount of basal nitrogen required by soil testing but were lower than that of total nitrogen, respectively. Among the green manure crops, C/N ratio of HV was the lowest at 11.8, showing a similar value to that of expeller cake, but that of B was the highest at 30.6. Total yield was no significant difference in all treatment plots although B/HV plot showed the highest yield, but initial yield in B plot with high C/N ratio was lower than that in EC plot.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.1
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• pp.59-67
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• 1992

The duration of raising seedling of infant rice seedling(IRS) in machine transplanting is 8 to 10 days. This experiment was conducted to investigate the minimum duration of IRS's raising seedling and its method by the combination of several treatments such as plant growth regulator, root-break-seat and temperature. The rice seeds of Hwaseongbyeo was soaked in the solution of metalaxyl for 24 hours at room temperature. Metalaxyl (25% wettable powder), a fungicide, was used in 1, 000 times dilution as a promting substance on the root-mat formation of IRS. The application of fungicide in the nursery soil for the controlling of damping-off and physiologyical seedling rot was omitted due to the metalaxyl seed-soaking treatment. Seeding rate was 220g per seed tray (30$\times$60$\times$3cm). To promote the root-mat formation of IRS, the sheets of polyethylene vinyl and absorptive paper were placed bottom the seed tray. The root-mat formation of IRS was promoted at higher temperature and longer duration of raising seedling. The metalaxyl-treated seeds markedly increased the root length and rooting activity of IRS as compared with the control, thus the root-mat formation was excellent. The absorptive paper with polyethylene vinyl as root-break-seat showed a better root-mat formation compared with control, polyethylene vinyl, alone. The minimum duration of raising seedling of IRS was 5 days after sowing based on the root-mat formation and seedling height under the condition of metalaxyl seed treatment, absorptive paper with polyethylene vinyl as a root-break-seat and the raising seedling temperature 30/2$0^{\circ}C$ (day /night).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.4
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• pp.385-397
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• 1982

The climatic impacts have been the environmental constraints with soil characteristics to achieve self sufficiency of food production in Korea. In this paper, the distribution and appearance of impacts and the changes in climatological status due to recent trend of early transplanting of rice are widely discussed to derive some countermeasures against the impacts, being focussed on cultural A long term analysis of the climatic impact appearances of the last 74 years showed that drought, strong wind, flood, cold spell and frost were the major impacts. Before 1970's, the drought damage was the greatest among the climatic impacts; however, the expansion and improvement of irrigation and drainage system markedly decreased the damage of drought and heavy rain. The appearance of cold damage became more frequent than before due to introduction of early transplanting for more thermophilic new varieties. Tongillines which were from Indica and Japonica crosses throw more attention to cold damage for high yields to secure high temperature in heading and ripening stages and lead weakness to cold and drought damage in early growth stage after transplanting. The plants became subject to heavy rain in ripening stage also. For the countermeasures against cold damage, the rational distribution of adequate varieties according to the regional climatic conditions and planting schedule should be imposed on the cultivation. A detoured water way to increase water temperature might be suggestable in the early growth stage. Heavy application of phosphate to boost rooting and tillering also would be a nutritional control method. In the heading and ripening stages, foliar application of phosphate and additional fertilization of silicate might be considerable way of nutritional control. Since the amount of solar radiation and air temperature in dry years were high, healthy plants for high yield could be obtained; therefere, the expansion of irrigation system and development of subsurface water should be performed as one of the national development projects. To minimize the damage of strong wind and rainfall, the rational distribution of varieties with different growing periods in the area where the damage occurred habitualy should be considered with installation of wind breaks. Not only vertical windbreaks but also a horizontal wind break using a net might be a possible way to decrease the white heads in rice field by dry wind. Finally, to establish the integrated countermeasures against the climatic impacts, the detailed interpretation on the regional climatic conditions should be conducted to understand distribution and frequency of the impacts. The expansion of observation net work for agricultural meteorology and development of analysis techniques for meteorological data must be conducted in future together with the development of the new cultural techniques.

• Journal of Practical Agriculture & Fisheries Research
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• v.15 no.1
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• pp.63-73
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• 2013

The research was conducted to determine a seed germination and seedling establishment of rice plant under seed coating materials such as iron, silicate, and phyllite and under covered with silicate and iron coated & silicate covered in the puddled wet hill seeding and wet line seeding methods. The seedling establishment was high in silicate and untreated control of 100%>phyllite coating of 91.5%>silicate coating of 88%>iron coating and silicate covered of 86%>silicate covered of 75.5% in the puddled wet hill seeding method, respectively. At 35days after treatment there was high in seedling height at silicate covered of 23.8cm>control of 23.6cm>silicate coating of 21.4cm>phyllite coating of 20.2cm>iron coating and silicate covered of 16.8cm>iron coating of 15.4cm. In puddle wet line seeding method rice seedling establishment was high at control and silicate covered of 100%>iron coating and silicate covered by 97.5%>phyllite coating by 94.8%>iron coating by 86%. Seedling height was high in silicate covered of 22.1cm>control of 21.2cm>silicate coating of 20.0cm>phyllite coating of 19.0cm>iron coating of 17.7cm>iron coating and silicate covered of 17.0cm, respectively.

• Journal of Practical Agriculture & Fisheries Research
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• v.5 no.1
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• pp.28-35
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• 2003

This study was conducted to investigate the nutrition status, growth and fruit quality of 'Campbell Early' grapes in Hwaseong area. Organic matter content of 3 vineyard soils was significantly lower than standard value. P₂O₅ and K contents of Y vineyard and P₂O₅ of C vineyard were very high. But there were no significant differences in contents of Ca, Mg and CEC. Compared to the standard value. T-N, Ca and Mg contents of petiole were adequate. P₂O₅ contents of Y and C vineyard and K contents of Y vineyard were significantly higher than standard value. Berry firmness, color and bloom occurrence on fruit skin showed no differences among 3 vineyard. Soluble solids content poorly, yield per tree and goods fruit of C vineyard decreased significantly compared to the fruit in Y and H vineyards. Russetted fruit of Y vineyard, colored fruit of H vineyard, and unfertilized fruit, cracked fruit, and bitter rot were observed frequently.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.97-102
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• 2007

Though the stability analysis of soil slopes widely employs the limit equilibrium method, the study on the jointed rock slopes must consider the direction of joint and the characteristics of Joint at the same time. This study analyzes the result of the change in the factors which show the characteristics of discontinuity and the shape factor of rock slopes, and so on, in an attempt to validate the propriety as to the interpretation of jointed rock slope stability which uses the general finite element program. First, the difference depending on the flow rules was compared, and the factor effect study was conducted. The selected independent variables included the direction of joint which displays the mechanical characteristics of discontinuity, adhesive cohesion, friction angle, the inclination and height of rock slope which reveal the shape of slope and surcharge load. And the horizontal displacement was numerically interpreted at the 1/3 point below the slope, a dependent variable, to compare the relative degree of factor effects. The findings of study on factor effects led to the validation that the result of horizontal displacement for each factor satisfied various engineering characteristics, making it possible to be applied to stability interpretation of jointed rock slope. A modelling is possible, which considers the application of the result of real geotechnical surveys & laboratory studies and the non-linear characteristics when designing the rock slope. In addition, the stress change which may result from the natural disaster, such as precipitation, and the construction, can be expressed. Furthermore, as the complicated rock condition and the ground supporting effect can be considered through FEM, it is considered to be very useful in making an engineering decision on the cut-slope, reinforcement and so on.

• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.99-109
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• 2008

The standard consolidation tests using the incremental loading technique test (IL) were performed on remolded normal consolidation and undisturbed clay samples to find out the effects of plastic index and loading period on consolidation in this study. The remolded samples used were prepared by mixing Gunsan-Samangum clay with bentonite so that they may have plasticity indexes of 15, 30, 45, and 60%, respectively. The undisturbed clay samples were collected from Inchon, Kwangyang, and Uoolsan. The samples were tested at the condition of 4 different loading periods (1, 2, 4, and 8 days). Settlement, coefficient of consolidation, compression index, secondary compression index, and pore water pressure characteristics were investigated from the plastic index and loading period aspects, and the compression index, coefficient of consolidation, and secondary compression index were formulated in terms of the plastic index and loading. To verify the applicability of proposed equations, the settlements obtained from Terzaghi's theory, modified Cam-Clay model (elasto-plastic model), and the Sekiguchi model (elasto-viscoplastic mode) were compared with the test results. The comparison indicates that the Sekiguchi model incorporating the secondary consolidation characteristic well predicts the results.

• Journal of the Korean Geotechnical Society
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• v.25 no.1
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• pp.65-76
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• 2009

The unsaturated characteristics of Korean weathered granite soils have been studied to investigate the influence of saturated permeability, rainfall intensity and soil-water characteristic curve (SWCC) on the slope stability. The upper, average and lower SWCCs were estimated from the publication and experimental results using the statistical concept. The roughly estimated SWCC can be used for the soils without experimental results by relating SWCC with the particle size distribution curve. An appropriate ratio between the saturated permeability and the rainfall intensity ($k_s$/i) was also suggested for practical use in designing the slopes by investigating the time-dependent variation of slope instability during the rainfall. The slope stability was deteriorated from the initiation of rainfall and recovered again after the factor of safety reached the critical value. The FS of the slope decreased at first and then increased after reaching the critical value during the rainfall. As a result, the slope instability was not related with an absolute rainfall intensity but with the ratio between the saturated permeability and the rainfall intensity. In case of the upper SWCC, the critical condition occurred when the ratio between the saturated permeability and the rainfall intensity was in the range of $1.0{\sim}2.0$.