• Journal of the Korean Geotechnical Society
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• v.38 no.9
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• pp.45-52
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• 2022

Because discontinuity in the rock mass and contact of soil-structure interaction exhibits coupled thermal-hydromechanical (THM) behavior, it is necessary to develop an interface element based on the full governing equations. In this study, we derive force equilibrium, fluid continuity, and energy equilibrium equations for the interface element. Additionally, we present a stiffness matrix of the elastoplastic mechanical model for the interface element. The developed interface element uses six nodes for displacement and four nodes for water pressure and temperature in a two-dimensional analysis. The fully coupled THM analysis for fluid injection into a fault can model the complicated evolution of injection pressure due to decreasing effective stress in the fault and thermal contraction of the surrounding rock mass. However, the result of hydromechanical analysis ignoring thermal phenomena overestimates hydromechanical variables.

• The Plant Pathology Journal
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• v.38 no.2
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• pp.90-101
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• 2022

Pathogenicity of eight Bacillus strains to seedlings of four cotton cultivars was evaluated under greenhouse conditions. Each of the tested cultivars was individually treated with powdered inoculum of each bacterial strain. Untreated seeds were planted as control treatments in autoclaved soil. Effects of the tested strains on levels and activities of some biochemical components of the infected seedlings were also assayed. The biochemical components included total soluble sugars, total soluble proteins, total free amino acids, peroxidase, polyphenol oxidase, phenols, and lipid peroxidation. ANOVA showed that Bacillus strain (B) was a very highly significant source of variation in damping-off and dry weight. Cotton cultivar (V) was a nonsignificant source of variation in damping-off while it was a significant source of variation in dry weight. B × V interaction was a significant source of variation in damping-off and a nonsignificant source of variation in dry weight. Bacillus strain was the most important source of variation as it accounted for 59.36 and 64.99% of the explained (model) variation in damping-off and dry weight, respectively. The lack of significant correlation between levels and activities of the assayed biochemical components and incidence of damping-off clearly demonstrated that these biochemical components were not involved in the pathogenicity of the tested strains. Therefore, it was hypothesized that the pathogenicity of the tested strains could be due to the effect of cell wall degrading enzymes of pathogenic toxins. Based on the results of the present study, Bacillus strains should be considered in studying the etiology of cotton seedling damping-off.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.7 no.1
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• pp.133-137
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• 1969

This experiment was conducted to determine the optimum row width and plant spacing within row under the tropical environment for a leading soybean variety Palmetto and it was carried out at Eakmat Experiment Station in Vietnam. The experiments were arranged in a split plot design with four replications and the test was repeated twice in two years. Variations for seed yield due to the distance between rows were significant at 1 per cent level in 1967 test(dry season growing) and at 5 per cent level in 1968 test. Significant differences for plant height, lodging, maturity, number of branches per plant, and number of pods per plant due to the row width were not found in both tests, while significant differences in difference spacing within row was found in all traits studied. Interaction between width of row and spacing within row for seed yield and plant height were found at five percent level in 1967 test. These results indicate that close planting may increase in seed yield and plant height in both seasons, and decrease in loadging. From these studies, one could be understood that the plant population, particularly in dry season, plays decisive roles on seed yield in soybean culture, and the maximum plant height and minimum value of lodging index were also observed in closest spacing plots. The highest soybean yield in late planting would be expected by a combinations of 30 cm(between rows)${\times}$5cm(between hills) plot, while 40cm ${\times}$ 5cm planting method would be suggested for rainy season growing. Highest seed yield was obtained at closet spacing in both dry and rainy season, and these results led to drilling method in seeding where about 20 seeds per meter of row could be recommended. Besides the seed yield, the close planting may produce some advantages, such as increase plant height and decrease lodging, weeds and erosion of surface soil.

• Journal of the Korean Geotechnical Society
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• v.39 no.9
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• pp.35-50
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• 2023

A preliminary study is conducted to develop seismic design guidelines for temporary retaining structures in a deep excavation. The study involved a comprehensive literature review of the seismic design standards applied domestically and internationally, as well as various methods to calculate seismic earth pressure for pseudostatic analysis. The FLAC 2D, a two-dimensional finite difference analysis program, was utilized to perform pseudostatic analysis using the Semirigid pressure method, Wood method, and Mononobe-Okabe method. The resulting analysis data for the wall moment and axial force of the strut were compared with the dynamic analysis outcomes to evaluate the applicability of pseudostatic analysis. The Semirigid pressure method predicted the most reasonable moment for Stiff walls experiencing horizontal displacements up to 0.4%H. Predicting the axial force of the strut exactly was challenging because the pseudostatic analysis cannot consider dynamic soil-structure interaction; however, it is deemed available for conservative preliminary review to ensure safety.

• Geomechanics and Engineering
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• v.34 no.2
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• pp.115-124
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• 2023

By conducting three-dimensional simulation with consideration of small-strain characteristics of soil stiffness, the effects of excavation geometry and tunnel cover to diameter ratio on deformation mechanisms of an existing tunnel located either at a side of basement or directly underneath the basement were systematically studied. Field measurements were used to verify the numerical model and model parameters. For basement excavated at a side of an existing tunnel, the maximum settlement and horizontal displacement of the tunnel are always observed at the tunnel springline closer to basement and tunnel crown, respectively, regardless of basement geometry. By increasing basement length and width by five times, the maximum movements of tunnel located at the side of basement and directly underneath the basement increase by 450% and 186%, respectively. Obviously, tunnel movements are more sensitive to basement length rather than basement width. For basement excavated at a side of an existing tunnel, tunnel movements at basement centerline become stable when basement length reaches 10 H_e (i.e., final excavation depth). Moreover, tunnel heaves due to overlying basement excavation become stable when the normalized basement length (L/H_e) is larger than 8.0. As tunnel cover to diameter ratio varies from 2.5 to 3.0, the maximum heave and tensile strain of tunnel due to overlying basement excavation decrease by up to 41.0% and 44.5%, respectively. If basement length is less than 8 H_e, the assumption of plane strain condition of basement-tunnel interaction grossly overestimates tunnel movements, and ignores tensile strain of tunnel along its longitudinal direction. Thus, three-dimensional numerical analyses are required to obtain a reasonable estimation of tunnel responses due to adjacent and overlying basement excavations in clay.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.467-475
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• 2023

To ensure the safety of the pipeline against large deformation of the pipeline during lowering construction, the analysis for pipeline becomes emphasized. The FE analysis has a lower efficiency at calculating time, while it could be obtained high accuracy. In this paper, a reasonable analytical model for analysis of pipeline is proposed during lowering-in. This analytical model is partitioned considering the geometrical characteristics and modeled as two parameters Beam On Elastic Foundation and Euler-Bernoulli beam considering the boundary condition. This takes into account the pipeline-soil interaction and the axial forces acting on the pipeline. Previous model can only be applied to standardized conditions, whereas the proposed model defined as Segmented Pipeline Model can be considered for the majority of construction conditions occurred during lowering-in. In addition, minimized assumptions and segmented elements lead to improve the convenience and applicability of modeling. Nevertheless, the model shows accurate results compared to the FE model. Accordingly, it is expected that it will be used efficiently for configuration management as well as safety assessment of pipeline during lowering-in.

• Journal of Korea Soil Environment Society
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• v.3 no.3
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• pp.93-107
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• 1998

Because of its stable quantity and quality, groundwater has long been a reliable source of drinking water for domestic users. Rapid economic growth and rising standards of living have in recent years put severe demands on drinking water supplies in Korea. Groundwaters that are currently being used for natural mineral water were hydrochemically evaluated and investigated in order to maintain their quality to satisfy strict health standards. There exist 15 natural mineral water plants in the Okcheon metamorphic belt. Characteristics of groundwaters are different from those of other areas in that electrical conductivity, hardness, contents of Ca, Mg and $HCO_3$are relatively high. The content of major cations is in the order of Ca>Mg, Na>K, whereas that of major anions shows the order of $HCO_3$>$SO_4$>Cl>F. The fact that the Ca-Mg-HCO$_3$type is mostly predominant among water types reflects that dissolution of carbonates that are abundantly present in the metamorphic rocks plays an important part in groundwater chemistry. Representative correlation coefficients between chemical species show Mg-$HCO_3$(0.92), Ca-$HCO_3$(0.88), Ca-Mg(0.80), Ca-Cl(0.78), Mg-$SO_4$(0.78), Ca-$SO_4$(0.71), possibly due to the effect by dissolution of carbonates, gypsum or anhydrite. Determinative coefficients between some chemical species represent a good relationship, especially for EC-(K+Na+Ca), Ca-$HCO_3$, Ca-Mg, indiacting that they are similar in chemical behaviors. According to saturation index, most chemical species are undersaturated with respect to major minerals, except for some silica phases. Groundwater is slightly undersaturated with respect to calcite and dolomite, whereas it is still greatly undersaturated with respect to gypsum, anhydrite and fluorite, Based on the Phase equilibrium in the systems $NA_2$O-$Al_2$$O_3$-$SiO_2$-$H_2$O and $K_2$O-$Al_2$$O_3$-$SiO_2$-$H_2$O, it is clear that groundwater is in equilibrium with kaolinite, evolved from the stability area of gibbsite during water-rock interaction. It is expected that chemical evolution of groundwater continue to proceed with increasing pH by reaction of feldspars, with calcite much less reactive.

• Journal of Soil and Groundwater Environment
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• v.7 no.3
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• pp.115-132
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• 2002

To distinguish the anthropogenic inputs from the chemical weathering with water-rock interaction on the chemical compositons of groundwater in Kwangju city, four different water groups were established based on the landuse type, lithology and topology. The sample from greenbelt area belongs to Group Ⅰ, whereas those from green buffer zone, urban area and industrial area belong to Group II, Group Ⅲ and Group Ⅳ, respectively. The geology of this city mainly consists of biotite granite and granitic gneiss. The concentration of main cations is subject to the behavior of feldspars, micas and carbonate minerals. Cl$\^$-/ and NO$_3$$\^$-/ are supplied by anthropogenic inputs such as domestic sewage whose concentration of these anions is highest in the Group Ⅲ samples. With the Piper diagram, the groundwaters of Group Ⅲ are mainly plotted in CaSO$_4$-CaCl$_2$ type, whereas those of other groups are plotted in Ca(HCO$_3$)$_2$ type, The calculation for the activities of ions and saturation indices of some minerals shows that most of the minerals are undersaturated and plotted in the area of equlibrium with kaolinite. Three factors were extracted from the factor analysis for chemical data. Factor 1 controlled by HCO$_3$$\^$-/, Ca$\^$2-/, SO$_4$$\^$2-/, Mg$\^$2+/ and Na$\^$+/, explains the dissolution of carbonate minerals. mica and plagioclase. Factor 2, controlled by Cl$\^$-/ and NO$_3$$\^$-/, explains the influence of artificial pollution. Factor 3, controlled by Mn, Fe and Zn is subject to the industrial waste water, but the evidence is not clear. Factor 1 is dominant in the Group I and II, indicating that those samples are subjected to natural chemical weathering, The higher scores of factor 2 in the Group Ⅲ samples indicate the potential artificial pollution.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.4
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• pp.177-191
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• 1998

For various kinds of waters including surface water, shallow groundwater (＜70 m deep) and deep groundwater (500∼810 m deep) from the Pungki area, an integrated study based on hydrochemical, multivariate statistical, thermodynamic, environmental isotopic (tritium, oxygen-hydrogen, carbon and sulfur), and mass-balance approaches was attempted to elucidate the hydrogeochemical and hydrologic characteristics of the groundwater system in the gneiss area. Shallow groundwaters are typified as the 'Ca-HCO$_3$'type with higher concentrations of Ca, Mg, SO$_4$and NO$_3$, whereas deep groundwaters are the 'Na-HCO$_3$'type with elevated concentrations of Na, Ba, Li, H$_2$S, F and Cl and are supersaturated with respect to calcite. The waters in the area are largely classified into two groups: 1) surface waters and most of shallow groundwaters, and 2) deep groundwaters and one sample of shallow groundwater. Seasonal compositional variations are recognized for the former. Multivariate statistical analysis indicates that three factors may explain about 86% of the compositional variations observed in deep groundwaters. These are: 1) plagioclase dissolution and calcite precipitation, 2) sulfate reduction, and 3) acid hydrolysis of hydroxyl-bearing minerals(mainly mica). By combining with results of thermodynamic calculation, four appropriate models of water/ rock interaction, each showing the dissolution of plagioclase, kaolinite and micas and the precipitation of calcite, illite, laumontite, chlorite and smectite, are proposed by mass balance modelling in order to explain the water quality of deep groundwaters. Oxygen-hydrogen isotope data indicate that deep groundwaters were originated from a local meteoric water recharged from distant, topograpically high mountainous region and underwent larger degrees of water/rock interaction during the regional deep circulation, whereas the shallow groundwaters were recharged from nearby, topograpically low region. Tritium data show that the recharge time was the pre-thermonuclear age for deep groundwaters (＜0.2 TU) but the post-thermonuclear age for shallow groundwaters (5.66∼7.79 TU). The $\delta$$\^$34/S values of dissolved sulfate indicate that high amounts of dissolved H$_2$S (up to 3.9 mg/1), a characteristic of deep groundwaters in this area, might be derived from the reduction of sulfate. The $\delta$$\^$13/C values of dissolved carbonates are controlled by not only the dissolution of carbonate minerals by dissolved soil CO$_2$(for shallow groundwaters) but also the reprecipitation of calcite (for deep groundwaters). An integrated model of the origin, flow and chemical evolution for the groundwaters in this area is proposed in this study.

• Journal of Korean Society of Forest Science
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• v.100 no.1
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• pp.52-61
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• 2011

Whereas recent researches have elucidated the positive ecological roles of large wood (LW) in fishbearing channels, LW is also recognized as a negative factor of log-laden debris flows and floods in densely populated areas. However in Republic of Korea, no study has investigated longitudinal variations of LW distribution and dynamic along the stream corridor. Hence to elucidate 1) physical factors controlling longitudinal distribution of LW and 2) their effect on variation in LW load amount, we surveyed the amount of LW with respect to channel morphology in a mountain stream, originated from Mt. Ki-ryong in Inje, Gangwondo. Model selection in the Generalized Linear Model procedure revealed that number of boulder (greater than or equal to 1.0 m in diameter), bankfull channel width and their interaction were the best predictors explaining LW load volume per unit channel segment area (unit LW load). In general, boulders scattered within small mountain streams influence LW retention as flow obstructions. However, in this study, we found that the effect of the boulders vary with the channel width; that is, whereas the unit LW load in the segment with narrow channel width increased continuously with increasing boulder number, it in the segment with wide channel width did not depend on the boulder number. This should be because that, in two channels having different widths, the rates of channel widths reduced by boulders are different although boulder numbers are same. Our findings on LW load varying with physical factors (i.e., interaction of boulder number and channel width) along the stream corridor suggest understanding for longitudinal continuum of hydrogeomorphic and ecologic characteristics in stream environments, and these should be carefully applied into the erosion control works for systematic watershed management and subsequent disaster prevention.