• Journal of the Korean Geotechnical Society
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• v.30 no.1
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• pp.37-47
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• 2014

Unsaturated hydraulic conductivity (HC) is integrated theoretically from soil water retention curves (SWRC) by Mualem capillary model, but the prediction of HC is extremely sensitive to small variation of matric suction near saturation. Near saturation, the Mualem HC based on smooth SWRC decreases abruptly and has problems in the reliability of hydraulic behavior and the stability of numerical solutions. To improve van Genuchten-Mualem (VGM) HC, the van Genuchten SWRC model is modified within range of low matric suction (arbitrary air entry pressure). At an arbitrary air entry pressure, the VG SWRC is linearized in log scale until full saturation. The modified VG SWRC does not affect the fit of actual retention behavior and either the parameters of original VG SWRC fit. Using the modified VG SWRC, the VGM HC is modified to integrate for each interval decomposed by arbitrary air entry pressure. An analytical solution on modified VGM HC is proposed each interval, to protect the rapid change in HC near saturation. For silty soils, VGM models of HC function underestimate the unsaturated permeability characteristics and especially show rapid reduction near saturation. The modified VGM model predicts more accurate HC functions for Korean weathered soils. Furthermore, near saturation, the saturated HC is conserved by the modified VGM model. After 2-D infiltration analysis of an actual slope, the hydraulic behaviors are compared for VGM and the modified models. The prediction by the proposed model conserved the convergence of solutions on various rainfall conditions. However, the solution by VGM model did not converge since the conductivity near saturation reduced abruptly for heavy rainfall condition. Using VGM model, the factor of safety is overestimated in both initial and final stage during heavy rainfall. Stability analysis based on infiltration analysis could simulate the actual slope failure by the proposed model on HC.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.45-54
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• 1999

It is known from the previous study on the behavior of sharter single pile during simulated seaquake induced by the vertical component of earthquake that the compressive capacity and the soil plugging resistance of single open-ended pipe pile were completely degraded. But, the capacity of single open-ended pipe pile with greater penetration and the capacity of piles group with shorter penetration were expected to be stable after seaquake motion. In this study, first single pile, 2-pile or 4-pile groups with several simulated penetrations were driven into the calibration chamber with saturated fine medium sand and the compressive load test for each installed pile or pile groups was performed. Then, about 95% compressive load of the ultimate capacity was applied on the pile head during the simulated seaquake motion. Finally, to confirm the reduction of pile capacity during the simulated seaquake motion, the compressive load test for each single pile or pile groups after seaquake motion was performed. During the simulated seaquake, compressive capacities of single open-ended pipe pile and piles group installed in shallow sea were not decreased. But, the stability of open-ended pile installed in deep sea was depended on the pile penetration depth. So, single open-ended pile with greater penetration of 27 m was stable, and 2-pile and 4-pile groups with penetration more than 13m were stable. But, 2-pile groups with penetration of 7m was failed, and the compressive capacity of 4-pile groups with penetration of 7m was degraded about 15%.

• Journal of the Korean Society of Clothing and Textiles
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• v.13 no.4
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• pp.400-411
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• 1989

Moisture related properties of fabrics in dynamic modes are considered to be important in the judgement of the subjective comfort characteristics of clothing fabrics. In the current study, an attempt to improve the cobaltous chloride test method was made which has been known as a convenient screening test for dynamic surface wetness. The color changes of cobaltous chloride treated fabrics on the simulated sweating skin were calibrated against standard color strips. The standard color strips were made of all typs of test fabrics and installed inside of the test tubes containing a series of saturated salt solutions, which gives more quantitative informations on dynamic moisture transfer Influences of fiber types and finishes on dynamic moisture transfer in textiles were studied using a single layer of fabric samples. Fiber types included $100\%$ cotton, C/P 50/50, C/P 35/65. Durable press and soil release finished cotton and C/P 50/50 fabrics were also included. There were significant fiber effects on the dynamic moisture transfer. The order of time taken to reach to the specified $\%$ RH was C/P 35/65$100\%$ cotton fabrics. It was possible to detect significant finish effects by increasing the concentrations of cobaltous chloride solutions. The order of time taken to reach to the specified $\%$ R.H was durable press$100\%$ cotton, C/P 50/50, C/P 35/65 and $100\%$ PET were placed at the inner side of the outer layer and tested. It was shown that cobaltous chloride treated $100\%$ cotton fabirc was easier to detect color changes than C/P blend fabic in the double layer experiments. By placing test sample under the cobaltous chloride treated cotton fabrics, it was able to detect the differences among the test samples, some of which were known to be difficult in padding with cobaltous chloride solutions. Besides, the double layer method would provide with the broader application of the cobaltous chloride method in !uture, since it is possible to test the dynamic moisture transfer of clothing as worn.

• Economic and Environmental Geology
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• v.38 no.5 s.174
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• pp.513-523
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• 2005

The contamination of soils and groundwaters in the Dalcheon mine area, Ulsan, is investigated, and a natural attenuation capacity on redox and pH is evaluated. Arsenopyrite, the major source of arsenic pollution in the Dalcheon mine area, is contained up to $2\%$ in tailings. Furthermore, As-bearing minerals such as loellingite, nicolite, rammelsbergite, gersdorffite cobaltite and pyrite are also source of arsenic contamination, which show various concentration of arsenic each other. Surface of pyrite and arsenopyrite in tailings partly oxidized into Fe-arsenates and Fe-oxides, which means a progressive weathering process. There is no relationship between pH and arsenic content in groundwaters, otherwise Eh and arsenic concentration in unsaturated and saturated groundwater shows positive relationship. RMB (Red Mud Bauxite) could be useful as a trigger on natural attenuation due to superior ability of removal capacity of arsenic when contaminated soil and groundwater in the Dalcheon mine area are remediated.

• Journal of Soil and Groundwater Environment
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• v.14 no.6
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• pp.53-64
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• 2009

Wetlands can remove organic contaminants, metals and radionuclides from wastewater through various biogeochemical mechanisms. In this study, a mathematical model was developed for simulating the fate and transport of chemical species in marsh wetland sediments. The proposed model is a one-dimensional vertical saturated model which is incorporated advection, hydrodynamic dispersion, biodegradation, oxidative/reductive chemical reactions and the effects from external environments such as the growth of plants and the fluctuation of water level due to periodic tides. The tidal effects causes periodic changes of porewater flow in the sediments and the evapotranspiration and oxygen supply by plant roots affect the porewater flow and redox condition on in the rhizosphere along with seasonal variation. A series of numerical experiments under hypothetical conditions were performed for simulating the temporal and spatial distribution of chemical species of interests using the proposed model. The fate and transport of a trace metal pollutant, chromium, in marsh sediments were also simulated. Results of numerical simulations show that plant roots and tides significantly affect the chemical profiles of different electron acceptors, their reduced species and trace metals in marsh sediments.

• Journal of Soil and Groundwater Environment
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• v.14 no.6
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• pp.87-94
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• 2009

Surfactant-enhanced air sparging (SEAS) was developed to suppress the surface tension of groundwater prior to air sparging resulting in higher air saturation and larger contact area between NAPL and gas during air sparging. Larger contacting interface between NAPL and gas means faster mass transfer of contaminants from NAPL to gas phase. This new technique, however, is limited to relatively volatile contaminants because vaporization is its basic mechanism of mass transfer. In this study, SEAS was tested at an elevated temperature for a semi-volatile n-decane, which is expected not to be a good candidate of SEAS application due to its low vapor pressure at ambient temperature. Three sparging experiments were conducted using 1-dimensional column (5 cm id, 80 cm length) packed with sand; (1) ambient temperature ($23^{\circ}C$), column saturated with distilled water, (2) SEAS at ambient temperature ($23^{\circ}C$), for n-decane contaminated sand, (3) SEAS at elevated temperature ($73^{\circ}C$), for n-decane contaminated sand. Higher air saturation was achieved by SEAS compared to that by air sparging without surfactant application. The n-decane removal efficiency of SEAS at elevated temperature was significantly higher(> 10 times) than that of ambient SEAS. The n-decane concentrations in the gas effluent from column during SEAS at $73^{\circ}C$ are found to be 10 times of those measured at ambient temperature. Thus, SEAS technique can be applied for removal of semi-volatile contaminants provided that an appropriate technique for elevating aquifer temperature is available.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.4
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• pp.247-252
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• 2000

Polyamine concentrations were clearly enhanced in leaves and chloroplasts by Cd treatment, but not in thylakoid and PSII. It appeared that newly synthesized polyamines by Cd are distributed in stromal space. The accumulated polyamines in stromal space could not be adjacent to thylakoid membranes, suggesting that they are already saturated. The levels of putrescine and spermine were about 36 and 20 fold lower in chloroplast than in whole leaf cells respectively, whereas agmatine level was only 3.7 fold lower. The inhibitory effect of Cd nn $O_2$ evolving process was obviously alleviated by 0.2mM spermine supplement. Polyamines stimulated $O_2$ evolution within the range of 0.5mM in spinach thylakoids. It was also found that stimulating effect of polyamines is about 2 fold higher in dicothyledonous spinach than in monocotyledonous wheat at same concentrations. Furthermore, the enhanced activity of $O_2$ evolution was lowered rather by agmatine treatment than by putrescine treatment in wheat, suggesting a difference between monocot and dicot.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.81-91
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• 2005

'Coarse grained material' refers to crushed stones or gravels, and the behaviour of soil containing coarse grained material is not easily defined using the conventional soil mechanics theory due to the influences of large particles, therefore large scale test is essential to investigate their effects. Previous studies have identified the major factors affecting the properties of coarse grained materials by using large scale shear testing apparatus, such as maximum particle size, water content, density and uniformity coefficients. In this paper, the effect of variation of maximum particle size and water content on shear strength was analyzed from the results of large scale shear test. In addition, the fiction coefficient at critical state per vertical load was estimated using the equation proposed by Wood (1998). The sample for the test was obtained from the local quarry sites. Tests results show that the shear strength for 50.8 m maximum particle size is relatively larger than that of 76.3 m and air-dry sample has larger shear strength than saturated sample. In the meantime, the friction coefficient at critical state shows $1.0\sim1.6$ according to the test conditions.

• Korean journal of applied entomology
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• v.22 no.1 s.54
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• pp.1-6
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• 1983

The survey on the occurrence and distribution of barley stripe disease was conducted in the farmer's field of 19 gun (county) throughout Yeongmm area in May of 1982, in order to obtain a basic information on the breeding of resistant varieties, and for control of the disease. The percent of infected culms of barley stripe disease in Gyeongnam province (Southern Yeongnam) was higher $(13.7\%)$ them in Gyeong-bug $(6.9\%)$, northern Yeongnam, and especially, Ham-an, Milyang, Eui-chang and Weol-seong were severly occurred. The cultivar of Millyang 6 was slightly infected while the cultivars Olbori and Oweolbori were severely infected by the disease. Among soil conditions, the barley plant grown in the loam, clay and clay loam texture which have more availble moisture, and that of the plant cultivated in the poorly drained soils were shown to have severe infection. The barley plant grown in the soils in local valley $(18.8\%)$ where is frequently over saturated with water showed the more infection the barley plant grown in plains $(9.5\%)$. Generally, the poorer the soil drainage the more severeinfection occurred. Among cultivation conditions, the earlier the sowing dates of the barley, the less the percent of infected culms was observed. The heavier or lighter application of N fertilizer than the optimum to barley plant seemed to cause more infection.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.2
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• pp.121-131
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• 2007

Despite the close linkage in changes between the ecological and hydrological processes in forest ecosystems, an integrative approach has not been incorporated successfully. In this study, based on the vegetation and hydrologic data of the Gwangneung headwater catchment with the Geographic Information System, we attempted such an integrated approach by employing the Regional Hydro-Ecologic Simulation System (RHESSys). To accomplish this, we have (1) constructed the input data for RHESSys, (2) developed an integrated calibration system that enables to consider both ecological and hydrological processes simultaneously, and (3) performed sensitivity analysis to estimate the optimum parameters. Our sensitivity analyses on six soil parameters that affect streamflow patterns and peak flow show that the decay parameter of horizontal saturated hydraulic conductivity $(s_1)$ and porosity decay by depth (PD) had the highest sensitivity. The optimization of these two parameters to estimate the optimum streamflow variation resulted in a prediction accuracy of 0.75 in terms of Nash-Sutcliffe efficiency (NSec). These results provide an important basis for future evaluation and mapping of the watershed-scale soil moisture and evapotranspiration in forest ecosystems of Korea.