• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.71-80
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• 2018

In this study, the seismic response of cut-and-cover box tunnels is evaluated from pseudo-static analyses and the fragility curves are derived. A series of site profiles were used to evaluate the effect of soil conditions. A total of 20 ground motions were used. The fragility curves were developed as functions of peak ground acceleration for three damage states, which are minor, moderate, and extensive states. The damage indices, defined as the ratio of the elastic moment to the yield moment, correlated to three damage states, were used. The curves are shown to greatly depend on the site profile. The curves are further compared to those derived in previous studies. The widely used empirically derived curves are shown not to account for the site effects, and therefore underestimate the response for soft sites.

• Mycobiology
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• v.49 no.1
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• pp.78-85
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• 2021

Morels (Morchella spp.) are valuable medicinal and edible mushrooms. In this study, chemical profiles of aromas and lipophilic extracts of black morel (Morchella importuna) grown in China were analyzed by gas chromatography/mass spectroscopy, along with the evaluation of antioxidant and antimicrobial activities for the lipophilic extracts. Sixty-five compounds in total were identified from the aromas, and 1-octen-3-ol was the main component for aromas of fresh (34.40%) and freeze-dried (68.61%) black morels, while the most abundant compound for the aroma of the oven-dried sample was 2(5H)-furanone (13.95%). From the lipophilic extracts, 29 compounds were identified with linoleic acid as the main compound for fresh (77.37%) and freeze-dried (56.46%) black morels and steroids (92.41%) as the main constituent for an oven-dried sample. All three lipophilic extracts showed moderate antioxidant activities against 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) with the IC50 values ranging 7.56~17.52 mg/mL and 5.75~9.73 mg/mL, respectively, and no obvious antimicrobial activity was observed for lipophilic extracts. The drying methods affect the chemical profile of black morel, and freeze-drying was favorable for retaining nutrients and morel smell. This is the first report on the aroma and lipophilic extracts of M. importuna grown in China.

• The Korean Journal of Food And Nutrition
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• v.35 no.3
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• pp.213-222
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• 2022

Sprouts have various health benefits. Specifically, wheat sprouts are rich in bioactive compounds, such as vitamins and polyphenols. Elicitation induces and enhances secondary metabolite biosynthesis in plants. Therefore, in this study, we investigated the effects of sodium chloride (NaCl) treatments on the growth profile, free amino acid content, and antioxidant activity of germinated wheat (Triticum aestivum). Wheat seeds were germinated at 20℃ for 10 days and treated with 0, 2, 4, 7.5, and 10 mM of NaCl 10 days before harvesting. Treating the soil bed with NaCl increased the nutritional component amounts, such as free amino acids and γ-aminobutyric acid. The chlorophyll a and b concentrations were the highest in the hydroponic system treated with 7.5 mM NaCl. In addition, the polyphenol and flavonoid contents of sprouts treated with 2 and 7.5 mM NaCl were 1.94 and 1.34 times higher than that of the control sprouts (0 mM NaCl, water only), respectively. These results suggest that 2 to 4 mM NaCl treatments improve the nutritional and food quality of wheat sprouts more than water only.

• Journal of the Korean Geotechnical Society
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• v.23 no.11
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• pp.27-37
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• 2007

Downhole seismic method is very economic and easy to operate because it uses only one borehole and simple surface source to obtain the shear wave velocity profile of a site. In this study, automatic shear wave source was developed for efficient downhole seismic testing. This source is motor-spring type and easy to control. It can lessen the labor of operator and the working time. Moreover, it can provide better and repetitive signals for data interpretation. By combining developed automatic source with automatic receiver system, PC based data acquisition system, advanced managing program, and semi-automatic downhole performing system were constructed. Through comparison test with manual source, advantages of automatic source were verified. Constructed semi-automatic downhole testing system including automatic shear wave source was applied to the soft soil site. The applicability and reliability were verified and the importance of automating testing system for obtaining reliable result was emphasized.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.73-83
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• 2022

The factors influencing landslide occurrence were analyzed for six points on the upper slope and the 24 points on the lower slope along a forest road around Sangsan village in Chungju, Korea, where landslides have occurred due to heavy rainfall. In terms of physico-mechanical properties of the soil layer, the lower slope seemed to loosen owing to the higher porosity, lower unit weight, and lower friction angle compared with the upper slope. With respect to topographic characteristics, the lower slope had thicker regolith, more concave profile and plan curvatures, lower slope angles, and higher topographic wetness index values than the upper slope. Therefore, all the properties (except for the slope angle) appear to make the lower slope of the forest road more vulnerable to landslides than the upper slope. Apart from the physico-mechanical and topographic characteristics, inadequate maintenance and management of drainage facilities are also considered as further major factors influencing landslide occurrence.

• Journal of the Korean Geosynthetics Society
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• v.22 no.4
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• pp.9-15
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• 2023

Compaction is performed in civil engineering sites to secure the stability of the ground and prevent settlement. While the process of compaction is crucial, it is also essential to evaluate the degree of compaction after the completion of the process. In domestic sites, the evaluation of compaction is mainly conducted on a small number of spot using point-based tests such as plate load tests and sand cone tests. The methods presented so far allow assessment of surface compaction, but evaluating compaction in deeper layers poses challenges. Moreover, due to the limited coverage of point-based testing, it is difficult to achieve an overall assessment of compaction. As a solution to these issues, the Spectral-Analysis-of-Surface-Waves (SASW) tests were utilized to evaluate compaction. SASW tests offer a broader measurement range compared to point-based tests, and depending on the test setup, this method can provide the stiffness of the ground at greater depths. In this study, SASW tests were conducted in a compacted soil site under different conditions to assess compaction. Additionally, Nuclear Density Gauge tests were conducted concurrently to compare and verify the results of SASW. The research results confirmed the feasibility of evaluating compaction using SASW at the geotechnical site.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.1
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• pp.8-15
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• 2003

If contaminated river water is sprayed over a floodplain, the microbial processes can simultaneously remove organic matter and nitrogen during the infiltration through the sediment profile. The effect of rhizosphere on the removal of organic matter and nitrogen from contaminated river water was investigated using floodplain lysimeters. River water was sprayed at a rate of $68.0L\;m^{-2}\;d^{-1}$ on the top of the lysimeters with or without weed vegetation on the surface, Concentrations of $NO_3$, $NH_4$ and dissolved oxygen (DO), and chemical oxygen demand (COD) and Eh in water were measured as functions of depth for 4 weeks after the system reached a steady state water flow and biological reactions. A significant reductive-condition for denitrification developed in the 30-cm surface profile of lysimeters with weeds. At a depth of 30 cm, COD and $NO_3$-N concentration decreased to 5.2 and $0.9mg\;L^{-1}$ from the respective influent concentrations of 18.2 and $9.8mg\;L^{-1}$. The removal of $NO_3$ in lysimeters with weeds was significantly higher than in those without weeds. Vegetation on the top was assumed to remove $NO_3$ directly by absorption and to create more favorable conditions for denitrification by supply of organic matter and rapid $O_2$ consumption, In the lysimeters without weeds, further removal of $NO_3$ was limited by the lack of an electron donor, i.e. organic matter. These results suggest that the filtration through native floodplains, which include rhizospheres of vegetation on the surface, can be effective for the treatment of contaminated river water.

• Korean Journal of Soil Science and Fertilizer
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• v.7 no.1
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• pp.17-21
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• 1974

This study was performed to find out the organic matter content, and what is more, the relation between its content and major morphological properties of cultivated upland soils in Korea. The results were as follows. 1. The average organic matter content of cultivated upland soils was 1.73 percent, mostly ranging from 0.6 to 2.5 percent. 2. Examining the organic matter content by subgroup of cultivated upland soils. It was found 13 percent in volcanic ash yellowish brown Cambisols and 6.3 percent in Humic yellowish brown Entisols, Fluventic yellowish brown Entisols was found 1.0 percent, lowest one. The average organic matter content of Entisols, Cambisols, and Argillisols was 1.1, 2.1, and 1.8 percent respectively. 3. According to organic matter content by texture of profile, the average content of sandy soils was 1.0 percent; 1.5 percent in coarse loamy soils; and 1.8 percent in fine loamy soils. The organic matter content increased with an increased clay content in coarse texture group, but there was no significant difference between fine loamy and clayey soil group. This tendency was also observed in surface soil texture. 4. In the relation between slope and organic matter content, its content in flat area was 1.3 percent that is rather low compared to 1.6 percent of sloping area. Especially, cultivated upland soils ranging brown 15 to 30 percent in slope were 1.8 percent which is relatively high. 5. The organic matter content have nothing to do with suitability groups. Itss ontent of I, II, III, IV and V class was 1.3, 1.6, 1.7, 1.2 and 2.0 percent respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.1
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• pp.1-7
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• 2010

This study was carried out to investigate plow pan characteristics and to grasp the relationship between its particle size distribution fractal dimension ($D_m$) and water transport in paddy plow pan. Twenty four soil sampling sites with different management groups, ordinary and sandy-textured, were selected and investigated for physical properties of soils such as Yamanaka hardness in April, non-submerged condition, before rice seedling transplanting. The plow pan appearing depth and thickness was determined by penetration resistance profile. Undisturbed core samples with five replicates were sampled at plow pan layerwith 2 inch cores for measuring soil bulk density and saturated hydraulic conductivity. The particle size distribution fractal dimension ($D_m$) was calculated by the method following the procedure Tylerand Wheacraft (1992), using the USDA-based particle size analysis datawith fractions of 0-0.002, 0.002-0.053, 0.053-0.1, 0.1-0.25, 0.25-0.5, 0.5-1.0, and 1.0-2.0 mm. The plow pan of investigated fields appeared at a range from 5 to 30 cm depth, showing minimum value in sandy-textured management group and maximum value in ordinary management group. The thickness of plow pan were distributed from 5 to 17 cm, showing both minimum and maximum values in sandy-textured management group. Averagely, the plow appearing depth were deeper in ordinary management group than in sandy-textured management group, whereas the reverse in the thickness of plow pan. The particle size distribution fractal dimension ($D_m$) had higher value with finer textures, with higher fractality in coarser texture. Saturated hydraulic conductivities, $K_s$, of plow pan soils distributed from 0.5 to 1420 mm $day^{-1}$, having the highest value in sandy skeletal soils. The $K_s$ decreased with decreasing clay content and $D_m$, showing power function relationships. The coefficient of determination, $R^2$, of the fitted power functions were higher in $D_m$ as x-axis than in clay content. This means that $D_m$ could give us more effective estimation than clay content. Especially, sandy-textured paddy soils had higher $R^2$, compared to ordinary paddy soils. $K_s$ of relatively coarse-textured soils with less than 18%of clay content, therefore, was more dependent on particle size distribution than that of relatively fine-textured soils. From these results, it could be concluded that the fractal scaling gives us a unique quantity describing particle size distribution and then can be applied to estimate saturated hydraulic conductivity, especially more effective in coarse-textured soils.

• Korean Journal of Soil Science and Fertilizer
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• v.21 no.4
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• pp.386-408
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• 1988

A study was conducted to develop a model for estimating evapotranspiration and yield of Chinese cabbages from meteorological factors from 1981 to 1986 in Suweon, Korea. Lysimeters with water table maintained at 50cm depth were used to measure the potential evapotranspiration and the maximum evapotranspiration in situ. The actual evapotranspiration and the yield were measured in the field plots irrigated with different soil moisture regimes of -0.2, -0.5, and -1.0 bars, respectively. The soil water content throughout the profile was monitored by a neutron moisture depth gauge and the soil water potentials were measured using gypsum block and tensiometer. The fresh weight of Chinese cabbages at harvest was measured as yield. The data collected in situ were analyzed to obtain parameters related to modeling. The results were summarized as followings: 1. The 5-year mean of potential evapotranspiration (PET) gradually increased from 2.38 mm/day in early April to 3.98 mm/day in mid-June, and thereafter, decreased to 1.06 mm/day in mid-November. The estimated PET by Penman, Radiation or Blanney-Criddle methods were overestimated in comparison with the measured PET, while those by Pan-evaporation method were underestimated. The correlation between the estimated and the measured PET, however, showed high significance except for July and August by Blanney-Criddle method, which implied that the coefficients should be adjusted to the Korean conditions. 2. The meteorological factors which showed hgih correlation with the measured PET were temperature, vapour pressure deficit, sunshine hours, solar radiation and pan-evaporation. Several multiple regression equations using meteorological factors were formulated to estimate PET. The equation with pan-evaporation (Eo) was the simplest but highly accurate. PET = 0.712 + 0.705Eo 3. The crop coefficient of Chinese cabbages (Kc), the ratio of the maximum evapotranspiration (ETm) to PET, ranged from 0.5 to 0.7 at early growth stage and from 0.9 to 1.2 at mid and late growth stages. The regression equation with respect to the growth progress degree (G), ranging from 0.0 at transplanting day to 1.0 at the harvesting day, were: $$Kc=0.598+0.959G-0.501G^2$$ for spring cabbages $$Kc=0.402+1.887G-1.432G^2$$ for autumn cabbages 4. The soil factor (Kf), the ratio of the actual evapotranspiration to the maximum evapotranspiration, showed 1.0 when the available soil water fraction (f) was higher than a threshold value (fp) and decreased linearly with decreasing f below fp. The relationships were: Kf=1.0 for $$f{\geq}fp$$ Kf=a+bf for f$$I{\leq}Esm$$ Es = Esm for I > Esm 6. The model for estimating actual evapotranspiration (ETa) was based on the water balance neglecting capillary rise as: ETa=PET. Kc. Kf+Es 7. The model for estimating relative yield (Y/Ym) was selected among the regression equations with the measured ETa as: Y/Ym=a+bln(ETa) The coefficients and b were 0.07 and 0.73 for spring Chinese cabbages and 0.37 and 0.66 for autumn Chinese cabbages, respectively. 8. The estimated ETa and Y/Ym were compared with the measured values to verify the model established above. The estimated ETa showed disparities within 0.29mm/day for spring Chinese cabbages and 0.19mm/day for autumn Chinese cabbages. The average deviation of the estimated relative yield were 0.14 and 0.09, respectively. 9. The deviations between the estimated values by the model and the actual values obtained from three cropping field experiments after the completion of the model calibration were within reasonable confidence range. Therefore, this model was validated to be used in practical purpose.