• Journal of the Korean Geotechnical Society
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• v.40 no.2
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• pp.55-64
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• 2024

While shield tunneling has demonstrated stability in international cases, the new Austrian tunneling method (NATM) encounters challenges in urban environments with shallow cover, weathered ground, and high groundwater levels. This paper introduces two typical collapse scenarios observed in urban areas, specifically within weathered bedrock and uncemented sandy soil layers. The collapses are analyzed using six stability evaluation methods, and the results are synthesized to assess the excavation face stability through a hexagonal diagram. The study finds a consistent agreement between the analysis results of the two collapsed tunnel sites and the evaluation outcomes. The employment of the stability evaluation diagram, a comprehensive method that considers the ground characteristics of the target tunnel, proves crucial for ensuring barrier stability during the tunnel design stage. This method is essential for a holistic evaluation, especially when addressing challenging ground conditions in urban settings.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.119-133
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• 2020

Underground utility tunnel, the most representative cut and cover structure, is subjected to seismic force by displacement of the surrounding soil. In 2020, Korea Infrastructure Safety Corporation has published "Seismic Performance Evaluation Guideline for Existing Utility Tunnel." This paper introduces two seismic evaluation methods, RDM (Response Displacement Method) and RHA (Response History Analysis) adopted in the guide and compares the methods for an example of an existing utility tunnel. The test tunnel had been constructed in 1988 and seismic design was not considered. RDM is performed by single and double cosine methods based on the velocity response spectrum at the base rock. RHA is performed by finite difference analysis that is able to consider nonlinear behavior of soil and structure together in two-dimensional plane strain condition. The utility tunnel shows elastic behavior for RDM, but shows plastic hinge for RHA under the collapse prevention level earthquake.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.779-788
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• 2019

The compaction grouting method is one of the conventional ground improvement methods, which consolidates and compacts the surrounding ground through the injection of grout materials with low mobility. Injecting the grout into the ground can improve the soil properties, as well as form a composite of soil-grout columns. However, the conventional grout pumping is not applicable to handle multiple injection holes at the same time, which may diminish its constructability when the construction time is not enough. This paper proposes a simultaneous multiple compaction-grouting method using a new pump system developed to cover up simultaneously three injection holes at a time. Field injection tests with a single injection hole and with triangular arrangement of injection holes were conducted to evaluate the applicability of the proposed method to soft clay ground. In addition, a series of standard penetration tests (SPTs) were performed to assess the efficiency of each arrangement in improving the soft ground. It is noted from the in-situ test results that the interval distances between injection holes and the elapse time for ground stabilization are the crucial factors governing the applicability of the simultaneous multiple compaction-grouting method to improve the soft clay ground.

• Journal of the Korean Association of Geographic Information Studies
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• v.20 no.3
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• pp.141-152
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• 2017

This paper presents a technical method for flood estimation based on satellite rainfall and satellite rainfall correction method for watersheds lacking measurement data. The study area was the Sebou Watershed, Morocco. The Integrated Flood Analysis System(IFAS) and Grid-based Rainfall-Runoff Model(GRM) were applied to estimate watershed runoff. Daily rainfall from ground gauges and satellite-derived hourly data were used. In the runoff simulation using satellite rainfall data, the composites of the daily gauge rainfall and the hourly satellite data were applied. The Shuttle Radar Topographic Mission Digital Elevation Model(SRTM DEM) with a 90m spatial resolution and 1km resolution data from Global map land cover and United States Food and Agriculture Organization(US FAO) Harmonized World Soil Database(HWSD) were used. Underestimated satellite rainfall data were calibrated using ground gauge data. The simulation results using the revised satellite rainfall data were $5,878{\sim}7,434m^3/s$ and $6,140{\sim}7,437m^3/s$ based on the IFAS and GRM, respectively. The peak discharge during flooding of Sebou River Watershed in 2009~2010 was estimated to range from $5,800m^3/s$ to $7,500m^3/s$. The flood estimations from the two hydrologic models using satellite-derived rainfall data were similar. Therefore, the calibration method using satellite rainfall suggested in this study can be applied to estimate the flood discharge of watersheds lacking observational data.

• Journal of the Korean Geosynthetics Society
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• v.14 no.2
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• pp.23-33
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• 2015

The earth pressure acting on underground structure was measured by application of the instrumentation system in the subway construction site constructed by the method of cut-and-cover tunnel. The measured earth pressure was compared with the earth pressure obtained from the existed theoretical equation, and the actual earth pressure diagram acting on the underground structure was investigated. As a result of investigation, the vertical earth pressure is mainly affected by the embankment height, and the lateral earth pressure is significantly affected by whether the existence of earth retaining structures or not. The measured vertical earth pressure is very similar to the theoretical earth pressure proposed by Bierbaumer. The measured lateral earth pressure is closed to the active earth pressure proposed by Rankine rather than the earth pressure at rest. The coefficient of earth pressure in soil deposit layer is about 0.35, and the coefficient in soft rock deposit layer is about 0.21. For design and construction the underground structures, therefore, it is reasonable estimation that the lateral earth pressure acting on structures installed in soil deposit layers is an average value between active earth pressure and earth pressure at rest. In rock deposit layers, the lateral earth pressure acting on structure is an active earth pressure only.

• Water for future
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• v.15 no.3
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• pp.49-55
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• 1982

The purpose of this study is to examine the methods of estimation, comparing U.S. SCS method and $\Phi$-index with effective rainfall. And also comparision was made among SCS method, Chow method and Mockus method as to the peak discharge of design storm hydrograph by small river basin. Hydrological data of the Shin river basin which was used in this study and the results of study are as follow; 1) As a result of applying the SCS method to determine the effective rainfall out of total rainfall, it turned out that the everage CN of the basin as obtained by the analysis of hydrologic soil-cover complex was varied as follows; AMC-I was 27.9%, AMC-II 16.4%, AMC-III 8.1% less than the value given by SC method using discharge measurement. 2) The comparision of effective rainfall by the ungaged SCS method with that of gauged $\Phi$-index method showed that the $\Phi$-index method showed that the $\Phi$-index method gives large value by 4.7% to those given by hydrograph. The result of analysis by the SCS method resulted in great difference from discharge measurement. 3) The comparision of SCS method, Chow method, and Mockus method showed that dimensionless hydrograph of SCS method and Chow method were close to the peak discharge of the gauged unit hydrograph, while the other methods gave far different results. 4) Attempts were made, for a better adaptation to the Shin river basin, to introduce lag time formula constant of dimensionless hydrograph of the SCS method by using the peak discharge of the gauged flow hydrograph.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.3
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• pp.208-212
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• 1993

Since ramie suckers distribute soil surface layer within 10cm depth, some of them are dead from low soil temperature in winter. An experiment was conducted to investigate the effects of various mulching methods on safe overwintering of sucker at three or four years old, fully-grown ramie plots. The sprouting dates of ramie was March 28 in transparent vinyl mulching(TPEF), April 1 in transparent vinyl mulching over cover of straw, manure or rice hull at the amount of 500kg /10a (CM), and April 6 in black vinyl mulching(BDEF). These treatments showed earlier sprouting date from 9 to 18 days than the conventional mulching with 1000 kg straw /10a the sprouting date of which was April 15. TPEF treatment showed the earliest but ununiform sprouting. In contrast, sprouts in CM treatment was uniform but emerged somewhat later compared with the treatment of TPEF. The number of stems per unit area increased 50 percent more in TPEF, and 35 to 39 percent more in CM than the treatment of conventional mulching.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.1
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• pp.115-123
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• 2005

Quantitative understanding of spatial characteristics of the study site is a prerequisite to investigate water and carbon cycles in agricultural and forest ecosystems, particularly with complex, heterogeneous landscapes. The spatial characteristics of variables related with topography, vegetation and soil in Gwangneung forest watershed are quantified in this study. To characterize topography, information on elevation, slope and aspect extracted from DEM is analyzed. For vegetation and soil, a land-cover map classified from LANDSAT TM images is used. Four satellite images are selected to represent different seasons (30 June 1999, 4 September 2000, 23 September 2001 and 14 February 2002). As a flux index for CO₂ and water vapor, normalized difference vegetation index (NDVI) is calculated from satellite images for three different grid sizes: MODIS grid (7km x 7km), intensive observation grid (3km x 3km), and unit grid (1km x 1km). Then, these data are analyzed to quantify the spatial scale of heterogeneity based on semivariogram analysis. As expected, the scale of heterogeneity decreases as the grid size decreases and are sensitive to seasonal changes in vegetation. For the two unit grids where the two 40 m flux towers are located, the spatial scale of heterogeneity ranges from 200 to 1,000m, which correspond well to the climatology of the computed tower flux footprint.

• Journal of the Korean Institute of Landscape Architecture
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• v.18 no.4
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• pp.73-85
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• 1991

Rhododendron mucronulatum for. albiflorum, native species is a shrub that has white flowers on May to June, and rare species endangered by people's rash digging or cutting. But its physiological ecological characteristics and propagation method are not being known at all. Therefore, this study was executed to utilize this species as the planting material for landscaping by analysing its habitat environment and growth form, and also experimenting its seed and vegetative propagation, and it field culture and utilization. The results are as follows; 1. The elevation, gradient and direction of this species were 295-1,350m, 10-36$^{\circ}$, northwest respectively. It was found that the species is shade-liking plant that grows under forest cover of average 51.33%. 2. The soil pH and water content of its habitat were 5.4, 25.41% respectively. The organic matter content was 6.29% that was higher than 3.2%, the average organic matter content of forest soil in Korea. 3. Representative plant community within which this species was living was Quercus mongolica community, and its main neighboring species were Lindea obtusiloba, Fraxinus sieboldiana, Rhus trichocarpa, Rhododendron Schlippenbachii, Rododendron mucronulatum. 4. The leaf length and width of this species were 39.18mm, 12.60mm respectively. This result showed that generally its leaf size was larger than that of R. micranthum, R. yedoense var. poukhanense and R. mucronulatum var. ciliatum and smaller than that of R. mucronulatum and R. schlippenbachii. 5. The whole size of its pollen was, as 59${\times}$61$\mu\textrm{m}$, the largest of plants of Rhododendron family including R. mucronulatum and R. mucronulatum var. ciliatum. 6. The result of seed germination experiment at intervals of 5$^{\circ}C$ from 15$^{\circ}C$ to 30$^{\circ}C$ presented the highest germination rate of 94.7% at 20$^{\circ}C$ numerically, but high percent germination at all temperature levels without significant difference. And the seed of this plant proved to be sun-liking seed at requiring dormancy in germination. 7. Through seed germination experiment by treatment of growth regulators such as GA. Thiourea and Kinetin under dark condition, it was found that the effect of GA treatment on germination increase and acceleration was the highest. 8. In greenwood cutting, rooted rate by treatment of various concentration of IBA and NAA on clay and vermiculite bed was not wholly high, but 100ppm plots of both IBA and NAA of clay bed showed relatively good rooted rate. 9. As result of field culture experiment for finding out optimum growth temperature and light intensity, growth conditions such as height, number of leaves, fresh weight and chlorophyll contents were the best at night/day temperature of 20/25$^{\circ}C$ and under 1/2sun. Also, the photosynthetic rate was the highest at 25$^{\circ}C$. Accordingly, it was found that optimum temperature and light intensity for growth of this plant are 25$^{\circ}C$ (day temperature), 50% of natural light respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.2
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• pp.122-128
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• 1997

A pot experiment was carried out using Seomjin-byeo and Samgang-byeo to investigate the effects of nitrogen and sulfur on the growth, yields, and sulfur containing amino acid content of rice. The yields and number of tillers at 50 days after transplanting were increased with the increase of the amounts of nitrogen and sulfur, but N/S ratio was decreased in both varieties. There were a positive correlations between yield and contents of nitrogen and sulfur in straw and brown rice, but a negative correlation between N/S ratio and yields at harvesting stage. Crude protein contents increased with the increase of amounts of nitrogen and sulfur. contents of amino acid containing sulfur in brown rice were positively correlated with the sulfur and nitrogen contents in rice straw.