• Journal of the Korean Geotechnical Society
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• v.22 no.6
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• pp.5-13
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• 2006

Effective stresses may decrease due to generation of excessive pore pressure at the interface between soil and reinforcement in undrained condition such as rapid drawdownof groundwater level, resulting in the decrease in pullout capacity of the reinforcement. In this research, a series of laboratory pullout tests have been performed on different materials (clean sand, 5, 10, 15 and 35% silty sand), different overburden pressures (30, 100 and 200 kPa), and different drainage conditions (drained and undrained) in order to compare drained pullout capacity with undrained pullout capacity. The test results show that both drained and undrained pullout capacity are influenced by silt contents and increase with the increase of friction angle of the soil. The pullout capacity and the pullout displacement required to reach the peak value also increase as the overburden pressure increases. In undrained condition, the effective stresses acting on the reinforcement decrease as excessive pore pressures are generated, resulting in the decrease in pullout capacity and pullout displacement.

• Journal of the Korean Geotechnical Society
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• v.26 no.1
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• pp.21-33
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• 2010

In this paper, the consolidation and the permeability characteristics of Songdo were evaluated based on the laboratory and field tests. The test results indicate that silty clay layer above approximately E.L-15 m are consolidation layer, and sand layers embedded in consolidation layers are drainage layers. Consolidation layer was overconsolidated state before the reclamation work; however, it transferred to normalized state after the reclamation work. In addition, the average and the range of consolidation properties and magnitude of anisotropy of coefficient of consolidation were evaluated according to the soil types such as clay, silty, and clayey silt since these properties are sensitive to soil types. These analysis results can be used as preliminary design parameters of consolidation and permeability m Songdo area.

• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.79-87
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• 2008

Recently, a new seismic probe, called "MudFork", has been developed and can be utilized for accurate and easy measurements of shear wave velocities of cohesive soils. To expand its use to estimate undrained shear strength and density, a preliminary investigation to correlate these properties with shear wave velocity was attempted. Cone penetration tests and a seismic test, using MudFork, were performed at a silty soil site near Incheon, Korea. Also, undisturbed samples were obtained using thin-wall tube samplers, and the shear wave velocities and undrained shear strengths of the samples were measured in the laboratory. A simple linear relationship between shear strength and shear wave velocity was obtained, and a tentative relationship between density and shear wave velocity was also defined.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.196-196
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• 2020

토양은 육상생태계에 있어 가장 많은 탄소를 저장하고 있으며, 대기 중 CO₂를 토양탄소로 전환하여 쉽게 방출되지 않고 토양 내에 저장하는 역할을 한다. 이렇듯 토양 유기탄소 배출관리는 기후변화에 있어 중요한 문제로 대두되고 있다. 하지만 토지이용의 변화와 무분별한 관리로 인하여 토양내에 저장되어 있는 토양 탄소배출이 지속적으로 증가 하고 있다. 따라서 토양탄소 배출로 인한 경제적 피해를 수치적으로 표현하는 가치평가가 필요하다. 현재 토양에 저장된 토양유기탄소 함량을 토양통별로 토양정보시스템에서 제공하고 있지만 국내 토양 토양탄소 저장량의 산정에 관한 연구는 미비한 실정이다. 따라서 본 연구에서는 토양 특성을 이용하여 토양 유기탄소 저장량을 산정하고, 산정된 토양 유기탄소 저장량과 정밀토양도를 이용하여 남한의 토양 유기탄소 가치평가를 실시하였다. 토양의 특성은 물리적 특성인 모래(Sand), 이토(Silt), 점토(Clay), 자갈(Gravel)함량과 화학적 특성인 유기물함량(Organic Matter)를 사용하였다. 토양 유기탄소저장량 산정의 검증을 위하여 전라남도 진도군의 토양유기탄소 저장량을 산정한 결과 486,696t으로, 선행연구와 유사한 결과를 나타내었다. 이러한 검증 결과를 바탕으로 남한의 토양 유기탄소 저장량을 산정한 결과 305.54Mt의 유기탄소가 저장된 것으로 나타났으며, 단위 면적당 유기탄소 저장량의 경우 3.11kg/㎡으로 나타났다. 또한 2019년 상반기 기준 평균 탄소거래권 가격(27,500원/톤)을 이용하여 우리나라 국토의 토양탄소 저장량 가치평가를 실시한 결과, 약 8조 4천억원의 경제적 가치가 있는 것으로 나타났다. 본 연구는 토양의 물리적·화학적 특성을 이용하여 토양의 유기탄소 저장량을 산정하였으며, 토양에 저장되어 있는 유기탄소의 가치평가를 수행하였다. 본 연구결과는 농업, 수문, 기후변화 등 다양한 분야에서 필요로 하는 기초자료로 활용될 수 있을 것으로 판단된다.

• Journal of The Geomorphological Association of Korea
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• v.28 no.4
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• pp.15-30
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• 2021

This study analyzed the changes in land-cover and sedimentary environment before and after flooding through drone images and sediment analysis for the Seomjin River Chimsil Wetland. The results showed that the area of some land-covers such as sand bar, grass, and trees were continuously changed. The acidity level of the sediments in the Seomjin River Chimsil Wetland was weakened gradually by flooding and EC was also decreased. The levels of organic matter, effective phosphoric acid, and CEC, however, were fluctuating depending on branches, which seems to be the result of landization as new sedimentary environment was developed and vegetation was settled after the flood. Average mean size of river sediments was found to be fine sand, and it exhibited various particle size characteristics from granule to medium silt depending on the location. As the sedimentary environment changed due to the effects of floods and typhoons, the particles were granulated or grain refined depending on the position. In the Seomjin River Chimsil Wetland, there were factors that could interfere with geomorphic development and sedimentary environment, contamination sources in and around the wetland, and natural threat factors. Therefore, in this study, a conservation and management plan was proposed to remove these threat factors and to preserve the scarcity, naturalness, and dynamics of Seomjin River Chimsil Wetland.

• Journal of The Geomorphological Association of Korea
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• v.26 no.1
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• pp.59-78
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• 2019

The physical and chemical characteristics of more than 5 m sandy deposits behind the beach in Sinji-do Island are investigated and its burial ages are estimated using Optically Stimulated Luminescence. By the estimated burial ages of the sandy deposits, this section is divided into four sub-units: Unit I (6.2 ka), Unit II (23.2 ka), Unit III (115.9 ka), and Unit IV (115.9 to 127.5 ka). It can be proposed that the Unit I of a coarse sand deposited during the Holocene Climatic Optimum. Unit II, supposed to be the aeolian sediments, formed during the Last Glacial Maximum (LGM). It can be supposed that the study area was not affected by the marine processes during the LGM, directly. Unit III is more consolidated deposits of coarse silt to fine sand and deposited during the Last Interglacial Period. Unit IV mainly consist of beach gravels with sandy matrix deposited during the Marine Isotope Stage 5e (MIS 5e), and thus indicates that the sea level of the southwest sea had risen 3 to 5 m above present sea level during the MIS 5e.

• Journal of The Geomorphological Association of Korea
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• v.18 no.4
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• pp.203-212
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• 2011

The objective of this paper is to identify the present-day surficial sediment distribution patterns of the tidal river, Gongneungcheon, through the grain size and statistical analysis. Four major findings of this study are as follows; First, the composition of sediments over the study area are mainly silt in texture. Second, the surficial sediment distribution reveals that grain size becomes coarser as they approach seawards not only in summer but also in winter. It can be concluded that tidal flows play a significant role, especially in winter, in the distribution of surficial sediments in Gongneungcheon. However, samples obtained in summer were relatively small in mean size and showed better sorting compared to those obtained in winter. Third, the mean sizes of the samples on the transects decrease as the distance from the channel increases. Finally, the artificial structure such as a floodgate affects the distribution of the sediments.

• Journal of the Korean GEO-environmental Society
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• v.25 no.7
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• pp.21-27
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• 2024

Frost heave, a significant engineering aspect of frozen ground, leads to various damages in Korea during the winter. Both the United States and Japan, encompassing regions with frozen ground, have actively researched frost heave and possess standardized experimental methods. Particularly, the Japanese Geotechnical Society (JGS) has introduced a frost heave standard testing method, offering the advantage of relatively simple specimen preparation and experimental procedures. However, issues persist regarding the ambiguous engineering interpretation of frost heave test results and the lack of clear criteria for frost heave susceptibility assessment. This paper presents laboratory testing results following the JGS testing method on sand and silt mixtures using a triaxial temperature-controllable cell, and thoroughly analyzes the frost heave rate calculation process. Furthermore, it evaluates the applicability of frost heave susceptibility criteria proposed in the United States to frost heave rates based on the JGS testing method.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.4
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• pp.27-39
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• 2024

Soil texture is determined by the proportions of sand, silt, and clay within the soil, which influence characteristics such as porosity, water retention capacity, electrical conductivity (EC), and pH. Traditional classification of soil texture requires significant sample preparation including oven drying to remove organic matter and moisture, a process that is both time-consuming and costly. This study aims to explore an alternative method by developing an AI model capable of predicting soil texture from images of pre-sorted soil samples using computer vision and deep learning technologies. Soil samples collected from agricultural fields were pre-processed using sieve analysis and the images of each sample were acquired in a controlled studio environment using a smartphone camera. Color distribution ratios based on RGB values of the images were analyzed using the OpenCV library in Python. A convolutional neural network (CNN) model, built on PyTorch, was enhanced using Digital Image Processing (DIP) techniques and then trained across nine distinct conditions to evaluate its robustness and accuracy. The model has achieved an accuracy of over 80% in classifying the images of pre-sorted soil samples, as validated by the components of the confusion matrix and measurements of the F1 score, demonstrating its potential to replace traditional experimental methods for soil texture classification. By utilizing an easily accessible tool, significant time and cost savings can be expected compared to traditional methods.

• Journal of Environmental Science International
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• v.33 no.7
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• pp.477-487
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• 2024

This study aimed to identify the growth environment of Cudrania tricuspidata by analyzing the site environment, soil characteristics, and vegetation structure of the species habitats and to provide basic data for identifying suitable cultivation sites for mass production. The study was conducted on 17 sites in five cities/counties of Gyeongnam and Jeonnam province. It was found that C. tricuspidata habitats were mainly distributed on gentle slopes in the southeast and southwest, with an average altitude of approximately 290 m. The soil of the C. tricuspidata habitats was sandy loam with a high proportion of sand, averaging 73.9%, 4.6%, and 21.5% sand, silt, and clay, respectively. The soil had a pH value of 5.41 (5.20-5.79), organic matter content of 8.2% (3.6-12.6%), total nitrogen content of 0.36% (0.19-0.54%), available phosphorus content of 3.50 ppm (0.95-7.61 ppm), and cation exchange capacity of 15.9 cmol⁺/kg (10.0-20.7 cmol⁺/kg) on average. The vegetation structure analysis showed that C. tricuspidata appeared in the tree layers of regions A (Jinju) and E (Yeosu), but the importance of C. tricuspidata was found to be high in the subtree and shrub layers in all regions. The ecological niche breadth was widest (0.874) in region B (Hadong) and narrowest (0.480) in region E (Yeosu).