• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.663-672
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• 2022

The purpose of this study is to evaluate the magnesium sulfate resistance of a geopolymer mixed with rice husk powder. General concrete, silica fume mixed concrete, and binary blended geopolymer were selected as comparison targets to confirm the magnesium sulfate resistance, and sulfate deterioration was calculated using the compressive strengths with ages. In addition, the weight change rate and the relative dynamic coefficient of the geopolymer were comparatively analyzed, and the degree of etteringite formation was confirmed using X-ray diffraction analysis. the experiment, the geopolymer mixed with 10% rice husk powder showed 10.8% higher compressive strength than concrete with silica fume when submerged for 56 days. Also, the geopolymer mixed with rice husk powder showed a small weight change rate of 0.9 to 1.45%. composition after immersion in magnesium sulfate through X-ray diffraction analysis, it was observed that a small amount of ettringite was dispersed in the geopolymer containing rice husk powder. Thus, there is a high correlation with the corrosion resistance of magnesium sulfate

• Korean Journal of Environment and Ecology
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• v.35 no.3
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• pp.294-304
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• 2021

This study aims to obtain basic data for systematic restoration by analyzing the monitoring results of the Shimwon Valley Ecological Landscape Restoration Project area in Jirisan National Park. In 2017, when the restoration project was completed, 12 monitoring plots and 4 control plots were installed for vegetation monitoring, and changes in the relative dominance, species diversity index and similarity between 2017 and 2020 were analyzed. The species diversity index of the surveyed areas where trees were planted during the restoration project was 0-1.4552, and the similarity index with the control group was 0% except for one survey area at 1.32%. The very low species diversity index and similarity index in the survey areas were attributed to the loss of trees planted during the restoration project due to death, damage by wild boars, or erosion by running water. On the other hand, the species diversity index was 0.9538-2.3222 in the monitoring plot where no tree was planted, and the similarity index was analyzed to be as high as 8.33%. It is necessary to continue the long-term monitoring for the development of ecological landscape restoration methods in the national park and analysis of the succession in monitoring plots where no trees were planted.

• Geophysics and Geophysical Exploration
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• v.25 no.3
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• pp.120-128
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• 2022

There are 17,000 reservoir dams in Korea, of which more than 85% were built over 50 years ago. Old embankment dams are weakened by internal erosion and suffusion phenomena due to preferential leakage paths and this ongoing weakening can cause their failure. Therefore, early warning associated with leakage in an embankment dam is crucial to prevent its failure. An electrical resistivity survey is a non-destructive, real-time and in-situ technique for detecting the development of leakage zones and general conditions of embankment dams. Because of its advantages, the electrical resistivity survey is widely used for reservoir safety inspections. However, the electrical resistivity survey is still not officially included in the precise safety inspection of reservoir dams because it cannot present a quantitative index of dam safety. In this study, we propose a method for calculating the leak index according to the water content evaluated from the electrical resistivity survey and/or induced polarization survey. Particularly, by proposing a quantitative leak index calculation method from monitoring surveys and independent surveys, we provide a theoretical basis for including electrical resistivity and induced polarization surveys as components of the precise safety inspection of reservoirs dams.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.1
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• pp.23-30
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• 2015

A shoreline mapping is essential for describing coastal areas, estimating coastal erosions and managing coastal properties. This study has planned to map the 3D shorelines with the airborne LiDAR(Light Detection and Ranging) data and the KOMPSAT-2 imagery, acquired in Uljin, Korea. Following to the study, the DSM(Digital Surface Model) is generated firstly with the given LiDAR data, while the NDWI(Normalized Difference Water Index) imagery is generated by the given KOMPSAT-2 imagery. The classification method is employed to generate water and land clusters from the NDWI imagery, as the 2D shorelines are selected from the boundaries between the two clusters. Lastly, the 3D shorelines are constructed by adding the elevation information obtained from the DSM into the generated 2D shorelines. As a result, the constructed 3D shorelines have had 0.90m horizontal accuracy and 0.10m vertical accuracy. This statistical results could be concluded in that the generated 3D shorelines shows the relatively high accuracy on classified water and land surfaces, but relatively low accuracies on unclassified water and land surfaces.

• Journal of the Korean earth science society
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• v.21 no.2
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• pp.188-200
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• 2000

On the basis of the Landsat TM scenes with 15 year's time differences, the topographic maps with 50 years differences, and the air photos with 25 years differences, we carried out the field survey for geology and forestry and analyzed the topographical change and the variation of the forest resource in Anmyundo. In terms of the discrimination of forest trees in Anmyumdo, the NDVI with larger than 0.5 in the winter season is the indicator of the surface of the pine tree land-cover. The peak values of NDVI appear on the surface of the pine aging 30 through 50 years and decrease a little and grossly stabilized over the more aging trees. The distinction of the deciduous forest and grass land from the pine tree was capable with the correlation with the abrupt seasonal variation of NDVI and the surface aspect. The great change of topography is detected in the region Changgiri due to the continuous tidal erosion since the canal construction about 370 years ago and along the all around coast of Anmyundo due to the reclamation for the paddy field. The surface area of the pine tree land-cover in Anmyundo was estimated 35.91 km$^2$ in 1986 and 33.15 km$^2$ in 1993, which is originated from the grassland development in the southeastern part of Anmyundo where the pine tree dominated by 1986. In the northen part of Anmyundo the surface area of the pine land-cover increased a little in 1993 comparing to 1986.

• Ecology and Resilient Infrastructure
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• v.2 no.4
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• pp.317-323
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• 2015

This study investigated the impact of the morphological change on a physical fish habitat in the downstream reach of a dam using long-term mobile bed simulation. The quasi-steady model was used for hydraulic simulation and the habitat suitability index model was applied for physical habitat simulation. For simulating long-term morphological change of the stream bed, The Exner equation was used. Sorting of bed material was also considered. The results of simulation showed that erosion and armoring process occurred in a reach downstream of the dam and change of physical habitat for Zacco platypus followed. These results indicate that channel morphology and substrate conditions effected the physical habitat for considering long-term investigation.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1053-1057
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• 2007

본 연구에서는 준분포형 물리모형인 SWAT 모형을 통하여 유역 유사량 및 오염부하량 발생의 시공간적 특성을 파악하기 위해 충주댐 상류유역을 대상으로 모형을 구축 적용하였다. 대상유역에 대한 유출 유사 영양물질 관련 매개변수의 보정 및 모형 검증을 수행한 결과, 유출에 대해서는 모형효율지수 0.8 정도의 안정적인 결과를 얻을 수 있었으며, 유사와 인에 대해서는 대략적인 정성적 경향을 파악할 수 있었다. 구축된 모형을 통하여 대상유역에 대해 배수면적별 비유사량의 일정한 관계를 도출할 수 있었으며, 식생에 따른 단위면적별 발생 유사량 및 오염부하량을 검토함으로써 식생별 침식 및 부하량 발생 정도를 평가할 수 있었다. 또한, 하도구간별 오염원에 따른 유사 및 오염부하량을 검토하고, 월별 평균 유사량과 오염부하량을 검토함으로써 시공간적인 분포 특성을 파악할 수 있었다. 아울러 유역내 토양보전기법의 적용에 따른 유사 및 총질소, 총인의 저감효과도 평가할 수 있었다.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.1
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• pp.73-82
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• 1994

This paper presents the experimental results of runoff and soil losses from sloping runoff plots under three cropping practices. Twenty-nine runoff plots having slopes of 10, 20, and 30 percent in gradient, and lengths of 10, 20 and 30 meter, respectively, were cultivated with soybean, alfalfa, and fallow conditions during 1989~1990 seasons. Crop stages were grouped based on crop canopy conditions and the cropping management factors of the Univer- sal Soil Loss Equation were derived as ratios of the soil losses to fallow conditions. The results from this study are summarized as follows : 1. Annual rainfall erosivity factor at Ichun station varied from 127 to 1336, averaging 472 and 200 in 1989. The month variations reach the peak in July, being 19& 2. Canopy cover percent for soybean that was taken by a photographic method increased sharply during 30 to 80 days after seeding and the results were used to identify periods for the six crop stages. 3. Annual average runoff rates from soybean and alfalfa plots were 35 and 16 percent of those from fallow ones, respectively. The runoff rates decreased as the crops grew. 4. Soil losses from soybean and alfalfa plots were 14 and 16 percent of those from fallow plots. And the crop coefficients were proposed for different crop stages.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1004-1009
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• 2011

Soil erosion in North Korea has been continued to accelerate by deterioration of topographical conditions. However, few studies have been conducted to predict the amount of soil loss in North Korea due to limited data so far. Rainfall erosivity is an important factor to predict the amount of long-term annual soil loss by USLE (universal soil loss equation). The purpose of this study is to investigate rainfall erosivity, which presented the potential risk of soil erosion by water, in North Korea. Annual rainfall erosivities for 27 stations in North Korea for 1983~2010 were calculated using regression models based on modified Institute of Agricultural Sciences (IAS) index in this study. The result showed that annual average rainfall erosivity in North Korea ranged from 2,249 to 7,526 and averaged value was $4,947MJmm\;ha^{-1}\;hr^{-1}\;yr^{-1}$, which corresponded to about 70% of annual average rainfall erosivity in South Korea. The finding was that the potential risk of soil erosion in North Korea has been accelerated by the increase of rainfall erosivity since the late 1990s.

• Journal of the Korean Institute of Landscape Architecture
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• v.38 no.3
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• pp.33-40
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• 2010

Many trails have been built and utilized in each sub-basin of Apsan Park. This study focused on the conditions and the present flora of several overused trails within three basins called Kun-Gol, Anjiroung-Gol, and Meaja-Gol in Apsan Park. There are two purposes for this study. The first is to make a plan for restoration by classifying the type of damage to these overused trails. The second is to provide preliminary data for reestablishing a more pleasant urban nature park. As a result of the survey, the average length of these trails is 9.0km and mean width is 2.0 to 2.6m. 2,108m of the sections studied(23.4% of the total) had exposed root, 3,199m of the sections studied (35.5% of the total) had exposed rock, 3,270m of the sections studied(36.6% of the total) displayed damaged pathways, and 4,841m of the sections studied (53.8% of the total) had higher soil hardness. Eighty-three areas of deterioration were found and there has been extensive property destruction. As an indication of human disturbances, the Naturalization Index and Urbanization Index appeared as: Kun-Gol, 7.0%, 5.5%; Anjiroung-Gol, 8.3%, 4.5%; Meaja-Gol 8.6%, 6.2%; in total, 7.8%, 8.3%. As a method of checking the level and extent of the damage process, an impact rating classification was used at each point on the trails. Kun-Gol had the highest rating and Anjiroung-Gol had the lowest rating in impact rating classification. With the impact rating classification, it was found that each trail would continue to worsen, meaning that roots and rocks are more likely to be further exposed and the trail width will continue to widen through overuse. An actual plan for reparations and restoration of the trails is needed through further study.