• Journal of the Korean GEO-environmental Society
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• v.24 no.11
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• pp.19-24
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• 2023

Ground anchor has been widely used specially for maintaining stability on reinforced cut slope in expressway. While the durability of the ground anchors should be ensured over the service life. However, the long-term loss of tensile force has occurred in most of field-installed anchors. Main causes are not clearly identified and very few studies have been made for analyzing long-term behavior of ground anchor in slopes. In this study, full-scale model tests and long-term measurements were made to obtain the load-displacement data and identified the causes of the long-term behaviors of ground anchor. As a result, the bond strength decreases exponentially with increasing water-binder ratio. Especially, groundwater is the most influencing factor to the bond strength. In the long-term behavior, the load decreases sharply until the initial settlement stabilized, and thereafter the tension force decreases constantly.

• Journal of Korean Society of Forest Science
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• v.45 no.1
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• pp.11-25
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• 1979

There was much mass movement at many different mountain side of Peong Chang area in Kwangwon province by the influence of heavy rainfall through August/4 5, 1979. This study have done with the fact observed through the field survey and the information of the former researchers. The results are as follows; 1. Heavy rainfall area with more than 200mm per day and more than 60mm per hour as maximum rainfall during past 6 years, are distributed in the western side of the connecting line through Hoeng Seong, Weonju, Yeongdong, Muju, Namweon and Suncheon, and of the southern sea side of KeongsangNam-do. The heavy rain fan reason in the above area seems to be influenced by the mouktam range and moving direction of depression. 2. Peak point of heavy rainfall distribution always happen during the night time and seems to cause directly mass movement and serious damage. 3. Soil mass movement in Peongchang break out from the course sandy loam soil of granite group and the clay soil of lime stone and shale. Earth have moved along the surface of both bedrock or also the hardpan in case of the lime stone area. 4. Infiltration seems to be rapid on the both bedrock soil, the former is by the soil texture and the latter is by the crumb structure, high humus content and dense root system in surface soil. 5. Topographic pattern of mass movement spot is mostly the concave slope at the valley head or at the upper part of middle slope which run-off can easily come together from the surrounding slope. Soil profile of mass movement spot has wet soil in the lime stone area and loose or deep soil in the granite area. 6. Dominant slope degree of the soil mass movement site has steep slope, mostly, more than 25 degree and slope position that start mass movement is mostly in the range of the middle slope line to ridge line. 7. Vegetation status of soil mass movement area are mostly fire field agriculture area, it's abandoned grass land, young plantation made on the fire field poor forest of the erosion control site and non forest land composed mainly grass and shrubs. Very rare earth sliding can be found in the big tree stands but mostly from the thin soil site on the un-weatherd bed rock. 8. Dangerous condition of soil mass movement and land sliding seems to be estimated by the several environmental factors, namely, vegetation cover, slope degree, slope shape and position, bed rock and soil profile characteristics etc. 9. House break down are mostly happen on the following site, namely, colluvial cone and fan, talus, foot area of concave slope and small terrace or colluvial soil between valley and at the small river side Dangerous house from mass movement could be interpreted by the aerial photo with reference of the surrounding site condition of house and village in the mountain area 10. As a counter plan for the prevention of mass movement damage the technics of it's risk diagnosis and the field survey should be done, and the mass movement control of prevention should be started with the goverment support as soon as possible. The precautionary measures of house and village protection from mass movement damage should be made and executed and considered the protecting forest making around the house and village. 11. Dangerous or safety of house and village from mass movement and flood damage will be indentified and informed to the village people of mountain area through the forest extension work. 12. Clear cutting activity on the steep granite site, fire field making on the steep slope, house or village construction on the dangerous site and fuel collection in the eroded forest or the steep forest land should be surely prohibited When making the management plan the mass movement, soil erosion and flood problem will be concidered and also included the prevention method of disaster.

• Journal of the Society of Disaster Information
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• v.16 no.3
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• pp.440-448
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• 2020

Purpose: Most of the studies in the country on earthquake-induced landslide predict the displacement of the slope. Until now, no studies have been conducted on the occurrence of landslides and damage characteristics by earthquakes. Therefore, this study was conducted to obtain basic data of landslides caused by earthquakes. Method: In order to analyze the characteristics of earthquake-causing landslides, we have collected data reported in the media over the past decade. Landslides in foreign countries were analyzed separately by cause of occurrences such as rainfall and earthquake. Landslides from abroad were analyzed according to the cause of the occurrence, and landslides caused by earthquakes were further analyzed as follows: the magnitude of an earthquake, year of occurrence, number of occurrences by continent, damage status, etc. Result: In the past 10 years, a total of 608 landslides have been reported from overseas, and the cause is the highest with 340 landslides due to rainfall. There were 70 cases of landslides caused by earthquakes, and it was analyzed as the second cause of landslides. The average magnitude for earthquakes that caused landslides was 6.5, and the minimum and maximum magnitude were 4.4 and 8.2 respectively. The earthquake-induced landslides were the most occurrence in 2011yr and 2012yr, and the continent was the most common in Asia. Also, It was analyzed that if an earthquake caused landslides, the number of casualties increased and the size of the damage increased. Conclusion: Currently, earthquakes are steadily increasing in Korea, and the possibility of strong earthquakes is also increasing. Earthquake-induced landslides are beyond human control due to natural disasters but can minimize damage through active prevention and response. It is expected that the results of this study will be used as basic data in establishing measures for earthquake landslides to reduce property and human damage in the future.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.1
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• pp.47-53
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• 2011

From 12 to 16 July 2006, 4 days' torrential rainfall in Deoksan-ri, Inje-up, Inje-gun, Gangwon-do caused massive landslide and debris flow. Huge losses of both life and property, including two people buried to death in submerged houses, resulted from this disaster. As the affected region is mostly mountainous, it was difficult to approach the region and to estimate the exact extent of damage. But using aerial photographs, we can define the region and assess the damage quickly and accurately. In this study the debris flow region in inje, Gangwon-do was analyzed using aerial photographs. This region was divided into three sections - beginning section, flow section and sedimentation section. Informations for each section were extracted by digitizing the shot images with visual reading. Topographic, forest physiognomic and soil characteristics and debris flow occurrences of this region were analyzed by overlaying topographic map, forest type map and soil map using GIS. Comprehensive analysis shows that landslide begins at slope of about $36^{\circ}$, flows down at $26^{\circ}$ slope, and at $21^{\circ}$ slope it stops flowing and deposits. Among forest physiognomic factors, species of trees showd significant relationship with debris flow. And among soil factors, effective soil depth, soil erosion class, and parent materials showed meaningful relationship with debris flow.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.79-87
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• 2017

In this paper, for 43 sites neighboring to western area of Gangwondo where disaster of debris flow occurred from 2006 to 2013, magnitude of debris flow was estimated from results of site investigation and correlation analysis between influencing factors to its magnitude was performed. Magnitude of channelized debris flow was found greater by 6.5 times of that of hill slope debris flow and approximately 5% of total volume was occurred at initiation part of channelized debris flow. As results of analyzing yield rate of debris flow, for channelized debris flow, yield rate values of $19m^3/m$ and $8m^3/m$ were obtained for total volume being over $10,000m^3/m$ as the large scale of debris flow and less than $10,000m^3/m$ respectively, and value of $5m^3/m$ was estimated for hill slope debris flow. As results of correlation analysis of influencing factors to magnitude of debris flow, runoff distance and erosion width were very highly correlated to its magnitude whereas average slope of basin and erosion depth showed relatively low correlation. In particular, value of erosion depth was in the range of 0.5-2.6 m, being similar range to the value proposed by Ikeya (1981). Triggering rainfall to debris flow such as continuous rainfall and maximum intensity of hour rainfall were analyzed to have low correlation with magnitude of debris flow.

• Journal of Wetlands Research
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• v.15 no.3
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• pp.423-430
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• 2013

An algorithm to allow shoreline movement during numerical experiment on sediment transport, deposition or resuspension for general coastal morphology is proposed here. The bed slope near shoreline, i.e. mean sea level, is influenced by bed material, tidal current, waves, and wave-induced current, but has been reported to remain within a stable range. Its annual variation is not large, either. The algorithm is adjusting the bathymetry, if the largest bed slope within shoreline band exceeds a given bed slope due to continuous erosion at zones below the shoreline. This algorithm automatically describes retreat of shoreline caused by erosion, when used within a numerical system. The algorithm was tested to a situation which includes a continuous dredging at a point, and showed satisfactory development of concentric circle contours. Next, the algorithm was tested to another situation which includes sinking of eroded part of bed plate, and produced satisfactory results, too. Finally, the algorithm was tested to a movable-bed laboratory experimental conditions. The shoreline movement behind detached breakwater was reasonably reproduced with this algorithm.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.143-152
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• 2016

To estimate the stability of a debris flow it is necessary to know the mass of surface soil, cohesion, slope, and friction angle. Given that the mass of surface soil is a function of soil thickness and mass density, it is important to obtain reliable estimates of soil thickness across a wide area. The objective of this paper is to estimate soil thickness using the elastic wave velocity with a new standard velocity. Tests are performed in debris-flow hazard areas, after which four profiles are selected to obtain the elastic wave velocity. Dynamic cone penetration tests are carried out to find the soil thickness at 18 points. The elastic wave velocity shows the area consists of 3~4 layers, and soil thicknesses are predicted by utilizing the new standard. The elastic wave velocity and dynamic cone penetration tests yield large differences in soil thickness. Therefore, this study shows that the new standard is useful not only in estimating soil thickness but also in improving the reliability of estimates of soil thickness.

• Journal of Korea Water Resources Association
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• v.49 no.7
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• pp.579-588
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• 2016

Changes in precipitation due to climate change is made to induce the local and intensive rainfall, it is increasing damage caused by inland inundation. Therefore, it requires a technique for predicting damage caused by flooding. In this study, in order to determine whether this flood inundated by any route when the levee was destroyed, Which can simulate the path of the flood inundation model was developed for the SIMOD (Simplified Inundation MODel). Multi Direction Method (MDM) for differential distributing the adjacent cells by using the slope and Flat-Water Assumption (FWA)-If more than one level higher in the cell adjacent to the cell level is the lowest altitude that increases the water level is equal to the adjacent cells- were applied For the evaluation of the model by setting the flooding scenarios were estimated hourly range from the target area. SIMOD model can significantly reduce simulation time because they use a simple input data of topography (DEM) and inflow flood. Since it is possible to predict results within minutes, if you can only identify inflow flood through the runoff model or levee collapse model. Therefore, it could be used to establish an evacuation plan due to flooding, such as EAP (Emergency Action Plan).

• Journal of the Geological Society of Korea
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• v.54 no.5
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• pp.557-566
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• 2018

Pohang earthquake (Main shock magnitude = 5.4) occurred in Southeastern region of South Korea in November 15, 2017. Groundwater levels of 6 monitoring wells with 5 minutes interval measurements located in that region and stream water levels of 4 stations located along the Hyeongsan-gang stream are used for the analysis of earthquake induced effects. Four groundwater monitoring wells show a short-term decrease of groundwater level after a main shock and one well does an increase and the maximum change is about 42.0 cm. Especially, groundwater levels at two monitoring wells near the epicenter are consistently maintained after a decrease. There is little relationship between earthquake magnitude or a distance to epicenter and changing amount of groundwater level and it may be due to the inhomogeneity of geologic material and unconsolidated sediments distribution. The changes in permeability of fractured zone and groundwater levels occasionally cause changes in stream flow rate, and water level of the Hyeongsan-gang stream in the study area decreases just after the earthquake and increases again up to the normal level and next shows an more gentle decreasing slope. Total increasing flow rates at S1 (upstream site) and S4 (downstream site) stations are about $12,096m^3$ and $116,640m^3$, respectively, during the increasing period.

• Journal of the Society of Disaster Information
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• v.18 no.1
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• pp.10-18
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• 2022

Purpose: For smooth performance of flood analysis due to heavy rain disasters at energy storage facilities in the Incheon area, field surveys, observational surveys, and pre-established reports and drawings were analyzed. Through the field survey, the characteristics of pipelines and rivers that have not been identified so far were investigated, and based on this, the input data of the SWMM model selected for inundation analysis was constructed. Method: In order to determine the critical duration through the probability flood analysis according to the calculation of the probability rainfall intensity by recurrence period and duration, it is necessary to calculate the probability rainfall intensity for an arbitrary duration by frequency, so the research results of the Ministry of Land, Transport and Maritime Affairs were utilized. Result: Based on this, the probability of rainfall by frequency and duration was extracted, the critical duration was determined through flood analysis, and the rainfall amount suggested in the disaster prevention performance target was applied to enable site safety review. Conclusion: The critical duration of the base was found to be a relatively short duration of 30 minutes due to the very gentle slope of the watershed. In general, if the critical duration is less than 30 minutes, even if flooding occurs, the scale of inundation is not large.