• Geomechanics and Engineering
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• v.28 no.3
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• pp.283-298
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• 2022

Landslides triggered by the combination of heavy precipitation and anthropological disturbance in hilly areas cause severe damage to human lives, properties, and infrastructure constructions. A comprehensive investigation of the influencing factors and failure mechanisms of landslides are significant for disaster mitigation and prevention. This paper utilized the combination of detailed geological investigation, physical experimental testing as well as numerical modelling to determine the failure mechanism, and proposed a countermeasures of the Lantian landslide occurred on 2, July 2017. The results reveal that the Lantian landslide is a catastrophic reactivated slide which occurred in an active tectonic region in Southwest China. Because of the unique geological settings, the fully to highly weathered basalts in the study area with well-developed fractures favored the rainwater infiltration, which is the beneficial to slide reactivation. Engineering excavation and heavy precipitation are the main triggering factors to activate the slide motion. Two failure stages have been identified in the landslide. The first phase involves a shallow mass collapse originated at the upper slopes, which extends from the road to platform at rear part, which is triggered by excavation in the landslide region. Subjected to the following prolonged rainfall from 19 June to 2 July, 2017, the pore water pressure of the slope continually increased, and the groundwater table successively rise, resulting in a significant decrease of soil strength which leads to successive large-scale deep slide. Thereinto, the shallow collapse played a significant role in the formation of the deep slide. Based on the formation mechanisms of the landslide, detailed engineering mitigation measures, involving slope cutting, anchor cable frame, shotcrete and anchorage, retaining wall and intercepting ditch were suggested to reduce the future failure risk of the landslide.

• Fire Science and Engineering
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• v.23 no.4
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• pp.32-39
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• 2009

In this study, 18 plots were selected for particular investigation on Gangneung area and Samcheok area and Uljin area, where forest fire was occurred after thinning in 2007. After selection, a relationship between a damage of forest fire and thinning were compared and analyzed. Many factor such as a damaged species, a thinning or non-thinning, a direction of forest fire head, DBH, a height of tree, a mortality of tree, a leeward scorching ratio, a crown damage ratio, a forest tree standing crop density, a crown base height, a leaving of thinning slash, a location of plot (GPS), elevation, an aspect of slope, an angle of slope, and a topography were measured. Therefore, we analyzed a relationship with forest fire. In the result of this analysis, it was founded that the leeward scorching ratio was 24.7% on thinning area whereas 60.2% on non-thinning area. Subsequently, leeward scorching ratio on thinning area was increased by about 35.5% more than on non-thinning area. In the result of analysis about tree species, a forest of pine tree was more damaged than forest of oak tree. The mortality of tree was increased by about 41.4% on non-thinning area. When stands were close to thinning slashes, these were more damaged by 10${\sim}$20% than other stands for increasing of amount of a combustion material. Especially, as potential of re-ignition increased for more cumulated thinning slash, it will be more important to require a method for a periodical removing or practical utilization of slash.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.3
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• pp.261-269
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• 2014

Most areas in Gangwon-do are mountainous regions where causes heavy damages due to landslides. It is important to analyze basic factors influencing the cause of landslides in order to prevent such landslides. For this study, a landslide occurring site is extracted from aerial images taken after the landslide caused by typhoon 'Ewiniar' in Pyeongchang area 2006. Also, the overlay analysis with the topographic, forest, and soil maps in this area is performed using GIS based methods. In addition, the topographic, forest, and soil characteristics relating to the landslide factors are analyzed. As a result, large numbers of landslides occurred at a slope angle of $20^{\circ}-40^{\circ}$. In the case of the forest factors, there are close relationships between the artificial pine and larch forests and the frequency of landslides. The low forest density represents a weakness in landslides. In the case of the soil factors, a higher level in the surface soil with a type of sandy loam soil, a higher gravel content in subsoil, and a higher degree of acid rocks in soil parent materials cause higher frequencies in landslides.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.413-422
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• 2016

With the rapidly increasing population density and development of infrastructure, the loss of life and property damage caused by landslides has increased gradually in urban area. Especially, Because Busan has high percentage of mountainous terrain among the metropolitan in Korea, it is unavoidable to develop mountainous region excessively. The objective of this evaluation is to study on landslide hazard possibility for Mt. Hwangryeong in Busan Metropolitan City using the infinite slope model considering the groundwater level. All data related to creating the thematic maps was carried out using ArcGIS 10.0. The results show that FS (Factor of Safety) for landslide is inversely proportional to groundwater level change as expected. Most area indicates stable state in dry condition, and unstable area increase due to high pore water pressure when the groundwater level rise. However, several places in high lineament density area where landslide has been previously occurred, are more stable than other places according to the analysis. This inconsistency between real situation and analysis results indicates that additional analytical method would be necessary to solve the problem. Therefore, we suggest that development of new infiltration theory for unsaturated zone would be helpful to evaluate groundwater level distribution as time goes by.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.4
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• pp.337-342
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• 2001

A natural disaster occupies a considerable part among various damages, and the damage of human lifes and property by heavy rain extends to hundreds, and billions in every you. In old times, flood was mainly occurred in big river or sudden slope, but these days, the damage of concentrated heavy rain is being extended to a city. Recently, very big floods occurred continuously, so real time submersion expectation system which can expect the inundation boundary according to the scale is needed so as to protect lifes and property. In this study, in and around Jungrang river, where the damage of flood is big, is chosen as a sample, and the submersion of that area is expected by analyzing the flux and overflowing using DEM, and connecting with Web GIS in real time.

• Journal of the Korean Geosynthetics Society
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• v.5 no.1
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• pp.9-14
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• 2006

The reinforced soil retaining wall structures of serious types with environmental are widely expanding more and more in Korea, which divided conventional type's reinforced soil retaining wall on segmental retaining wall. The causes of most crack occurred at block in reinforced soil retaining wall structure caused by the differential settlement of foundation. It is difference of settlement for significant factor that with overall slope stability. In this study, design assessment of foundation bearing capacity related to differential settlement of foundation ground was considered. And, also, through case study, the countermeasure methods and its application were suggested that the bearing capacity of foundation had to stabilize. The foundation ground in charge of bearing capacity should be affected by the resisting force of sliding, because the foundation parts of reinforced soil retaining wall were belongs to potential slope sliding area in overall stabilizing including retaining wall structures. Therefore, the analyzing or the designing of bearing capacity for foundation should be considered control capacity on the overall slope sliding.

• Journal of Korean Society of Rural Planning
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• v.21 no.2
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• pp.127-135
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• 2015

In recent years, meteorological disasters have frequently occurred in rural areas. As a result, there have been growing concerns over the protective measures needed. In order to avoid natural risks and damage, and to strengthen countermeasure to meteorological disasters, local governments needs to be prepared. Therefore, this paper seeks to prevent meteorological disasters through mapping of inundation vulnerability in agricultural land, Chungcheongnam-do. In doing so, this study were considered 5 variables (i.e. precipitation, region of altitude below 50m, region of slope gradient is below 10 degree, distance from river within less 50m) for creating vulnerability map. The precipitation was excluded in five variables. Since, the precipitation which include Daily maximum precipitation, 2-Daily maximum precipitation, summer precipitation was not any correlation among them. The results of analysing four variables, exclusive of precipitation, were showed that the agricultural lands where located in Dangjin, Buyeo, Hongseong and Asan were low correlation of inundation vulnerability by overlapping analysis. Moreover, The correlation analysis was showed low correlation between each factors and the annual average area of agricultural lands' inundation, whereas, the correlation analysis which was overlapping each factor showed high correlation. In conclusion, in order to create reliable vulnerability map in agricultural lands, Chungcheongnam-do, it must be considered to overlap analysis of the four main factors such region of altitude below 50m, region of slope gradient is below 10 degree, distance from river within less 50m. We suppose that this study's analysis can help to set the preparedness site of agricultural lands inundation.

• Journal of Korean Society of Forest Science
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• v.94 no.6
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• pp.377-386
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• 2005

This study was carried out to analyse the landslide characteristics by ground investigation, borehole image processing system, field seismic test, laboratory test and ground stability analysis at the landsliding area occurred in Maeri, Sangdong-myeon, Gimhaesi, Gyeongsangnam-do. Region I needs to install data logger system to monitor a land displacement during the heavy rainfall events because the region can be liable to occur the land slide by land creeping. It is needed to restore rapidly, if the land displacement occurs in Region I. Region II needs to monitor and repair because of the possibility of slope failure by long-term soil loss. Region III needs constructions to remove ground runoff and ground water to be infiltrated from talus. Region IV where is a stable region, needs to be protected from land cutting or other man-made damage.

• Journal of Korea Water Resources Association
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• v.43 no.1
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• pp.105-117
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• 2010

This paper presents a new and simple technique to perform MUSCL reconstruction for solving 2D shallow water equations. The modified MUSCL scheme uses weighted area ratio to apply non-uniform grid in stead of the previous method that equally distributed the difference of conservation variables to each interface. The suggested method can physically reconstruct conservation variables in case of uniform grid as well as non-uniform grid. In this study, Unsplit scheme applicable to unstructured grid is used and efficient slope limiter of TVD scheme is used to control numerical oscillation which can be occurred in modified MUSCL scheme. For accurate and efficient treatment of bed slope term, the modified MUSCL scheme is coupled with the surface gradient method. The finite volume model applied to suggested scheme is verified through a comparison between numerical solution and laboratory measurements data such as the simulations of isolated building test case and Bellos's dam break test case.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.3
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• pp.133-145
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• 2010

This study analyzed the characteristics of sediment produce by landslide triggered by rainfall. One-dimensional unsaturated groundwater model and infinite slope stability analysis were used to estimate the behavior of soil moisture and slope stability according to rainfall, respectively. Slope stability analysis was performed considering on soil depth and characteristics of trees. As the results considering on recovery of the failed slopes, much amount of sediment was produced in 1963, 1970, and 2002. As the results of verification of simulation results using Landsat 5 TM images, we can find differences of landslide location between the results from model and satellite images. These differences can be caused by uncertainties of the rough parameters in the model. However, in the case that Obong-dam basin was divided into two subbasin, Wangsan-chun and Doma-chun basin, the results of each subbasin show errors around 20%. And only 4% of error occurred in the case of comparing landslide area on the entire Obong-dam basin. These errors seem insignificant considering on the errors which can be caused from the analyses in this study such as estimation of sediment produce, soil cover classification, and estimation of landslide area.