• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.191-195
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• 2007

Recently, landslides frequently happen at a natural slope during period of intensive rainfall. With rapidly increasing population of steep terrain in Korea, landslides have become one of the most significant natural hazards. Thus, it is necessary to protect people from landslides and to minimize the damage of houses, roads and other facilities. To accomplish this goal, many landslide prediction methods have been developed in the world. In this study, a simple landslide prediction system that enables people to escape the endangered area is developed. The system is focused to debris flows which happen frequently during periods of intensive rainfall at steep slopes in Kangwondo. This system is based on the wireless sensor network that is composed of sensor nodes, gateway, and server system. Sensor nodes that are composed of sensing part and communication part are newly developed to detect sensitive ground movement. Sensing part is designed to measure tilt angle and acceleration accurately, and communication part is deployed with Bluetooth (IEEE 802.15. I) module to transmit the data to the gateway. To verify the feasibility of this landslide prediction system, a series of laboratory tests is performed at a small-scale earth slope supplying rainfall by artificial rainfall dropping device. It is found that sensing nodes installed at slope can detect the ground motion when the slope failure starts. It is expected that the landslide prediction system by wireless senor network can provide early warnings when landslides such as debris flow occurs, and can be applied to ubiquitous computing city (U-City) that is characterized by disaster free.

• Journal of the Society of Disaster Information
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• v.16 no.3
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• pp.586-593
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• 2020

Purpose: This study aims to develop an algorithm for predicting sediment discharge by debris flow, and develop GIS-based decision support system for optimal arrangement of check dam. Method: The average stream width and flow length were used to predict the cumulative sediment discharge by debris flow. At this time, the amount of slope failure on source area and average flow length were utilized as input factors. Result: The predicted sediment discharge calculated through the algorithm was 1.1 times different on average compared to the actual sediment discharge by debris flow. In addition, the program is an objective indicator that selects the location and size of the check dam, and it can help practitioners make rational decisions. Conclusion: The soil erosion control works are being implemented every year. Therefore, it is expected that the GIS-based decision support system for location and size of the check dam will contribute to the prevention of sediment-related disasters.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1227-1240
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• 2014

Abandoned mines often cause environmental problems, such as alteration of landscape, metal contamination, and landslides due to a heavy rainfall. Geotechnical and rheological tests were performed on waste materials corrected from Imgi waste rock dump, located in Busan Metropolitan City. Debris flow mobility was examined with the help of 1-D BING model which was often simulated in both subaerial and subaqueous environments. To determine flow curve, we used a vane-penetrated rheometer. The shear stress (${\tau}$)-shear rate (${\dot{\gamma}}$) and viscosity(${\eta}$)-shear rate (${\dot{\gamma}}$) relationships were plotted using a shear stress control mode. Well-known rheological models, such as Bingham, bilinear, Herschel-Bulkley, Power-law, and Papanastasiou concepts, were compared to the rheological data. From the test results, we found that the tested waste materials exhibited a typical shear shinning behavior in ${\tau}$-${\dot{\gamma}}$ and and ${\eta}$-${\dot{\gamma}}$ plots, but the Bingham behavior is often observed when the water contents increased. The test results show that experimental data are in good agreement with rheological models in the post-failure stage during shearing. Based on the rheological properties (i.e., Bingham yield stress and viscosity as a function of the volumetric concentration of sediment) of waste materials, initial flowing shape (5 m, 10 m, and 15 m) and yield stress (100 Pa, 200 Pa, 300 Pa, and 500 Pa) were input to simulate the debris flow motion. As a result, the runout distance and front velocity of debris flow are in inverse propositional to yield stress. In particular, when the yield stress is less than 500 Pa, most of failed masses can flow into the stream, resulting in a water contamination.

• Wind and Structures
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• v.13 no.2
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• pp.145-167
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• 2010

By using the 'failure' model approach, the effects of wind direction on the flight of sheathing panels from the roof of a model house in extreme winds was investigated. A complex relationship between the initial conditions, failure velocities, flight trajectories and speeds was observed. It was found that the local flow field above the roof and in the wake of the house have important effects on the flight of the panels. For example, when the initial panel location is oblique to the wind direction and in the region of separated flow near the roof edge, the panels do not fly from the roof since the resultant aerodynamic forces are small, even though the pressure coefficients at failure are high. For panels that do fly, wake effects from the building are a source of significant variation of flight trajectories and speeds. It was observed that the horizontal velocities of the panels span a range of about 20% - 95% of the roof height gust speed at failure. Numerical calculations assuming uniform, smooth flow appear to be useful for determining panel speeds; in particular, using the mean roof height, 3 sec gust speed provides a useful upper bound for determining panel speeds for the configuration examined. However, there are significant challenges for estimating trajectories using this method.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1090-1094
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• 2009

Many problems in geotechnical engineering such as slop failure, debris flow, ground heaving due to embankment, and lateral flow caused by liquefaction are related to large deformation rather than small deformation. Traditional numerical methods such as finite element and finite difference methods have a difficulty to solve such large deformations because they use grids. A particle method was developed for fluid dynamics. The particle method can solve large deformation problems because it uses particles to discretize differential equations. It can also include soil constitutive model and thus solve soil behavior on various boundary conditions. In this study, a particle method, which is based on particles rather than grids, is introduced and used to simulate large deformation including soil failure. The developed method can be applied for various large deformation problems in geotechnical engineering because it incorporates soil constitutive models.

• Nuclear Engineering and Technology
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• v.32 no.4
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• pp.395-409
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• 2000

Parametric studies were performed to assess the sensitivity in determining the maximum in-vessel heat removal capability from the core material relocated into the lower plenum of the reactor pressure vessel (RPV）during a core melt accident. A fraction of the sensible heat can be removed during the molten jet delivery from the core to the lower plenum, while the remaining sensible heat and the decay heat can be transported by rather complex mechanisms of the counter-current flow limitation (CCFL) and the critical heat flux (CHF）through the irregular, hemispherical gap that may be formed between the freezing oxidic debris and the overheated metallic RPV wall. It is shown that under the pressurized condition of 10MPa with the sensible heat loss being 50% for the reactors considered in this study, i.e. TMI-2, KORI-2 like, YGN-3&4 like and KNGR like reactors, the heat removal through the gap cooling mechanism was capable of ensuring the RPV integrity as much as 30% to 40% of the total core mass was relocated to the lower plenum. The sensitivity analysis indicated that the cooling rate of debris coupled with the sensible heat loss was a significant factor The newly proposed heat removal capability map (HRCM) clearly displays the critical factors in estimating the maximum heat removal from the debris in the lower plenum. This map can be used as a first-principle engineering tool to assess the RPV thermal integrity during a core melt accident. The predictive model also provided ith a reasonable explanation for the non-failure of the test vessel in the LAVA experiments performed at the Korea Atomic Energy Research Institute (KAERI), which apparently indicated a cooling effect of water ingression through the debris-to-vessel gap and the intra-debris pores and crevices.

• Journal of Korean Society of Forest Science
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• v.101 no.3
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• pp.412-425
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• 2012

Concrete Soil Erosion Control Dam, which blocks flow of debris flow in torrential stream, are reported to lose expected functions due to structural failure and collapses, caused by poor construction, material deterioration and external impacts. In this paper, an integrity assessment technique for debris barriers was proposed, which allows preliminary detection of problems inherent in debris barriers. The proposed integrity assessment technique is a non-destructive method based on SASW method, one of surface-wave tests. In this paper, a practical procedure and analysis guidelines in applying the SASW technique to debris barrier was proposed and its validity was verified using five decrepit debris barriers older than 20-year old. As a result, the SASW method was validated for the reliable grade evaluation method for concrete soil erosion control dam, and the resulting grades turned out to agree with the results determined by Sabang Associations.

• Journal of the Korean Geotechnical Society
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• v.29 no.11
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• pp.73-84
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• 2013

When a slope failure or a debris flow occurs, a shear strength on failure plane becomes nearly zero and soil begins to flow like a non-cohesive liquid. A consistency of cohesive soils changes as a water content increases. Even a cohesive soil existing at liquid limit state has a small amount of shear strength. In this study, a water content, at which a shear strength of cohesive soils is zero and then cohesive soils will start to flow, was proposed. Three types of clays (kaolinite, bentonite and kaolinite (50%)+bentonite (50%)) were mixed with three different solutions (distilled water, sea water and microbial solution) at liquid limit state and then their water contents were increased step by step. Then, their undrained shear strength was measured using a portable vane shear device called Torvane. The ranges of undrained shear strength at liquid and plastic limits are 3.6-9.2 kPa and 24-45 kPa, respectively. On the other hand, the water content that corresponds to the value of the undrained shear strength changing most rapidly is called flow water content. The flow limit refers to the water content when undrained shear strength of cohesive soils is zero. In order to investigate the relationship between liquid limit and flow limit, the cohesive index was defined as a value of the difference between flow limit and liquid limit. The new plasticity index was defined as the value of difference between flow limit and plastic limit. The new liquidity index was also defined using flow limit. The values of flow limit are 1.5-2 times higher than those of liquid limit. At the same time, the values of new plasticity index are 2-5.5 times higher than those of original plasticity index.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.611-614
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• 2006

매년 발생하는 산사태에 대한 피해를 최소화하기 위하여 일본의 사면 붕괴와 대책방안에 대한 조사를 실시하였다. 지난 2006년 7월 강원도 영서지방에 발생한 산사태 피해 현황을 살펴보고 사방기술의 선진국인 일본을 방문, 이에 대한 자료를 수집 분석하였다. 산악지형으로 구성된 지형이 국내와 매우 유사하고 자연재해가 더욱 많은 일본의 선진 사방대책에 대한 기술을 습득하여 국내형의 기술개발과 정책결정에 도움을 얻고자 본 조사를 실시하였다. 본고는 수집된 자료를 바탕으로 국내의 정황과 비교하며 정리한 것이다.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.107-116
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• 2005

Korea has been suffering from various natural disasters. Slope-stability related disasters such as landslides usually occur during typhoon and torrential rain season. Types of slope-stability related disasters can be classified as failures in cut slopes along constructed roads, landslides in natural terrain, and retaining structure failures in urban area. This paper summarizes human casualties for the last 29 years in Korea, reviews field studies for the disaster sites that caused human casualties due to torrential rains in the Summer of 2005, analyzes causes of slope-stability related disasters and includes recommendations for an effective management system.