• Title/Summary/Keyword: Debris Flow

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Slope Stability and Development of Debris Flow Deposit in the Ulleung Basin, East Sea (동해 울릉분지의 사면안정성 및 쇄설류 퇴적체의 발달)

  • Lee, Sun-Jong;Lee, Jeong-Min;Yoo, Dong-Geun;Lee, Go-Eun;Park, Soo-Chul
    • Economic and Environmental Geology
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    • v.50 no.2
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    • pp.129-143
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    • 2017
  • The shallow sediments in the southwestern Ulleung Basin consist of mass flow deposits such as slide/slump and debris flow deposits (DFD), caused by slope failure. These sediments are proven to be important in studying geological disaster and stability of the seafloor. In this paper, we analysised the flow accumulation and slope failure susceptibility of the Ulleung Basin on the basis of multi-beam data, collected in this area. We also studied the distribution pattern and the seismic characteristics of the DFD in the uppermost layer of the Ulleung Basin on the basis of seismic data. The slope susceptibility was calculated as the frequency ratio of each factors including slope, aspect, curvature and stream power index (SPI), which causes the slope failure. These results indicate that the slope failure is frequently to occur in the southern and western continental slope of the Ulleung Basin. The sediment flow (mass flow) caused by the slope failure converges to the north and northwest of the Ulleung Basin. According to the seismic characteristics, the uppermost layer in study area can be divided into four sedimentary unit. These sedimentary units develop from the south and southwest to the north and northwest in association with slope susceptibility and flow accumulation.

Landslide Hazard Evaluation using Geospatial Information based on UAV and Infinite Slope Stability Model (UAV 기반의 공간정보와 무한사면해석모형을 활용한 산사태 위험도 평가)

  • Lee, Geun-Sang;Choi, Yun-Woong
    • Journal of Cadastre & Land InformatiX
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    • v.45 no.2
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    • pp.161-173
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    • 2015
  • The influence of climate change on rainfall patterns has triggered landslide and debris flow with casualties and property damage. This study constructed DSM and Orthophoto by using UAV surveying technique and evaluated landslide risk area by applying GIS data into the infinite slope stability model. As a result of the estimation of slope stability in a site, the slope instability has $SI{\leq}1.0$ with cover area 46,396m2, and the distribution percentage was 18.2%. The most dangerous section has $SI{\leq}0.0$ with its cover area 7,988m2, and the ratio was 0.8%. The reviews regarding the risk of landslide and debris flow risk by stability index and river channel analysis respectively help being able to designate the hazard zone due to heavy rainfall. Therefore the analysis result of this study will need to reinforce soil slope and plan their safety measures in the future.

Study on the Development of Ubiquitous-Based Landslide with a Debris Flow Monitoring System (유비퀴터스 기반 토석류 산사태 모니터링 시스템 개발에 관한 연구)

  • Kim, Yong-Gyun;An, Dae-Young;Kang, Dea-Woo;Han, Byung-Won
    • The Journal of Engineering Geology
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    • v.18 no.4
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    • pp.511-522
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    • 2008
  • Domestic slope related measuring system are mainly depending on manual and visual measurements and technical development for natural slopes is poor since the technology is developed focusing on artificial cut slopes. In addition, landslide with a debris flow is occurring frequently due to recent climate abnormally and heavy rains but early forecasts and prevention of disasters are in poor condition. Therefore, construction of ubiquitous sensor network (USN) capable of detecting dangers of landslide for rapid countermeasures is necessary. In this study, new measurements devices and measurement management techniques in compliance with domestic conditions are prepared by establishing ubiquitous based landslide monitoring system and standards of measurement management.

The Experimental Study for Variance of Depositation Due to Sediment Volume Concentration of Debris Flow (토석류의 토사체적농도에 따른 퇴적 특성 변화에 관한 실험 연구)

  • Choi, Youngdo;Kim, Sungduk;Lee, Hojin
    • Journal of Korean Society of Disaster and Security
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    • v.15 no.3
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    • pp.15-21
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    • 2022
  • The purpose of this study is to investigate the sedimentation area and runout distance in the downstream when debris flow occurred on a mountain slope through an experimental performance. Super typhoons and torrential rains caused by climate change cause large-scale debris flow disasters in the downstream areas of mountainous areas, mainly where sediments are deposited and flowed downstream. To analyze the characteristics of the sediment deposited downstream, the disposition area and runout distance were investigated through experiments in the case of a straight channel and channel with berm, respectively. As experimental conditions, changes in sediment volume concentration and channel slope, and channel with or without berm, reduction rates in sedimentation area and runout distance were investigated. In the straight channel, the steeper the channel slope and the lower the sedimentation concentration, the sedimentation area and runout distnace were increased. In a channel with berm, the runout distance and sediment area increased as the slope became steeper and the sediment area decreased.

Estimating Soil Thickness in a Debris Flow using Elastic Wave Velocity (탄성파 속도를 활용한 토석류 위험지역의 표토층 두께 결정)

  • Min, Dae-Hong;Park, Chung-Hwa;Lee, Jong-Sub;Yoon, Hyung-Koo
    • 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.