• Title/Summary/Keyword: Debris Analysis

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A Study on the 3D Analysis of Debris Flow Based on Large Deformation Technique (Coupled Eulerian-Lagrangian) (대변형 해석기법(Coupled Eulerian-Lagrangian)을 이용한 3차원 토석류 거동분석)

  • Jeong, Sang-Seom;Lee, Kwang-Woo;Ko, Jun-Young
    • Journal of the Korean Geotechnical Society
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    • v.31 no.12
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    • pp.45-57
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    • 2015
  • This paper presents the application of the Coupled Eulerian-Lagrangian (CEL) technique to simulate the debris flow. The main objective of this study is to investigate the applicability of CEL technique to the behavior of debris flow, such as flow velocity and influence area. Comprehensive studies to verify the behavior of debris flow are presented in this study. Through comparison with measured flow velocity from Umyeonsan (Mt.), CEL approach was found to be in good agreement with the general trend observed by in actual debris flow. In addition, CEL technique accurately simulated the behavior of debris flows, therefore, it can be used for designing the countermeasure structure.

Smart monitoring system with multi-criteria decision using a feature based computer vision technique

  • Lin, Chih-Wei;Hsu, Wen-Ko;Chiou, Dung-Jiang;Chen, Cheng-Wu;Chiang, Wei-Ling
    • Smart Structures and Systems
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    • v.15 no.6
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    • pp.1583-1600
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    • 2015
  • When natural disasters occur, including earthquakes, tsunamis, and debris flows, they are often accompanied by various types of damages such as the collapse of buildings, broken bridges and roads, and the destruction of natural scenery. Natural disaster detection and warning is an important issue which could help to reduce the incidence of serious damage to life and property as well as provide information for search and rescue afterwards. In this study, we propose a novel computer vision technique for debris flow detection which is feature-based that can be used to construct a debris flow event warning system. The landscape is composed of various elements, including trees, rocks, and buildings which are characterized by their features, shapes, positions, and colors. Unlike the traditional methods, our analysis relies on changes in the natural scenery which influence changes to the features. The "background module" and "monitoring module" procedures are designed and used to detect debris flows and construct an event warning system. The multi-criteria decision-making method used to construct an event warring system includes gradient information and the percentage of variation of the features. To prove the feasibility of the proposed method for detecting debris flows, some real cases of debris flows are analyzed. The natural environment is simulated and an event warning system is constructed to warn of debris flows. Debris flows are successfully detected using these two procedures, by analyzing the variation in the detected features and the matched feature. The feasibility of the event warning system is proven using the simulation method. Therefore, the feature based method is found to be useful for detecting debris flows and the event warning system is triggered when debris flows occur.

A Study on the Behavior of Floating Debris in a Flood Control Dam Using the Lagrangian Particle Traking Method (라그랑지안 입자 추적기법을 이용한 홍수조절용댐 내 부유쓰레기 거동 모의에 관한 연구)

  • Jang, Suk-Hwan;Oh, Kyoung-Doo;Oh, Ji-Hwan
    • Journal of Environmental Science International
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    • v.25 no.9
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    • pp.1253-1267
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    • 2016
  • After large-scale flooding damage occurred along the Imjin river in 1996, 1998, and 1999, the Hantan river flood control dam was planned, and it has since been under construction. Unlike existing dams in Korea, the Hantan river flood control dam will remain fully open except during high floods, when the dam will store flood water temporarily to reduce flood peaks and flood water volume downstream. During past flooding seasons, floating debris has caused difficulties in the management of large-scale dams. Most of the existing multipurpose dams in Korea have installed nets to collect floating debris based on many years of experience with and data about inflow and distribution of floating debris in the dams. For the Hantan river flood control dam, however, collection of data about inflow and distribution of floating debris is not possible as the dam is located near the border area between North and South Korea. In order to devise a preliminary plan to collect floating debris in the Hantan river flood control dam, an EFDC hydrodynamic model was used to analyze the behavior of floating debris during high floods. The Lagrangian particle tracking method was utilized to simulate the behavior of floating debris in the dam. Based on the analysis of paths and final destinations of the particles, seven collection points were selected where it seemed to be effective to collect floating debris, as debris is likely to accumulate there in high density.

Analysis of Debris Flow Disaster Area according to Location Change of Check Dam using Kanako-2D (Kanako-2D를 이용한 사방댐 위치 변화에 따른 토석류 피해지 분석)

  • Kim, Young Hwan;Jun, Kye-Won
    • Journal of the Korean Society of Safety
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    • v.33 no.1
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    • pp.128-134
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    • 2018
  • With the increase in frequency of typhoons and heavy rains following the climate change, the scale of damage from the calamities in the mountainous areas has been growing larger and larger, which is different from the past. For the case of Korea where 64% of land is consisted of the mountainous areas, establishment of the check dams has been drastically increased after 2000 in order to reduce the damages from the debris flow. However, due to the lack of data on scale, location and kind of check dams established for reducing the damages in debris flow, the measures to prevent damages based on experience and subjective basis have to be relied on. Under this study, the high-precision DEM data was structured by using the terrestrial LiDAR in the Jecheon area where the debris flow damage occurred in July 2009. And, from the numerical models of the debris flow, Kanako-2D that is available to reflect the erosion and deposition action was applied to install the erosion control facilities (water channel, check dam) and analyzed the effect of reducing the debris flow shown in the downstream.After installing the erosion control facilities, most of debris flow moves along the water channel to reduce the area to expand the debris flow, and after installing the check dam, the flow depth and flux of the debris flow were reduced along with the erosion. However, as a result of analyzing the diffusion area, flow depth, erosion and deposition volume of the debris flow generated from the deposition part after modifying the location of the check dams with the damages occurring on private residences and agricultural land located on the upstream area, the highest reduction effect was shown when the check dam is installed in the maximal discharge points.

Analysis of Erosion in Debris Flow Experiment Using Terrestrial LiDAR (지상 LiDAR를 이용한 토석류 실험의 침식량 분석)

  • Won, Sangyeon;Lee, Seung Woo;Paik, Joongcheol;Yune, Chan-Young;Kim, Gihong
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.34 no.3
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    • pp.309-317
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    • 2016
  • Debris flows are rapidly flowing masses of water mixed with soil and gravel from landslides which are caused by typhoons or rainstorms. The combination of Korea’s mountain dominated topography (70%) and seasonal heavy rains and typhoons causes landslides and large-scale debris flows from June to August. These phenomena often cause property damage and casualties that amount up to 20% of total annual disaster fatalities. The key point to predicting debris flow is to understand its movement mechanism, erosion, and deposition. In order to achieve a more accurate estimation of debris flow path and damage, this study incorporates quantitative analysis of high resolution LiDAR DEM (GSD 10cm) to delineate geomorphic and topographic changes induced by Jinbu real scale debris flow test.

A Study on the Kinetic Energy and Dispersion Behavior of High-velocity Impact-induced Debris Using SPH Technique (SPH 기법을 이용한 고속충돌 파편의 운동에너지와 분산거동 연구)

  • Sakong, Jae;Woo, Sung-Choong;Kim, Tae-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.5
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    • pp.457-467
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    • 2016
  • In this study, we investigate the dispersion behavior of debris and debris cloud generated by high-velocity impacts using the smoothed particle hydrodynamics (SPH) technique. The projectile and target plate were made of aluminum, and we confirm the validity of the SPH technique by comparing the measured major and minor axis lengths of the debris cloud in the reference with the predicted values obtained through the SPH analysis. We perform high-velocity impact and fracture analysis based on the verified SPH technique within the velocity ranges of 1.5~4 km/s, and we evaluate the dispersion behavior of debris induced by the impact in terms of its kinetic energy. The maximum dispersion radius of the debris on the witness plates located behind the target plate was increased with increasing impact velocity. We derive an empirical equation that is capable of predicting the dispersion radius, and we found that 95% of the total kinetic energy of the debris was concentrated within 50% of the maximum dispersion radius.

Capture Simulation Study for Space Debris Using Space-Nets (우주 그물을 이용한 우주 쓰레기 포획 시뮬레이션 연구)

  • Hwang, Ui-Jin;Jang, Mi;Lim, Jun-Hyun;Shin, Hyun-Cheol;Sim, Chang-Hoon;Park, Jae-Sang
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.50 no.6
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    • pp.435-444
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    • 2022
  • This study conducts capture simulations of space debris using a space-net. The present capture simulations are performed using ABAQUS, a nonlinear structural dynamics analysis code. A square space-net with 1 m × 1 m and a space debris with a cube configuration(0.3 m × 0.3 m × 0.3 m and 30 kg) are considered as baseline models. Using the baseline models, the capture simulation using ABAQUS is conducted to understand the capture process and establish the criteria of capture success or fail. In addition, the capture simulations are performed when various properties of the space-net are considered, and it is investigated that major design factors of the space-net are recognized to capture successfully the space debris.

Transient heat transfer and crust evolution during debris bed melting process in the hypothetical severe accident of HPR1000

  • Chao Lv;Gen Li;Jinchen Gao;Jinshi Wang;Junjie Yan
    • Nuclear Engineering and Technology
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    • v.55 no.8
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    • pp.3017-3029
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    • 2023
  • In the late in-vessel phase of a nuclear reactor severe accident, the internal heat transfer and crust evolution during the debris bed melting process have important effects on the thermal load distribution along the vessel wall, and further affect the reactor pressure vessel (RPV) failure mode and the state of melt during leakage. This study coupled the phase change model and large eddy simulation to investigate the variations of the temperature, melt liquid fraction, crust and heat flux distributions during the debris bed melting process in the hypothetical severe accident of HPR1000. The results indicated that the heat flow towards the vessel wall and upper surface were similar at the beginning stage of debris melting, but the upward heat flow increased significantly as the development of the molten pool. The maximum heat flux towards the vessel wall reached 0.4 MW/m2. The thickness of lower crust decreased as the debris melting. It was much thicker at the bottom region with the azimuthal angle below 20° and decreased rapidly at the azimuthal angle around 20-50°. The maximum and minimum thicknesses were 2 and 90 mm, respectively. By contrast, the distribution of upper crust was uniform and reached stable state much earlier than the lower crust, with the thickness of about 10 mm. Moreover, the sensitivity analysis of initial condition indicated that as the decrease of time interval from reactor scram to debris bed dried-out, the maximum debris temperature and melt fraction became larger, the lower crust thickness became thinner, but the upper crust had no significant change. The sensitivity analysis of in-vessel retention (IVR) strategies indicated that the passive and active external reactor vessel cooling (ERVC) had little effect on the internal heat transfer and crust evolution. In the case not considering the internal reactor vessel cooling (IRVC), the upper crust was not obvious.

A Combined Method for Rainfall-induced Landslides and Debris Flows in Regional-scale Areas (광역적 산사태-토석류 연계해석기법 제안)

  • Hong, Moonhyun;Jeong, Sangseom
    • Journal of the Korean Geotechnical Society
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    • v.35 no.10
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    • pp.17-31
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    • 2019
  • This study describes a prediction method for rainfall-induced landslides and subsequently debris flows in a regional scale areas. Special attention is given to the calculation of the propagation of debris flows by considering rainfall infiltration into soil slopes and soil entrainments by debris flows. The proposed method was verified by comparing the analytical results and the measured ones reported by the previous research. As a result, predictions and observations were quite similar in terms of the front position, the velocity, volume and momentum of debris flows. Even when applied to natural mountain slope with complicated terrain, numerical results and observations were similar. At last, the combined analysis of landslides and debris flows were conducted. The landslides prediction showed a predictive rate of about 83%, and the result of the final volume of debris flow showed an error rate of 3%. As a result, the proposed combined method for landslides and debris flows overcomes the problem of separating the landslides analysis and the debris flows simulation. Especially, the proposed method can analyze the effects of rainfall on entrainments by debris flows as well as rainfall-induced landslides and the behavior of debris flows.

Analysis of Topographical Factors in Woomyun Mountain Debris Flow Using GIS (GIS를 이용한 우면산 토석류 지형인자 분석)

  • Lee, Hanna;Kim, Gihong
    • Journal of the Korean Society of Industry Convergence
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    • v.23 no.5
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    • pp.809-815
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    • 2020
  • A number of investigations and studies have been conducted in various fields regarding the sediment disasters of Mt. Woomyeon that occurred in July 2011. We collected and compared the topographic information of the general points where debris flows did not occur and the collapse points where the debris flow occurred in order to find out the characteristics of the collapse points in Woomyeon mountain. The collected topographic information is altitude, curvature, slope, aspect and TPI(topographic position index). As a result of comparison, there were relatively many collapse points at an altitude of 210m to 250m, and at a slope of 30° to 40°. In addition, the risk of collapse was low in a cell where the curvature was close to 0, and the risk was higher in concave terrain than in convex terrain. In the case of TPI, there was no statistical difference between the general points and the collapse points when the analysis radius was larger than 200m, and there was a correlation with the curvature when the analysis radius was smaller than 50m. In the case of debris flows that are affected by artificial structures or facilities, there is a possibility of disturbing the topographic analysis results. Therefore, if a research on debris flow is conducted on a mountain area that is heavily exposed to human activities, such as Woomyeon mountain, diversified factors must be considered to account for this impact.