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The Study of Relationship between Berm Width and Debris Flow at the Slope (사면에서 토석류와 소단폭의 관계성에 관한 연구)

  • Kim, Sungduk;Oh, Sewook;Lee, Hojin
    • Journal of the Korean GEO-environmental Society
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    • v.14 no.11
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    • pp.5-12
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    • 2013
  • The purpose of this study is to estimate the behavior and the mechanism of debris flow at the end of mountain side when a berm was set on the inclined plane. The numerical model was performed by using the Finite Difference Method(FDM) based on the equation for the mass conservation and momentum conservation. In order to measure the behavior of the debris flow, the debris flow of a straight channel slope and the debris flow of channel slope with 3 types of berms were compared. First, the flow discharge and the sediment volume concentration at the downstream of the channel slope, depending on the various berm width and the different inflow discharges at the upstream of the channel were analyzed. The longer the berm width, the flow discharge at the downstream of the channel was decreased and the high flow fluctuation was reduced by a berm. And it means that a berm can effect for the delay of the debris flow. Through Root Mean Square ratio(RMS) comparison, the flow discharge of the channel slope with a berm was lower than that of a straight channel slope. The longer the berm width, for the sediment volume concentration, an inflection point did not show but mild curve. Because the low sediment concentration with water mixture by a berm continuously flow at the downstream end, it will be effect for reducing the disaster caused by debris flow. The results of this study will provide useful information in predicting and preventing disaster caused by the debris flow.

The Analysis of Regional Scale Topographic Effect Using MM5-A2C Coupling Modeling (국지규모 지형영향을 고려하기 위한 MM5-A2C 결합 모델링 특성 분석)

  • Choi, Hyun-Jeong;Lee, Soon-Hwan;Kim, Hak-Sung
    • Journal of the Korean earth science society
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    • v.36 no.3
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    • pp.210-221
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    • 2015
  • The terrain features and surface characteristics are the most important elements not only in meteorological modeling but also in air quality modeling. The diurnal evolution of local climate over complex terrain may be significantly controlled by the ground irregularities. Such topographic features can affect a thermally driven flow, either directly by causing changes in the wind direction or indirectly, by inducing significant variations in the ground temperature. Over a complex terrain, these variations are due to the nonuniform distribution of solar radiation, which is highly determined by the ground geometrical characteristics, i.e. slope and orientation. Therefore, the accuracy of prediction of regional scale circulation is strong associated with the accuracy of land-use and topographic information in meso-scale circulation assessment. The objective of this work is a numerical simulation using MM5-A2C model with the detailed topography and land-use information as the surface boundary conditions of the air flow field in mountain regions. Meteorological conditions estimated by MM5-A2C command a great influence on the dispersion of mountain areas with the reasonable feature of topography where there is an important difference in orographic forcing.

Characteristics of Meteorological Variables in the Leeward Side associated with the Downslope Windstorm over the Yeongdong Region (영동지역 지형성 강풍과 관련된 풍하측 기상요소의 특징)

  • Cho, Young-Jun;Kwon, Tae-Yong;Choi, Byoung-Cheol
    • Journal of the Korean earth science society
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    • v.36 no.4
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    • pp.315-329
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    • 2015
  • We investigated the characteristics of meteorological conditions related to the strong downslope wind over the leeward side of the Taebaek Mountains during the period 2005~2010. The days showing the strong wind exceeding 14ms1 in Gangwon province were selected as study cases. A total of 15 days of strong wind were observed at Sokcho, Gangneung, Donghae, and Taebaek located over the Yeongdong region. Seven cases related to tropical cyclone (3 cases) and heavy snowfall (2 cases) and heavy rainfall (2 cases) over the Yeongdong region were excluded. To investigate the characteristics of the remaining 8 cases, we used synoptic weather chart, Sokcho radiosonde, Gangneung wind profiler and numerical model. The cases showed no precipitation (or 1mmday1). From the surface and upper level weather chart, we found the pressure distribution of southern high and northern low pattern over the Korean peninsula and warm ridge over the Yeongdong region. Inversion layer (or stable layer) and warm ridge with strong wind were located in about 1~3 km (925~700 hPa) over mountains. The Regional Data Assimilation and Prediction System (RDAPS) indicated that warm core and temperature ridge with horizontal temperature gradient were 0.100.23Ckm1 which were located on 850 hPa pressure level above mountaintop. These results were summarized as a forecasting guidance of downslope windstorm in the Yeongdong region.

A Case Study on the Impact of Ground-based Glaciogenic Seeding on Winter Orographic Clouds at Daegwallyeong (겨울철 대관령지역 지형성 구름에 대한 지상기반 구름씨뿌리기 영향 사례연구)

  • Yang, Ha-Young;Chae, Sanghee;Jeong, Jin-Yim;Seo, Seong-Kyu;Park, Young-San;Kim, Baek-Jo
    • Journal of the Korean earth science society
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    • v.36 no.4
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    • pp.301-314
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    • 2015
  • The purpose of this study was to investigate the impact of ground-based glaciogenic seeding on orographic clouds in the Daegwallyeong area on 13 March, 2013. The experiments was conducted by releasing silver iodide (AgI) under following conditions: surface temperature below 4C, wind direction between 45 and 130, and wind speed less than 5ms1. Two seeding rates, 38gh1 (SR1) and 113gh1 (SR2), were tested to obtain an appropriate AgI ratio for snowfall enhancement in the Daegwallyeong area. Numerical simulations were carried out by using the WRF (Weather Research and Forecast) model with AgI point-source module which predicted dispersion fields of AgI particles. The results indicated that the target orographic clouds contained adequate amount of supercooled liquid water and that the dispersion of AgI particles tended to move along the prevailing wind direction. To validate the seeding effects, the observation data from FM-120 and MPS as well as PARSIVEL disdrometer were analyzed. In this case study, glaciogenic seeding significantly increased the concentration of small ice particles below 1 mm in diameter. The observation results suggest that SR1 seeding be reasonable to use the ground-based seeding in the Daegwallyeong area.

Finite Element Analysis on the Behavior of Soyanggang Dam and its Comparison with Observed (소양강(昭陽江)댐의 거동(擧動)에 대한 유한요소해석(有限要素解析)과 실측치(實測値)와의 비교(比較))

  • Kim, Sang Kyu;Lim, Heui Dae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.7 no.1
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    • pp.141-150
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    • 1987
  • The Soyanggang Dam completed in 1973 was well instrumented during construction period. The measured results for stresses and movements of the embankment have already been published elsewhere, but theoretical analyses have not been made until now. This study intends to analyze the stress and deformation behavior of the embankment numerically which have been subjected to the load of materials during construction and water load during impounding. The constitutive law used for the analyses is hyperbolic model developed by Duncan et al., and a nonlinear incremental finite element analysis simulating its contruction steps is. used in this study. Hyperbolic parameters for each Zone are estimated from literature. The results obtained from the theoretical analyses clearly show deformation characteristics and stress vectors in arbitrary section of the dam. The analytical results ate well agreed with the measured deformations at the maximum cross section, however, there are some discrepancy in horizontal movements and in stresses generated in the core zone. From the numerical analyses and its comparison with the measured values, it is charaterized that relatively large construction settlements occurred in core zone, overburden pressure in the core zone was considerably reduced by arching effect, and tension zones might occur near both abutments because of the large horizontal displacement.

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Study on Thermal Performance of Energy Textile in Tunnel (터널 지열 활용을 위한 에너지 텍스타일의 열교환 성능 연구)

  • Lee, Chulho;Park, Sangwoo;Sohn, Byonghu;Choi, Hangseok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.5
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    • pp.1907-1914
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    • 2013
  • Textile-type heat exchangers installed on the tunnel walls for facilitating ground source heat pump systems, so called "energy textile", was installed in an abandoned railroad tunnel around Seocheon, South Korea. To evaluate thermal performance of the energy textile, a series of long-term monitoring was performed by artificially applying daily intermittent cooling and heating loads on the energy textile. In the course of the experimental measurement, the inlet and outlet fluid temperatures of the energy textile, pumping rate, temperature distribution in the ground, and air temperature inside the tunnel were continuously measured. From the long-term monitoring, the heat exchange rate was recorded as in the range of 57.6~143.5 W per one unit of the energy textile during heating operation and 362.3~558.4 W per one unit during cooling operation. In addition, the heat exchange rate of energy textile was highly sensitive to a change in air temperature inside the tunnel. The field measurements were verified by a 3D computational fluid dynamics analysis (FLUENT) with the consideration of air temperature variation inside the tunnel. The verified numerical model was used to evaluate parametrically the effect of drainage layer in the energy textile.

An Experimental Study for Reduction of Energy losses at Surcharged Four-way Combining Square Manhole (과부하 4방향 사각형 합류맨홀에서의 에너지 손실 저감을 위한 실험 연구)

  • Kim, Jung Soo;Kim, Chae Rin;Yoon, Sei Eui
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.37 no.2
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    • pp.311-324
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    • 2017
  • Energy loss at manholes under surcharged flow is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the flow characteristics to reduce the energy loss in the surcharged four-way combining manhole. In this study, hydraulic experimental apparatus was constructed considering the results of the present survey. Square manholes and pipe diameters were reduced to 1/5 by applying sewer facility standards. Numerical simulations were carried out with the Fluent 6.3 model to derive the invert condition which can reduce the energy loss in the surcharged four-way combining square manhole. The hydraulic experiments were carried out according to the various conditions of the lateral flow rate(Qlat/Qout), discharge of outflow pipe (2.0, 3.0, 4.0, 4.8 l/sec), and invert shape (rectangle and square open conduit type). The crossed invert was not found to improve the drainage capacity of the surcharged four-way rectangular combining manhole. However, the improved rectangle open conduit type invert and square open conduit type invert were analyzed to improve the drainage capacity by reducing the head loss coefficients by about 8% and 28%, respectively. Therefore, in order to increase the drainage capacity of urban facilities, it is possible to install and use the improved invert proposed in this study.

Wave Control by Bottom-Mounted and Fluid-Filled Flexible Membrane Structure (유체가 채워진 착저신 유연막 구조물에 의한 파랑제어)

  • 조일형;강창익
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.12 no.3
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    • pp.139-148
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    • 2000
  • In this paper, the interaction of oblique incident waves with a bottom-mounted and fluid-filled flexible membrane structure is investigated in the frame of linear hydro-elastic theory. The static shape of a membrane structure containing the fluid of a specific density is initially unknown and must be calculated before the hydrodynamic analysis. To solve hydrodynamic problem, the fluid domain is divided into the inner and outer region. The inner solution based on discrete membrane dynamic model and simple-source distribution over the entire fluid boundaries is matched to the outer solution ba~ed on an eigenfunction expansion method. The numerical results were compared to a series of Ohyama's experimental results. The measured reflection and tran¬smission coefficients reasonably follow the trend of predicted values. Using the computer program developed, the performance of a bottom-mounted and fluid-filled flexible membrane strocture is tested with various system parameters (membrane shape, internal pressure, density ratio) and wave characteristics (wave frequencies, incident wave angle). It is found that a bottom-mounted and fluid-filled flexible membrane structure can be an effel;tive wave barrier if properly designed.

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Deterministic Lateral Displacement as a Function of Particle Size Using a Piecewise Curved Planar Interdigitated Electrode Array (다중예각 평면 교차전극을 이용한 입자 크기에 따른 측면방향 변위)

  • Han, Song-I;Joo, Young-Dong;Han, Ki-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.3
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    • pp.241-249
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    • 2012
  • This paper presents the lateral displacement of a particle passing over a planar interdigitated electrode array at an angle as a function of particle size. The lateral displacement was also measured as a function of the angle between the electrode and the direction of flow. A simplified line charge model was used for numerical estimation of the lateral displacement of fluorescent polystyrene (PS) beads with three different diameters. Using the lateral displacement as a function of particle size, we developed a lateral dielectrophoretic (DEP) microseparator, which enables the continuous discrimination of particles by size. The experiment using an admixture of 3-, 5-, and 10μm PS beads showed that the lateral DEP microseparator could continuously separate out 99.86% of the 3μm beads, 98.82% of the 5μm beads, and 99.69% of the 10μm beads. The lateral DEP microseparator is thus a practical device for the simultaneous separation of particles according to size from a heterogeneous admixture.

Prediction of Preceding Crown Settlement Using Longitudinal Displacement Measured on Tunnel Face in Fault Zone (단층대가 분포하는 터널에서 굴진면 수평변위를 이용한 선행 천단변위 분석)

  • Yun, Hyun-Seok;Do, Kyung-Ryang;Seo, Yong-Seok
    • The Journal of Engineering Geology
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    • v.27 no.1
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    • pp.81-90
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    • 2017
  • Preceding displacements in tunnel are difficult to predict since the measurements of displacements after excavation can not be performed immediately. In the present study, The longitudinal displacements which can be measured immediately after excavation are used to predict the crown settlements occurring before excavation only if fault is located at the tunnel crown. Three-dimensional finite element analysis was conducted using 28 numerical models with various fault attitudes to analyze the correlation between the longitudinal displacements on tunnel face and preceding crown settlements. The results, Lface/C ratio show 2~12% in the drives with dip models and 2~13% in the drives against dip models individually. In addition, each model has a certain Lface/C ratio. The result of the regression analysis show that the coefficient of determination is over 0.8 in most models. Therefore, crown settlements occurring before excavation can be predicted by analyzing the longitudinal displacements occurring on tunnel faces.