• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.818-823
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• 1998

Three Mile Island Unit-2 (TMI-2)의 사고 후 OECD-NEA 주관의 연구에 의하면 압력용기 하부의 노즐이 국부열점(hot spot) 영역의 경우 거의 압력용기 바닥까지 용융되었음이 조사되었다. [1]. 이러한 재배치된 용융노심의 열속에 의하여 압력용기의 외부와 통하는 penetration tube weld(노즐 용접부)가 파손된다면 내부의 고압상태로 인해 penetration tube ejection 사고 및 이에 따르는 용융노심의 압력용기 외부로의 유출 가능성까지 배제할 수 없을 것이다. 본 연구의 출발점은 중대사고시 이러한 압력 및 열속에 따르는 노즐 용접부의 파손확률을 결정하는데 있다. 크리프 파출시 기존의 해석에서 쓰인 deterministic approach를 개선하여 probabilistic approach를 개발하였다. 또한 기존의 해석에서 쓰인 단순한 안전 여유도(margin-to-failure)의 개념과 비교하여 용접부에서의 파손확률을 계산하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2303-2315
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• 2013

In general, the waterway was installed for drain water from steep slope and waterway cover was set up to prevent overflow and water separation at berm of waterway. In this study, hydraulic experiment was conducted to analyze the flow characteristics and enact standard design criteria of the waterway. Hydraulic experimental apparatus which can change the slope of waterway and the length of berm were installed to analyze of flow characteristics at the waterway. The slopes of waterway were $40^{\circ}$, $50^{\circ}$, $60^{\circ}$, and $70^{\circ}$ and the range of discharge were 1.0~5.6 ${\ell}/s$. The flow in berm was distinguished two types such as hydraulic jump and splash flow. These kinds of flows depended on the rates of discharge in waterway. When inlet discharge was below 1.1~2.0 ${\ell}/s$, the separation phenomenon of water was generated at upper and lower portion in berm by the splash flow. The scattering range of water particles and length of water separation was measured depending on the slope of waterway. The start point of scattering was about 20 cm(1.3B) from the place connected upper waterway with brem and the length of water separation was till 210 cm(3.5B) from the place connected lower waterway with brem. Therefore, the waterway cover needed to install from starting of berm to 1B and from the lower part of berm to 3.5B.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.789-799
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• 2019

The settlement hardly occurs in structures supported by pile foundation such as abutment, culvert but a cavity is formed in the lower part of a structure. As a result, soil discharged from the lateral ground to the cavity accelerates the settlement of the lateral ground of the structure, resulting in a larger settlement. Therefore, in order to prevent problems caused by cavity under the structure supported by pile foundation, soil Flow Protector (briefly called 'FLP'), which can be easily installed on the side of structure, was developed. In this study, an laboratory model test was carried out to prove the reduction effect of settlement and to estimate the optimal installation length of the FLP. As a result, the installation of the FLP reduced the settlement of the lateral ground and prevented the leakage of lateral ground soil into the cavity. If the stiffness of the FLP is small, the state or active earth pressure is generated in the upper part, which is not favorable for stability. But if the stiffness of the FLP is high enough, the passive earth pressure area is generated in the upper part, which will be advantageous for the stability. Also, the increased installation length of FLP is effective to reduce the settlement. And the ratio of the optimal length of the FLP to the box structure height (H = 250 mm) are flexible FLP 1.38, stiff FLP 0.73.

• Journal of the Society of Disaster Information
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• v.16 no.1
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• pp.60-69
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• 2020

Purpose: Cavity growth process monitoring is to periodically monitor changes in common size and topography for general and observational grades to predict the rate of common growth. The purpose of this study is to establish a systematic cavity management plan by evaluating the general and observational class community in a non-destructive method. Method: Using GPR exploration equipment, the acquired surface image and the surrounding status image are analyzed in the GPR probe radargram in depth, profile, and cross section of the location. The exact location is selected using the distance and surrounding markings shown on the road surface of the initial detection cavity, and the test cavity is analyzed by calling the radar at the corresponding location. Result: As a result of monitoring tests conducted at a cavity 30 sites of general and observation grade, nine sites have been recovered. Changes in scale were seen in 21 cavity locations, and changes in size and grade occurred in 13 locations. Conclusion: The under road cavity is caused by various causes such as damage to the burial site, poor construction, soil leakage caused by groundwater leakage, waste and ground vibration. Among them, indirect factors could infer the effects of groundwater and localized rainfall.

• Journal of the Korean Geosynthetics Society
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• v.15 no.3
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• pp.39-47
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• 2016

In order to prevent leakage of leachate in offshore landfill, hydraulic barrier is indispensable. In the case of rubble mound revetment at offshore landfill, HDPE sheet in slope should be installed. In this study, seepage analysis were performed to evaluate seepage and flow in the seabed and revetment according to extended length of HDPE sheet by using SEEP/W. Results show that, in the case of low permeability layer is distributed where extended length of HDPE sheet was more than 1m, seepage flux in seabed and revetment was greatly reduced. In order to prevent seepage in seabed and revetment in the case of sand layer of high permeability is existed above low permeable layer, extended length of HDPE sheet and impermeable improvement width of permeable layer should be more than 1m at seabed.

• Journal of Korea Water Resources Association
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• v.30 no.1
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• pp.23-34
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• 1997

The Nanji-Do ladnfill is an ill-conditioned reclaimed land without pollution intercepting facilities, and has high ground water table and deep stratum. The purpose of this study is to analyze the solute transport in steady-state groundwater flow and to predict the solute dispersion in Nanji-Do landfill using HST-3D model. As results, the groundwater flows radially outward from the center of No. 1 and No. 2 landfills, and large amount of runoff is moved into Han River. The predicted relative concentration of total dissolved solute(TDS) at two years later was 0.25 in the weathering zone, 0.26 in the lower alluvium, and 0.28 in the upper alluvium. Thus, the further pollution to bottom rock and Han River was predicted by comparing the corresponding present values of 0.29, 0.32 and 0.35.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.8
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• pp.878-883
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• 2006

Removal efficiency of As(III) was investigated with a pilot-scale filtration system packed with an equal amount(each 21.5 kg) of manganese-coated sand(MCS) in the bottom and iron-coated sand(ICS) in the top. Height and diameter of the used column was 200 cm and 15 cm, respectively. The As(III) solution was introduced into the bottom of the filtration system with a peristaltic pump at a speed of $5{\times}10^{-3}$ cm/s over 148 days. Breakthrough of total arsenic in the mid-sampling position(end of the MCS bed) and final-sampling position(end of the ICS bed) was started after 18 and 44 days, respectively, and then showed a complete breakthrough after 148 days. Although the breakthrough of total arsenic in the mid-sampling position was started after 18 days, the concentration of As(III) in this effluent was below 50 ppb up to 61 days. This result indicates that MCS has a sufficient oxidizing capacity to As(III) and can oxidize 92 mg of As(III) with 1 kg of MCS up to 61 days. When a complete breakthrough of total arsenic occurred, the removed total arsenic by MCS was calculated as 79.0 mg with 1 kg MCS. As variation of head loss is small at each sampling position over the entire reaction time, it was possible to operate the filtration system with ICS and MCS for a long time without a significant head loss.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.21-32
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• 2023

Interrill erosion dominates in forest areas, and the erosion rate in surface-disturbed areas is significantly increased by the development and expansion of rill. In this study, soil erosion experiments using simulated rainfall and inflow were performed to understand the development and the micromorphological changes of rill on steep slopes. The characteristic factors of the micromorphology, such as the rill cross section, rill volume, rill density, rill order, and rill sharpness, were analyzed according to steepness and location (upper or lower) of slope. The head-cut of the simultaneous incised rills by rainfall simulation moved rapidly upslope, and the randomly developed rills expanded deeply and widely with their connection. The rill cross section evolved to downslope gradually increased. The rill volume occupied about 78 % of the sediment volume, confirming that the contribution of the sediment from the rill erosion is greater than that of the interrill erosion. Although the rate of increase in rill order slowed as the slope increased, the total length and density of the rill generally increased. As the slope increased from 15° to 20°, the bed incision of rills became larger than the sidewall expansion, and the rill sharpness increased by 1.6 times. The runoff coefficient on the lower slope decreased by 12.3 % than that on the upper slope. It was evaluated that the subsoil exposures and formation changes by the rill expansion increased the infiltration rate. Although the sediment accompanying the rills generally increased with slope increase, it was directly influenced by the hydraulic velocity of enhanced rill with the local convergence and expansion in the process of the rill evolution.

• Journal of the Korean Geotechnical Society
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• v.27 no.10
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• pp.93-104
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• 2011

In this paper, a numerical procedure of probabilistic steady seepage analysis that considers the spatial variability of soil permeability is presented. The procedure extends the deterministic analysis based on the finite element method to a probabilistic approach that accounts for the uncertainties and spatial variation of the soil permeability. Two-dimensional random fields are generated based on a Karhunen-Lo$\grave{e}$ve expansion in a fashion consistent with a specified marginal distribution function and an autocorrelation function. A Monte Carlo simulation is then used to determine the statistical response based on the random fields. A series of analyses were performed to verify the application potential of the proposed method and to study the effects of uncertainty due to the spatial heterogeneity on the seepage behavior of soil foundation beneath water retaining structure with a single sheet pile wall. The results showed that the probabilistic framework can be used to efficiently consider the various flow patterns caused by the spatial variability of the soil permeability in seepage assessment for a soil foundation beneath water retaining structures.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.37-47
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• 2008

Design and construction of tunnels require understanding the influence of groundwater. Particularly, it is essential to know how the drainage conditions at the tunnel boundary affect flow behavior of ground adjacent to the tunnels. In this study flow behavior of a leaking tunnel was investigated using physical model tests for tunnel depths and various hydraulic boundary conditions. Particular concerns were given to flow lines toward tunnels. Test results showed that the boundary conditions hardly influence on flow patterns and time required to reach steady state conditions. It is revealed that with an increase in water depth, flow lines concentrated to the drain holes. The physical tests were numerically simulated. Numerical results showed that the flow behavior was represented appropriately by considering filter-drain hole drainage rather than boundary drainage all over the lining.