• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.937-941
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• 2006

본 연구에서는 비상여수로와 같은 치수능력 증대를 위한 구조물의 이수적 측면의 활용성에 대해 검토하였다. 이를 위해 대청댐 유역을 대상으로 홍수기와 비홍수기로 구분하여 수문분석을 실시하고, 대청댐 하류부 무피해 방류량을 산정하였으며, 저수지 모의운영을 통하여 비홍수기 운영수위인 상시만수위와 홍수기 운영수위인 제한수위를 검토하였다. 본 연구 결과 비홍수기 상시만수위와 홍수기 제한수위를 가변적으로 운용하여 다목적댐의 이수능력을 증대시킬 수 있는 것으로 분석되었다.

• Journal of the Korean Geophysical Society
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• v.9 no.2
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• pp.121-128
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• 2006

Recently, spillways are need to control stable water level for supporting main dams because of floods by unusual change of weather such as Typhoon Rusa. This study has been focused on the amount of leakage through the rock mass distributed fractures and joints under the opened emergency spillway. It is very important to evaluate the amount of leakage as these affect stability of spillway by interaction between effective stress and pore pressure. The commercial program MAFIC has been used for analyzing groundwater flow in fractured rock mass. The results showed that the values of range, average and deviation of leakage were 2.85∼ 3.79×10-1, 3.32×10-1 and 1.70×10-2 m3/day/m2 respectively. Secondary, we have estimated the effect of grouting after the transmissivity(Tf) of joint 1 as main pathway of leakage known from above results was changed from 1.78×10-7 to 1.59×10-9 m2/s. The results showed that the values of range, average and deviation of leakage were 7.80×10-4∼1.53×10-3, 1.18×10-3 and 1.32×10-4 m3/day/m2 respectively. As the result, the amount of leakage after grouting has been decreased by a ratio of 1 to 277.

• Geomechanics and Engineering
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• v.34 no.1
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• pp.29-41
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• 2023

The 3D geospatial modeling of geotechnical information can aid in understanding the geotechnical characteristic values of the continuous subsurface at construction sites. In this study, a geostatistical optimization model for the three-dimensional (3D) mapping of subsurface stratification and the SPT-N value based on a trial-and-error rule was developed and applied to a dam emergency spillway site in South Korea. Geospatial database development for a geotechnical investigation, reconstitution of the target grid volume, and detection of outliers in the borehole dataset were implemented prior to the 3D modeling. For the site-specific subsurface stratification of the engineering geo-layer, we developed an integration method for the borehole and geophysical survey datasets based on the geostatistical optimization procedure of ordinary kriging and sequential Gaussian simulation (SGS) by comparing their cross-validation-based prediction residuals. We also developed an optimization technique based on SGS for estimating the 3D geometry of the SPT-N value. This method involves quantitatively testing the reliability of SGS and selecting the realizations with a high estimation accuracy. Boring tests were performed for validation, and the proposed method yielded more accurate prediction results and reproduced the spatial distribution of geotechnical information more effectively than the conventional geostatistical approach.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1919-1924
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• 2014

Recently, due to the climate change, the frequency and intensity of extreme rainfall events have been continuously increased in regions of South Korea. As a consequence, safety issues have been raised especially in the hydrologic safety of old dams designed and constructed by the old standards. In general, for improving hydrologic safety of existing dams, two options are considered: 1) raising dam crest; and 2) constructing or expanding an emergency spillway. In this process, the main criteria of alternative selection are overtopping possibility and cost efficiency of each alternative. This approach is easy to implement but it is subject to major limitation for the proper evaluation of alternatives, overlooking downstream flood damages by any controlled flow of water that is intentionally released from dams to eliminate the possibility of overtopping. Therefore, this study suggests a framework for evaluating the dam safety strengthening alternatives in terms of a comprehensive flood control by applying the concept of resilience. The case study shows that the resilience-based evaluation framework which considering downstream flood damages is effective in the selection of dam safety strengthening alternatives.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.4
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• pp.21-35
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• 2016

This study is to evaluate the applicability of SWAT (Soil and Water Assessment Tool) model for multi-purpose dams and multi-function weirs operation in Namhan river basin ($12,577km^2$) of South Korea. The SWAT was calibrated (2005 ~ 2009) and validated (2010 ~ 2014) considering of 4 multi-purpose dams and 3 multi-function weirs using daily observed dam inflow and storage, evapotranspiration, soil moisture, and groundwater level data. Firstly, the dam inflow was calibrated by the five steps; (step 1) the physical rate between total runoff and evapotranspiration was controlled by ESCO, (step 2) the peak runoff was calibrated by CN, OV_N, and CH_N, (step 3) the baseflow was calibrated by GW_DELAY, (step 4) the recession curve of baseflow was calibrated by ALPHA_BF, (step 5) the flux between lateral flow and return flow was controlled by SOL_AWC and SOL_K, and (step 6) the flux between reevaporation and return flow was controlled by REVAPMN and GW_REVAP. Secondly, for the storage water level calibration, the SWAT emergency and principle spillway were applied for water level from design flood level to restricted water level for dam and from maximum to management water level for weir respectively. Finally, the parameters for evapotranspiration (ESCO), soil water (SOL_AWC) and groundwater level fluctuation (GWQMN, ALPHA_BF) were repeatedly adjusted by trial error method. For the dam inflow, the determination coefficient $R^2$ was above 0.80. The average Nash-Sutcliffe efficiency (NSE) was from 0.59 to 0.88 and the RMSE was from 3.3 mm/day to 8.6 mm/day respectively. For the water balance performance, the PBIAS was between 9.4 and 21.4 %. For the dam storage volume, the $R^2$ was above 0.63 and the PBIAS was between 6.3 and 13.5 % respectively. The average $R^2$ for evapotranspiration and soil moisture at CM (Cheongmicheon) site was 0.72 and 0.78, and the average $R^2$ for groundwater level was 0.59 and 0.60 at 2 YP (Yangpyeong) sites.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.5-12
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• 2011

When choosing the support pattern of tunnel, the characteristics of rock are identified from the result of the surface geologic survey, boring, and geophysical prospecting and laboratory test. And a rock mass rating is classified and excavation method and standard support pattern are designed considering rock classification, domestic and international construction practices, numerical analysis. According to the revised design standard for tunnel, it was recommended to classify the rock mass rating for the design of tunnel into a rating based on RMR. If necessary, it proposed a flexible standard allowed applying more atomized the rock mass rating and Q-System. Also, the resonable verification of the support pattern must be accompanied because the factors affecting the structure and behavior of ground during the construction of tunnel are the main factors of uncertainty factors such as the nature of ground, ground water and the characteristics of structural materials. These days, such verification method is getting more specialized and diversified. In this study, the empirical method, numerical analysis and comparative analysis of in situ measurements were used to prove the reasonableness in the support pattern by RMR and Q-value on the Imha Dam emergency spillway.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.775-784
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• 2023

With the increasing trend of extreme rainfall that exceeds the design frequency of man-made structures due to extreme weather, it is necessary to review the safety of agricultural reservoirs designed in the past. However, there are no local government-managed reservoirs (13,685) that can be discharged in an emergency, except for reservoirs over a certain size under the jurisdiction of the Korea Rural Affairs Corporation. In this case, it is important to quickly deploy a mobile siphon to the site for preliminary discharge, and this study evaluated the applicability of a mobile siphon with a diameter of 200 mm, a minimum water level difference of 6 m, 420 (m²/h), and 10,000 (m²/day), which can perform both preliminary and emergency discharge functions, to the Yugum Reservoir in Gyeongju City. The test bed, Yugum Reservoir, is a facility that was completed in 1945 and has been in use for about 78 years. According to the hydrological stability analysis, the lowest height of the current dam crest section is 27.15 (EL.m), which is 0.29m lower than the reviewed flood level of 27.44 (EL.m), indicating that there is a possibility of lunar flow through the embankment, and the headroom is insufficient by 1.72 m, so it was reviewed as not securing hydrological safety. The water level-volume curve was arbitrarily derived because it was difficult to clearly establish the water level-flow relationship curve of the reservoir since the water level-flow measurement was not carried out regularly, and based on the derived curve, the algorithm for operating small and medium-sized old reservoirs was developed to consider the pre-discharge time, the amount of spillway discharge, and to predict the reservoir lunar flow time according to the flood volume by frequency, thereby securing evacuation time in advance and reducing the risk of collapse. Based on one row of 200 mm diameter mobile siphons, the optimal pre-discharge time to secure evacuation time (about 1 hour) while maintaining 80% of the upper limit water level (about 30,000 m²) during a 30-year flood was analyzed to be 12 hours earlier. If the pre-discharge technology utilizing siphons for small and medium-sized old reservoirs and the algorithm for reservoir operation are implemented in advance in case of abnormal weather and the decision-making of managers is supported, it is possible to secure the safety of residents in the risk area of reservoir collapse, resolve the anxiety of residents through the establishment of a support system for evacuating residents, and reduce risk factors by providing risk avoidance measures in the event of a reservoir risk situation.