• Journal of the Korean GEO-environmental Society
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• v.22 no.10
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• pp.21-29
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• 2021

Most concrete gravity-type dams in and out of the country were constructed by column method to control cracks caused by concrete hydration heat generated during construction, resulting in a certain level of leakage after impoundment through various causes, such as contraction joints and construction joints. However, due to the characteristics of concrete structures that shrink and expand according to temperature, concrete dams have vertical joints and drains to allow penetration. PVC waterproof shows excellent effects in completion of the dam, which however increases the possibility of interfacial failure due to different thermal expansion. Other causes of penetration may include problems with quality control during installation, generation of cracks due to heat of hydration of concrete, waterproofing methods, etc. In the case of Bohyunsan Dam in Yeongcheon, North Gyeongsang Province, the amount of drainage in the gallery was checked and underwater, and it was confirmed that there are many penetrations from drainage holes connected to vertical joints, and that some of the PVC waterproofs are not fully operated. As a new method to prevent penetration through vertical joints, D.S.I.M. (Dam Sealing Innovation Method) developed by World E&C was applied to Bohyunsan Dam and checked the amount of drainage in the gallery. As a result of first testing three most leaking vertical joints, the drain in the gallery was reduced by 87% on the average and then applied to the remaining 13 locations, which showed a 83% reduction effect based on the total drain in the gallery. Summing up these results, it was found that D.S.I.M. preventing water leakage from the upstream face is a valid construction method to reduce the water see-through and penetration quantity seen in downstream faces of concrete dams. If D.S.I.M. is applied to other concrete dams at domestic and abroad, it is expected that it will be very effective to prevent water leakage through vertical joints that are visible from downstream faces.

• Geophysics and Geophysical Exploration
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• v.13 no.1
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• pp.9-23
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• 2010

In current design practice, the shear wave velocity (Vs) of the core and rock-fill zone of a dam, one of the characteristics essential for seismic response design, is seldom determined by field tests. This is because the borehole seismic method is often restricted in application, due to stabilisation activities and concern for the security of the dam structure, and surface wave methods are limited by unfavourable in-situ site conditions. Consequently, seismic response design for a dam may be performed using Vs values that are assumed, or empirically determined. To estimate Vs for the core and rock-fill zone, and to find a reliable method for measuring Vs, seismic surface wave methods have been applied on the crest and sloping surface of the existing 'M' dam. Numerical analysis was also performed to verify the applicability of the surface wave method to a rock-fill dam. Through this numerical analysis and comparison with other test results, the applicability of the surface wave method to rock-fill dams was verified.

• Geophysics and Geophysical Exploration
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• v.16 no.3
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• pp.109-118
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• 2013

On and near the 23-m high earthen Cheongcheon dam in Boryeong City, Korea, short seismic refraction and surface-wave profiles were conducted using a 5-kg sledgehammer. From vertical and horizontal components of the seismic waves, near-surface P-wave velocities (${\nu}_p$) and S-wave velocities (${\nu}_s$) were derived by inverting first-arrival refraction times and dispersion curves of Rayleigh waves. Average ${\nu}_p$ and ${\nu}_s$ for the Jurassic sedimentary basement were determined to be 1650 and 950 m/s at a depth of 30 m directly beneath the dam and 1650 m/s and 940 m/s at a depth of 10 m at the toe of the dam, respectively. The dynamic Poisson's ratio for these strata were therefore in the range of 0.24 to 0.25, which is consistent with ratios for consolidated sedimentary strata. Near a 45-m borehole 152 m downstream from the dam crest, an SH tomogram indicates a refraction boundary with an average ${\nu}_s$ of 870 m/s at depths of 10 ~ 12 m. At this site, the overburden comprises the upper layer with relatively constant ${\nu}_p$ and ${\nu}_s$ around 500 and 200 m/s, respectively, and the lower layer in which both ${\nu}_p$ and ${\nu}_s$ increase with depth almost linearly. The dynamic Poisson's ratios for the overburden were in the range of 0.30 to 0.43.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.725-733
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• 2019

Sand dams are structures that can be used as auxiliary water resources in case of drought as sand accumulates due to barriers crossing valley rivers and valley water is stored in the voids, increasing the water level. This structure, which is mainly used in arid regions such as Africa, has not been installed in Korea. In Korea, there are only a few cases where water is taken from debris barriers that prevent debris flow. The purpose of this study is to evaluate the effect of water supply when the sand dam is installed downstream of the existing intake barrier in Seosang-ri valley, Chuncheon. For this purpose, modeling was performed by linking the basin hydrologic model and reservoir routing model. Changes in the water level, storage and discharge in the sand dam reservoir according to the size and intake of the sand dam are presented on a case-by-case basis. As a result of application, it was found that the water supply capacity due to the sand dam installation was improved at 95% reliability. Especially, when the size is L × B × H_o = 25 m × 15 m × 1 m and the pumping rates from intake barrier and sand dam are (Q₁, Q₂) = (30, 20), (35, 15) ㎥/day, the efficiency was the best for water supply of 50 ㎥/day.

• Journal of the Korean Geophysical Society
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• v.6 no.3
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• pp.189-207
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• 2003

The purpose of this paper is to analyze the behavior and to study the safety evaluation of the Unmun Dam located in Cheongdo-Gun of GyeongBuk Province, Korea. For this purpose, soil analyses including boring data, geophysical surveys and monitoring the buried geotechnical gauges, such as pore-pressure gauge, earth-pressure gauge, displacement gauge, multi-layer settlement gauge, leakage flow-meter, were conducted. In addition to these data, numerical analyses of behavior of dam were performed to predict and to compare the data which were obtained from the above methods. Since many defects, such as gravel and weathered rock blocks in the dam core, and lots of amounts of leakage, by boring analyses were found, reinforcement by compaction grouting system (CGS) has been conducted in some range of dam. Some geotechnical gauge data were also used to confirm the effects of reinforcement. Analyses of monitoring the data of geotechnical gauges buried in the dam, such as pore-pressure gauge, earth-pressure gauge, displacement gauge, multi-layer settlement gauge, and leakage flow-meter shows the load transfer of dam and the possibility of hydraulic fracturing. As a conclusion, some problems in the dam found. Especially, the dam near spillway shows the high possibility of leakage. It should be pointed out that only the left side of he dam has not a leakage problem. As a whole, the dam has problems of weakness, because of unsatisfactory construction. It is strongly recommended that highly intensive monitoring is required.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1302-1306
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• 2007

여름철의 강우시 저수지에 주로 유입되는 고탁수층은 저수지내의 수체에 대하여 밀도차와 유속차를 가지며, 난류혼합을 일으키면서 주변수를 유입하며 하류방향으로 이송 확산되어 간다. 임하댐과 같은 대형 저수지는 수심이 30 m가 넘는 관계로 여름철에 2개의 수온약층이 존재한다. 따라서 댐체에 도달한 고탁수층은 저수지내의 밀도성층으로 인하여 주로 중층에 분포하게 되며, 가을철에 발생하는 수평확산과 전도현상으로 인해 저수지 전역에 분포하게 되어 탁질입자의 분포에 따라 탁수현상의 장기화를 유발하기도 한다. 이와 같은 탁수문제의 저수지내 대책으로는 홍수기에 고탁수층을 우선적으로 취수하는 방법이 있다. 고탁수층은 이와같이 수온약층과 밀접한 관계를 가지며, 취수탑 주변의 선택취수 결과에 영향을 받는다. 형성된 탁수층을 효율적으로 선택배제하기 위해서는 취수시설에 접근하는 성층흐름을 정확하게 이해해야 한다. 본 연구에서는 3차원 CFD를 사용하여 밀도성층에 따른 취수탑 주변의 접근흐름을 수치해석하여 방류수심, 방류유속 및 밀도성층구조의 선택배제에 대한 영향을 분석하였다. 임하댐 취수설비에 적용한 결과에 의하면 상층, 중층, 하층에서 취수탑 문비를 개도하였을 경우, 취수탑 주변에서만 유속이 증가하였을 뿐 저수지 내에서는 유속이 크게 증가되지 않은 것으로 나타났다. 하지만 문비 개도구간의 변화에 따라 수심별 유속분포는 크게 변화하는 것을 확인할 수 있다. 따라서 문비를 조절하는 것은 저수지 전체의 유동을 깨뜨리지 않으면서 취수탑 인근에서 선택취수가 가능하다는 것을 확인할 수 있었다. 또한 본 연구에서는 정밀한 현장조사를 수행하여 저수지와 방류수의 탁도변화를 모니터링하였으며, 취수탑 개구부 주변의 연직 유속분포를 측정하였다. 3차원 수치모의 결과와 현장에서 관측한 유속장을 비교함으로써 본 연구에서 제시한 실제 탁수배제능력을 검증하였다.를 구축하였다는데 의의가 있다.로와 접하는 건물의 경우 모서리부 광고 효과가 지배적이며 대부분 곡선돌출형이 사용되고 있었다. 그러므로 모서리 저층부를 필로티로 계획하여 보행흐름을 원활하게 하고 대신 입면을 투명하게 하여 간접광고(내부전시) 효과를 유도하는 것이 좋다. 특히 원형모서리는 건물 특화 성격이 강하므로 불가피할 경우 소형 액센트 광고 위치를 미리 벽면으로 할애하는 것이 경관 및 입면계획에 유리한 것으로 분석되었다. 불확실도 해석모형 등의 새로운 기능을 추가하여 제시하였다. 모든 입출력자료는 프로젝트 단위별로 운영되어 data의 관리가 손쉽도록 하였으며 결과를 DB에 저장하여 다른 모형에서도 적용할 수 있도록 하였다. 그리고 HyGIS-HMS 및 HyGIS-RAS 모형에서 강우-유출-하도 수리해석-범람해석 등이 일괄되게 하나의 시스템 내에서 구현될 수 있도록 하였다. 따라서 HyGIS와 통합된 수리, 수문모형은 국내 하천 및 유역에 적합한 시스템으로서 향후 HydroInformatics 구현을 염두에 둔 특화된 국내 수자원 분야 소프트웨어의 개발에 기본 토대를 제공할 것으로 판단된다.았다. 또한 저자들의 임상병리학적 연구결과가 다른 문헌에서 보고된 소아 신증후군의 연구결과와 큰 차이를 보이지 않음을 알 수 있었다. 자극에 차이가 있지 않나 추측되며 이에 관한 추후 연구가 요망된다. 총대장통과시간의 단축은 결장 분절 모두에서 줄어들어 나타났으나 좌측결장 통과시간의 감소 및 이로 인한 이 부위의 통과시간 비율의 저하가 가장 주요하였다. 이러한 결과는 차가운 생수 섭취가 주로 결장 근위부를 자극하는 효과를 발휘하는 것이 아닌가 해석된다. 이와 같은 연구결과를 통해 생다시마를 주원료로 개발된 생다시마차와 생다시마 음료가 만성 기능성 변비 증세를 개선하는 효능이 잠재적으로 있음을 확인하였다. 그러나 생약제재의 변비약 수준으로

• Journal of the Korean earth science society
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• v.38 no.2
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• pp.161-171
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• 2017

Observed ground motions are composed of three factors such as, seismic source, attenuation, and site amplification effect. Among them, the site amplification characteristics should be considered significantly when estimating seismic source and attenuation characteristics with more confidence. The site effect is also necessary when estimating not only seismic hazard in seismic design engineering but also rock mechanical properties. This study uses the method of H/V spectral ratio of observed ground motion between target site and reference site called a reference site method. In addition to using the vertical Fourier spectrum of the reference site, we try out the horizontal Fourier spectrum as a new method in this study. We analyze H/V spectral ratio of six ground motions respectively, observed at four sites close to Yedang Reservoir. We then compare site amplification effects at each site using 3 kinds of seismic energies including S waves, Coda waves energy, and background noise. The results suggest that each site showed similar site amplification patterns in S waves and Coda waves energy. However, the site amplification of background noise shows much different characteristics from those of S waves and Coda wave energy, which suggests that the background noises at each site have their own developing mechanism. Each station shows its own characteristics of specific resonance frequency and site amplification properties in low, high and specific resonance frequency ranges. Comparison of the method used in this study to the others that used different methods can provide us with more information about the dynamic amplification of a site characteristics and site classification.

• Journal of the Korean Geotechnical Society
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• v.29 no.5
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• pp.53-64
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• 2013

Resistivity monitoring is based on the fact that a change in the porosity leads to the changes in water content and fine particles, which alter the electrical resistivity. At every embankment dam, internal erosion always occurs as time passes. The internal erosion generally develops into piping over a long time by backward erosion and concentrated leak, and finally leads to dam failure. Resistivity is known to be very sensitive to the changes in porosity in embankment dams. Thus resistivity monitoring is a reasonable method to find out the leakage zone. However, resistivity is strongly influenced by seasonal variation of temperature, TDS of reservoir water and water level. In this paper. we first installed electrodes permanently at the center of the crest. The electrical resistivity monitoring data was acquired every 6 hours from Apr. 3, 2011 to July. 31, 2012. To analyze the characteristics of monitoring data, each resistivity data was calculated from up to 2,950 data sets. The result indicated a seasonal resistivity variation due to related temperature. Finally, a quantitative method to estimate porosities of the embankment dam from the resistivity monitoring data was analyzed. The applicability and reliability were verified and the importance of electrical resistivity monitoring for obtaining reliable result was emphasized.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.6
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• pp.427-435
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• 2021

An analysis considering the fluid-structure interaction is required to strictly evaluate the seismic behavior of facilities such as, environmental facilities and dams, that store fluids. Specifically, in the case of an infinite domain in the upstream direction, such as a dam-reservoir system, this should be carefully considered. In this study, we proposed a practical numerical model for both wave propagation and fluid-structure interaction analyses of an infinite domain, for a system with a semi-infinite domain such as a dam-reservoir system. This method was applicable to the time domain, and enabled accurate boundary analysis. For an infinite fluid domain, a small number of mid-point integrated acoustic finite elements were applied instead of a general acoustic finite element, and a viscous boundary was imposed on the outermost boundary. The validity and accuracy of the proposed method were secured by comparing analytic solutions of a reservoir having infinite domain, with the parametric analysis results, for the number of elements and the size of the modeling region. Furthermore, the proposed method was compared with other fluid-structure interaction methods using additional mass.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.308-308
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• 2021

다목적댐의 홍수조절운영에 있어서 댐유입량은 직접 관측의 어려움과 오차로 인해 정확한 유량을 산정하는데 한계가 있다. 남강댐 유역의 경우 유역면적대비 과소한 저수용량으로 말미암아 급격한 홍수유입이 발생할 경우 유출률이 비정상적 수치를 보이는 경우가 종종 발생하고 있다. 본 연구에서는 물리기반의 격자형 유출모형을 댐 직상류 잔유역에 적용하여 유출률을 산정 후 남강댐 계측유입량의 타당성을 간접적으로 검증할 수 있는 방법론을 제시하고자 한다. 댐유역에서 잔유역은 직상류 수위표지점 하류의 유역을 일컬으며, 이들 수위표지점에서 홍수시의 배수영향은 최소화될 만큼 이격되어 있고, 댐체 혹은 취수탑에 부착된 수위표와는 달리 기계적 진동의 영향이 최소화되어 있다고 가정한다면, 수위계측지점의 유량을 경계조건으로 활용하여 작은 면적에 대한 정밀한 수문학적 유출모델링을 통하여 비교적 신뢰성있는 유출값을 추정할 수 있다는 장점이 있다. 남강댐 잔유역은 유역 내 산청, 신안, 창촌 수위관측소를 기준으로 상류의 유역을 제외한 부분으로 설정하였다. 본 연구에서는 210m 격자에 대하여 모든 입력자료를 가공하였으며, 입력자료 중 지형자료는 WAMIS에서 제공한 DEM, 토지피복도, 토양도를 활용하였다. 강우자료는 유역 내 위치한 25개 강우관측소의 시단위 강우자료를 활용하였고, 강우사상은 진주 기상관측소의 일우량 100mm 이상을 기준으로 총 8개의 강우사상을 선정하였다. 남강댐 유역의 유출률을 산정하기 위해 산청, 창촌, 신안 등 3개의 수위관측소의 관측유량을 경계조건으로 사용하였고, 모의된 수문곡선의 총유량과 첨두유량을 관측값과 비교하였다. 유출률을 산정하기 위한 기준시간은 강우시작부터 강우종료 후 48시간으로 설정하였다. 유출률은 강우사상별로 편차가 심한 특성을 보이고 있었으며, 전체적으로는 계측유량기준 106~39.1%의 유출률이 보정된 유량을 통해서는 85~33%의 유출률로서 계측유량이 전반적으로 과대추정 되는 경향이 있었음을 확인할 수 있었다. 이들 중 2010년 7월 강우사상은 관측 유입량 기준 95.6%의 유출률을 보여, 추정유량 58.5%대비 상당한 과대추정 경향을 보인 사례로 판단할 수 있었다. 수문학적 유입량 추정방법은 현장계측을 대체할 수 있는 기법으로는 무리가 있으나 현장계측의 신뢰도를 평가하기 위한 목적으로는 유용한 대안이 될 수 있을 것으로 기대된다.