• 한국지반공학회논문집
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• 제39권10호
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• pp.27-39
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• 2023

극한홍수에 대응하기 위한 홍수 위험도 관리의 필수 요소인 홍수 위험도 평가를 위해서는 댐 및 하천제방과 같은 홍수방어시설에 대하여 여러 파괴 메커니즘을 고려한 신뢰도 해석을 수행해야 한다. 본 연구에서는 수위급강하에 의한 제체 사면의 시간에 따른 확률론적 안정성 평가에 대하여 연구하였다. 유한요소 해석에 의한 침투해석 결과를 사면안정 해석에 연동하여 Monte Carlo Simulation을 수행함으로써 수위급강하에 따른 제체의 시간의존적 거동을 연구하고 파괴확률을 계산하여 제방의 취약도 곡선을 작성하였다. 수위급강하에 의한 사면의 파괴확률은 특정 수위까지는 매우 작은 값을 유지하지만, 그 이상에서는 수위가 증가함에 따라 급격하게 증가하는 현상을 보였다. 또한 취약도 곡선은 수위 하강 속도에 크게 영향을 받았다. 수위 저하 속도는 수문 시나리오에 의한 수위의 변동해석을 통하여 결정되므로 수위급강하에 따른 제방 제외지 사면의 안정성은 기후변화에 따라 크게 영향을 받을 것으로 판단된다.

• 한국농공학회논문집
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• 제54권3호
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• pp.11-17
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• 2012

In this study, an experiment with large-scale model was performed according to raising embankment in order to investigate the cause of collapse by a change in water level of reservoir. Also, the settlement and pore water pressure by high water level and a rapid drawdown were compared and analyzed. After raising embankment for inclined core, there was no infiltration by leakage. For the vertical core, the pore water pressure showed a largely change by faster infiltration of pore water than in the inclined core. In a rapid drawdown, inclined core was remained stable but vertical core showed a largely change in pore water pressure. A settlement after a raising embankment showed a larger measure of settlement than before the raising embankment. The leakage quantity before a raising embankment and an inclined extension showed no leakage. Leakage in vertical extension was measured 160 $l$. From the result, a instrument system that can accurately estimate a change of pore water pressure shall be established for a rational maintenance and stabilization of raising embankment for agricultural reservoir.

• Journal of Ecology and Environment
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• 제43권2호
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• pp.271-281
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• 2019

Background: The plant communities within reservoir drawdown zones are ecologically important as they provide a range of ecosystem services such as stabilizing the shoreline, improving water quality, enhancing biodiversity, and mitigating climate change. The aim of the study was therefore to identify the major environmental factors affecting these plant communities within the drawdown zone of the Soyangho Reservoir in South Korea, which experiences a monsoonal climate, and thereafter to (1) elucidate the plant species responses and (2) compare the soil seedbank composition along main environmental gradients. Results: Two main environmental gradients affecting the plant community structure were identified within the drawdown zone; these were a vertical and longitudinal gradient. On the vertical dimension, a hydrological gradient of flood/exposure, the annual-dominated plant community near the water edge changed to a perennial-dominated community at the highest elevation. On the longitudinal dimension from the dam to the upstream, plant species composition changed from an upland forest-edge community to a lowland riverine community, and this was correlated with slope degree, soil particle size, and soil moisture content. Simultaneously, the composition of the soil seedbank was separated along the vertical gradient of the drawdown zone, with mainly annuals near the water edge and some perennials at higher elevations. The species composition similarity between the seedbank and extant vegetation was greater in the annual communities at low elevation than in the perennial communities at higher elevation. Conclusions: The structures of plant community and soil seedbank in the drawdown zone of a monsoonal riverine reservoir were changed first along the vertical and secondly along the longitudinal gradients. The soil seedbank could play an important role on the vegetation regeneration after the disturbances of flood/exposure in the drawdown zone. These results indicate that it is important to understand the vertical and longitudinal environmental gradients affecting shoreline plant community structure and the role of soil seedbanks on the rapid vegetation regeneration for conserving and restoring the drawdown zone of a monsoonal reservoir.

• 농업과학연구
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• 제39권1호
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• pp.97-110
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• 2012

This study was carried out for safety evaluation, the practical application and improvement of design method of the agricultural reservoir embankment according to backside extension. Seepage analysis, slope stability analysis and finite element analysis were performed for steady state and transient conditions. Also, the pore water pressure, seepage quantity, safety factor and stress-strain behavior according to high water level and rapid drawdown were compared and analyzed. The pore water pressure at contact region between backside extension and old embankment was kept high after rapid drawdown. Therefore, backside extension is recommended that design method is required to be improved and reinforced more than the others raising embankment. The hydraulic gradients before and after backside extension showed high value at the base of the core, but they showed stable state at the upstream slope and downstream slope. The seepage quantity per 1 day and the leakage per 100 m for the steady state and transient conditions appeared to be safe against the piping. The safety factor of slope stability showed high at the steady state, and transient conditions did not show differences depending on the rapid drawdown. The safety factor was appeared high at the upstream slope before backside extension and downstream slope after extension. The excess pore water pressure for steady state and transient conditions showed negative(-) at the upstream slope, it was small at the downstream slope. The mean effective stress (p') showed high at the base of the core and to be wild distribution after the extension. The displacement after extension showed 0.02-0.06 m in the upstream slope, the maximum shear strain after extension was smaller than that before extension.

• Geomechanics and Engineering
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• 제35권5호
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• pp.511-523
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• 2023

Canal-side roads frequently collapse due to an unexpectedly greater soft-clay thickness with a rapid drawdown situation. This causes annually increased repair and reconstruction costs. This paper aims to explore the effect of soft-clay thickness on the failure in the canal-side road in the case study of Phra Nakhon Si Ayutthaya rural road no. 1043 (AY. 1043). Before the actual construction, a field vane shear test was performed to determine the undrained shear strength and identify the thickness of the soft clay at the AY. 1043 area. After establishing the usability of AY. 1043, the resistivity survey method was used to evaluate the thickness of the soft clay layer at the failure zone. The screw driving sounding test was used to evaluate the undrained shear strength for the road structure with a medium-stiff clay layer at the failure zone for applying to the numerical model. This model was simulated to confirm the effect of soft-clay thickness on the failure of the canal-side road. The monitoring and testing results showed the tendency of rapid drawdown failure when the canal-side road was located on > 9 m thick of soft clay with a sensitivity > 4.5. The result indicates that the combination of resistivity survey and field vane shear test can be successfully used to inspect the soft-clay thickness and sensitivity before construction. The preliminary design for preventing failure or improving the stability of the canal-side road should be considered before construction under the critical thickness and sensitivity values of the soft clay.

• 농업과학연구
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• 제39권3호
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• pp.427-439
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• 2012

In this study, an experiment with large-scale model was performed according to raising embankment in order to investigate the behaviour of failure due to overtopping. The pore water pressure, earth pressure and settlement by high water level, a rapid drawdown and overtopping were compared and analyzed. Also, seepage analysis and slope stability analysis were performed for steady state and transient conditions. The pore water pressure and earth pressure for inclined core type showed high value at the base of the core, but they showed no infiltration by leakage. The pore water pressure and earth pressure by overtopping increased at the upstream slope and core, it is considered a useful data that can accurately estimate the possibility of failure of the reservoir. The behavior of failure due to overtopping was gradually enlarged towards the downstream slope from reservoir crest, and the inclined core after the raising embankment was influenced significantly to prevent the reservoir failure. The pore water pressure distribution for steady state and transient condition showed positive (+) pore water pressure on the upstream slope, it was gradually changed negative (-) pore water pressure on the downstream slope. The pore water pressure by overtopping showed a larger than the high water level at the downstream slope, it was likely to be the piping phenomenon because the hydraulic gradients showed largely at the inclined core and reservoir crest. The safety factor showed high at the steady state, and transient conditions did not show differences depending on the rapid drawdown.

• 한국수자원학회논문집
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• 제48권3호
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• pp.149-158
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• 2015

비상방류시설은 안전한 댐 운영 및 유지관리를 위해서 절대적으로 필요한 시설임에도 불구하고 국내 댐의 경우 이를 고려한 설계가 이루어지지 않아 각 댐의 비상방류 대응 적정성을 판단하기 곤란한 상황이다. 특히 국내 댐의 경우 비상방류시설규모를 산정하는 기준이 일정치 않을 뿐만 아니라 대부분의 용수댐은 별도의 방류시설 조차도 없는 실정이다. 따라서 본 연구에서는 기존댐 방류시설 현황 분석, 국내외 비상방류시설 설계기준 등의 검토와 함께 국내 댐설계기준을 적용한 가상 댐체와 수어댐을 대상으로 수위에 따른 방류능 분석을 수행하였다. 또한 SEEP 프로그램 등을 활용, 수위저하 속도에 따른 제체의 사면 안정성을 검토함으로써 비상방류 시설의 적정규모 산정기준을 제시하고자 하였다. 이를 위하여 수리학적 해석을 통해 저류수심에 따른 제체에 작용하는 힘을 분석하였으며 수위저하 속도 변화에 따른 제체의 안정성을 검토하여 허용수위저하 속도 범위를 제시하였다. 수위 25% 저감은 하중을 50%까지 감소시켜 초기수위 저감이 중요한 것을 알 수 있었다. 가상 댐체는 물론 수어댐에 수위저하 속도 1 m/일을 적용하더라도 제체의 안전성은 보장됨을 확인하였다. 다만, 방류능과 방류 소요일수는 수위별 저류용량 등 저류지 특성과 밀접한 관계가 있어 초기대응을 위해서는 7~10일 이내에 저류수심의 25%를 먼저 방류시키고 나머지 방류량은 1~2개월 이내에 방류할 것을 제안하였다.

• 미생물학회지
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• 제29권6호
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• pp.361-370
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• 1991

Physical and chemical environmental factors influencing on the outbreak of freshwater red tide by Peridinium bipes (dinoflagellate) in Soyang Reservoir were studied. Red tide occured in the site of inflowing of tributary streams annually, but the extent and severity of red tide varied from year to year. Several environmental factors such as water level, nutrient releasing from sediment, cyst resuspension, and concentrations of $Ca^{2+}$ and $Mg^{2+}$were studiedin relation to development, extent, and duration of red tide. In June of 1989 and 1991, the red tides of Peridinium bipes were very severe, and these red tides coincided with notable and rapid drawdown of lake water in late spring. Nutrient releasing and cyst resuspension by turbulence during drawdown were suggested as main causes of red tide. The quanity of nutrient releasing from sediment and hydrometeorological factors such as run-off and wind may determine the extent and duration of red tide.

• 대한토목학회논문집
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• 제5권4호
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• pp.1-8
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• 1985

수위변화(水位變化)에 따른 상이(相異)한 자유수면(自由水面)으로 인(因)하여 제체내부(堤體內部)에 응력상태(應力狀態)가 달라지므로 제체(堤體)의 안정해석(安定解析)이 필요(必要)하다. 수위(水位)가 급강하(急降下)할 경우 상류측(上流側) 사면(斜面)에서의 자유수면방향(自由水面方向)이 기초(基礎)쪽으로 바뀌어질 때, 상류측(上流側) Fill의 안전율(安全率)을 찾아 보았다. 여기서 하강(下降)하는 자유수면(自由水面)과 파괴형태(破壞形態)를 찾았으며, 또 안전율(安全率)을 구(求)하였고. 이로 강하속도(降下速度) 및 동수경사(動水傾斜)를 비교(比較)하였다. 실험(實驗)에 의한 결과(結果)는 다음과 같다. 1. 자유수면(自由水面)의 강하(降下)로 인(因)하여 상류측(上流側) Fill에 침투류(浸透流)에 의한 골동파괴(滑動破壞)가 일어나고, 파괴고(破壞高)는 각(各) 각(各)의 모형(模型)에 따라, 5~10, 9~15, 13~21(cm)이다. 2. 침투류(浸透流)에 의한 간극수압(間隙水壓)의 영향(影響)을 고려(考慮)하여 안전율(安全率)을 구하였으며, 이때 강하속도(降下速度)와 안전율(安全率)과의 관계(關係)에서 제체(堤體)의 안전상(安全上) 강하속도(降下速度)는 0.21~0.28(cm/sec)이어야 하고, 동수경사(動水傾斜)와 안전율(安全率)과의 비교(比較)에서 동수경사(動水傾斜)는 각(各) 모형(模型)에서 0.36~0.43 값보다 적어야 함을 실험상(實驗上) 알았다.

• 한국지반공학회논문집
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• 제31권8호
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• pp.51-62
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• 2015

지반공학적으로 제방(또는 댐) 월류에 대한 근거를 제시하기 어렵다. 수문학적인 안정성 평가에서 댐의 초기수위(만수위)를 고정시키고 강우량을 계산하기 때문에 월류 가능성은 매우 희박하다. 그러나 Copula 함수를 사용하여 초기수위가 고정된 댐의 만수위가 아닌 변동성 있는 확률수위를 적용해서 국내 40년간의 빈도를 고려할 때, 월류 가능성을 확인할 수 있었다. 수문학적 댐의 위험성 분석은 다양한 불확실성 인자 중 댐 초기수위에 대한 모의기법 개발이 필요한 복잡한 수문학적 해석을 요구한다. 본 연구에서는 기존 댐 위험도 분석 시 초기수위는 상시만수위 또는 홍수기 제한수위로 가정하지만, 이러한 보수적인 가정에 의한 연구는 기상변동성 및 기후변화의 영향을 고려하지 못하며, 댐의 월류확률 및 이에 따른 붕괴확률을 추정하는데 있어서 지반공학적인 접근이 필요하다. Copula 함수를 이용하여 댐 특성에 맞는 초기수위를 결정하였으며, HEC-5 모형을 활용하여 강우-유출 모형 매개변수의 사후분포를 정량적으로 추정하여 댐 월류확률을 산정하였다. 지반공학적인 측면에서 댐 안정성 해석은 상류사면(upstream)의 수위급강하(drawdown)에 대한 안전율과 하류사면(downstream) 월류상태에서의 불안정성을 비교하여 지반공학적 위험도를 비교 분석하였다.