• 농업과학연구
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• 제38권3호
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• pp.493-504
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• 2011

This study was carried out to safety evaluation, the practical application and improvement of design method of the agricultural reservoir due to raising embankments. Also, it was to compare and analyze the pore water pressure (PWP), seepage (leakage) quantity and piping phenomenon according to high water table and rapid drawdown. The seepage analysis by finite element analysis was used for steady state and transient condition. The pore water pressure distribution for steady state and transient condition showed positive(+) PWP on the upstream slope, it was gradually changed negative(-) PWP on the downstream slope. The PWP in the core ranged from 100 ~ -33 kPa, the seepage line in the incline-type core suddenly decreased towards the lower levels from the higher levels. The PWP according to rapid drawdown is remained in the vicinity of the upstream slope, therefore, it is investigated to be in an unstable state by the slope stability analysis. The PWP after raising embankments showed smaller than in the before raising embankments. It was likely to be the piping phenomenon because the gradients in the before raising embankments showed largely at downstream slope, and the stability for piping in the after raising embankments increased stable state. The seepage quantity per 1 day and the leakage per 100m for the steady state and transient condition appeared to be safe against the piping. It reduced slightly regardless of the transient condition before the raising embankments and it decreased largely about 2.4 times in the early days after the raising embankments.

• 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.

• 한국농공학회지
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• 제34권1호
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• pp.87-99
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• 1992

A mathematical model, UNSATR which predicts the seepage flow through the body of dike especially under the tidal fluctuation has been developed. This model has been revised from UNSAT2 model which was developed on the basis of the saturated-unsaturated theory by Neuman. UNSATR has been verified and applied to the hydraulic model in order to estimated the seepage quantity, the formation of free water surface etc. The results lead to the following conclusions : 1. Seepage rates between the mathematical model and hydraulic model experiment are very similar to each other both in constant and transient water level conditions. 2. The lapsed time to be steady state of the free water surface becomes late as the tidal levels are relatively low mainly due to the seepage flow from the unsaturated zone of the body of dike. 3. Under the transient state of water levels, owing to the flow from the unsaturated domain, streamlines crossing to the free water surface are found and time lag during a falling tide may allow the free water surface inside the body of dike to stand at a high level than the outside water level. 4. The utility and validity of UNSATR model are convinced when the analyses on seepage problems through the porous embankment of the soil structures on the conditions of the steady and unsteady states are carried out.

• 한국지반환경공학회 논문집
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• 제6권4호
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• pp.47-58
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• 2005

지하공간의 효율적인 이용을 위하여 여러 분야에서 활발한 연구와 개발이 이루어지고 있으며 최근 들어 해안지역의 대심도 굴착을 통한 지하공간 활용방안에 관한 연구와 시공이 지속적으로 이루어지고 있다. 해안지역 및 매립지반의 침투류 거동은 조위영향에 의한 부정류 흐름이 발생되므로 부정류 흐름해석의 지배인자인 불포화토의 함수특성에 대한 연구가 요구된다. 본 연구에서는 불포화 함수특성에 따른 대심도 굴착지역의 침투류 거동을 분석하기 위하여 해안 준설매립지역 토사에 대한 함수특성시험을 수행하였으며, 불포화 함수특성에 따라 침투류 해석을 수행하여 실제 계측된 침투유량과 비교 분석하였다. 해안 매립지 토사에 대한 함수특성시험 결과 및 함수특성 계수에 대한 분석결과, Fredlund and Xing의 경험방정식이 해안 매립지반 토사에 대하여 높은 정확도로 실험결과 값을 나타내었다. 함수특성을 고려한 침투해석 결과, 부정류해석 결과가 정류해석 결과에 비하여 양수시험 결과 및 실제 계측된 용수량과 근접한 침투유량이 도출되어 해안 준설매립지반과 같이 불포화토 특성이 지배적인 지반에 대해서는 함수특성을 고려한 부정류 침투해석을 적용하여야 할 것으로 판단된다.

• 한국농공학회지
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• 제40권5호
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• pp.43-51
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• 1998

In design and management of sea0dikes, engineers need to study various transient seepage conditions through dikes not only for the sea water infiltration into dikes due to cyclic rises of sea water level also for the seepage flow out from dikes toward the sea due to cyclic drawdown of sea water level. Characteristics of seepage flow toward the sea from dikes are more complicated than as known and remained unclearly. The case of such seepage flow may be explained by figuring out seepage characteristics in filter as a part of sea-dikes. Filters in most sea-dikes in Korea are inevitably placed with reversely inclined shape due to field construction conditions. Most computer programs for seepage analysis based on the various numerical methods give practically acceptable results, but for the case of reversely inclined section of filters any verification to apply them might be needed. In this study, large scaled model tests were executed to verify and understand seepage flow through earth-filled sea-dikes. The results from numerical analysis and model tests show some remarkable differences in pore pressure distribution under cyclic changes of see level, and some of the results need to be considered in design and construction practices with further study.

• 대한토목학회논문집
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• 제4권2호
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• pp.13-24
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• 1984

본(本) 논문(論文)은 필 댐에서의 침투해석(浸透解析)에 유한요소법(有限要素法)을 이용(利用)한 수치해석(數値解析)과 기하학적(幾何學的) 해석법(解析法)을 실험적(實驗的)으로 고찰(考察)하였다. 자유수면(自由水面) 경계법(境界法)에 따른 포화(飽和), 불포화법(不飽和法)은 본문(本文)에서와 같이 장단점(長短點)이 있으며 통상(通常) 자유수면형(自由水面形)에서의 미지영역내(未知領域內)에 터널 및 공동(空洞)이 있을 경우를 고려하고 있으며 방법(方法)에 따라 적용범위는 다양하다. 또한 암반분할내(巖盤分割內)의 침투류(浸透流)를 해석(解析)하였으며 특(特)히 측면(側面)에서는 복잡다양한 절리(節理) 및 구열(龜裂)이 있어서 저수지(貯水池)의 침투성(浸透性)이 크며 또한 이의 해석(解析)에는 시간적(時間的)으로도 많은 시간(時間)이 걸리는 애로점이 있다.

• 한국지반공학회논문집
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• 제39권10호
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• pp.19-26
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• 2023

콘크리트 표면차수벽형 석괴댐의 기초지반을 통한 침투량 예측 방법을 제시하기 위해 침투량에 영향을 주는 수위, 댐 크기, 투수계수 등 다양한 조건을 고려한 수치해석을 실시하였다. 기초 그라우팅과 침투량의 관계에서는 그라우팅 재료의 투수계수와 암반 투수계수의 적정성이 침투량에 영향을 미치는 중요한 인자로 작용하였다. 또한 수치해석 결과 침투량이 초기에는 급격히 감소하다가 댐 면적이 증가함에 따라 완만하게 감소하는 경향을 보였다. 연구 결과를 통하여 다양한 매개변수를 고려한 수치해석 입력인자 및 결과가 댐의 설계 시 중요한 기초자료로 활용할 수 있으며 운영 및 유지관리 단계에서 합리적인 댐의 침투량을 산정하는 방법으로 활용할 수 있을 것으로 판단된다.

• 한국지반공학회지:지반
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• 제12권6호
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• pp.65-78
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• 1996

한반도 중부지역에 위치한 청평양수발전소의 상부저수지는 준공후 16년이 경과한 사력댐으로 매일 수위 상승 및 저하를 경험하므로써, 제체의 거동이 일반 댐과는 달리 여러 가지 지반공학적 관심을 불러 일으키고 있다. 침투류에 대한 안정성을 판단하기 위하여 종래에는 심벽만을 대상으로 하여 저수지의 수위변동을 고수위 및 저수위의 두 경우로 고정시킨 정상상태의 해석을 주로 사용함에 따라 임의의 시간에서의 전체적인 침투현상 규명이 어려웠으나, 본 연구에서는 수위변동을 경계조건에 반영한 2차원 비정상류 유한요소해석을 댐 전체단면을 대상으로 수행하여 정상상태의 해석과 비교하였으며, 수위 변동에 따라 해당시간에서의 동수 경사, 침투력 벡타, 간극수압 등을 정량적으로 규명하였고, 산정된 침투수량을 계측치와 비필하였다. 그 결과 본 댐은 파이핑, 내부 침식 또는 제체 내부로의 투수 등에 대하여 안전하다고 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1991년도 추계학술발표회 논문집 지반공학에서의 컴퓨터 활용 COMPUTER UTILIZATION IN GEOTECHNICAL ENGINEERING
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• pp.235-254
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• 1991

In the analysis of seepage behavior through the porous media, unsaturated domain should be included for obtaining more accurate results. The seepage programs considering its domain have been developed and practically used widely. The programs are reviewed and two case studies are presented in this paper. The case studies are performed using PC-SEEP and obtained good results for the cases of saturated-unsaturated transient flow.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.955-962
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• 2008

This study concerns the effect of drainage in reinforced soil on its stability during rainfall. A series of finite-element analysis based transient seepage analysis were performed on a number of cases with different drainage conditions in terms of layers of geotextiles installed in the reinforced zone. The results were then coupled with the limit-equilibrium slope stability analysis to investigate the variation of global stability factor of safety with rainfall infiltration into the reinforced wall. The results were thoroughly analyzed to get insight into the mechanism of pore water pressure reduction effect of the geotextile and into its effect on overall slope stability. It is shown that layers of geotextile installed in the reinforced zone can prevent decrease in suction in the reinforced zone during rainfall, thereby reducing potential risk of decreasing shear strength of the reinforced zone. Practical implications of the findings were discussed.