• 한국농공학회논문집
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• 제57권1호
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• pp.11-23
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• 2015

In this study the laboratory test for hydraulic conductivity and the seepage analysis with finite element method on measurement section of sea dike embankment were performed for the purpose of estimating the relative density of embankment from the measured pore water pressures, and both results of the test and the analysis were coupled with the method of estimating seepage blocking state with the hydraulic head loss rate in sea dike embankment. The relationship of void ratio vs hydraulic head loss rate was obtained by setting hydraulic conductivity as common ordinate on the relationships between the void ratio and the hydraulic conductivity and between the hydraulic conductivity and the hydraulic head loss rate. The void ratio on the segment between measuring points was calculated from the coupled relationship of the void ratio vs the hydraulic conductivity. The allowable upper and lower limits of hydraulic head loss rate and those of void ratio on the safety were generated from the coupled relationship between the laboratory compaction test and the sedimentation test. Current hydraulic head loss rate and void ratio were evaluated in the allowable range between upper and lower limits.

• 한국농공학회논문집
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• 제56권6호
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• pp.159-167
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• 2014

In this study the process of normalizing hydraulic head loss rate was developed for the purpose of estimation of seepage blocking state at each seepage segment in sea dike embankment. Pore water pressure sensors were installed with some interval along seepage path, then the hydraulic head loss rate at each segment between pore water pressure sensors was calculated, and then the calculated hydraulic head loss rate was normalized based on seepage path length. The comparison of normalized hydraulic head loss rates showed that the cross section of sea dike embankment was homogeneous approximately and the width of cross section was long enough to blocking tide water.

• 한국농공학회논문집
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• 제56권6호
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• pp.1-9
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• 2014

In this study the pore water pressures were measured in sea dike constructed with the sand dredged in the sea, and they were analyzed with the hydraulic head loss rate to estimate quantitatively the state of blocking seepage in the sea dike embankment. Blocking state was expressed as the number between 0 and 1. the number of 1 means the state of perfectly blocking seepage and the number of 0 means the state of sea water being passing free. The deeper the installed position was the lower the hydraulic head loss rate was and the longer the seepage path length was the higher the hydraulic head loss rate was. The estimated R-squareds were close to 1, which means that the embankment was steady state without movement of soil particles.

• 한국농공학회논문집
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• 제57권1호
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• pp.1-9
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• 2015

In this study it was adopted on sea dike monitoring that the safety monitoring with statistical limits which was adapted usually on safety monitoring by measuring pressures, stresses or deformations. And also the hydraulic head loss rate change according to passage of time was calculated for the purpose of safety monitoring. Safety monitoring by setting the statistical limit on the measured pore water pressure graphs need to be supplemented with an additional method of monitoring because the difference between the rise and fall of the tide was irregular. Safety monitoring by the limits set from values predicted by linear regression and standard errors on the hydraulic head loss graph was not affected by irregularity of tide. But if the condition of an embankment is changed gradually and slowly, it will not be detected on the hydraulic head loss graph. The graph of hydraulic head loss rate for every 24 hours vs date showed clearly that the sea water blocking state was getting better or not even though it was changed gradually and slowly.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.60-68
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• 2010

In this study, the seepage flow monitoring method by hydaulic head loss rate graph was developed for the purpose of monitoring the seepage flow from the see side or from the lake on sea dike in which seepage force was varied periodically. The hydraulic head loss rate was defined in this method. The value of the rate is in the range from 0 to 1. the value of 0 means perfectly free flow of seepage. the value of 1 means perfect waterproofing. The value of coefficient of determination in the hydraulic head loss rate graph closer to 1 means that the seepage flow way is stable. The value of coefficient of determination in the hydraulic head loss rate graph closer to 0 means that the hole may exist or the piping may be in the progress. The pore water pressure data measured in Saemangeum sea dike was analyzed with the developed method The result showed that the variation of seepage flow state was detected sensitively by this method and the interception effect of sea dike could be estimated quantitatively.

• Journal of Advanced Marine Engineering and Technology
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• 제30권2호
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• pp.291-295
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• 2006

Recently, greenhouse effect by $CO_2$ gas emitted by use of fossil fuel causes earth environmental problem. As a countermeasure of the global warming. micro hydropower under 100kW becomes the focus of attention for its clean and renewable energy sources. Newly developed micro positive displacement hydraulic turbine shows high efficiency and good applicability for the micro hydropoewer. The purpose of this study is to clarify the influence of leakage loss and effective head on the performance of the positive displacement hydraulic turbine for the further improvement of the turbine performance. The results show that the turbine. with a smaller side clearance. has much higher efficiency than that with bigger side clearance and it can sustain the high efficiency under the wider range of operation conditions. The turbine torque is proportional to the effective head and independent of the flow rate. The leakage is also dependent on the effective head but nearly independent of the flow rate.

• 상하수도학회지
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• 제23권4호
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• pp.447-458
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• 2009

Energy loss at manholes, often exceeding friction loss of pipes under surcharged flow, is considered as one of the major causes of inundation in urban areas. Therefore, it is necessary to analyze head loss at manholes, especially in case of surcharged flow. Hydraulic experiments were conducted with three cases. Case A is to test whether the shapes of the manholes influence head loss coefficients. Case B and C were proposed to further reduce head losses by improving the manhole hydraulic efficiency. In case B, the joining part of the pipe at both shapes of manholes is shifted from central part to side part. The test in case C is to check the average head loss coefficient by installing the side benching in square manhole, based on shifted joining part model. The average head loss coefficient for circular and square manhole on case A was 1.6. This did not show much difference of the head loss coefficients in spite of the discharge variation in this case. However, case B and C show large difference between head loss coefficients due to the strong oscillation of water surface and the horizontal swirl motion. The circular and square manholes in case B reduced the head loss by 30% and 6% than ones in case A, respectively. The average head loss coefficient for circular manhole in case B was 1.1. Case C reduced average loss coefficients of the square manhole in case A from 1.6 to 1.1. Accordingly, the circular manhole in case B and the square manhole in case C showed the effective way to reduce the head loss. These head loss coefficients could be available to apply to the urban sewer system with surcharged flow.

• 한국지반공학회논문집
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• 제26권5호
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• pp.37-48
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• 2010

본 연구에서는 침투압이 주기적으로 변화하는 연근해 가물막이 시공현장에 적용하기 위해서 수두손실그래프에 의한 침투류 감시기법을 개발하였다. 이 기법에서 새로이 정의된 수두손실율은 0~1 사이의 값으로 나타나며 0이면 완전통수상태, 1이면 완전차수상태를 나타낸다. 수두손실그래프의 결정계수가 1에 가까우면 침투경로상의 지반은 안정된 상태에 있음을 나타내고 0에 가까우면 공동이 존재할 수도 있고 파이핑이 진행 중일 수도 있다. 수두손실그래프에 의한 안전관리기법은 침투상태의 변화를 민감하게 감지할 수 있도록 하며 전체 현장에 적용할 경우 각 위치별 하부지반의 침투상태를 세부적으로 판단할 수 있도록 한다.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.731-734
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• 2008

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at circular manholes are usually not significant. However, the energy loss at manholes, often exceeding the friction loss of pipes under surcharge flow, is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharge flow. Hydraulic experimental apparatus with two circular manholes was installed for this study. The range of the experimental discharges were from $1.0\ell/sec$ to $4.4\ell/sec$. Head loss coefficient was maximum because of strong oscillation of water surface when the range of manhole depth ratios$(h_m/D_{in})$ were from 1,2 to 1.25. The average head loss coefficients for upstream manhole and downstream manhole were 0.58 and 0.23 respectively. Head loss at upstream manhole is nearly 2.5 times more than one at downstream manhole.

• 대한토목학회논문집
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• 제37권6호
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• pp.989-999
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• 2017

본 연구에서는 분기수로에서 발생되는 에너지손실을 계산하기 위한 손실계수의 경험식을 산정하기 위해 수리모형실험을 수행했다. 수리모형은 유입수로와 90도의 각도를 갖는 두 유출수로로 구성되어 있으며, 유입수로과 유출수로에서 압력수두와 속도수두를 측정하여 분기수로에서 발생되는 에너지손실을 분석했다. 각 측선에서 동수경사선의 변화를 비교한 결과, 수로의 분기점에서 동수경사선이 급격히 하강하여 에너지손실이 분기점에서 발생되었으며, 유량비의 증가에 따라 속도수두의 감소폭이 증가했다. 유량비와 Froude수가 증가함에 따라 유출량이 더 큰 수로에서 수두손실량이 지수적으로 증가하는 결과를 보였으며, 손실계수 또한 증가했다. 반면에, 유출량이 작은 수로에서는 유량비와 Froude수의 증가에 따라 손실계수가 감소하는 결과가 나타났다. 손실계수 계산결과를 이용하여 두 유출수로에서 손실계수 경험식을 제안하였으며, 경험식의 계산오차가 각각 3.91%, 5.19%로 나타났다. 그리고 두 경험식을 이용하여 계산한 총 손실계수를 실험결과와 비교하여 3.62%의 오차가 발생했다.