• 한국지하수토양환경학회지:지하수토양환경
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• 제16권3호
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• pp.17-27
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• 2011

Recently, a physically based model of water-table fluctuation due to precipitation is developed based on aquifer water balance model. In the model, it was assumed that the water infiltration into ground surface is advection dominant and immediately reaches to water-table. The assumption may be suited for the sites where the water-table is shallow and/or the permeability of the unsaturated zone is high. However, there are more cases where the model is not directly applicable due to thick and low permeable unsaturated zone. For the low permeability unsaturated zone, the pattern of water flux passing through unsaturated zone is diffusive as well as advective. In this study, to improve the previously developed water-table fluctuation model, we combined the delayed drainage model, which has long been used in well hydraulics, to the water-table fluctuation model. To test the validity of the development, we apply the developed model to 5 different domestic sites. The model parameters are calibrated based on the groundwater hydrograph and the precipitation time series, and the correlation analyses among the parameters are pursued. The overall analyses on the delineated model parameters indicate that the delayed drainage parameters or delay index used in the developed model are able to reveal drainage information in the unsaturated zones.

• 한국지하수토양환경학회지:지하수토양환경
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• 제13권1호
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• pp.67-76
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• 2008

본 연구에서는 지하수위 변동모델과 비포화대 함수모델을 적용한 지하수 함양율 산정 기법을 제안하였다. 기법의 적용성을 살펴보기 위하여 연구지역인 국내 4개 국가지하수 관측소를 선정하였으며 1996년부터 2005년에 이르는 국가 지하수 관측망(포항 연일, 기북, 순천 외서, 홍천 홍천) 수위자료와 포항, 순천, 홍천의 기상청 강우자료가 이용되었다. 각 관측소 주변 토양형에 따른 지하수 함양율은 홍천 관측소가 최소 0.5%에서 최대 61.4%, 포항 연일 관측소는 1.1%에서 27.4%, 포항 기북 관측소는 5.1%에서 41.4%, 및 순천 외서 관측소는 1.1%에서 8.3%의 분포를 보였다. 본 연구에서 이용된 지하수위 변동예측 모델은 지하수위 변동이 강우에 의해서만 발생하는 것으로 가정하였으며 향후 보다 정확한 지하수위 예측을 위해서 지하수 채수나 증발산의 영향을 추가 고려할 필요가 있을 것이라 판단된다. 또한 제안된 기법의 보다 넓은 범위의 적용을 위해서는 비포화 암반의 함수 모델을 도입할 필요가 있을 것이라 판단된다. 현재 본 연구를 공간적으로 확장하여 지역화 하기 위한 연구가 진행 중이다. 본 연구에서 제안하는 지하수 함양율 산정 기법은 가정을 최소화함으로써 방법론적으로 합리적이며 실제 지하수 시스템을 잘 반영하는 과학적인 모델로 기존 지하수 함양율 산정 기법을 충분히 대체할 수 있을 것이라 판단된다.

• 한국환경과학회지
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• 제24권4호
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• pp.461-470
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• 2015

As hydrogeologic parameters such as hydraulic conductivity and specific yield are estimated by aquifer test, these are dependent on specific points at which field test was conducted. To overcome these site-specific limitations, a method of estimating transmissivity of aquifer using distribution features for parameters in Water table fluctuation model is newly suggested. Distribution features in reaction factor, specific yield and transmissivity having the function of pore space in aquifer are used to derive empirical equation for estimating transmissivity. From the result for applying the equation for 10 groundwater stations in Northeast Jeju Island, this equation is available for estimating transmissivity compared to the value estimated by existing equations. The estimated transmissivity ranged from 14.2 to $3,716.9m^2/day$, and its average was $821.8m^2/day$.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1988년도 제30회 수공학연구발표회논문초록집
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• pp.85-92
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• 1988

A model for the transient one-dimensional moisture movement in the saturated-unsaturated zone using a finite difference method is developed. Hysteresis in the soil water retention is incorporated. The model considers layered geologic formations. Monte Carlo simulation, together with the nearest neighbor model is used. Outputs of the model include pressure head, water content, and the water table elevation. Two Monte Carlo simulations of 100 realizations each are made for a 12-day simulation period with different input values. The simulation results show that the S.D. of the outputs increases with an increase in the input, the S.D. of the log K$$. The model is applied to predict a long term water table fluctuation, and the predicted water table agress well with the observed one.

• 한국지하수토양환경학회지:지하수토양환경
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• 제18권5호
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• pp.65-76
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• 2013

The water-table fluctuation (WTF) method has been often used for estimating groundwater recharge by analysis of waterlevel measurements in observation wells. An important assumption inherent in the method is that the water level rise is solely caused by precipitation recharge. For the observation wells located near a stream, however, the water-level can be highly affected by the stream level fluctuations as well as precipitation recharge. Therefore, in applying the WTF method, there should be consideration regarding the effect of stream-aquifer interactions. Analysis of water-level hydrographs from the National Groundwater Monitoring Wells of Korea showed that they could be classified into three different types depending on their responses to either precipitation recharge or stream level fluctuations. A simple groundwater flow model was used to analyze the errors of the WTF method, which were associated with stream-aquifer interactions. Not surprisingly, the model showed that the WTF method could greatly overestimate recharge, when it was used for the observation wells of which the water-level was affected by streams. Therefore, in Korea, where most groundwater hydrographs are acquired from wells nearby a stream, more caution is demanded in applying the WTF method.

• 한국지반공학회논문집
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• 제17권6호
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• pp.149-162
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• 2001

삼랑진에 위치한 삼랑진양수발전 상.하부댐의 댐마루에 시공 후 종방향 균열이 발생하였다. 이 댐들은 전력을 생산하기 위한 양수발전댐으로 상부댐과 하부댐으로 구성되어 있으며, 매일 10m이상의 수위변화를 받아왔다. 본 논문은 이들 댐중 상부댐에 발생한 종방향 균열의 원인을 찾는데 있다. 균열의 주요 원인은 수위변동으로 인한 것으로 판단되었으며, 이를 검토하기 위해 hyperbolic model을 이용한 수치해석을 수행하였다. 수치해석을 위한 입력자료를 얻기 위해 심벽재료와 사석재료에 대해 일련의 삼축압축시험을 수행하였다. 또한 수위변동으로 인한 주기적인 응력변화를 검토하기 위한 입력자료를 얻기 위해 진동삼축압축시험을 수행하였다. 수치해석결과 반복하중이 작용했을 경우 댐마루에서 깊이 4m까지 구속압력이 음이 되는 것으로 나타났으며, 이로 인해 종방향균열이 발생한 것으로 판단되었다. 이 종방향균열의 깊이는 댐 마루에서 수행한 시험굴에서 확인하였으며, 현장 조사결과와 잘 부합하였다.

• 한국환경과학회지
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• 제23권4호
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• pp.615-623
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• 2014

The groundwater level varies according to the characteristics and composite materials of aquifer. In this study, specific yield and reaction factor which are the major two hydrogeological parameters in the WTF(Water Table Fluctuation) method were estimated and analyzed spatial characteristics. 8 groundwater level stations which have enough measuring period and high correlation with rainfall in the Hancheon watershed were used. The results showed that specific yield was randomly distributed and reaction factor showed inverse trend with altitude. If the enough data were collected, reaction factor according to altitude in ungauged points could be estimated by using these parameter characteristics.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.213-220
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• 2010

This study presents a numerical simulation model of vertical ground heat exchangers, considering unsaturated hydro static ground conditions induced by the ground water table fluctuation. Heat transfer in ground and grout is modeled by a 3-D FEM transient conductive heat transfer model, where heat transfer between circulating fluid and heat exchanging pipe is treated as 1-D quasi steady state forced convective elements. To take into account the unsaturated ground condition, soil thermal conductivity and heat capacity which are dependent on the matric suction are applied to ground elements. Parametric studies considering various ground water table conditions are conducted to investigate the influence of unsaturated hydro static ground condition on the mean heat exchange rate of ground heat exchanger. Simulation results considering water table fluctuation show 60~100% of mean heat exchange rate for a saturated soil condition and 125~208% of that for a dry soil condition. Thus consideration of unsaturated soil condition is substantially recommended for more accurate design and performance evaluation for ground heat exchangers.

• 한국터널지하공간학회 논문집
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• 제18권6호
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• pp.581-591
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• 2016

최근 사회기반시설의 투자효율성을 높이기 위하여 평상 시 도로터널로 운영되지만 홍수 시 수로로 이용되는 수로 도로 다목적 터널의 계획이 시도되고 있다. 이러한 다목적 터널은 수로터널로의 이용이 한시적이기 때문에 내수압과 지하수위가 일정하지 않아 터널 내부와 외부의 압력변화가 상당할 수 있다. 특히 지하수위 아래에 건설 된 다목적 터널의 경우 장기간 운영 중에 발생하는 계절적 압력변화는 터널에 반복하중으로 작용하여 구조물과 인접지반의 열화로 이어질 가능성이 있다. 본 연구에서는 다목적 터널의 외부 및 내부 수위조건에 따라 발생할 수 있는 구조물의 거동특성을 모형실험 및 수치해석을 통하여 조사하였다. 그 결과 수위변화로 인한 터널 거동의 주 원인은 부력이며, 터널 내부 및 외부의 반복적인 수위변화는 터널 주변지반의 이완영역을 확대시키는 것으로 나타났다. 따라서 다목적 터널의 설계 시 수위변화에 따른 영향검토가 필요하며 경우에 따라 저항성을 유지시킬 수 있는 대책의 검토가 필요하다.

• 한국환경과학회지
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• 제23권4호
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• pp.605-613
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• 2014

In this work, the delay time for groundwater recharge was estimated by comparing simulated recharges by means of SWAT(Soil and Water Assessment Tool) model and WTF(Water Table Fluctuation) method. The delay time for groundwater recharge means that the time when the water from rainfall travelled through vadose zone just after getting out of soil zone bottom. As measuring this delay time is almost impossible, we used to compare the estimated values from modeling(SWAT) and analytic method(WTF). The test site is Hancheon watershed which has 8 groundwater measurement stations. The results show that the altitude has a linear relationship with the estimated delay time values. To validate these results, we conducted corelation analysis between transformed groundwater levels and observed ones. The results showed that computed groundwater levels have good corelation($R^2$=0.97, 0.87, respectively). The estimated delay time would be used for the groundwater behaviour characteristics in vadose zone. As recharge rates vary according to the height, the delay time is thought to be an import variable for the proper groundwater recharge estimation.