• The Journal of Engineering Geology
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• v.29 no.3
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• pp.329-337
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• 2019

Bottled water companies in Korea are required to conduct an environmental impact assessment of their drinking water supply at least six months before the expiration of their five-year marketing and production license. The water level drawdown, production well water quality, and monitoring well observation results are the most important items that are evaluated in the assessment report. Here we evaluate the relationship between well drawdown and pumping capacity with pumping time from the production wells of bottled water manufacturers located in Cretaceous granite (site A) and Precambrian gneiss (site B). The method to reduce the pumping capacity is more effective in decreasing the drawdown than the method to simultaneously control the pumping and recovery times. Furthermore, the monitoring data from the pH monitoring sensors that were installed in Precambrian gneiss (site C) yield pH values that increase with time and eventually plateau at a certain value. We therefore propose that pH monitoring is either discontinued or improved to provide more reliable and usable results.

• Journal of the Korean Geotechnical Society
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• v.39 no.10
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• pp.27-39
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• 2023

To effectively manage flood risk, it is crucial to assess the stability of flood defense structures like levees under extreme flood conditions. This study focuses on the time-dependent probabilistic assessment of embankment slope stability when subjected to rapid water level drops. We integrate seepage analysis results from finite element analysis with slope stability analysis and employ Monte Carlo simulations to investigate the time-dependent behavior of the slope during rapid drawdown. The resulting probability of failure is used to develop fragility curves for the levee slope. Notably, the probability of slope failure remains low up to a specific water level, sharply increasing beyond that threshold. Furthermore, the fragility curves are strongly influenced by the rate of drawdown, which is determined through hydraulic analysis based on flood scenarios. Climate change has a significant impact on the stability of the water-side slope of the embankment due to water level fluctuations.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.4
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• pp.361-375
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• 2007

This paper presents the results of investigation on tunnelling-induced ground surface settlement characteristics in water bearing ground using finite element (FE) stress-pore pressure coupled analysis. Fundamental interaction mechanism of ground and groundwater lowering was first examined and a number of influencing factors on the results of the coupled FE analysis were identified. A parametric study was then conducted on the influencing factors such as rock type, thickness of soil layer, permeability of shotcrete lining, among others. The results indicate that the tunneling-induced groundwater drawdown results in a deeper and wider settlement trough than without groundwater drawdown, and that the Error function approach does not yield satisfactory result in predicting a settlement profile. The results of analysis are summarized so that the relationship between the settlement and the influencing factors can be identified.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.76-80
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• 1998

In order to identify the cause of ground water drawdown of a piezometer installed around the LPG storage cavern, parameter estimations were conducted by inverse and forward numerical models. An inverse model, SK-EST developed by SK Engineering & Construction Co., Ltd.(SKEC,1997) was performed to estimate the change of the hydraulic conductivity. It was verified by the commercial forward model, AQUA3D (VATNASKIL,1995). The simulation results showed that the hydraulic diffusivity of the rock mass between the piezometer and the cavern had been increased and the change rate of the hydraulic head had been abruptly increased in response to the change of the operation pressure. Finally the statistical analysis for observed data showed the increase of the change rate of the hydraulic head and thus proved the applicability of SK-EST.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.3
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• pp.373-382
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• 2020

This study proposes a method of separating uranium (U) and minor actinides from rare earth (RE) elements in the LiCl-KCl salt system. Several RE metals were used to reduce UCl₃ and MgCl₂ from the eutectic LiCl-KCl salt systems. Five experiments were performed on drawdown U and plutonium (Pu) surrogate elements from RECl₃-enriched LiCl-KCl salt systems at 773 K. Via the introduction of RE metals into the salt system, it was observed that the UCl₃ concentration can be lowered below 100 ppm. In addition, UCl₃ was reduced into a powdery form that easily settled at the bottom and was successfully collected by a salt distillation operation. When the RE metals come into contact with a metallic structure, a galvanic interaction occurs dominantly, seemingly accelerating the U recovery reaction. These results elucidate the development of an effective and simple process that selectively removes actinides from electrorefining salt, thus contributing to the minimization of the influx of actinides into the nuclear fuel waste stream.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.3
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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 the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.139-145
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• 2009

An analytical solution of groundwater flow is applied to design soil vacuum extraction for removing volatile organic compounds from the unsaturation zone. The governing equation of gas or vapor flow in porous media is nonlinear in that gas density depends on gas pressure. A linear equation suggested by researcher is similar to that of groundwater flow. The pressure drawdowns of confined and leaky aqufiers are calculated using Massmann's field data, and the pressure drawdowns are compared. A solution of Theis equation calculated by Massmann is modified using GASSOLVE9 program in this paper. The pressure drawdown using Hantush's analytical solution for leaky aquifer also compared to that of Massmann. Hantush's analytical solution gives good approximations to pressure drawdown.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.255-265
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• 2017

We have determined the optimal pumping rate of the PW-2 water well (depth=100 m) at Imgokri, Sangju City. Cutting analysis and geophysical logging data reveal water-producing horizons at 26.1-26.5, 28.0-30.0, 33, 58, and 71 m. For pumping rates of 40, 55, 70, 90, and $132m^3/d$ over 70 days, the estimated drawdown from the PW-2 well was 6.48, 11.56, 18.07, 28.99 and 60.26 m, respectively. During a constant-rate pumping test at a rate of $117m^3/d$, the cone of depression intersected an impermeable boundary after 120-150 min of pumping. Therefore, we consider the critical pumping rate for well PW-2 to be $90m^3/d$. After pumping at $90m^3/d$ for 70 days, the calculated drawdown was 28.82-31.27 m. We suggest an optimal pumping rate for well PW-2 of $70-90m^3/d$, as the optimal pumping rate should be similar to the critical pumping rate. Sharp increases in the slope of the time-drawdown relationship, dissolved oxygen concentrations, and oxidation-reduction potential during the constant-rate pumping test indicate the limited development of bedrock aquifers around PW-2.

• Journal of Soil and Groundwater Environment
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• v.12 no.4
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• pp.1-7
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• 2007

Slug/bail tests were conducted in sand layer (sbt-1 well), silty sand layer (sbt-2 well), and mixed sand and silty sand layer (sbt-3 well). Hydraulic conductivity and specific storage coefficient were estimated through slug/bail tests. Pore volumes of groundwater level drawdown zone for bail test were estimated by using hydraulic conductivity and specific storage coefficient. KGS model was most suitable interpretation method of slug/bail tests. Average hydraulic conductivity for slug/bail tests were estimated to be $6.65{\times}10^{-5}$ m/sec in sbt-1 well, $6.33{\times}10^{-6}$ m/sec in sbt-2 well, and $3.72{\times}10^{-5}$ m/sec in sbt-3 well. Average specific storage coefficient for slug/bail tests were estimated to be 0.0225 in sbt-1 well, 0.0177 in sbt-2 well, and 0.0259 in sbt-3 well. Dimensionless time and dimensionless wellbore storage were estimated by use of transmissivity, storativity, test time, and specification of test wells. And, dimensionless drawdown were selected by parameter ${\alpha}\;and\;{\beta}$ parameter from Cooper et al. (1967). Radius of influence were estimated by estimated dimensionless time, dimensionless wellbore storage, and dimensionless drawdown. The average radius of influnce for slug/bail tests were estimated to be 1.377 m in sbt-1 well, 1.253 m in sbt-2 well, and 1.558 m in sbt-3 well. Pore volume at groundwater level drawdown zone by dummy withdrawal for bail tests were estimated to be $145,636cm^3$ in sbt-1 well, $71,561cm^3$ in sbt-2 well, and $100,418cm^3$ in sbt-3 well. Pore volume excepted well volume at groundwater level drawdown zone by dummy withdrawal for bail tests were estimated to be $145,410cm^3$ in sbt-1 well, $71,353cm^3$ in sbt-2 well, and $100,192cm^3$ in sbt-3 well.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.36-36
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• 2011

일반적으로 저수지 퇴사는 연간 저수지의 유효용량의 0.5~1%을 감소시키고 홍수 시에는 홍수위를 상승시키는 등 저수지에 여러 가지 문제를 일으킨다. 따라서 댐 설계시 장기적으로 저수지 퇴사를 적절히 예측하고, 유지 관리 중에는 주기적인 퇴사 조사를 하여 퇴사의 진행 상황과 분포 등을 분석하여 필요시 댐 조작 방법의 개선이나 나아가 배사와 같은 적극적인 대책이 요구된다. 이에 본 연구는 저수지 배사작업의 지침을 제시하기 위하여 1차원 저수지 퇴 배사 모형을 제시하였다. 1차원 배사수치모의는 수위하강(drawdown)에 의한 배사를 고려하였으며, 준정류가정을 적용한 비연계 모형으로 구현하였다. 소류사량 산정을 위해서는 MPM 공식을 사용하였다. 모형의 적합성을 검증하기 위해 기존 선행 연구에서 수행한 수리실험의 제원 및 실험조건들을 적용하여 수치모의를 수행하였고, 수치모의 결과와 실험결과를 비교하였을 때, 본 연구에서 제시한 1차원 배사 수치모형의 적용성을 확인할 수 있었다.