• Economic and Environmental Geology
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• v.50 no.4
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• pp.267-276
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• 2017

Seawater intrusion into coastal fractured rock aquifer, resulting in groundwater contamination, is of serious concern in coastal areas of Jeolla Namdo, Korea, which heavily depends on groundwater resources. Time series analysis and forecasting were carried out to analyze and predict EC which is a major indicator of seawater intrusion. Two time series models of autoregressive integrated moving average (ARIMA) and seasonal autoregressive integrated moving average (SARIMA) were tested for suggesting appropriate time series model. Time series data of EC measured over one year showed a increasing trend with short periodic fluctuations, due to tidal effect and pumping, which indicated that EC time series data tended to be non-stationary. SARIMA model was found better fitted to observed EC than any other time series model. Time series analysis and modeling was found to be a useful tool to analyze EC at coastal fractured rock aquifer subject to seawater intrusion.

• Journal of Soil and Groundwater Environment
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• v.7 no.1
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• pp.3-14
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• 2002

We analyzed hydrologic time-series data obtained from a fractured aquifer in Wonju and a porous shallow aquifer in Uiwang area. Auto-correlation, spectral density, and cross-correlation functions were used for the analyses. Water level at a shallow well in Wonju was weakly auto-correlated and it was sensitive to direct infiltration from rainfall through soil zone while that at a well screened in the fractured zone showed a relative stability to an outer stress (rainfall), which was derived from a delayed transmission of recharge stress through a fracture network from a remote area. Characteristics of time-series data in Uiwang area were similar to those in the fractured zone in Wonju. This was caused by a regional recharge from a distant area rather than a direct infiltration. This study demonstrated a usefulness of time series analyses for identification of recharge mechanism.

• New & Renewable Energy
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• v.17 no.3
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• pp.32-41
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• 2021

A groundwater source heat pump (GWHP) was developed in this study by adapting a borehole heat exchanger with closed-loop and open-loop systems in a new building. In the pilot test building, the air-conditioning on the second floor was designed to employ a closed-loop system and that on the third floor had an open-loop system. The GWHP design is based on the feasibility of groundwater resources at the installation site. For the hydrogeological survey of the study site, pumping and injection tests were conducted, and the feasibility of GWHP installation was evaluated based on the air-conditioning load demand of the building. The site was found to be satisfactory for the design capacity of the thermal load and water quality. In addition, the effect of groundwater movement on the performance of the closed-loop system was tested under three different operational scenarios of groundwater pumping. The performance of the system was sustainable with groundwater flow but declined without appropriate groundwater flow. From long-term observations of the operation, the aquifer temperature change was less than 2℃ at the observation well and 5℃ at the injection well with respect to the initial groundwater temperature. This pilot study is expected to be of guidance for developing GWHPs at fractured rock aquifers.

• Tunnel and Underground Space
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• v.33 no.5
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• pp.348-372
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• 2023

In relation to the high-level radioactive waste disposal project in deep fractured rock aquifer environments, it is essential to evaluate hydrogeological characteristics for evaluating the suitability of the site and operational stability. Such subsurface hydrogeological data is obtained through in-situ tests using boreholes excavated at the target site. The accuracy and reliability of the investigation results are directly related to the selection of appropriate test methods, the performance of the investigation system, standardization of the investigation procedure. In this report, we introduce the detailed procedures for the representative test method, the constant pressure injection test (CPIT), which is used to determine the key hydrogeological parameters of the subsurface fractured rock aquifer, namely hydraulic conductivity and storativity. This report further refines the standard test method suggested by the KSRM in 2022 and includes practical field application case conducted in volcanic rock aquifers where this investigation procedure has been applied.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.132-135
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• 2001

To understand and compare tracer transport in fractured and porous media. multiple tracer tests were conducted in Wonju and Uiwang sites. The target media were fractured in Wonju site and porous in Uiwang site. It was known that groundwater flow for the two hydrogeologic systems could be represented using a EPM approach. However, the tracer transport in the two aquifer systems was greatly different. In this study, we analyzed the different tracer transport behavior in the two systems, from which our understanding of the tracer dispersion was greatly enhanced. we used bromide and chloride as tracers.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.497-500
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• 2003

If ground water levels of a confined fractured rock aquifer fluctuate with sea tides, individual values of hydrogeologic parameters can be determined. Tidal efficiency and time lag are first calculated from the water level data recorded at an observation device situated inland from the sea. The tidal efficiency factor of the aquifer at the seacoast is then determined from the observation in monitoring wells and used to calculate storage coefficient. Tidal efficiency factor and the tidal time lag are utilized to calculate storage coefficient and the results are compared. This method is tested in the southeastern coastal area of Busan, Korea. This is a simple and inexpensive way to test confined aquifer but the analysis should be performed according to the coastal environment.

• The Journal of Engineering Geology
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• v.4 no.2
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• pp.127-138
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• 1994

The stationary dual-porosity model is not sufficient to describe the hydraulic characteristics of fractured aquifers as the groundwater flow in fractured aquifers is often controlled by the fractal geometry of fractures. This study deals with new stationary dual-porosity fractal model. This model simulates pseudo-steady state flow from matrix block to fissure in the fractal aquifer. Furthermore, it considers storage capacity and well loss effect at the production well. Type curves for different flow dimensions with different drainage factors are plotted. This new model has been applied to experimental data. The result of the interpretation shows a good accordance between the theoretical model and the observed data.

• Economic and Environmental Geology
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• v.36 no.1
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• pp.49-58
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• 2003

To analyze the anisotropic characteristics of fractured aquifer, variations of streaming potential were measured during and after pumping over several wells at the two test sites. Surface electrical resistivity survey, normal resistivity logging, and slug test were performed at the wells to identify the hydrogeological structure. Applying the results to the recently suggested model, the aquifer of the two test sites showed confined characteristics. Anisotropic direction appeared in using equi-potential maps from self-potential monitoring results matched well with the results of the hydrogeological test. The self-potential monitoring method adopted in this study would be useful for providing a more reliable information on the anisotropy of aquifer in the pumping test at single well.

• The Journal of Engineering Geology
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• v.26 no.4
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• pp.505-513
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• 2016

The qualitative distribution of a fractured aquifer was characterized by electrical resistivity surveying as a part of basic groundwater investigation in Jangseong. The results were then used to choose sites for observation wells. The locations and distributions of permeable discontinuities were studied by analyses of temperature logs, a borehole image-processing system (BIPS), and hydraulic pressure testing using a double packer. The pressure test showed that the size of the discontinuities correlated with the Lugeon value and the results of the temperature log. The results show that temperature measurement is an effective method to identify permeable discontinuities, with the temperature difference correlating with the size of the aperture of the discontinuity.

• Journal of the Korean Society of Groundwater Environment
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• v.4 no.2
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• pp.95-102
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• 1997

So far, several fractal models of fluid flow in a fractured aquifer have been developed. In this study, a new fractal model is derived that considers transient flow in the dual-porosity aquifer with the fracture skin between the fissure and the block, and the storage capacity and the wellbore skin on the pumping well. Constant-head upper boundary is specified in the block. This model is a generalized one which comprises both modified Hantush equation (1960) and Boulton-Streltsova equation (1978). Type curves are plotted for different flow dimensions (0.5, 1, 1.5, 2, 2.5 and 3) with various values of the leakage factor and the fracture skin. They show dimensionless drawdown in the pumping well and observation wells located either in the fissure system or in the matrix block.