• Tunnel and Underground Space
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• v.21 no.5
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• pp.370-376
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• 2011

To design the drainage system of a mine, it is very important to evaluate the groundwater inflow to the mine workings. In this study, continuous steady state flow through rock mass around mine openings developed in Sungok area of Gagok Mine was analyzed. Saturated only model and Saturated/unsaturated model were used as material models of rock mass. Groundwater quantities flowing into Sungok 160 level which is 1216 m long are computed as 1450 $m^3$/day in case of a saturated model and as 1071 $m^3$/day in case of a saturated/unsaturated model. An effect that hydraulic conductivity has on inflow turned out be greater than precipitation and inflow increased linearly with increase of hydraulic conductivity. It was found that change of hydraulic conductivity ratio and orientation have an impact on the variation of inflow and water table.

• Geomechanics and Engineering
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• v.20 no.3
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• pp.267-273
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• 2020

Solutions of the water pressure and groundwater inflow distribution along the tunnel perimeter in a half-infinite aquifer were investigated considering the conditions of the constant head and constant water pressure. It is assumed that the circular tunnel is buried in a fully saturated, homogeneous, isotropic and half-infinite space. Coordinate transformation technique was adopted, the problem of solving the control equations of water pressure in the Cartesian coordinate was transformed to that in the bipolar coordinate system, which can significantly simplify the derivation procedure of the water pressure and inflow distribution. The validation results show the accuracy and advantage of the proposed approach.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.227-234
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• 2013

The vertical shaft of a selective intake structure, which is constructed in a large reservoir, is required to be impermeable and to employ a grouting technology to prevent water inflow from the reservoir or surrounding ground. In this study, groundwater inflow is estimated using a numerical model for two cases (i.e., grouting or non-grouting cases at the exterior of a vertical shaft) and compared with data measured during an excavation at the construction site of a selective intake structure in the Soyang reservoir, Korea. Groundwater inflow is estimated to range from 444 to 754 $m^3/d$ in the case of non-grouting and from 58 to 95 $m^3/d$ in the case of grouting. The groundwater inflow measured in a vertical shaft, which ranges from 30 to 100 $m^3/d$, is similar to the simulated amount. It is recommended that before the excavation of a shaft, water inflow is estimated using a numerical model and a grouting test to ensure excavation stability and improve excavation efficiency.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.403-421
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• 2021

Most of the urban tunnels in Korea, which are represented by the 1st to 3rd subways, use the drainage tunnel by NATM. Recently, when a construction project that actively utilizes large-scale urban space is promoted, negative effects that do not conform to the existing empirical rules of urban tunnels may occur. In particular, there is a high possibility that groundwater fluctuations and hydrodynamic behavior will occur owing to the practice of tunnel technology in Korea, which has mainly applied the drainage tunnel. In order to solve the problem of the drainage tunnel, attempts are being made to control groundwater fluctuations. For this, the establishment of tunnel groundwater management standard concept and the analysis of the tunnel hydraulic behavior were performed. To prevent the problem of groundwater fluctuations caused by the construction of large-scale tunnels in urban areas, it was suggested that the conceptual transformation of the empirical technical practice, which is applied only in the underground safety impact assessment stage, to the direction of controlling the inflow in the tunnel, is required. And the relationship between the groundwater level and the inflow of the tunnel required for setting the allowable inflow when planning the tunnel was derived. The introduction of a tunnel groundwater management concept is expected to help solve problems such as groundwater fluctuations, ground settlement, depletion of groundwater resources, and decline of maintenance performance in various urban deep tunnel construction projects to be promoted in the future.

• Journal of Korea Water Resources Association
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• v.50 no.11
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• pp.795-802
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• 2017

This study shows the assessment methodology for the water resources of subsurface dams. The study area is SSangcheon subsurface dam. It is at the estuary of SSangcheon watershed forming the unconfined alluvial aquifer. there are several candidate area which are geologically similar to it at East coast. The groundwater level was computed by a 2-D FDM model, where the watershed discharge is the input as the infiltration term. The baseflow computed as the mean value of 3 watershed dischrge model is $0.5m^3/sec$. And considering the inflow near the baseflow as the dry season inflow, The groundwater level according to the change of inflow and pumping rate was computed. Specifically, Using the real pumping rate $28000m^3/day$ which is equal to the supply amount of drinking water to Sokcho city, The inflow which induce the descended groundwater level to the bottom of aquifer or the ascended groundwater level that cause the surface flow was eatimated. The simulation for increased pumping rate and additional well construction to increase the water resources, was executed. And at the extreme dry season, available pumping rate was estimated.

• The Journal of Engineering Geology
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• v.20 no.1
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• pp.25-33
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• 2010

Most of contaminated groundwater in the study area was contaminated by $NO_3-N$ due to inflow of contaminated shallow surface groundwater inflow into groundwater well. Poor grouting and teared screen have increased contaminated shallow surface groundwater inflow into groundwater well. Contaminated shallow surface groundwater was inflowed into groundwater well throughout faults, joints and fracture zone of ESE-WNW, NNW, NW-SE and NS direction. The objective of this paper is to evaluate an improvement of water quality for contaminated groundwater by $NO_3-N$ using compression packer. For this study groundwater samples collected from 46 groundwater wells were analyzed to clarify $NO_3-N$ contents. Groundwater wells over 10 mg/L in $NO_3-N$ content is 9 wells showing 20% among total samples. $NO_3-N$ contents after compression packer installation showed 26~81% low value compared with before compression packer.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.2
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• pp.207-214
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• 2013

To evaluate characteristics of water quality in Jeju, a study was implemented for Han stream and retention ponds. Inflow water quality of retention ponds was heavily dependent on precedent rainfall, and no pesticide was detected due to the little artificial pollution sources. A smooth settling efficiency curve was noticed because heavy particles were already settled down in front of the retention pond. There were weak relationships between retention time and water quality, and this can be attributable to high concentration of pollutants influx at peak inflow. In addition, as Han stream retention pond has a role of groundwater recharge, inflow control based on water quality as well as quantity is needed to maximize pollutant removal at the retention ponds.

• Journal of the Korean GEO-environmental Society
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• v.15 no.6
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• pp.5-15
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• 2014

This study is to quantitatively evaluate the impact on surrounding groundwater of waterway tunnel excavation and cofferdam construction in which A-dam and B-dam, so prediction of groundwater fluctuation and tunnel lining installation was studied. As a result, drawdown of groundwater level during tunnel excavation and cofferdam construction occurred about 3.58 m in the tunnel shaft. The initial condition of groundwater level recovered by up to 90 % was simulated after the completed the construction of the tunnel and lining installation. Groundwater inflow in the tunnel evaluated was analyzed to have exceeding water design criteria of the tunnel. The groundwater inflow is reduced to maximum $0.006m^3/min/km$ after lining installation done in the tunnel, so effect of lining installation was evaluated as 93 % or more. Drawdown of about 0.04~0.31 m occurs in the houses and temples analysis of groundwater system of the surrounding area from construction. Drawdown has occurred nearly by considering annual groundwater level fluctuation of National Groundwater Observation Network.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.1
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• pp.79-89
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• 2024

Excessive inflow of groundwater during tunnel excavation not only affects the stability and constructability of the tunnel, but is also one of the main causes of ground settlement due to groundwater level drawdown. The most commonly applied measure against excessive groundwater inflow during tunnel excavation in soil or fractured zone is to reduce the ground permeability coefficient by injecting grout material. Generally, the grouting area is assumed to be same as the plastic zone that occurs during tunnel excavation, but injecting grout material in the area of plastic zone is appropriate only for reinforcement grouting. In order to determine the thickness of cutoff grouting, the amount of reduction in the water permeability coefficient due to the application of cutoff grouting must be considered. In this study, a method for estimating the range of cutoff grouting considering the reduction in permeability coefficient was mathematically derived and evaluated through computer numerical analysis.

• Tunnel and Underground Space
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• v.4 no.1
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• pp.1-16
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• 1994

The study on the flow characteristics and analysis of groundwater in discontinuous rock mass is very important, since the water inflow into the underground opening during excavation induces serious stability and environmental problems. To investigate the flow through single rock joint, the effect of various aperture distribution on the groundwater flow has been analyzed. Observed through the analysis is the "channel flow", the phenomenon that the flow is dominant along the path of large aperture for given joint. The equivalent hydraulic conductivity is estimated and verified through the application of the joint network analysis for 100 joint maps generated statistically. Both the analytic aproach based on isotropic continuum premise and the joint network analysis are tested and compared analyzing the gorundwater inflow for underground openings of different sizes and varying joint density. The joint network analysis is considered better to reflect the geometric properties of joint distribution in analyzing the groundwater flow.ater flow.