• Proceedings of the KSEG Conference
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• 2000.04a
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• pp.95-102
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• 2000

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.312-315
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• 2006

배수공법으로 터널을 설계할 때 다양한 지질조건에 따라 터널내로 유입되는 지하수 용수량과 배수관의 배수능력을 비교 검토하였다. 기존 설계 기준에 의한 터널 배수관은 다양한 지질조건을 가지는 대수층의 수리전도도에 따라 안정성 여부가 달라지는 것을 알 수 있었다. 기존 배수관 (${\Phi}300m/m$)으로 터널을 설계할 경우 투수성이 좋은 석회암 구간 및 파쇄대 구간에서는 문제가 생길 가능성이 높고, 풍화 받지 않은 암반층의 경우에는 터널길이 20km까지 지하수 용수량을 수용 가능한 것으로 판단된다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.3
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• pp.561-573
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• 2018

In order to design the ventilation in the road tunnel, it is necessary to know the ratio of average annual daily traffic by vehicle type. In general, the road tunnels are onedirectional tunnel, so the traffic of each vehicle type does not change along the tunnel. On the other hand, in the case of network road tunnels, since the connections in the tunnels are complex, the traffic of vehicle-type varies depending on the network composition of tunnels. In the studying the easy method for calculating the ratio of vehicle type for the network road tunnel are proposed with using incidence matrix.

• The Journal of Engineering Geology
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• v.14 no.3 s.40
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• pp.287-300
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• 2004

By using a simple conceptual model, a sensitivity analysis is performed to examine the effects of changing model parameters on the model outputs, the groundwater discharge and the radius of influence, induced by tunnel construction. The results indicate that the model outputs are most sensitive to the tunnel depth and the hydraulic conductivity, and their sensitivities vary with time. It is also revealed that the sensitivity of the specific yield in- creases constantly with time, and therefore it is as important as the hydraulic conductivity for constructing a wet-system tunnel. A transient model is suggested to simulate the stepwise tunnel excavation and the watertight lining. The model is used for a tunnel construction site to predict groundwater mow into the tunnel and the transient response of the surrounding aquifer system. The predicted results are highly sensitive to the hydraulic conductivites assigned by model calibration. Thus, a postaudit should be made to reduce the uncertainty of the predictive model.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.2
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• pp.97-114
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• 2011

It is not uncommon that private wells and small streams are used for daily life in the regions where mountain tunnels are located. Then serious social problems such as well water level fall, being attributable to tunnel excavation can occur. In the design stage, firstly we evaluated that the quantity of leakage water into tunnels. And groundwater drawdown area was simulated using numerical modeling such as MODFLOW to reduce adverse effects on life environment around tunnel. In addition we also used hydrological method to evaluate the groundwater change of tunnel area.

• Tunnel and Underground Space
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• v.16 no.4 s.63
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• pp.281-287
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• 2006

Intake of groundwater by tunneling in a mountainous area mostly results from groundwater flow through fractured parts of total rock mass. For reasonable analysis of this phenomenon the representative joint groups 1, 2, and 3 have been selected by previous investigations, geological/geophysical field tests and boring works. Three dimensional fractures were generated by the FracMan and MAFIC which is a three dimensional finite element model has been used to analyse a groundwater flow through fractured media. Monte Carlo simulation was applied to reduce the uncertainty of this study. The numerical results showed that the average and deviation of amounts of groundwater intaked into tunnel per unit length were $5.40{\times}10^{-1}$ and $3.04{\times}10^{-1}m^3/min/km$. It is concluded that tunnel would be stable on impact of groundwater environment by tunneling because of the lower value than $2.00{\sim}3.00m^3/min/km$ as previous and present standard on the application of tunnel construction.

• The Journal of Engineering Geology
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• v.20 no.4
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• pp.449-459
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• 2010

We performed numerical simulations of the excavation of an underground structure (the Giheung Tunnel) in order to evaluate the rate of groundwater flow into the structure and to estimate the groundwater level around the structure. The tunnel was constructed in Precambrian bedrock in Gyeonggi Province, South Korea. Geological and electrical resistivity data, as well as hydraulic test data, were used for the numerical modeling. The modeling took into account the strike-slip faults that cross the southern part of Giheung Tunnel, as these structures influence the discharge of groundwater into the tunnel. The transient modeling estimated a groundwater flow rate into the tunnel of $306\;m^3$/day, with a grout efficiency of 40%, yielding good agreement between the calculated change in groundwater level (6.20 m) and that observed (6.30 m) due to tunnel excavation.

• 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.13 no.6
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• pp.465-475
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• 2003

Groundwater inflow into the caverns constructed in fractured rock mass was simulated by numerical modeling, NAPSAC (DFN, discrete fracture network model) and NAMMU (CPM, continuous porous media model), a finite-element software package for groundwater flow in 3D fractured media developed by AEA Technology, UK. The input parameters for modeling were determined on surface fracture survey, core logging and single hole hydraulic test data. In order to predict the groundwater inflow more accurately, the anisotropic hydraulic conductivity was considered. The anisotropic hydraulic conductivities were calculated from the fracture network properties. With a minor adjustment during model calibration, the numerical modeling is able to reproduce reasonably groundwater inflows into cavern and the travel length and times to the ground surface along the flow paths in the normal, dry and rainy seasons.