• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.493-496
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• 2003

이 연구는 우리나라 균열암반 대수층의 수리적 특성을 해석ㆍ평가하기 위하여 양수시험 해석해(Theis, 1935; Cooper-Jacob, 1946; Papadopulos-Cooper, 1967; Hantush, 1962a,b; Moench, 1985; Hantush-Jacob, 1955) 및 일반화 방사상 유동 모델을 이용하여 균열암반 대수층(화강암, 화산암, 변성암, 백악기퇴적암, 제3기 퇴적암에 굴착된 100개 조사공)에서 수행되어진 양수시험으로부터 얻은 122개의 양수시험자료(수위강하 자료)를 분석하였다. AQTESOLV 전산프로그램을 이용한 양수시험자료 분석에 의하면, 122개 자료중 86개(71%)의 자료들이 이 연구에 사용된 해석해와 일치하며, 양수시험자료 해석해 중에 누수(leaky) 및 경계조건(boundary condition)을 고려한 해석해들이 53개(43%)로 가장 많이 나타났다. 그러므로, 양수시험자료의 해석은 균열암반 대수층의 수리지질학적 특성에 적합한 개념모델의 설정이 중요하다. 일반화 방사상 유동(GRF)모델을 적용해보면, 122개의 자료중 77개(63%)의 자료들이 Barker(1988)의 표준곡선에 의한 차원(1.1차원-2.9차원)을 보여준다. 이중 44.2%에 해당하는 39개 자료가 1.1차원과 1.9차원 사이의 분할 유동차원을 보여주는 반면에 26개(6.5%)만이 Theis 이론에 맞는 2차원의 방사상 흐름을 보여주며, 38개(49.3%)는 2.1차원에서 2.9차원에 속한다. 따라서 우리나라 균열암반 대수층에서 지하수 유동은 대부분 분할차원의 유동을 보여주는 것으로 평가된다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.577-582
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• 1996

지하수 유동체계 해석 모델인 2차원의 TRAFRAP 모델과 3차원의 MODFLOW모델을 사용하여 삼광광산 주변일대를 모델링하였다. 그 결과 암반내의 평균 지하수 유동속도는 1m/년 총 지하수 유출량은 640㎥/일로 분석되었다. 또한 열극대를 고려하여 유동체계를 해석하면, 열극대 주변에서는 물이 빠르게 유동하므로 수두값이 작아지고 지하수 유동로는 평균 100 m 정도 깊은 곳에 형성됨을 알 수 있다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.2
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• pp.59-65
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• 1990

This study investigates the effects of human impact and precipitation on groundwater flow conditions at a small area in Dejima Upland using a transient three-dimensional simulation. To show the utility of the transient three-dimensional model, the results of the numerical model are compared with those of Theis problem for which analytical solution is available. It appears that over the time period studied, the results of the model agree well with the analytical solution. Simulation is undertaken for a period of 30days starting from May 1st, when irrigation starts. Groundwater flow patterns determined by a numerical model are presented in the form of plotted potential lines and discussed. Results of simulation clearly indicate that the groundwater flow system should be analysed using a transient three-dimensional model, especially for the region which is effected by human impact.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.250-254
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• 2003

본 연구에서는 여러가지 해석해를 이용하여 균열암반 대수층에서 얻어진 양수시험자료를 해석하였다. 균열암반 대수층의 수리적 특성을 연구해 본 결과, 1.3차원에서 2.9차원까지 다양한 분포 차원을 나타나며, 양수시험 자료중 52%에 해당하는 자료가 1차원과 2차원 사이의 분할 유동차원을 보여준다. 이에 대하여 6.3%만이 Theis 이론에 맞는 2차원의 방사상 흐름을 보여준다 2∼3차원의 대수층이 암반대수층에서 나타나기는 어려우며, 만약 2차원 이상으로 해석되는 경우는 다른 방향으로 해석하는 것도 검토해야 한다. 즉, Leaky, constant head boundary, no flow boundary 등을 고려해야 한다.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.2
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• pp.80-87
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• 1998

Since groundwater flow paths have one of the major roles to transport the radioactive nuclides from the radioactive waste repository to the biosphere, the discrete fracture network model is used for the rock block scale flow instead of the porous continuum model. This study aims to construct a three dimensional discrete fracture network to interpret the groundwater flow system in the study site. The modeling work includes the determination of the probabilistic distribution function from the fracture geometric and hydraulic parameters, three dimensional fracture modeling and model calibration. The results of the constant pressure tests performed in a fixed interval length at boreholes indicate that the flow dimension around boreholes shows mainly radial to spherical flow pattern. The fracture transmissivity value calculated by Cubic law is 6.12${\times}$10$\^$-7/ ㎡/sec with lognormal distribution. The conductive fracture intensity estimated by FracMan code is 1.73. Based on this intensity, the total number of conductive fractures are obtained as 3,080 in the rock block of 100 m${\times}$100 m${\times}$100 m.

• Journal of Korea Water Resources Association
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• v.36 no.1
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• pp.129-142
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• 2003

In this study, the conduct of underground water flow system with 3 dimensions is interpreted in order to examine closely the actual condition regarding the flow of the underground water which is forecast from the tunnel segment and the interpretation result which selects the design and the construction technique of the tunnel segment was applied. Also, an obstacle to construct that relates with the underground water flow in construction duration in advance will be able to apply with information that is necessary in order to establish the countermeasure. The objective tunnel is the BEOPGI tunnel segment that is 2 parallel tunnels that are a one-way 2 lane and the parameters of the MODFLOW model executing the boring investigation and the permeability examination were presumed. The underground water flow of the excavation tunnel inside was interpreted by the MODFLOW model using the parameters which is presumed and two values which compared with calculated value and observed value are the same almost. Also, when the underground water discharge quantify that followed in tunnel excavation tries to compare, the underground water total discharge quantity from tunnel point of start until destination was presumed as 0.0269㎥/day/$m^2$.

• The Journal of Engineering Geology
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• v.9 no.1
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• pp.17-29
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• 1999

There are three major processes to impact the groundwater flow near underground storage caverns in the coastal area; effect of topography, effect of sea water intrusion, and effect of excavation. In this paper, the effects of three items were numerically studied to identify the major cause for altering the flow pattern. It turned out that the excavation is the most significant effect on the groundwater flow system. The groundwater pressure distributions and consequent groundwater pathways were significantly altered near the openings. By increasing the groundwater pressures from water curtain holes, the potential leakage of storage cavern was properly prevented

• Tunnel and Underground Space
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• v.14 no.4
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• pp.287-294
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• 2004

To predict the temperature distribution around a underground rock storage cavern, two- and three- dimensional numerical analysis using FLAC was conducted. The effects of groundwater and latent heat on thermal properties were considered in numerical calculation. The temperature estimated by FLAC are compared with the temperature measured for 5-year operation at Gonjiam storage cavern. Estimated and measured temperatures showed great discrepancy when thermal properties from laboratory tests were used and showed good agreement when the effects from 20% of volumetric water fraction and latent heat were considered. However, the discrepancy still increased with operation time due to the heat flow from ground surface. Three-dimensional numerical models were established to closely approximate the boundary condition of the test site, and numerical results better agreement when groundwater and latent heat effects were considered.

• Tunnel and Underground Space
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• v.15 no.2 s.55
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• pp.145-156
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• 2005

MODFLOW, 3-D finite difference code, is widely used to model groundwater flow and has been used to assess the effect of excavations on the groundwater system due to construction of subways and mountain tunnels. The results of numerical analysis depend on boundary conditions, initial conditions, conceptual models and hydrogeological properties. Therefore, its accuracy can only be enhanced using more realistic and field oriented input parameters. In this study, SA(simulated annealing) was used to integrate hydraulic conductivities from a few of injection tests with geophysical reference images. The realizations of hydraulic conductivity random field are obtained and then groundwater flows in each geostatistically equivalent media are analyzed with a numerical simulation. This approach can give probabilistic results of groundwater flow modeling considering the uncertainty of hydrogeological medium. In other words, this approach makes it possible to quantify the propagation of uncertainty of hydraulic conductivities into groundwater flow.

• The Journal of Engineering Geology
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• v.3 no.2
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• pp.149-165
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• 1993

Nowadays, the field hydraulic test is still an only method to evaluate groundwater characteristics in subsurface. The results of hydraulic test are very important for the concept model of fracture hydrogeology as well as the geometric pattern of fractures. The hydraulic tests performed in Korea are generally analysed under such assumption as steady radial flow in homogeneous aquifer or along simple geometry of fractures. Also the transmissivity measured in a fixed interval length is equivalent to a sum of individual fracture transmissivities in test legth. The boundary effects of weH hydraulics and the geometry of flow paths are hardly obtained from the test results analysed by a steady flow method. To circumvent this problem, the flow dimensional analysis was attempted from the results of constant pressure injection test carried out in a fractured granite area. A comparison of the hydraulic conductivity values from the transient and steady analysis shows that the latter is about a factor of 2~3 higher than the former. However, it was possible to analyse a flow dimension of each test interval from flow rate variation with time. The upper part of the bedrock(<10m deep) indicates an open boundary and the flow dimension shows nearly steady states, while the lower part of the bedrock(>25m deep) is characterized as sublinear flow dimension with a dosed boundary. In one of the test sections(15m deep), the flow dimension was changed from linear flow to spherical flow. From the experience of this study, one of the immediate problems to be solved is to enhance the field testing equipments, i.e., an accurate flowmeter with autorecording and a pressure detecting device to be able to install in the test section.