• Tunnel and Underground Space
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• v.13 no.1
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• pp.52-63
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• 2003

Discontinuities such as faults, fractures and joints in rock mass play the dominant role in the mechanical and hydraulic properties of the rock mass. The key factors that influence on the flow of groundwater are hydraulic and geometric characteristics of discontinuities and their connectivity. In this study, a program that analyzes groundwater flow in the 3D discontinuity network was developed on the assumption that the discontinuity characteristics such as density, trace length, orientation and aperture have particular distribution functions. This program generates discontinuities in a three-dimensional space and analyzes their connectivity and groundwater flow. Due to the limited computing capacity In this study, REV was not exactly determined, but it was inferred to be greater than 25$\times$25$\times$25 ㎥. By calculating the extent of aperture that influences on the groundwater flow, it was found that the discontinuities with the aperture smaller than 30% of the mean aperture had little influence on the groundwater flow. In addition, there was little difference in the equivalent hydraulic conductivity for the the two cases when considering and not considering the boundary effect. It was because the groundwater flow was mostly influenced by the discontinuities with large aperture. Among the parameters considered in this study, the length, aperture, and orientation of discontinuities had the greatest influence on the equivalent hydraulic conductivity of rock mass in their order. In case of existence of a fault in rock mass, elements of the equivalent hydraulic conductivity tensor parallel to the fault fairly increased in their magnitude but those perpendicular to the fault were increased in a very small amount at the first stage and then converged.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1057-1061
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• 2004

본 연구에서는 준분포형 지표수 유출모형인 SWAT과 3차원 지하수 유동모형인 MODFLOW의 완전연동형 결합모형을 독자적으로 개발했다. SWAT의 지하수 모형성분은 집중형이므로 분포형 매개변수와 변화하는 양수량, 지하수위의 변화등을 고려하지 못하며 MODFLOW모형은 주요 입력자요인 함양량의 정확한 산정이 어렵다. 두 프로그램의 연결작업은 지하수 함양량의 전달과정과 하천네트워크-대수층간의 상호작용을 고려하여 완성하였으며 경안천유역의 오산천 소유역에 모형을 시험구동을 수행했다. 시험구동결과 결합모형은 수문모형 혹은 지하수 모형만으로는 해결되지 않는 하천-대수층간의 경계유량을 고려한 유출해석이 가늠해짐으로써 유역내 지하수 유출량 및 총 유출량의 신뢰성이 증대될 것으로 기대된다.

• Journal of Korean Society of Disaster and Security
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• v.11 no.2
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• pp.17-28
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• 2018

The purpose of this study is to investigate the effect of underground facilities around excavation zone on groundwater flow characteristics during excavation. The scenarios were constructed considering the size of the underground facility, the separation distance, and the hydraulic gradient. As a result, as the size of the underground facility increases, the difference of head and the hydraulic gradient become large. The shorter the separation distance of underground facility is, the more the difference of head and the hydraulic gradient occur. The effect of hydraulic gradient on model area was relatively small. As a result of analysis of groundwater flow rate for the scenario, groundwater flow rate tends to decrease as the size of underground facility increases or groundwater flow rate tends to decrease as the separation distance decreases. It is necessary to examine the effect of underground facilities on the groundwater flow analysis in the ground excavation.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.248-248
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• 2015

제주도의 연평균 강수량은 지속적으로 증가하고 있으나 강우일수는 감소하는 추세로 기후변화에 의한 가뭄재해 피해가 우려되고 있다. 제주도는 전체 수자원의 대부분을 지하수로 사용되어 면적 대비 많은 지하수관정이 개발 이용되고 있으며, 용수이용에 따른 고갈 및 오염이 발생되지 않도록 분석 관리가 필요한 지역이다. 제주지역의 지하수위는 계절적 변동특성이 확연히 나타나지만 평시에는 큰 변동이 없는 지하수위 수준을 보이며, 실제 지하수 이용률은 허가량의 30%이하로 양수에 의한 지하수위변동은 크게 체감되지 못하고 있다. 그러나 극심한 가뭄재해 발생 시 기존 사용량을 초과 양수하는 문제가 발생하여 지하수위는 급격하게 하강되고, 제주 수자원관리에 문제가 발생될 것으로 지속적인 지하수 개발이 지하수위에 미치는 영향에 대하여 정량적인 분석이 필요하다. 본 연구에서는 지하수 유동 및 수위변동 분석이 가능한 수치해석 모형을 이용하여 제주도 성산유역을 대상으로 1993년부터 2013년까지 10년 주기 양수에 따른 지하수위 하강 특성을 분석하였다. 1993년 이전 개발된 지하수관정은 55개소, 2003년까지 개발된 지하수관정은 108개소로 지하수 개발은 약 1.9배 증가되었으나 양수능력을 적용하여 지하수위 변동을 분석한 결과 2.5배~3.1배 하강되는 것으로 확인되었다. 2003년부터 2013년까지 지하수 개발은 유역 상부에 집중되었으며 상류부 지하수 양수에 따라 해안지역의 지하수위까지 영향을 미치는 것으로 확인되었다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.286-288
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• 2006

삼중수소는 물분자중 수소원소의 동위원소로서 물의 유동연구에 가장 이상적인 추적자로서 활용된다. 이러한 삼중수소 분석결과는 지표수 지하수 상관관계 해석 및 지하수의 연대측정등 수문학 연구의 중요한 자료로 활용되고 있다. 지하수 연구에 필요한 삼중수소의 측정법을 확립코자 극저준위 액체섬광계수기를 도입하였으며 NIST 표준시료를 사용하여 실험방법을 확립하였다. 삼중수소의 측정효율은 25.7 % 였으며, 전기분해법을 사용하지 않고 단순 분리법만을 사용하였을 경우 10 ml의 측정 시료와 섬광액으로 Ultima-Gold LLT를 사용하여 0.18 Bq(1.5 TU)의 검출한계를 얻었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.241-245
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• 2004

최근 국가에서 수자원 개발의 다변화를 모색함에 따라 지하수가 새로운 수자원으로 대두되고 있다. 이러한 지하수를 이용하는 방안 중 하나가 하천의 하류부에 지하댐을 건설하여 지하수자원을 이용하는 것이다. 본 논문에서는 속포시 쌍천 지하댐 유역을 적용대상으로 선정하여 USGS의 MODFLOW 모형을 이용한 수치모형 실험을 통해 양수로 인한 지하수위의 변동 양상을 살펴보았다. 또한 지하댐의 위치와 형태를 조절하여 지하수의 최적 관리방안을 모색해 보았다. 지하댐 건설 지역에서의 수자원 보존과 지속 가능한 개발을 위하여 양수량에 대한 지속적인 평가와 규제가 필수적이고 또한 신뢰성이 높은 모델의 구축이 필요하다. 이를 위해서는 장기간의 지하수 수위 변동자료, 정밀 지질도와 대수층의 분포에 대한 data base 구축 등이 요구되면, 대수층에 대할 수리매개변수 등과 같은 기본 자료의 정확한 평가가 요구된다.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.217-228
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• 1999

The three methods of analysis (i) REV(representative elemental volume), (ii) non-REV and (iii) joint network analysis are introduced in this paper to analyze the groundwater flow in jointed rock mass and the inflow into underground excavations. The results from those methods are compared one another to reveal their characteristics by varying the number of joints and the diameter of the opening. The pre-processor, the so-called sequential analysis, is introduced to predict the equivalent hydraulic conductivity of a jointed rock mass having a number of intersecting joints. Using the finite element mesh, joint map and sequential analysis, the equivalent hydraulic conductivities are calculated for all 445 elements. The hydraulic inhomogeneity and the determination of the representative properties of jointed rock masses are discussed. In the REV analysis where the entire rock mass is homogenized through the representative properties, the inflow is increased regularly and consistently by increasing the joint density, the opening size and the conductivity contrast value. Though the non-REV analysis showed irregular variation of the inflow due to the local inhomogeneity allowed to individual elements, the inflow approached the REV results as the characteristic length increases. The joint network analysis showed the most sensitive reaction to the joint density, the opening size and the presence of the network crossing the opening. The reliability of the network analysis depends on the geometric data of individual joints. In view of the limited field data on joint geometry and possible uncertainty the REV and non-REV methods are considered more practical and rational than the joint network analysis.

• Journal of Korean Society of Disaster and Security
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• v.10 no.1
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• pp.19-27
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• 2017

In recent years, ground subsidence has been frequently occurred by underground cavities due to the excessive groundwater inflow, caused by poor construction and management, during tunnel excavation and underground structure construction. In this study, a numerical model (SEEFLOW3D) was developed to estimate groundwater fluctuations for saturated-unsaturated poros media, evaluates the impact on ground excavation with open cut and non-open cut scenarios. In addition, the visual MODFLOW was applied to demonstrate the verification of the model compared with both results. Our results indicated that the RMSE and NRMSE was obtained to range over -3.95~5.7% and 0.56~4.62%, respectively. The developed model was expected to estimate groundwater discharges and apply analysis tool for optimum design of waterproof wall in future.

• Journal of Soil and Groundwater Environment
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• v.12 no.3
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• pp.66-74
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• 2007

Stationary and trolling methods in measuring flow using flowmeter were adopted to investigate the hydraulic connectivity of fractures and to evaluate the applicability of the measurement methods. Stationary method was useful for identifying the inflow and outflow patterns in the measured section, which enabled us to analyze the hydraulic connectivity of fractures between the wells. Trolling method failed to find the inflow and outflow patterns in the well, but was very effective for locating the conductive fractures. Measuring flow in the borehole by both stationary and trolling methods was found to be very efficient for identifying conductive fractures and their hydraulic connectivity in fractured rock aquifer.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2007.03a
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• pp.311-324
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• 2007