• Tunnel and Underground Space
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• v.10 no.3
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• pp.278-290
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• 2000

불연속면이 발달한 암반 내에서 터널을 굴착하는 경우 불연속면을 고려한 터널의 역학적 안정성을 검토하는 것이 중요하다. 불연속 암반 내에 터널을 굴착하게 되면 대부분의 거동은 불연속면에서 발생하게 된다. 이는 암반블록보다 암반 내 불연속면의 강성이 현저하게 작기 때문이다. 불연속면을 고려한 터널의 안정성 해석은 암반을 연속체로 가정할 때 필요한 입력변수 외에 여러 종류의 입력변수가 추가로 필요하다.(중략)

• Computational Structural Engineering
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• v.4 no.4
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• pp.117-124
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• 1991

In order to predict properly the effects of ground motion associated with earthquakes on underground radioactive waste disposal facilities, an understanding of the structural behavior of an underground opening in discontinuous rock masses subjected to dynamic loadings is essential. This paper includes literature review on computational models for discontinuous rock masses and on mathematical models for the structural analysis of underground opening. Then, structural analyses of underground openings using the distinct element computer program written for the static and dynamic analysis of discontinuous rock masses have been performed.

• Tunnel and Underground Space
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• v.22 no.3
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• pp.181-187
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• 2012

Many researches on disaster prevention using computer simulation methods can be performed to minimize the damage of property and to protect human life. Discontinuous deformation analysis (DDA) is a new computer simulation method to analyze the behavior of discontinuous rock masses. Since most rock slope problems are 3-dimensional in nature, 2-dimensional deformation analysis has limited application. In this study, the basic principles of 3-dimensional discontinuous deformation analysis are described. The newly developed 3-dimensional discontinuous deformation analysis method is proposed as the computer simulation method for discontinuous rock masses. Then, the failure behavior of rock slopes are simulated using 3-dimensional discontinuous deformation analysis. The simulation results are compared and examined with the failure behavior at the rock slopes. The results show the applicability of 3-dimensional discontinuous deformation analysis to analyze the deformation and failure mechanisms of rock slopes.

• Tunnel and Underground Space
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• v.29 no.5
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• pp.318-331
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• 2019

A three-dimensional(3D) equivalent continuum modeling was performed to analyze hydraulic behavior of rock mass considering discontinuities by using DFN model and smeared fracture model. DFN model was generated by FLAC3D and smeared fracture model was applied by using FISH functions, which is built-in functions in FLAC3D, for equivalent continuum model of fractured rock mass. Comparative analysis with 3DEC, which is for discontinuum analysis, was conducted to verify reliability of equivalent continuum analysis by using FLAC3D. Similar results of hydraulic analysis under the same conditions could be achieved. Equivalent continuum analysis of fractured rock mass by using DFN model was implemented to compare with existing analytical methods for inflow into the tunnel.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1994.03a
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• pp.70-74
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• 1994

암반내 지하수의 흐름은 공학적인 측면에서 중요한 역할을 한다. 지하공간 개발 및 터널건설에 있어서 지하수의 유출은 굴착과 보강공사의 진행을 대단히 어렵게 할 뿐만 아니라 구조물의 안정성에 심각한 문제를 야기시키기도 한다. 이는 다양한 원인에 의해서 생성된 암반내 불연속면의 존재에 기인한다. 불연속 암반의 지하수 유동해석에는 크게 두 가지 접근방식이 사용되어 왔다. (중략)

• Tunnel and Underground Space
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• v.10 no.3
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• pp.291-300
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• 2000

암반은 여러 가지 지질학적 요인들에 의해 형성된 수많은 절리면들을 경계로 하는 다양한 크기와 형상의 암석블럭들이 맞물려 평행상태를 이루고 있는 불연속체이다. 불연속 암반의 거동은 암석블럭을 이루는 무결암의 역학적 특성뿐만 아니라 암석블럭의 경계를 이루는 절리면들의 공간적 분포특성과 역학적 특성에도 큰 영향을 받는다. 불연속 암반의 거동해석을 목적으로 개발되고 있는 최근의 수치해석 기법들도 대부분 절리면의 영향을 효과적으로 해석에 반영시킬 수 있는 방법을 찾는데 집중하고 있다.(중략)

• Tunnel and Underground Space
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• v.9 no.2
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• pp.149-157
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• 1999

A powerful numerical method that can be used for that purpose is the Discontinuous Deformation Analysis (DDA) method developed by Shi in 1988. In this method, rock masses are treated as systems of finite and deformable blocks. Large rock mass deformations and block movements are allowed. Although various extensions of the DDA method have been proposed in the literature, the method is not capable of modeling water-block interaction that is needed when modeling surface or underground excavation in fractured rock. This paper presents a new extension to the DDA method. The extension consists of hydro-mechanical coupling between rock blocks and water flow in fractures. A example of application of the DDA method with the new extension is presented. The results of the present study indicate that fracture flow could have a destabilizing effect on the tunnel stability.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.03a
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• pp.17-34
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• 1997

• Tunnel and Underground Space
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• v.32 no.6
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• pp.464-477
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• 2022

DFN (discrete fracture network) models that take account of spatial variability and correlation between rock fractures have been demanded for analysis of fractured rock mass behavior for wide areas with high reliability, such as that of underground nuclear waste repositories. In this regard, this report describes the spatial distribution characteristics of fracture networks, and the DFN modeling methodologies that aim to represent such characteristics. DFN modeling methods have been proposed to represent the spatial variability of rock fractures by defining fracture domains (Darcel et al., 2013) and the spatial correlation among fractures by genetic modeling techniques that imitate fracture growth processes (Davy et al., 2013, Libby et al., 2019, Lavoine et al., 2020).These methods, however, require further research for their application to field surveys and for modeling in-situ rock fracture networks.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.221-234
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• 1999

This paper deals with the application of joint element in the finite element modeling of discontinuities encountered during rock tunneling. A nodal displacement joint element was implemented in a two dimensional finite element program GEOFE2D. The applicability of the joint element for modeling of discontinuities and the numerical stability of the implemented algorithm were examined by comparing the results of reduced small scale model tests as well as commercially available FEM program. The GEOFE2D was then used to analyze a tunnel crossed by a major discontinuity for the purpose of understanding the effect of discontinuity on the tunnel behavior. In addition, a modeling technique for the junction of discontinuity and shotcrete lining was presented. The results of analysis indicated that the stress-strain field around the tunnel is significantly altered by the presence of discontinuity, and that the stresses in the shotcrete lining considerably increase at the junction of the shotcrete lining and the discontinuity. It is therefore concluded that the major discontinuities must be carefully modeled in the finite element analysis of a tunneling problem in order to obtain more reliable results close to actual tunnel behavior.