• Computational Structural Engineering
• /
• v.11 no.4
• /
• pp.169-176
• /
• 1998

불연속적 거동이 탁월한 벽식 프리캐스트 구조물을 해석하기 위한 방법으로 유한요소법과 강체요소법 등이 있으나, 이들 해석법은 접합부의 거동을 정확히 반영하지 못하고 있다. 본 연구에서는 패널은 강체적 거동을 하고, 판널과 판널 사이의 접합부는 고체적 거동을 가정하는 강체-고체 복합모델(Coupled Model by Rigid and Solid bodies)에 의한 해석법을 제안하며, 간단한 모델의 예를 통해 검증하였다.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.11 no.2
• /
• pp.141-150
• /
• 2009

When constructing a subsea tunnel in discontinuous rock mass, fluid flow in joints has a great influence on the behavior of the tunnel so that hydro-mechanical coupled analysis should be performed for the stability estimation. In practice, relaxed rock load is generally used for the design of tunnel concrete lining. In a continuum analysis, a method based on the distribution of local safety factor around a tunnel was proposed for the estimation of a potential relaxed zone. However, in the case of discontinuous rock mass in which joints are developed, the whole stability of tunnels depends on the behavior of the joints. In this study, therefore, a method is proposed for the estimation of a potential relaxed zone occurred by the excavation of a tunnel in discontinuous rock mass. The suggested method is validated by sensitivity analysis and the comparison with the results of continuum analysis.

• Proceedings of the Korean Society for Rock Mechanics Conference
• /
• 2000.09a
• /
• pp.163-170
• /
• 2000

The distinct element method has been effectively applied to the analysis of stability and behavior of jointed rock masses. In this paper the modelling characteristics of different types of distinct element model were investigated. Arch tunnel examples were chosen to compare the calculation results of two computer codes, NURBM and CBLOCK, where the former is based on implicit algorithm, and the other on explicit one. CBLOCK calculations show that joint properties are very important parameters in the stability analysis and that the joint stiffness ratio associated with joint configuration could be used as an indicator, whereas NURBM differ from that. Some other disagreements were also identified.

• Tunnel and Underground Space
• /
• v.10 no.3
• /
• pp.410-417
• /
• 2000

The distinct element method has been effectively applied to the analysis of stability and behavior of jointed rock masses. In this paper the modelling characteristics of different types of distinct element model were investigated. Arch tunnel examples were chosen to compare the calculation results of two computer codes, NURBM and CBLOCK, where the former is based on implicit algorithm, and the other on explicit one. CBLOCK calculations show that joint properties are very important parameters in the stability analysis and that the joint stiffness ratio associated with joint configuration could be used as an indicator, whereas NURBM differ from that. Some other disagreements were also identified.

• The Journal of Engineering Geology
• /
• v.31 no.1
• /
• pp.55-66
• /
• 2021

Hydraulic-mechanical (H-M) coupled numerical modeling was used to evaluate the evolution of hydrogeological properties in response to the installation and expansion of a borehole. A domain with a discrete fracture network was adopted for discontinuum modeling to simulate changes in fracture apertures. Comparison with real hydraulic test data shows that the effects of principal stress direction and expansion of borehole diameter were reasonably simulated by H-M coupled numerical modeling. The modeling confirmed that aperture changes depended on the principal stress direction, with an increase in aperture size due to vertical displacement being the dominant effect. A concentration of shear dilation around the borehole had an additional, subsidiary, effect on the hydrogeological evolution. These results show that the permeability of fractured rock can be increased by changing the hydraulic properties of a fracture through stress redistribution caused by the installation and expansion of a borehole.

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

• Tunnel and Underground Space
• /
• v.26 no.2
• /
• pp.131-142
• /
• 2016

Investigation for rock joints, inspection for rock core, and laboratory tests for rock specimens, in this study, have been performed for identification of the extent and properties of Excavation Damaged Zone in a underground limestone mine, which plans to enlarge the size of openings to improve the production rate. Properties of EDZ and surrounding rock masses have been used numerically for discontinuum analysis, and it is concluded that the effect of EDZ can be increased with increasing the opening size and a blasting pattern of high precision can be suggested for the counterplan.

• Computational Structural Engineering
• /
• v.4 no.1
• /
• pp.42-43
• /
• 1991

균열성암반의 모형화 기술은 계속적으로 보완발전되어 UDEC이 개발되었으며, 현재 UDEC의 최신판은 블록 내부를 다시 유한차분요소로 분할하여 블록의 소성거동(Mohr-Coulomb Model) 및 쪼개짐을 고려할 수 있고, 절리면에서의 유체흐름 및 유압의 발생, 그리고 열응력 해석 등 평면변형 문제의 정적해석과 지진 및 폭발하중을 고려한 동적해석이 가능하다. UDEC은 전처리 기능이 뛰어나 최소한의 입력데이타로써 전체 모형의 데이타를 자동생성시키며 절리면의 통계학적 자동생성 및 터널형상의 자동생성도 가능하다. UDEC은 실용적인 보강요소를 구비하여 Rock Bolt 뿐만 아니라 그라우트를 고려한 Cable Bolt를 모형화할 수 있으며 국부적인(Key Block)보강으로써 불연속체 전체의 안정을 검토할 수 있다.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.11 no.2
• /
• pp.189-198
• /
• 2009

Recently the concern about the construction of underground structures such as oil and food storage caverns is increasing in Korea and abroad. The stability of those underground caverns is greatly influenced by shape factor and the size of excavation area as well as the joint conditions. In this study, therefore, the effect of the shape factor of an underground cavern on its stability was analyzed in terms of safety factor. To this end, four different shape factors of a cavern excavated in good rock conditions were investigated and sensitivity analyses were performed based on overburden, lateral earth pressure coefficient, joint spacing, properties, and orientation. The stability of a cavern is evaluated in terms of safety factor estimated numerically based on the shear strength reduction technique. In future, this study is expected to be helpful in designing and evaluating the stability of caverns excavated in discontinuous rock masses.

• The Journal of Engineering Geology
• /
• v.20 no.1
• /
• pp.13-23
• /
• 2010

Toppling failure of a slope is defined as failure behavior accompanying the rotation of rock block which is different from other failure such as sliding along with discontinuities and so on. It generally occurs in the region that discontinuities were developed with inverse dip direction to a slope and it could play a critical role in judging stability of slope. In this study, the stability evaluation was performed about toppling failure on a jointed road cut-slope. To check the deformation behavior, numerical analysis is widely used. However common analysis programs are based on continuum model. Recently, many methods that discontinuity properties can be considered in continuum analysis are suggested. In this study, numerical analysis based on FEM(Finite Element Method) was performed using interface element applied in heterogeneous boundary to simulate effects of discontinuities.