• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.163-173
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• 2003

In this paper, a numerical comparison of predictions by limit equilibrium analysis and 3D analysis is presented for slope/pile system. Special attention is given to the coupled analysis based on the explicit finite difference code, FLAC 3D. To this end, an internal routine (FISH) was developed to calculate a factor of safety for a file reinforced slope according to shear strength reduction technique. The case of coupled analyses was performed for stabilizing piles in slope in which the pile response and slope stability are considered simultaneously. In this study, by using these methods, the failure surfaces and factors of safety were compared and analyzed in several cases, such as toe, middle and top of the slope, respectively. Furthermore, the coupled method based on shear strength reduction technique was verified by the comparison with other analysis results.

• Geomechanics and Engineering
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• v.14 no.2
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• pp.141-149
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• 2018

In this paper, the creep behavior of bolted rock was analyzed by using the unconfined creep tests and the numerical results. Based on the test results, the Bolted Burgers creep model (B-B model) was proposed to clarify the creep mechanism of rock mass due to rock bolts. As to the simulation of the creep behaviour of bolted rock, a new user-defined incremental iterative format of the B-B model was established and the open-source $FLAC^{3D}$ code was written by using the object-oriented language (C++). To check the reliability of the present B-B creep constitutive model program, a numerical model of a tunnel with buried depth of 1000 m was established to analyze the creep response of the tunnel with the B-B model support, the non-support and the bolt element support. The simulation results show that the present B-B model is consistent with the calculated results of the inherent bolt element in $FLAC^{3D}$, and the convergence deformation can be more effectively controlled when the proposed B-B model is used in the $FLAC^{3D}$ software. The big advantage of the present B-B creep model secondarily developed in the $FLAC^{3D}$ software is the high computational efficiency.

• 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.

• Tunnel and Underground Space
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• v.32 no.2
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• pp.144-159
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• 2022

The present study developed a sequential approach-based numerical simulator for modeling coupled thermal-hydrological-mechanical (THM) processes in the ground and investigated the computational performance of the coupling analysis algorithm. The present sequential approach linked the two different solvers: an open-source numerical code, OpenGeoSys for solving the thermal and hydrological processes in porous media and a commercial code, FLAC3D for solving the geomechanical response of the ground. A benchmark test of the developed simulator was carried out using a THM problem where an analytical solution is given. The benchmark problem involves the coupled behavior (variations in temperature, pore pressure, stress, and deformation with time) of a fully saturated porous medium which is subject to a point heat source. The results of the analytical solution and numerical simulation were compared and the validity of the numerical simulator was investigated.

• Geomechanics and Engineering
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• v.28 no.5
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• pp.437-454
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• 2022

The hydro-mechanical (HM) two-way sequential coupling in the TOUGH2-FLAC3D linking algorithm is validated completely and successfully in both M to H and H to M directions, which are initiated by mechanical surface loading for geomechanical validation and hydrological groundwater pumping for hydrogeological validation, respectively. For such complete and successful validation, a TOUGH2-FLAC3D linked numerical model is developed first by adopting the TOUGH2-FLAC3D linking algorithm, which uses the two-way (fixed-stress split) sequential coupling scheme and the implicit backward time stepping method. Two geomechanical and two hydrogeological validation problems are then simulated using the linked numerical model together with basic validation strategies and prerequisites. The second geomechanical and second hydrogeological validation problems are also associated with the Mandel effect and the Noordbergum and Rhade effects, respectively, which are three phenomenally well-known but numerically challenging HM effects. Finally, sequentially coupled numerical solutions are compared with either analytical solutions (verification) or fully coupled numerical solutions (benchmarking). In all the four validation problems, they show almost perfect to extremely or very good agreement. In addition, the second geomechanical validation problem clearly displays the Mandel effect and suggests a proper or minimum geometrical ratio of the height to the width for the rectangular domain to maximize agreement between the numerical and analytical solutions. In the meantime, the second hydrogeological validation problem clearly displays the Noordbergum and Rhade effects and implies that the HM two-way sequential coupling scheme used in the linked numerical model is as rigorous as the HM two-way full coupling scheme used in a fully coupled numerical model.

• Tunnel and Underground Space
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• v.20 no.1
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• pp.7-14
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• 2010

A quarry with 105 m height large cut slope was analyzed. Beside RMR and SMR methods, FLAC2D were adopted to analyze slope stability. As a result, slope of andesite had a possibility of failure. Wet slope showed low safety factor. Soil nailing was recommended to solve it. Since safety factor of slope largely depend on underground level, investigation for it seemed necessary.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.63-66
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• 2000

Stress variation due to size variation and the eccentricity of ring type tensile specimen was analyzed by FLAC program. To get the stable tensile strength the ratio of inner to outer ring diameter should be within a certain range. Diameter ratio of 0.3 was suggested to be adequate. It seemed to be difficult to determine the tensile strength because of stress distortion if eccentricity exceeded home limit. To limit the error in 10%, lateral and axial eccentricity was analyzed to be in the limits of 3% and 10%, respectively.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.316-319
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• 2000

Stress variation due to size variation and the eccentricity of ring type tensile specimen was analyzed by FLAC program. To get the stable tensile strength the ratio of inner to outer ring diameter should be within a certain range. Diameter ratio of 0.3 was suggested to be adequate. It seemed to be difficult to determine the tensile strength because of stress distortion if eccentricity exceeded some limit. To limit the error in 10%, lateral and axial eccentricity was analyzed to be in the limits of 3% and 10%, respectively.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.41-70
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• 1999

The benefits of utilizing internal reinforced members, such as soil nails and ground anchors, in maintaining stable excavations and slopes have been known among geotechnical engineers to be very effective. Occasionally, however, both soil nails and ground anchors are simultaneously used in one excavation site. In the present study, a method of limit equilibrium stability analysis of the excavation zone reinforced with the vertically or horizontally mixed nail-anchor system is proposed to evaluate the global safety factor with respect to a sliding failure. The postulated failure wedges are determined based on the results of the $FLAC^{2D}\; 및\; FLAC^{3D}$ program analyses. This study also deals with a determination of the required thickness of the shotcrete facing. An excessive facing thickness may be required due to both the stress concentration and the relative displacement at the interface zone between the soil nailing system and the ground anchor system. A simple finite element method of analysis is presented to estimate the corresponding relative displacement at the interface zone between two different support systems. As an efficient resolution to reduce the facing thickness, the modified bearing plate system is also proposed. Finally with various analysis related to the effects of design parameters, the predicted displacements are compared with the results of the $FLAC^{2D}$ program analyses.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2001.03a
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• pp.177-187
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• 2001

암반사면의 안정성은 암반 내에 발달한 불연속면의 방향성과 파괴특성에 지대한 영향을 받는다. 두 조의 연속성이 좋은 절리가 발달한 암반의 거동을 해석하기 위해 FLAC의 FISH 언어로 작성된 편재 절리모델을 사용하여 절리암반사면의 안정성을 평가하였다. 해석 결과는 절리의 간격과 방향성을 달리하면서 수행된 UDEC 해석과 저면 마찰 모델 시험결과와 비교하였다. UDEC 해석과 저면 마찰 모형시험 의해 발생된 파괴면의 형상은 유사하였으며, 이 결과로부터 편재절리모델에 의한 FLAC 해석에서의 파괴면은 두 조의 교차하는 절리를 따라 계단식으로 파괴면이 발생함을 추정할 수 있었다.