• 터널과지하공간
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• 제10권3호
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• pp.395-402
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• 2000

고속철도터널 시공전에 폐광된 광산의 채굴공동의 변형거동이 철도터널의 안정성에 마치는 영향을 조사하고자 이 지역에서 지질조사, 암반의 공학적 평가 및 평가요소에 대한 다중회귀분석, 수치해석 입력자료의 취득을 위한 많은 조사를 수행하였다. 암반의 공학적 분류결과 절리면에 대한 상태가 RMR 값을 결정하는데 가장 중요한 변수로 나타났고 ,Q값을 결정하는데는 절리군의 수가 가장 중요한 변수인 것으로 분석되었다. FLAC에 의한 해석결과 고속철도구간 서측 하부 50m 지점에 위치한 채굴적의 변형거동은 암반의 역학적 특성에 따라 변형양상은 다를 수 있으나 고속철도터널에 침하성 변위를 유발시킬 가능성이 있을 것으로 판단되었다. 그러나 채굴적을 광체와 같은 역학적 특성을 갖는 재료로 충전 시켰을 때 침하성 변위는 나타나지 않는 것으로 나타났다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.105-112
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• 2001

The purpose of this study is to assess the stability of tunnel for a high speed railway crossing the fault zone. The area where the tunnel crossed the fault zone can be unstable during construction and operation. Geotechnical investigations have been conducted to determine an optimum excavation method by obtaining the material properties around the fault zone and to check the stability of the tunnel. For the numerical analysis, the FLAC, numerical analysis code based on finite difference method, was utilized to analyze the behavior of the fault at three points having typical ground conditions. Based on the results of numerical analysis, the combinations of compaction grouting and LW grouting were determined as suitable methods for pre-excavation Improvement of the ground surrounding the tunnel opening. In conclusion, the stability of the tunnel construction for the high speed railway within the fault zone may be obtained by adopting the optimum excavation method and the reinforcement method. The numerical analysis based on FLAC program contains errors caused by assumptions used in numerical analysis, therefore constant monitoring with respect to the change of ground condition and groundwater is highly recommended to minimize the numerical error and the possibility of damage to tunnel.

• 터널과지하공간
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• 제15권6호
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• pp.391-399
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• 2005

본 연구에서는 횡등방성 암반에서 이방성 정도에 따른 응력 차와 3차원 주응력 하의 터널방향, 이방성 정도에 따른 터널 단면에서의 2차원 응력 차를 이론적으로 구하였다. 구해진 응력상황 하의 터널에 대하여 $FLAC^{2D}$를 이용하여 이방성 고려여부에 따른 천단, 측벽, 바닥의 응력 차를 비교${\cdot}$검토하였다. 그 결과 이방성을 무시할 경우 응력 조건에 무관하게 주응력의 크기와 방향이 다르게 나타나며, 이방성 정도가 커질수록 응력차가 증가함을 알 수 있다. 이방성의 방향에 따라 응력 차가 달리 나타나며, 특히 이방성의 방향이 x축으로부터 시계반대방향으로 $45^{\circ}$와 $135^{\circ}$에서 가장 큰 응력 차가 발생함을 확인하였다.

• 터널과지하공간
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• 제13권2호
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• pp.138-152
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• 2003

지하 수백미터 심부에 위치하는 고준위방사성 폐기물 처분장에서의 열-역학적 안정성 평가를 위해 FLAC3D를 이용한 3차원 해석이 수행되었다. 효과적인 해석을 위해 FISH프로그램이 작성되었으며 고성과 유성 의 시추부지에서 얻어진 지질, 암반 물성자료가 사용되었다. Factional factorial design을 적용한 실험설계를 거쳐 얻어진 응력, 온도에 대한 민감도 분석이 실시되었으며 이를 통해 처분장 안정성에 영향을 미치는 주요 설계 인자의 선정 및 인자 상호간의 영향을 분석할 수 있었다. 연구 결과 열-역학적 안정성에 가장 큰 영향을 미치는 인자는 처분공의 간격으로 나타났으며 처분터널의 간격과 완충재의 두께가 그 다음으로 주요한 인자인 것으로 나타났다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.411-414
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• 2014

Numerical modeling was conducted to estimate the amount of dislocation that may occur across a frictionless fracture during an earthquake using commercial code FLAC3D (Fast Lagrangian Analysis of Continua in 3 Dimensions). The applied motion was calculated to represent a Richter 6.0 magnitude earthquake at distances of 2 km from the fracture. The velocity-time history was generated from Svensk $K{\ddot{a}}arnbr{\ddot{a}}anslehantering$ AB report. In the report, The velocity field resulting from an earthquake on a fault located in the near-field (2 km distance) was modelled using a finite difference program, WAVE. The stress-time history was substituted for velocity-time history to perform dynamic analysis using FLAC3D. During the earthquake, the maximum dislocation and change of shear stress were about 1 cm and 2MPa, respectively. Because the fracture is frictionless in this study, all dislocations relax to zero after the earthquake motions have ceased.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 사면안정 학술발표회
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• pp.213-220
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• 2000

Numerical modeling of cut slope has some limits in simulating the real slopes. In the case of 2D analysis of slope stability, it is assumed that slope is simply straight even when it is concave or convex in plan view. In this study, 3D analysis in curved shape slopes has been conducted for the comparison with 2D analysis in terms of failure mode and factor of safety. For this, 3D analysis by FLAC3D was compared with 2D analysis in plane strain condition and axi-symmetric model condition by FLAC. It was also observed how safety factors of slopes were affected by the variation of the tensile strength and cohesion, which are important variables to decide whether the slope fails or not. 2D analysis of concave slopes under plane strain condition showed much smaller safety factors by 16-40 % errors depending on the radius of curvature of slopes, compared to the more realistic values from 3D analysis. In case of convex slopes, the lower values by 7-10 % has been reported. 2D analysis of axi-symmetric model showed also smaller safety factors by 6-10 % and by 2-4 %, in case of concave and convex slopes, respectively. Such results are expected to contribute to the better understanding of failure process and could be applied for improved design of slopes.

• 한국방재학회 논문집
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• 제7권1호통권24호
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• pp.39-46
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• 2007

발파를 통한 지반굴착 시 화약의 폭발로 인해 발생되는 지반의 진동은 인근 지상구조물과 지하매설물에 영향을 미치게 된다. 이러한 영향은 구조물에 피해를 발생시킬 뿐만 아니라 도심지 공사의 경우 민원에 의한 문제로 많은 경제적, 시간적 피해를 야기하므로 이에 대한 사전 영향성 평가가 필요하다. 본 연구에서는 터 널상부에 재개발을 통한 주거시설 건립을 위해 부지조성을 목적으로 한 발파작업 시 터널의 안정성을 이론식과 유한차분해석 프로그램인 $FLAC^{2D}$를 이용하여 검토하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1441-1446
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• 2009

Numerical analysis is a powerful method in evaluating the soil-pile-structure interaction under the dynamic loading, and this approach has been applied to the practical area due to the development of computer technology. Finite Difference Method, one of the most popular numerical methods, is sensitive to the shape and the number of mesh. However, the trial and error approach is conducted to obtain the accurate results and the reasonable simulation time because of the lack of researches about mesh size and the number. In this study, FLAC 3D v3.1 program(FDM) is used to simulate the dynamic pile model tests, and the numerical results are compared with the 1G shaking table tests results. With the different size and shape of mesh, the responses of pile behavior and the simulation time are estimated, and the optimum mesh sizes in dynamic analysis of single pile is studied.

• Geomechanics and Engineering
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• 제7권1호
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• pp.105-131
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• 2014

In this paper, the effects of variability of smear zone characteristics induced by installation of prefabricated vertical drains on the preloading design are investigated employing analytical and numerical approaches. Conventional radial consolidation theory has been adopted to conduct analytical parametric studies considering variations of smear zone permeability and extent. FLAC 2D finite difference software has been employed to conduct the numerical simulations. The finite difference analyses have been verified using three case studies including two embankments and a large-scale laboratory consolidometer with a central geosynthetic vertical drain. A comprehensive numerical parametric study is conducted to investigate the influence of smear zone permeability and extent on the model predictions. Furthermore, the construction of the trial embankment is recommended as a reliable solution to estimate accurate smear zone properties and minimise the post construction settlement. A back-calculation procedure is employed to determine the minimum required waiting time after construction of the trial embankment to predict the smear zone characteristics precisely. Results of this study indicate that the accurate smear zone permeability and extent can be back-calculated when 30% degree of consolidation is obtained after construction of the trial embankment.

• Geomechanics and Engineering
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• 제32권5호
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• pp.523-540
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• 2023

The failure of slope can cause remarkable damage to either human life or infrastructures. Stabilizing piles are widely utilized to reinforce slope as a slip-resistance structure. The workability of pile-stabilized slopes is affected by various parameters. In this study, the performance of earth slope reinforced with piles and the behavior of piles under static load, by shear reduction strength method using the finite difference software (FLAC^3D) has been investigated. Parametric studies were conducted to investigate the role of pile length (L), different pile distances from each other (S/D), pile head conditions (free and fixed head condition), the effect of sand density (loose, medium, and high-density soil) on the pile behavior, and the performance of pile-stabilized slopes. The performance of the stabilized slopes was analyzed by evaluating the factor of safety, lateral displacement and bending moment of piles, and critical slip mechanism. The results depict that as L increased and S/D reduced, the performance of slopes stabilized with pile gets better by raising the soil density. The greater the amount of bending moment at the shallow depths of the pile in the fixed pile head indicates the effect of the inertial force due to the structure on the pile performance.