• Title, Summary, Keyword: 불연속 변형해석법

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내접구를 이용한 3차원 불연속 변형해석의 접촉문제 연구

  • An, Tae-Yeong;Song, Jae-Jun
    • Proceedings of the Korean Society for Rock Mechanics Conference
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    • pp.153-159
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    • 2009
  • 불연속변형해석(DDA)은 유한요소법(FEM)과 개별요소법(DEM)의 장점을 모두 가지고 있는 해석법이다. 3차원 불연속변형해석의 안정성과 해석속도는 접촉찾기(Contact Detection) 알고리즘과 벌칙스프링(Penalty spring)을 이용한 접촉처리 알고리즘에 의해 크게 좌우되는데, 블록의 꼭지점(vertex) 간의 접촉이 발생할 경우, 적합한 접촉면을 결정하는 과정에서 많은 해석오류와 시간적 손실이 발생할 가능성이 있다. 본 연구에서는 블록의 꼭지점에 내접하는 구(inscribed sphere)를 삽입하여 가상의 접촉점과 접촉면을 생성하는 알고리즘을 연구하였다. 이로 인해 발생할 수 있는 해석의 오차의 크기를 확인하고, 간단한 불연속 변형해석의 해석 실례에 적용해 보았다.

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Rockfall and Toppling Failure Simulation of Rock Slopes using 3-Dimensional Discontinuous Deformation Analysis (3차원 불연속변형해석법을 이용한 암반사면의 낙석과 전도 파괴 시뮬레이션)

  • Hwang, Jae-Yun;Ohnishi, Yuzo
    • 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.

Application of New Edge-to-Edge Contact Algorithm to Discontinuous Deformation Analysis (불연속 변형해석에서의 새로운 선-선 접촉 해석 적용)

  • Lee Chung-In;Moon Young-Sam;Choi Yong-Keun;Ahn Tae-Young
    • Tunnel and Underground Space
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    • v.15 no.4
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    • pp.305-315
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    • 2005
  • DDA (Discontinuous Deformation Anlaysis) is one of the latest numerical analysis which has merits of both FEM and DEM. In this research a new edge-to-edge contact algorithm was applied on DDA. With adoption of new edge-to-edge contact state definition, sub-algorithm was improved about open-close iteration, contact state judge, contact detecting, and friction forces acting on joints. Newly applied DDA was verified based on two different cases. The DDA results show good agreement with numerically predicted one.

Modeling the Water-Block Interaction with Discontinuous Deformation Analysis Method (불연속 변형 해석법에 의한 지하수-암반블록 상호작용 모델링)

  • 김용일
    • 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.

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Modeling the Effect of Excavation Sequence and Reinforcement on the Response of Tunnels with Discontinuous Deformation Analysis Method (불연속 변형 해석법에 의한 굴착순서 및 지반보강이 터널의 거동에 미치는 영향 모델링)

  • 김용일;김영근
    • Tunnel and Underground Space
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    • v.10 no.1
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    • pp.25-32
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    • 2000
  • This paper presents two new extensions to the DDA method. The extensions consist of sequential loading or unloading and rock reinforcement by rockbolts, shotcrete or concrete lining. Examples of application of the DDA method with the new extensions are presented. Simulations of the underground excavation of the Unju Tunnel of Kyungbu High Speed Railway Project in Korea were carried out to evaluate the influence of excavation sequence and reinforcement on the tunnel stability. The results of the present study indicate that improper selection of excavation sequence could have a destabilizing effect on the tunnel stability. On the other hand, reinforcement by rockbolts and shotcrete can stabilize the tunnel. It is found that, in general, the DDA program with the three new extensions can now be used as d practical tool in the design of underground structures. In particular, phases of construction (excavation, reinforcement) can now be simulated more realistically.

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Implementation of semi-infinite boundary condition for dynamic finite element analysis (동적 유한요소해석에서의 반무한 경계조건의 실행)

  • Choi, Chang-Ho;Chung, Ha-Ik
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.600-606
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    • 2006
  • 실제 지반은 경계가 없는 무한상태로 존재하기 때문에 지반구조물의 동적거동을 유한요소법을 이용하여 해석할 시 모델의 영역을 성립하는 것은 특별한 고려가 필요하다. 유한요소법에서의 동적해석은 파동의 전달을 포함하기 때문에 모델의 경계에서 인공적인 경계조건이 필요하다. 인공적인 경계 조건은 유한요소내의 지반상태를 무한상태로 변형시킬 수 있어야 하며, 경계에 도달하는 응력 파동을 모델내로 반사시키지 않고 흡수 할 수 있어야 한다. 본 논문에서는 간단한 점 탄성 반무한 불연속 요소를 이용하여 지반구조물의 동적해석을 수행하는 방법을 보여준다. 반무한 요소의 실행은 OpenSees라는 유한요소 해석프로그램을 이용하여 수행되었으며, 예를 통하여 불연속 요소가 경계에 도달하는 응력 파동을 충분히 흡수하여 유한요소 모델을 반무한 상태로 전환 시킬 수 있다는 것을 보여준다.

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Deformation Analysis of Soft Foundation with Vertical Drain Wells using the Interface Element Method -With Emphasis on Model Foundation and Actual Sand Drain Well Foundation- (접합요소에 의한 Vertical Drain Well 지반의 변형해석 - 모델지반과 실제 Sand Drain Well 지반을 중심으로 -)

  • Lee, Jean Soo
    • Journal of The Korean Society of Civil Engineers
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    • v.13 no.4
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    • pp.227-237
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    • 1993
  • This paper dealt with numerical analysis of sand drain considering the smear effect around drain wells and discontinuous deformation behavior due to difference in rigidity between drain materials and adjacent clayey soils. Biot's equation was selected as governing equation coupled with MODCAM (Modified Cam-clay) model or EVP(Elasto-Viscoplastic) model as constitutive equation. The validity as well as the accuracy of the method developed by author was checked by comparing the proposed method with those by Siriwardane and Ghaboussi using joint element. The FEM analysis developed in this study was applied to both 2-dimensional model foundation and actual foundation. the result of which proved to be satisfactory.

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The Effect of Cement Milk Grouting on the Deformation Behavior of Jointed Rock Mass (시멘트현탁액 주입에 의한 절리암반의 역학적 특성 변화)

  • 김태혁;이정인
    • Tunnel and Underground Space
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    • v.13 no.5
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    • pp.331-343
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    • 2003
  • Though the Grouting has been in use for a long time, it is still regarded as an technique rather than engineering. The study of ground improvement by grouting is rare especially in jointed rock mass. In this study, biaxial compression tests were performed in the jointed rock mass models with .ough surfBce joints assembled with blocks before and after grouting. The load-deformation curves of the jointed rock masses showed a non-linear relationship before grouting but showed a relatively linear deformaion behavior after grouting. Improvement ratio (deformation modulus after grouting/deformation modulus before grouting) decreased with increasing joint spacing and lateral stress. Improvement ratio decreased exponentially with increasing deformation modulus of the rock mass model before grouting. Three-dimensional FDM analysis was performed to a highway tunnel case using experimental data of grouted rock. The convergence of the tunnel predicted after grouting by the numerical modelling coincided with those attained from the field measurement.

Modeling the Effect of Geology on Uplift in Concrete Gravity Dam Foundations with the Discontinuous Deformation Analysis (불연속 변형 해석을 통한 콘크리트 중력댐 기초에 작용하는 부양력에 대한 지질구조의 영향 모델링)

  • Kim, Yong-Il
    • Tunnel and Underground Space
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    • v.13 no.4
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    • pp.304-315
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    • 2003
  • In this paper, the DDA method with a new hydro-mechanical algorithm is used to study the effect of rock discontinuities on uplift and seepage in concrete gravity dam foundations. This paper presents an alternative method of predicting uplift and seepage at the base of concrete gravity dams. A sensitivity analysis was carried out to study the importance of several parameters on dam stability such as the orientation, spacing, and location of discontinuities. The study shows that joint water flow and adverse geological conditions could result in unusual uplift at the base of concrete gravity dams, well in excess of what is predicted with the classical linear or hi-linear pressure assumption. It is shown that, in general, the DDA program with the hydro-mechanical algorithm can be used as a practical tool in the design of gravity dams built on fractured rock masses.

Estimation of Strength and Deformation Modulus of the 3-D DFN System Using the Distinct Element Method (개별요소법을 이용한 삼차원 DFN 시스템의 강도 및 변형계수 추정)

  • Ryu, Seongjin;Um, Jeong-Gi;Park, Jinyong
    • Tunnel and Underground Space
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    • v.30 no.1
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    • pp.15-28
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    • 2020
  • In this study, a procedure was introduced to estimate strength and deformation modulus of the 3-D discrete fracture network(DFN) systems using the distinct element method(DEM). Fracture entities were treated as non-persistent square planes in the DFN systems. Systematically generated fictitious fractures having similar mechanical characteristics of intact rock were combined with non-persistent real fractures to create polyhedral blocks in the analysis domain. Strength and deformation modulus for 10 m cube domain of various deterministic and stochastic 3-D DFN systems were estimated using the DEM to explore the applicability of suggested method and to examine the effect of fracture geometry on strength and deformability of DFN systems. The suggested procedures were found to effective in estimating anisotropic strength and deformability of the 3-D DFN systems.