• Title/Summary/Keyword: Rock block

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Characterization of the Spatial Distribution of Fracture System at the Rock Block Scale in the Granitic Area (화강암지역의 암반블록규모 단열체계 분포특성 연구)

  • 김경수;배대석;김천수
    • Tunnel and Underground Space
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    • v.12 no.3
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    • pp.198-209
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    • 2002
  • To assess deep geological environment for the research and development of hish-level radioactive waste disposal, six boreholes of 3" in diameter were installed in two granitic areas. An areal extent of the rock block scale in the study sites was estimated by the lineament analysis from satellite images and shaded relief maps. The characterization of fracture system developed in rock block scale was carried out based on the acoustic televiewer logging in deep boreholes. In the Yuseong site, the granite rock mass was divided into the upper and lower zones at around -160m based on the probabilistic distribution characteristics of the geometric parameters such as orientation, fracture frequency, spacing and aperture size. Since the groundwater flow is dependent on the fracture system in a fractured rock mass, the correlation of the fracture frequency and cumulative aperture size to the hydraulic conductivity was also discussed.

Estimating and Analyzing the Appropriate Pressing Force of the Rock Cutting Splitting Method (암반 커팅 스플리팅 공법의 적정 압입력 추산을 위한 분석해)

  • Lee, Sang-Min;Kim, Mun-Gyu;Cho, Jung-Woo;Yu, Sang-Hwa
    • Tunnel and Underground Space
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    • v.31 no.6
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    • pp.415-427
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    • 2021
  • This technical report briefly introduced the rock cutting splitting method under development. This method is a method of excavating the rock by splitting the block after the rock cutting process. After designing the cutting geometry of the rock face, the chisel is press-fitted to remove the rock block. At this time, when the cutting block is properly designed, the tensile crack propagates smoothly at the bottom of the rock block. An analytical solution was devised to estimate the indentation force required for splitting rock blocks using fracture toughness mode 1 required for tensile crack growth. The impact force of the hydraulic breaker of the excavator was analyzed, and the grade of the excavator that can be constructed according to the rock block design geometry was analyzed.

Analysis of Rock Masses and Rock Supports by Rigid Block Method (강성블록법에 의한 지반 및 지보재 해석)

  • 김문겸;황학주;엄인수;허택녕
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1991.04a
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    • pp.84-90
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    • 1991
  • Underground structures usually consist of rock masses or concretes which can be cracked or have cracks. This study aims to develop an analysis program which can deal with the effect of discontinuous behavior due to those cracks using the block theory. It is assumed that rock masses form blocks along the discontinuity lines, and deformation within the block is relatively small. The behavior of discontinuity plane of the structures is divided into sliding along the discontinuity plane. separation of discontinuity by tensile force, and degradation of asperity angle of discontinuity plane by external force with sliding of rock Basses. These behaviors are implemented using constitutive relation and relevent load-displacement relation defined through normal and shear stiffnesses. Time varying displacements and block velocities are calculated by explicit time stepping algorithm. The effect of rock supports including rockbolts is also considered, and the tending effects which occurs in relatively thin lining is also considered.

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New hybrid stochastic-deterministic rock block analysis method in tunnels (터널의 신 하이브리드 추계학적-확정론적 암반블럭 해석기법)

  • Hwang, Jae-Yun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.12 no.3
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    • pp.265-274
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    • 2010
  • In many tunnels, falling or sliding of rock blocks often occur, which cannot be predicted because of the complexity of rock discontinuities and it has brought an exponential increase in costs and time to manage. It is difficult to estimate the properties of rock masses before the tunnel excavation. The observational design and construction method in tunnels has been becoming important recently. In this study, a new hybrid stochastic-deterministic rock block analysis method for the prediction of the unstable rock blocks before the tunnel excavation is proposed, and then applied to the tunnel construction based on actual rock discontinuity information observed in the field. The comparisons and investigations with the analytical results in the tunnel construction have confirmed the validity and applicability of this new hybrid stochastic-deterministic rock block analysis method in tunnels.

New Observational Design and Construction Method for Rock Block Evaluation of Tunnels in Discontinuous Rock Masses (불연속성 암반에서의 터널의 암반블럭 평가를 위한 신 정보화설계시공법)

  • Hwang Jae-Yun
    • Tunnel and Underground Space
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    • v.16 no.1 s.60
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    • pp.1-10
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    • 2006
  • Rock masses in nature include various rock discontinuities such as faults, joints, bedding planes, fractures, cracks, schistosities, and cleavages. The behavior of rock structures, therefore, is mainly controlled by various rock discontinuities. In many tunnels, enormous cost and time are consumed to cope with the failing or sliding of rock blocks, which cannot be predicted because of the complexity of rock discontinuities. It is difficult to estimate the properties of rock masses before the rock excavation. The observational design and construction method of tunnels in rock masses is becoming important recently. In this paper, a new observational design and construction method for rock block evaluation of tunnels in discontinuous rock masses is proposed, and then applied to the tunnel based on actual rock discontinuity information observed in the field. It is possible to detect key blocks all along the tunnel exactly by using the numerical analysis program developed far the new observational design and construction method. This computer simulation method with user-friendly interfaces can calculate not only the stability of rock blocks but also the design of supplementary supports. The effectiveness of the proposed observational design and construction method has been verified by the confirmation of key block during the enlargement excavation.

Fast Analysis of Rock Block Behavior on Underground Opening considering Geostatic Stress Conditions (지체응력조건을 고려한 지하공동 주변부 암석블록의 신속한 거동 안정성 분석)

  • Kang, Il-Seok;Song, Jae-Joon
    • Tunnel and Underground Space
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    • v.29 no.1
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    • pp.64-74
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    • 2019
  • Behavior of a rock block consisting of rock joints during excavation of an underground opening is an important factor for the mechanical stability of the opening. In this study, the behavior of a rock block under different geostatic stress and joint property conditions was analyzed quantitatively. The behavior of the rock block analyzed by 3DEC numerical analysis was compared with that of the theoretical calculation, and the error between the theoretical value and the numerical analysis result was analyzed under various geostatic stress and joint property conditions. The result of the stability analysis of a rock block showed less than 5% of error with numerical simulation result, which verified the applicability of the purposed analytic solution.

A Case Study on Joint System Simulation Results Application to Rock Slope Design (절리계 모사결과의 암반사면설계 적용 사례)

  • Kim, Dong-Hee;Jung, Hyuk-Il;Kim, Seouk-Ki
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.10a
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    • pp.669-680
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    • 2005
  • It is very difficult to determine the failure block scale in great rock slopes. Especially, postulating entire slope domain as a failure block without attention to discontinuity trace lenth makes very confuse and difficult to design rock slopes. In this paper, we estimate realistic failure block scale using joint system simulation method and introduce the application procedures on rock slope analysis. Besides, presenting how joint characteristics measurement and statistical analysis results are applicated to slope stability analysis design flow.

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Stability Analysis of Discontinuous Rock by the Block Theory (블록이론에 의한 불연속성 암반내 터널의 안정성 해석)

  • 양형식
    • Tunnel and Underground Space
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    • v.1
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    • pp.66-74
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    • 1991
  • The block theory with stereographic projection was applied and analyzed on the tunnel section of Samcheok Coal Mine. The results were as follows ; 1) Prevail orientations of discontinuity of sandstone around the main driftway of Samcheok Coal Mine were $(327^{\circ},\;44^{\circ}),\;(13^{\circ},\;24^{\circ}),\;(204^{\circ},\;65^{\circ})$ and $(225^{\circ},\;77^{\circ})$ in dip and dip direction, respectively. 2) Movable blocks of the site were 0110, 0111, 1110(roof), 0100, 0110, 1110(right wall) and 0001, 1001, 1011(left wall). Because of the direction of tunnel, blocks of the left wall was safe. thus key blocks were those of the roof and the right wall. Maximum height of key block was larger than the width of the tunnel but 2m of the yielded zone is expected in general for 5m width tunnel. 3) It is shown that block theory is applicable to large cavern in hard rock analysis.

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Characteristics of Block Hydraulic Conductivity of 2-D DFN System According to Block Size and Fracture Geometry (블록크기 및 균열의 기하학적 속성에 따른 2-D DFN 시스템의 블록수리전도도 특성)

  • Han, Jisu;Um, Jeong-Gi
    • Tunnel and Underground Space
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    • v.25 no.5
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    • pp.450-461
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    • 2015
  • Extensive numerical experiments have been carried out to investigate effect of block size and fracture geometry on hydraulic characteristics of fractured rock masses based on connected pipe flow in DFN systems. Using two fracture sets, a total of 72 2-D fracture configurations were generated with different combinations of fracture size distribution and deterministic fracture density. The directional block conductivity including the theoretical block conductivity, principal conductivity tensor and average block conductivity for each generated fracture network system were calculated using the 2-D equivalent pipe network method. There exist significant effects of block size, orientation, density and size of fractures in a fractured rock mass on its hydraulic behavior. We have been further verified that it is more difficult to reach the REV size for the fluid flow network with decreasing intersection angle of two fracture sets, fracture plane density and fracture size distribution.