• Title/Summary/Keyword: Rock discontinuity

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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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A study on the determination of shear strength and the support design of pre-failed rock slope (일차파괴된 암반사면의 전단강도 및 보강설계법 고찰)

  • 조태진;김영호
    • Tunnel and Underground Space
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    • v.5 no.2
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    • pp.104-113
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    • 1995
  • Shear strength of the discontinuity on which the pre-failure of rock slope was occurred during surface excavation was measured through the direct shear test using core samples obtained in-situ. Internal friction angle was increased as the roughness of discontinuity surface(JRC) was increased. Results of the tilt test using core samples of higher JRC also showed very similar trend as those of the direct shear test. When the samples replicated from natural cores were used int he tilt test, results of friction angles showed almost perfect continuation of the residual friction angles from the direct shear test. However, when the gouge material existed in the discontinuity the internal friction angle strongly depended upon the rate of filling thickness to the height of asperity irrespective of the JRC. Based on the results of both direct shear test and tilt test internal friction angle and cohesion of discontinuity, which reflect the in-situ conditions fo pre-sliding failure and also can be used for the optimum design of support system, were assessed. Two kinds of support measures which were expected to increase the stability of rock slope were considered; lowering of slope face angle and installation of rock cable. But, it was found that the first method might lead to more unstable conditions of rock slope when the cohesion of discontinuity plane was negligibly low and in that case the support systems of any kind which could exert actual resisting force were needed to ensure the permanent stability of rock slope.

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Rock Joint Trace Detection Using Image Processing Technique (영상 처리를 이용한 암석 절리 궤적의 추적)

  • 이효석;김재동;김동현
    • Tunnel and Underground Space
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    • v.13 no.5
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    • pp.373-388
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    • 2003
  • The investigation on the rock discontinuity geometry has been usually undergone by direct measurement on the rock exposures. But this sort of field work has disadvantages, which we, for example, restriction of surveying areas and consuming excessive times and labors. To cover these kinds of disadvantages, image processing could be regarded as an altemative way, with additional advantages such as automatic and objective tools when used under adequate computerized algorithm. This study was focused on the recognition of the rock discontinuities captured in the image of rock exposure by digital camera and the production of the discontinuity map automatically. The whole process was written using macro commands builtin image analyzer, ImagePro Plus. ver 4.1(Media Cybernetic). The procedure of image processing developed in this research could be divided with three steps, which are enhancement, recognition and extraction of discontinuity traces from the digital image. Enhancement contains combining and applying several filters to remove and relieve various types of noises from the image of rock surface. For the next step, recognition of discontinuity traces was executed. It used local topographic features characterized by the differences of gray scales between discontinuity and rock. Such segments of discontinuity traces extracted from the image were reformulated using an algorithm of computer decision-making criteria and linked to form complete discontinuity traces. To verify the image processing algorithms and their sequences developed in this research, discontinuity traces digitally photographed on the rock slope were analyzed. The result showed about 75~80% of discontinuities could be detected. It is thought to be necessary that the algorithms and computer codes developed in this research need to be advanced further especially in combining digital filters to produce images to be more acceptable for extraction of discontinuity traces and setting seed pixels automatically when linking trace segments to make a complete discontinuity trace.

Evaluation of Rock Discontinuity Roughness Anisotropy based on Digital 3D Point Cloud Data (디지털 3차원 점군데이터 기반 암반 불연속면 거칠기 이방성 평가)

  • Taehyeon Kim;Kwang Yeom Kim
    • Tunnel and Underground Space
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    • v.33 no.6
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    • pp.495-507
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    • 2023
  • The roughness of discontinuity significantly influences the mechanical characteristics of rock masses and extensively affects thermal and hydraulic behaviors. In this study, we utilized photogrammetry to generate 3D point cloud data for discontinuity and applied this data to characterize the roughness of discontinuity. The discontinuity profiles, reconstructed from the 3D point cloud data, were compared with those manually measured using a profile gauge. This comparison served to validate the accuracy and reliability of the acquired point cloud data in replicating the actual configurations of rock surfaces. Subsequent to this validation, influence of the number of profiles for representative JRC assessment was further investigated followed by suggestion of roughness anisotropy evaluation method with application of it to actual rock discontinuity surfaces.

Parameter Effect on Elastic Modulus of Discontinuity Rock-mass Based on Homogenization Method (균질화 이론에 근거한 불연속성 암반의 탄성계수에 영향을 미치는 불연속면의 조사 인자에 관한 연구)

  • Baek, Yong
    • Journal of the Korean Geotechnical Society
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    • v.16 no.4
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    • pp.63-70
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    • 2000
  • The quantitative analyses and the mechanical interpretation of discontinuity planes are the most important factor for the study of strength and deformation properties of rock masses containing discontinuity planes. However, the relationship between the factors investigated in the field and the actual mechanical properties of discontinuity planes is not fully understood. The main purpose of this study is to investigate the effects of density, length, and spacing of joints on elastic modulus of rock masses as these values vary. A new parameter which has a direct relation with the elastic modulus of discontinuity planes is also preposed in this study. The combination of finite element methods and homogenization methods has been used for the numerical analyses of a uintcell with discontinuity planes, which is generated using random-number generation methods. The elastic modulus of the discontinuity plane is found from the numerical analyses. The final results propose not only the relation between the investigation parameters of discontinuity planes and the elastic modulus of rock masses but also a new parameter, an effect area ratio having a linear relation with the elastic modulus of rock masses.

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Characterization of Discontinuity Orientation based on Direction of Excavation (굴착방향에 따른 불연속면 방위각의 특성화)

  • Ro, Byung-Don;Han, Byeung-Hyun
    • Proceedings of the KSR Conference
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    • 2007.05a
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    • pp.1861-1863
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    • 2007
  • In rock mass, great many discontinuity exists that is caused to various factors of formation. But these are parted to some groups by specific category, so called these as discontinuity set. This discontinuity set has unique special characteristics in original rock mass, but for the moment, differ the special quality if external force such as digging etc. acts, specially, change of stress condition. Also, geometrical relation change between discontinuity orientation and direction of excavation various characteristic is seen. Therefore, we introduce here the useful chart that can do specification these relation.

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Estimation of Discontinuity Orientations in Excavation Faces (굴착면에서의 분리면방향성 평가)

  • Ro, Byung-Don;Han, Byeong-Hyeon
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.1484-1489
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    • 2005
  • An inhomogeneous and anisotropic rock has different properties at different location. Thus, this refers to any of the properties which we may be measuring. There are two concepts of rock mass, namely, CHILE(Continuous, Homogeneous, Isotropic, Linear Elastic) material and DIANE(Discontinuous, Inhomogeneous, Anisotropic, Non-linear Elastic) rock. The former is essentially the properties of intact rock, the latter is essentially the properties governed by the structure of rock. In geotechnical aspect, the most important parameter is strength of rock or rock mass. In particular, characteristics of strength of rock mass depend upon the orientation of discontinuities And this orientation of discontinuities has different properties at different direction of excavation. Therefore, it needs for characterization of different properties of discontinuity orientation against different direction of excavation.

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Deterioration State and Behavior of Discontinuity System of the Seosan Maaesamjonbulsang (Rock-carved Triad Buddha in Seosan), Korea (서산 마애삼존불상의 훼손상태 및 불연속면의 거동특성)

  • Lee, Sun-Myung;Lee, Chan-Hee;Choi, Seok-Won;Yun, Seok-Bong
    • Journal of Conservation Science
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    • v.19
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    • pp.85-98
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    • 2006
  • Rock property of the Seosan Maaesamjonbulsang is composed of biotite granite with medium grained texture. The triad Buddha is highly deteriorated by the joint, fracture, break-out, exfoliation, dew condensation of the surface and discoloration of the secondary pollutant. Host rock of the triad Buddha is divided dozens of rock blocks with various shape, and developed irregular discontinuity planes. Besides, the host rock is promoted biological pollution due to the surrounding crowded vegetation and high humidity environment. As the results of structural stability, it is confirmed that developed discontinuity system in the host rock is exposed instability sloping environment. Therefore, the host rock and surroundings are required maintenance, and required preservation by continuance monitoring for understand behavior of discontinuity system.

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Groundwaterflow analysis of discontinuous rock mass with probabilistic approach (통계적 접근법에 의한 불연속암반의 지하수 유동해석)

  • 장현익;장근무;이정인
    • Tunnel and Underground Space
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    • v.6 no.1
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    • pp.30-38
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    • 1996
  • A two dimensional analysis program for groundwater flow in fractured network was developed to analyze the influence of discontinuity characteristics on groundwater flow. This program involves the generation of discontinuities and also connectivity analysis. The discontinuities were generated by the probabilistic density function(P.D.F.) reflecting the characteristics of discontinuities. And the fracture network model was completed through the connectivity analysis. This program also involves the analysis of groundwater flow through the discontinuity network. The result of numerical experiment shows that the equivalent hydraulic conductivity increased and became closer to isotropic as the density and trace length increased. And hydraulic head decreased along the fracture zone because of much water-flow. The grouting increased the groundwater head around cavern. An analysis of groundwater flow through discontinuity network was performed around underground oil storage cavern which is now under construction. The probabilistic density functions(P.D.F) were obtained from the investigation of the discontinuity trace map. When the anisotropic hydraulic conductivity is used, the flow rate into the cavern was below the acceptable value to maintain the hydraulic containment. But when the isotropic hydraulic conductivity is used, the flow rate was above the acceptable value.

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The Application of Genetic Algorithm for the Identification of Discontinuity Sets (불연속면 군 분류를 위한 유전자알고리즘의 응용)

  • Sunwoo Choon;Jung Yong-Bok
    • Tunnel and Underground Space
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    • v.15 no.1 s.54
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    • pp.47-54
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    • 2005
  • One of the standard procedures of discontinuity survey is the joint set identification from the population of field orientation data. Discontinuity set identification is fundamental to rock engineering tasks such as rock mass classification, discrete element analysis, key block analysis. and discrete fracture network modeling. Conventionally, manual method using contour plot had been widely used for this task, but this method has some short-comings such as yielding subjective identification results, manual operations, and so on. In this study, the method of discontinuity set identification using genetic algorithm was introduced, but slightly modified to handle the orientation data. Finally, based on the genetic algorithm, we developed a FORTRAN program, Genetic Algorithm based Clustering(GAC) and applied it to two different discontinuity data sets. Genetic Algorithm based Clustering(GAC) was proved to be a fast and efficient method for the discontinuity set identification task. In addition, fitness function based on variance showed more efficient performance in finding the optimal number of clusters when compared with Davis - Bouldin index.