• Title, Summary, Keyword: orientation of discontinuities

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A Study on the Stability of Underground Structure considering the Orientation and the Stiffness of Discontinuity (불연속면의 경사와 강성을 고려한 지하구조물 안정성에 관한 연구)

  • Lee, Seung-Ho
    • Tunnel and Underground Space
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    • v.7 no.1
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    • pp.65-74
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    • 1997
  • Underground structures show different behaviors depending upon the space and the mechanical characteristics of discontinuities, such as joints, beddings, faults and shear zone. Desingning the rock structeres without considering the significance of these discontinuities can lead to false conclusions. This paper includes study on the following topics; the numerical analysis of continuous rock and discontinuous rock around a tunnel, the influences on shotcrete moment and rock-bolt axial force of tunnel due to different joint orientation and stiffness.

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Orientations of Tecto-lineaments and Discontinuities for Different Rock Types in Andong Area (안동지역의 암종별 선구조선과 불연속면의 방위특성)

  • Kim Gyo-Won;Ihm Myeong-Hyeok
    • The Journal of Engineering Geology
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    • v.16 no.1
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    • pp.23-30
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    • 2006
  • This study was carried out to understand the relationship between orientation of tecto-lineaments obtained from aero-photograph and orientation of discontinuities measured at field for the rock types of igneous, sedimentary and metamorphic rocks in Andong area. Total 847 tecto-lineaments were extracted from the aero-photographs and total 1,940 discontinuities including joints, foliations and faults were measured during geologic survey. By using the software DIPS, preferred trends of tecto-lineaments were deduced as N30E-N40E for igneous rocks and N50E-N60E for both sedimentary and metamorphic rocks, while the trends of discontinuities were found as N40E-N50E for igneous rocks, N50E-N80E for sedimentary rocks and N50E-N60E for meta morphic rocks. Even though both orientations for a given rock type showed relatively good agreement in its trend, some discrepancy is also appeared. Since construction safety of geo-structures such as tunnel and slope, etc., is significantly affected by the orientation of discontinuities in rock masses, it is highly recommended to perform a detailed geologic survey as well as an aero-photograph interpretation at a design stage.

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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    • 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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Sampling Bias of Discontinuity Orientation Measurements for Rock Slope Design in Linear Sampling Technique : A Case Study of Rock Slopes in Western North Carolina (선형 측정 기법에 의해 발생하는 불연속면 방향성의 왜곡 : 서부 North Carolina의 암반 사면에서의 예)

  • 박혁진
    • Journal of the Korean Geotechnical Society
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    • v.16 no.1
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    • pp.145-155
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    • 2000
  • Orientation data of discontinuities are of paramount importance for rock slope stability studies because they control the possibility of unstable conditions or excessive deformation. Most orientation data are collected by using linear sampling techniques, such as borehole fracture mapping and the detailed scanline method (outcrop mapping). However, these data, acquired by the above linear sampling techniques, are subjected to bias, owing to the orientation of the sampling line. Even though a weighting factor is applied to orientation data in order to reduce this bias, the bias will not be significantly reduced when certain sampling orientations are involved. That is, if the linear sampling orientation nearly parallels the discontinuity orientation, most discontinuities orientation data which are parallel to sampling line will be excluded from the survey result. This phenomenon can cause serious misinterpretation of discontinuity orientation data because critical information is omitted. In the case study, orientation data collected by using the borehole fracture mapping method (vertical scanline) were compared to those based on orientation data from the detailed scanline method (horizontal scanline). Differences in results for the two procedures revealed a concern that a representative orientation of discontinuities was not accomplished. Equal-area, polar stereo nets were used to determine the distribution of dip angles and to compare the data distribution fur the borehole method versus those for the scanline method.

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Reliability-Based Analysis for Rock Slopes Considering Failure Modes (파괴형태를 고려한 암반사면의 신뢰도해석)

  • 이인모;이명재
    • Journal of the Korean Geotechnical Society
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    • v.15 no.6
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    • pp.3-16
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    • 1999
  • This paper presents the results of sensitivity analysis based on an example study to verify a newly developed reliability-based model for rock slopes considering uncertainties of discontinuities and failure modes-plane, wedge, and toppling. The parameters that are needed for sensitivity analysis are the variability of discontinuity properties (orientation and strength of discontinuities), the loading conditions, and the rock slope geometry. The variability in orientation and friction angle of discontinuities, which can not be considered in the deterministic analysis, has a great influence on the rock slope stability, The stability of rock slopes including failure modes is more influenced by the selection of dip direction of cutting rock face than any other design variables, The example study shows that the developed reliability-based analysis model can reasonably assess the stability of rock slope.

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A scheme of tunnel design considering rock discontinuities (불연속면을 고려한 터널의 설계 및 보강 방안)

  • 문상조;허도학;장석부
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.231-237
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    • 2001
  • This paper presents some proposed methods for discontinuum analysis with rock discontinuities data acquisited in tunnel design stage. The limit equilibrium method for rock block sliding and falling proposed in this paper can consider the tunnel excavation and support stage, and, to the extent, the standard deviations and means of joint set orientation. Simple Distinct Elemet modelling methods are recommended in estimating the stability of tunnels in jointed rock masses. Because, the simple models are likely to show more consistent and clear than very complex model with finite joint length and joint deviation parameters.

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A Study of Simple Rock Mass Rating for Tunnel Using Multivariate Analysis (다변량분석을 이용한 터널에서의 간편 RMR에 관한 연구)

  • 위용곤;노상림;윤지선
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.493-500
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    • 2000
  • Rock Mass Rating has been widely applied to the underground tunnel excavation and many other practical problems in rock engineering. However, Rock Mass Rating is hard to make out because it is difficult to estimate each valuation items through all kind of field situations and items of RMR have interdependence. So the experts of tunnel assessment have problems with rating rock mass. In this study, using multivariate analysis based on domestic data(1011EA) of water conveyance tunnel, we presented rock mass rating system which is objective and easy to use. The constituents of RMR are decided to RQD, condition of discontinuities, groundwater conditions, orientation of discontinuities, intact rock strength, spacing of discontinuities in important order. In each step, we proposed the best multiple regression model for RMR system. And using data which have been collected at other site, we examined that presented multiple regression model was useful.

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An investigation into the effects of voids, inclusions and minor cracks on major crack propagation by using XFEM

  • Jiang, Shouyan;Du, Chengbin;Gu, Chongshi
    • Structural Engineering and Mechanics
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    • v.49 no.5
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    • pp.597-618
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    • 2014
  • For the structures containing multiple discontinuities (voids, inclusions, and cracks), the simulation technologies in the framework of extended finite element method (XFEM) are discussed in details. The level set method is used for representing the location of inner discontinuous interfaces so that the mesh does not need to align with these discontinuities. Several illustrations have been given to verify that the implemented XFEM program is effective. Then, the implemented XFEM program is used to investigate the effects of the voids, inclusions, and minor cracks on the path of major crack propagation. For a plate containing cracks and voids, two possibly crack path can be observed: i) the crack propagates into the void; ii) the crack initially curves towards the void, then, the crack reorients itself and propagates along its original orientation. For a plate with a soft inclusion, the final predicted crack paths tend to close with the inclusion, and an evident difference of crack paths can be observed with different inclusion material properties. However, for a plate with a hard inclusion, the paths tend to away from the inclusion, and a slightly difference of crack paths can only be seen with different inclusion material properties. For a plate with several minor cracks, the trend of crack paths can still be described as that the crack initially curves towards these minor cracks, and then, the crack reorients itself and propagates almost horizontally along its original orientation.

A Study of Efficient Rock Mass Rating for Tunnel Using Multivariate Analysis (다변량분석을 이용한 터널에서의 효율적인 암반분류에 관한 연구)

  • Wye, Yong-Gon;No, Sang-Lim;Yoon, Ji-Son
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.2 no.2
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    • pp.41-49
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    • 2000
  • Rock Mass Rating has been widely applied to the underground tunnel excavation and many other practical problems in rock engineering. However, Rock Mass Rating is hard, even by the experts of tunnel assessment owing to lack of investigation system. In this study, using multivariate analysis we presented rock mass rating system that is objective and easy to use. The constituents of RMR are decided to RQD, condition of discontinuities, groundwater conditions, intact rock strength, orientation of discontinuities, spacing of discontinuities in important order. In each step, we proposed the best multiple regression model for RMR system.

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A Study fo rthe determination of optimum cutangle for the heavily jointed rock slope (절리가 심하게 발달된 암반사면의 최적 절취각 고찰)

  • 홍예성;조태진;한공창
    • Tunnel and Underground Space
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    • v.6 no.2
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    • pp.166-174
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    • 1996
  • Stability of rock slope is greatly affected by the geometry and strength of discontinuities developed in the rock mass. In this study an analytical method which is capable of analyzing the effect of relative orientation between the discontinuities and the slope face on the safety of slope by assessing their vector components was used to evaluate the stability and the maximum cut-angle for the proposed slope design. The results of computerized vector analysis revealed that slope area under investigation might be divided into 3 sections of different face directions. The safety factors for benches in each 3 sections were calculated using the limit-equilibrium theory. Then, by utilizing the concept of probabilistic risk analysis, the susceptibility of entire slope failure was estimated. Based on the distribution of safety factor in each bench, the maximum cut angle of each section could be selected differently ot achieve the permanent stability of the entire slope.

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