• Title/Summary/Keyword: Discontinuity in rock-mass

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Prediction and Evaluation of Rock Mass Condition by Seismic Profiling Method in Tunnel (터널내 탄성파 탐사를 이용한 전방 지질 예측 및 평가)

  • Lee, Jong-Man;Kwak, Hyun-Joon;Kim, Young-Geun;Baek, Ki-Hyun;Cho, Chul-Hyun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.3 no.3
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    • pp.45-56
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    • 2001
  • It is very important to survey in construction for acquiring informations about geological structure which influence the tunnel construction. Usually, TSP(Tunnel Seismic Prediction) one of the seismic survey method in tunnels in Korea has been used for prediction of geological condition ahead of tunnel face, but in this study HSP(Horizontal Seismic Profiling) was used. As a result of field application, we predicted that there exist rock discontinuity such as fault, joints and bedding planes. In addition, RMR value from rock mass evaluation coincided with that from seismic survey for rock condition. We compared with rock classifications and evaluation results for proving.

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A Study on the Roughness Measurement for Joints in Rock Mass Using LIDAR (LIDAR를 이용한 암반 절리면의 거칠기 측정에 관한 연구)

  • Lee, Sudeuk;Jeon, Seokwon
    • Tunnel and Underground Space
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    • v.27 no.1
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    • pp.58-68
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    • 2017
  • According to the development of optical technology, the capacity of LIDAR equipments has been greatly improved to get rock mass characteristics precisely and accurately enough and it has been lightened and popularized so that it can be easily used in the field. In this study, we examined the applicability of roughness measurement for joints in a rock slope using LIDAR technique. A triangular irregular network was constructed using LIDAR and a patch, which is a plane structure of discontinuity on rock mass measured from LIDAR scanning, was extracted to estimate the roughness of the rock slope. Four different kinds of roughness parameters were analyzed to find out their correlation with JRC for various point intervals. Among them, $R_s$ parameter was used to measure the roughness of a patch. Regression analysis between four roughness parameters and JRC with respect to point interval was performed. All the roughness parameters decreased with the increase of point interval. In addition, the parameter value showed greater decrease for rougher surfaces. A method of roughness measurement using $R_s$ parameter on rock slope discontinuities was suggested which showed slight overestimation of the real roughness value.

Validation of 3D discrete fracture network model focusing on areal sampling methods-a case study on the powerhouse cavern of Rudbar Lorestan pumped storage power plant, Iran

  • Bandpey, Abbas Kamali;Shahriar, Kourush;Sharifzadeh, Mostafa;Marefvand, Parviz
    • Geomechanics and Engineering
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    • v.16 no.1
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    • pp.21-34
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    • 2018
  • Discontinuities considerably affect the mechanical and hydraulic properties of rock mass. These properties of the rock mass are influenced by the geometry of the discontinuities to a great extent. This paper aims to render an account of the geometrical parameters of several discontinuity sets related to the surrounding rock mass of Rudbar Lorestan Pumped Storage Power Plant powerhouse cavern making use of the linear and areal (circular and rectangular) sampling methods. Taking into consideration quite a large quantity of scanline and the window samplings used in this research, it was realized that the areal sampling methods are more time consuming and cost-effective than the linear methods. Having corrected the biases of the geometrical properties of the discontinuities, density (areal and volumetric) as well as the linear, areal and volumetric intensity accompanied by the other properties related to four sets of discontinuities were computed. There is an acceptable difference among the mean trace lengths measured using two linear and areal methods for the two joint sets. A 3D discrete fracture network generation code (3DFAM) has been developed to model the fracture network based on the mapped data. The code has been validated on the basis of numerous geometrical characteristics computed by use of the linear, areal sampling methods and volumetric method. Results of the linear sampling method have significant variations. So, the areal and volumetric methods are more efficient than the linear method and they are more appropriate for validation of 3D DFN (Discrete Fracture Network) codes.

Fuzzy Clustering Method for the Identification of Joint Sets (절리군 분석을 위한 퍼지 클러스터링 기법)

  • 정용복;전석원
    • Tunnel and Underground Space
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    • v.13 no.4
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    • pp.294-303
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    • 2003
  • The structural behaviour of rock mass structure, such as tunnel or slope is critically dependent on the various characteristics of discontinuities. Therefore, it is important to survey and analyze discontinuities correctly for the design and construction of rock mass structure. One inevitable Procedure of discontinuity survey and analysis is joint set identification from a lot of raw directional joint data. The identification procedure is generally done by a graphical method. This type of analysis has some shortcomings such as subjective identification results, inability to use extra information on discontinuity, and so on. In this study, a computer program for joint set identification based on the fuzzy clustering algorithm was implemented and tested using two kinds of joint data. It was confirmed that fuzzy clustering method is effective and valid for joint set identification and estimation of mean direction and degree of clustering of huge joint data through the applications.

Load Transfer Characteristics of Rock-Socketed Drilled Shafts Considering Hole Roughness (굴착면 거칠기를 고려한 암반 근입 현장타설말뚝의 주면하중전이 특성)

  • Seol, Hoon-Il;Jeong, Sang-Seom;Woo, Sang-Yoon
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.494-505
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    • 2006
  • In this study, using constant normal stiffness(CNS) direct shear tests, side shear load distribution were analyzed by the influencing parameters of unconfined compressive strength, surface roughness, confining stress, and material properties. Based on the CNS tests, side shear load transfer function of drilled shafts in rock is proposed using geological strength index(GSI), which indicates discontinuity and surface condition of rock mass in Hoek-Brown criterion. Though comparisons with results of nine drilled shafts's load tests, it is found that the load-transfer curve by this study is in good agreement with the general trend observed by in situ measurements, and thus represents a significant improvement in the prediction of bearing capacity of drilled shaft.

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Effective Measuring Method of Discontinuity Orientation (불연속면 방향의 효율적인 측정 방안)

  • 김해경;고영구
    • The Journal of Engineering Geology
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    • v.13 no.3
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    • pp.321-334
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    • 2003
  • This study is aimed at the effective measurement plan of discontinuity orientation on rock mass. The discontinuity orientation is expressed as three methods. strike/dip. dipdirection/dip (a three digit number / a two digit number) and right hand rule. Generally, strike/dip is measured with clinometer. and dipdirection/dip with silva compass(type15). A sign of strike/dip. discontinuity orientation is used to geological survey. and dipdirection/dip to engineering. Dipdirection/dip converted by strike/dip measured with clinometer is useful on the statistical analysis of a lot of data. To measure the azimuth of the dip with clinometer and to change strike/dip to dipdirection/dip may have potential errors in each person. The newly designed apparatus, clinometer equipped by a rotational azimuth plate and an arrow to measuring strike and dipdirection, has been developed to measure effectively the discontinuity orientation with two method (strike/dip and dipdirection/dip). The measuring method of discontinuity orientation with clinometer having newly designed apparatus is effective one for accurate measurement of strike as well as dipdirection which is degrees counted clockwise from true north. Used by clinometer with newly designed apparatus, concurrent measuring strike/dip and dipdirecton/dip of discontinuity is possible. In application to measuring discontinuity orientation on rock slope, it has been recognized that the newly designed method, unambiguously, led to drop measuring errors comparing with existing measuring apparatuses. Therefore, it is considered that measuring method of discontinuity orientation (strike/dip and dipdirecton/dip) by the newly designed apparatus is useful to one in geological engineering investigation of road design, and to unskilled investigator.

Measurement of Joint-Orientation and Monitoring of Displacement in Tunnel using 3D Laser Scanning System (3차원 레이저 스캐닝 시스템을 이용한 불연속면의 방향성 측정과 터널 변위 모니터링)

  • Shon, Ho-Woong;Oh, Seok-Hoon;Kim, Young-Kyung
    • Journal of the Korean Geophysical Society
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    • v.9 no.1
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    • pp.47-62
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    • 2006
  • More than 70% of Korean Peninsula is consisted of mountains, so that lots of roads, rail-roads and tunnel,which play a pivotal role in the industry activity, are existed along the rock-slope and in the rock-mass. Thus,it is urgent that tegration of management system through the optimum survey and design of rock-slope excavation, proper stabilization method and database of rock-slope. However, conventional methods have shortcoming with the economy of survey time and human resources, and the overcome of difficulties of approach to the in-situ rock-slope. To overcome the limitation of conventional method, this paper proposed the development of remote measurement system using Terrestrial Laser Scanning System. The method using Terrestrial 3D Laser Scanning System, which can get 3D spatial information on the rock-slope and2)Dept. Geosystem Engineering, Kangwon National University, Korea tunnel, has an advantage of reduction of measurement time and the overcome of difficulties of approach to the in-situ rock-slope/dam/tunnel. In the case of rock-slope, through the analysis of 3D modeling of point-cloud by Terrestrial Laser Scanning System, orientation of discontinuity, roughness of joint surface, failure shape and volume were successively achieved. in the case of tunnel face, through reverse-engineering, monitoring of displacement was possible.

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A Case Study for the Support Pattern Appropriateness in Rock Tunneling Designs (지하철 설계시의 지보형식 적정성에 관한 연구)

  • 김수정;장태우
    • The Journal of Engineering Geology
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    • v.5 no.2
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    • pp.167-179
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    • 1995
  • The only three elements such as RQD, N -value and Es were used as a quantitative standard for the design of supporr pattern determidetion on subway line 8th in Seoul. Because the support pattern that was obtained by these elements could not he determined on the basis of the quantitative of geology and the orientations and properties of discontinuity planes, there have been some problems in determining the economic support pattern and tunnel stability. Therefore, in an attempt to determine the stable and economic support pattern with more quantitative elements, more flerrible rock mass classification with geologic conditions was performed by using RMR at 1745 sections and Q-system at 374 sections within Seongnam block on subway line 8th. Then, rusults by these two methods were compared with standard support pattern of the subway line 8th. Moreover, relationships between geology, geologic structures and topography to rock mass grades were studied. According to the rusult of this study, it is judged that the standard support pattern designed with PD-4 or PS - 4 should have been subdivided into 4~6 support patterns. Some sections where geologic structures such as faults and joints are developed tend to have rock mass grades. And they also have low rock mass grades near valley. On thr other hand, they show intermediate grades at piedmont area and the greatest ones at high mountains.

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A Study of the Relationships among RMR, Q-system and GSI Applied to Classify Rock Mass of Limestone Mine (석회석 광산의 암반 분류에 적용된 RMR, Q-system, GSI 간의 상관성 연구)

  • Yoon, Yong-Kyun;Lee, Hong-Woo
    • Explosives and Blasting
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    • v.35 no.4
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    • pp.27-35
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    • 2017
  • A total of 22 sites around openings of limestone mine are chosen to assess rock mass classification schemes such as RMR, Q-system, and GSI. RMR and Q are modified to estimate the relationship with GSI. Q' is the modified Q with SRF=1.0 and $J_w=1.0$. Rock mass is assumed to be completely dry and very favorable discontinuity orientations are assumed to estimate ${RMR_{89}}^{\prime}$. Relationships of Q-Basic RMR, Q-Total RMR, ${GSI-RMR_{89}}^{\prime}$, and GSI-Q' are analyzed, in which a correlation of ${GSI-RMR_{89}}^{\prime}$ is found to be the highest. Failure strains are calculated using the modulus ratios and most measuring sites appear to be stable with low failure strain class.

Probability Analysis of Rock Slope Stability using Zoning and Discontinuity Persistence as Parameters (사면의 구역 및 절리의 연장성을 고려한 암반사면의 안정성 확률해석)

  • Jang, Bo-An;Sung, Suk-Kyung;Jang, Hyun-Sic
    • The Journal of Engineering Geology
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    • v.20 no.2
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    • pp.155-167
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    • 2010
  • In analysis of slope stability, deterministic analysis which yields a factor of safety has been used until recently. However, probability of failure is considered as a more efficient method because it deals with the uncertainty and variability of rock mass. In both methods, a factor of safety or a probability of failure is calculated for a slope although characteristics of rock mass, such as characteristics of joints, weathering degree of rock and so on, are not uniform throughout the slope. In this paper, we divided a model slope into several zones depending on conditions of rock mass and joints, and probabilities of failure in each zone are calculated and compared with that calculated in whole slope. The persistence of joint was also used as a parameter in calculation of probability of failure. A rock slope located in Hongcheon, Gangwondo was selected and the probability of failure using zoning and persistence as parameter was calculated to confirm the applicability of model analysis.