Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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Calculation of Joint Center Volume (JCV) for Estimation of Joint Size Distribution in Non-Planar Window Survey

비평면 조사창에서의 암반절리 크기분포 추정을 위한 Joint Center Volume (JCV) 산정 기법 제안

  • Lee, Yong-Ki (Department of Energy Systems Engineering, Seoul National University) ;
  • Song, Jae-Joon (Department of Energy Systems Engineering, Seoul National University)
  • 이용기 (서울대학교 공과대학 에너지시스템공학부) ;
  • 송재준 (서울대학교 공과대학 에너지시스템공학부)
  • Received : 2019.04.22
  • Accepted : 2019.04.25
  • Published : 2019.04.30
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Abstract

Rock joints have an extremely important role in analyzing the mechanical stability and hydraulic characteristics of rock mass structures. Most rock joint parameters are generally indicated as a distribution by statistical techniques. In this research, calculation technique of Joint Center Volume (JCV) is analyzed, which is required for estimating the size distribution having the largest uncertainty among the joint parameters, then a new technique is proposed which is applicable regardless of the shape of survey window. The existing theoretical JCV calculation technique can be applied only to the plane window, and the complete enumeration techniques show the limitations in joint trace type and analysis time. This research aims to overcome the limitations in survey window shape and joint trace type through calculating JCV by using Monte Carlo simulation. The applicability of proposed technique is validated through the estimation results at non-planar survey windows such as curved surface and tunnel surface.

암반구조물의 역학적 안정성과 수리적 특성을 분석하는데 있어 암반절리는 매우 중요한 역할을 한다. 방향, 크기, 체적빈도, 위치 등 대부분의 암반절리 파라미터들은 일반적으로 통계적인 기법에 의해 분포로 나타낸다. 본 연구에서는 이러한 암반절리 파라미터들 중 가장 불확실성이 큰 크기분포를 추정하는데 요구되는 Joint Center Volume(JCV) 산정 기법에 대해 분석하고, 조사창의 형상과 관계없이 적용할 수 있는 새로운 기법을 제안하였다. 기존 JCV의 이론적 산정법은 평면 조사창에만 적용이 가능하고, 전수조사 기법은 절리선 종류의 제약 및 해석시간 문제 등의 한계를 보였다. 본 연구에서는 몬테카를로 시뮬레이션을 이용하여 JCV를 산정하여, 조사창 형상 및 절리선 종류의 제약이라는 한계를 극복하고자 하였다. 제안된 기법은 곡면형, 터널형과 같은 비평면 조사창에서의 추정결과를 통해 적용성을 검증하였다.

Keywords

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Fig. 1. Joint discs and traces in a rectangular sampling window (Song, 2005)

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Fig. 2. Variation of the parallelepiped volume of disc center according to the change in joint diameter for a constant trace length (Song, 2005)

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Fig. 3. The trace center zones of dissecting traces whose partial length within a window is l΄ (Song, 2009)

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Fig. 4. The trace center zones of transecting traces according to the whole and partial trace lengths (Song, 2009)

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Fig. 5. Model for JCV calculating in cylindrical window (Jeon et al., 2011)

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Fig. 6. Trace types in cylindrical window (one trace by the one joint)

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Fig. 7. Trace types in cylindrical window (two traces by the one joint)

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Fig. 8. Algorithm of JCV calculation using Monte Carlo simulation

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Fig. 9. Curved window survey

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Fig. 10. Horseshoe window survey

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Fig. 11. Hypothetic population distribution for Monte Carlo simulation

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Fig. 12. Estimation results of joint size distribution in curved window

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Fig. 13. Estimation results of joint size distribution in horseshoe window

Table 1. JCV matrices used in this study

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Table 2. Error rates of estimation in curved window

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Table 3. Error rates of estimation in horseshoe window

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