• Geomechanics and Engineering
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• 제28권2호
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• pp.117-133
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• 2022

Determination of the mechanical behaviour of jointed rock masses has been a challenge for rock engineers for decades. This problem is more pronounced for non-persistent jointed rock masses due to complicated interaction of rock bridges on the overall behaviour. This paper aims to study the effect of a non-persistent joint set configuration on the mechanical behaviour of rock materials under both uniaxial and biaxial compression tests using a discrete element code. The numerical simulation of biaxial compressive strength of rock masses has been challenging in the past due to shortcomings of bonded particle models in reproducing the failure envelope of rock materials. This problem was resolved in this study by employing the flat-joint contact model. The validity of the numerical model was investigated through a comprehensive comparative study against physical uniaxial and biaxial compression experiments. Good agreement was found between numerical and experimental tests in terms of the recorded peak strength and the failure mode in both loading conditions. Studies on the effect of joint orientation on the failure mode showed that four zones of intact, transition to block rotation, block rotation and transition to intact failure occurs when the joint dip angle varies from 0° to 90°. It was found that the applied confining stress can significantly alter the range of these zones. It was observed that the minimum strength occurs at the joint dip angle of around 45 degrees under different confining stresses. It was also found that the joint orientation can alter the post peak behaviour and the lowest brittleness was observed at the block rotation zone.

• 터널과지하공간
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• 제7권1호
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• pp.20-30
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• 1997

A discrete joint finite element with joint surface degradation was developed to investigate the shear behavior of rough rock joint. Isoparametric formulation was used for facilitating the implementation of the element in existing Finite Element Codes. The elasto-plastic joint deformation model with the discontinuity constitutive law proposed by Plesha was applied to the element. The reliability of the developed finite element code was successfully testified through numerical direct shear tests conducted under both constant normal stress and constant normal displacement conditions. The result of the numerical direct shear test showed that the code can capture characteristic deformation features envisaged in the direct shear test of rough rock joint.

• 화약ㆍ발파
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• 제23권2호
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• pp.37-44
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• 2005

현지암반 조건 중에서 자연상태 암석블록의 크기와 절리방향은 다른 요인들에 비해 상대적으로 암석파쇄도에 큰 영향을 미치는 것으로 최근의 연구에서 확인되었다. 이러한 최근의 연구결과를 검증하기 위해 이 연구에서는 고강도 시멘트 몰탈 재료의 축소 모형을 이용한 발파실험을 실시하였다. 실험 결과 절리간격이 같을 때 절리방향에 따라 암석의 파쇄도가 달라지며, 절리간격에 따라 파쇄도에 차이를 보이는 등 현장조사에서 얻어진 것과 같은 결과를 얻었다.

• 터널과지하공간
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• 제4권3호
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• pp.261-273
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• 1994

Direct shear tests were carried out on the rock joints and artificial discontinuities to investigate the influence of joint roughness on the shear strength and deformation behaviour. Single direct shear testing apparatus used in experiment was designed and manufactured. Its capacity is 200 tons of shear load, 20 tons of normal load and 50$\textrm{cm}^2$ of maximum shear area. Test samples were cement mortar with artificial discontinuity and sandstone with natural joint. Peak shear strength was increased as joint roughness or normal stress was increased, especially, linearly increased with roughness angle in cement mortar. If joint roughness angle was constant at low normal stress, shear strength was not affected by width and height of joint roughness in cement mortar. Peak shear strengths obtained from tests were larger than the values calculated by Barton's equation, and shear stiffness was increased with joint roughness coefficient.

• 터널과지하공간
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• 제17권2호
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• pp.102-108
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• 2007

일반적으로 암판정을 수행하기 인해 가장 널리 사용되는 방법은 암석의 강도와 절리의 발달빈도를 고려하는 것이다. 하지만 미세균열과 연장성이 긴 절리들이 암반에 존재하고 있는 경우에는 이러한 방법이 합리적이지 않다. 그러므로 복잡한 지질조건을 가지고 있는 암반에서의 굴착난이도 결정은 절리빈도와 실내시험(일축압축강도, 점하중강도, 실내탄성파속도 등)과 현장탄성파속도와의 상관관계를 종합하여 암판정을 수행하는 것이 더욱 더 합리적이라고 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 지반공학 공동 학술발표회
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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.

• 한국터널지하공간학회 논문집
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• 제3권2호
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• pp.3-12
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• 2001

본 논문은 절리암반 터널의 안정성 해석을 위한 2차원 개별요소모델링방법에 대한 개선방안을 제안하였다. 먼저, 절리군과 터널의 상대방위를 고려하여 터널단면상에서 불연속거동이 가능한 절리군을 구별하는 기준을 제시하였다. 이 기준에 따라 불연속거동이 가능한 절리군은 개별요소(암석블록)의 변이 되도록 하고 그 외 절리군은 암석블록의 탄성특성을 보정하는 방법을 제시하였다. 또한, 주어진 절리의 기하학적 특성에 대해서 절리의 방위편차와 유한길이를 고려한 복잡한 모델과 절리의 평균방위와 무한길이를 고려한 단순한 모델의 특성을 분석하였다. 그 결과, 후자의 모델이 일관성 있는 터널의 국부적 파괴양상과 명료한 암반의 불연속거동을 보여줌으로써 터널설계목적에 적절함을 확인하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.501-508
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• 2002

The percentage of a mountainous district in our country is comparatively high but the concern for rock mass has been disregarded for a long time. Especially for rock slope, the most important factors are geometric characteristics and their shear strength parameter. In this paper, parametric studies are performed using the distinct element computer program UDEC-BB for rock slopes. Parameters adopted in this paper are joint angle, spacing, persistence, aperture and shear strength parameters (JRC, JCS, basic friction angle). To estimate slope stability, shear strength reduction method is used. The most important factors affecting rock slope stability are joint angle and spacing. The relationship between average displacement calculated by UDEC-BB and safe factor by shear strength reduction method is researched.

• 터널과지하공간
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• 제19권1호
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• pp.1-10
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• 2009

암반 내 구조물을 시공하는 경우 역학적 안정성을 평가하기 위하여 암반의 특성을 조사한다. 이 경우 암반의 특성은 주로 암반 내 절리의 특성에 의하여 좌우된다. 지금까지는 암반 내 절리의 특성을 조사하기 위하여 암반이 노출된 사면이나 노두에 접근하고 육안으로 직접 관찰하였다. 이때 급사면과 같은 곳에서 접근의 문제, 작업의 안전 문제, 많은 시판이 걸리는 문제, 조사시간에 비하여 얻은 정보량의 부족, 정보의 재현 문제, 측정 오차 문제 등의 제한이 있었다. 따라서 이와 같은 문제를 개선하기 위하여 LIDAR (light detection and ranging)로 암반을 스캔하여 얻은 포인트 클라우드(point cloud)글 Split-FX 소프트웨어로 처리한 결과 절기의 방향과 간격 및 절리면의 거칠기 등 절리의 특성을 정확하고 효율적으로 분석할 수 있었다.

• Geomechanics and Engineering
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• 제21권3호
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• pp.227-236
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• 2020

Non-destructive exploration using elastic waves has been widely used to characterize rock mass properties. Wave propagation in jointed rock masses is significantly governed by the characteristics and orientation of discontinuities. The relationship between spatial heterogeneity (i.e., joint spacing) and wavelength for elastic waves propagating through jointed rock masses have been investigated previously. Discontinuous rock masses can be considered as an equivalent continuum material when the wavelength of the propagating elastic wave exceeds the spatial heterogeneity. However, it is unclear how stress-dependent long-wavelength elastic waves propagate through a repetitive rock-joint system with multiple joints. A preliminary numerical simulation was performed in in this study to investigate long-wavelength elastic wave propagation in regularly jointed rock masses using the three-dimensional distinct element code program. First, experimental studies using the quasi-static resonant column (QSRC) testing device are performed on regularly jointed disc column specimens for three different materials (acetal, aluminum, and gneiss). The P- and S-wave velocities of the specimens are obtained under various normal stress levels. The normal and shear joint stiffness are calculated from the experimental results using an equivalent continuum model and used as input parameters for numerical analysis. The spatial and temporal sizes are carefully selected to guarantee a stable numerical simulation. Based on the calibrated jointed rock model, the numerical and experimental results are compared.