• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.301-315
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• 2001

본 연구에서는 최근 5년간 국내 각 지역에서 채취한 802개의 절리면 시료에 대하여 전단시험을 실시하여 얻은 결과를 이용하여, 절리면의 여러 공학적 성질들을 조사, 연구하였다. 절리면 전단시험에서 얻어진 최대마찰각 및 잔류마찰각을 지체구조별, 암종별로 분류하고 통계적으로 구하였으며, Barton의 전단강도식의 입력변수인 JRC, JCS를 측정하고 Barton식의 적용성에 대해서도 검토하였다. 그 결과 설계의 기초자료로 활용할 수 있는 지역별, 주요 암종별 최대마찰각, 잔류마찰각을 제시하였다. 또한, JRC, JCS, 수직응력에 따른 마찰각과 전단강성 및 팽창각의 변화를 분석하였다. 마지막으로, Barton의 식에서 구한 이론적 전단강도와 이 실험에서 얻어진 전단강도를 비교한 결과, Barton의 경험식은 높은 상관도로 암석 절리면 전단강도를 예측할 수 있음을 확인하였다.

• Tunnel and Underground Space
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• v.26 no.5
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• pp.384-395
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• 2016

Both the roughness measurement tests and the multi-stage shear tests were carried out on the 110 rock joint samples in order to investigate the influences of rock type, joint roughness and normal stress on the shear behaviour of rock joints. Test samples were composed of quartz porphyry, dacite, granite and gneiss, which were classified into three detailed groups according to their JRC values. Roughness parameters of rock joints were analyzed by roughness measurement tests, and shear characteristics were also investigated by multi-stage shear tests. Both peak shear strength and shear stiffness were increased as both joint roughness and normal stress were increased, whereas dilation angles showed lower values at the lower roughness and higher normal stress conditions. Besides, shear characteristics obtained from all tests of four different rock types with different rock strengths showed irrelevant details, therefore the influences of both joint roughness and normal stress on shear behaviors were found to be more considerable than the strength of intact rock. The results obtained from both multi-stage shear tests and direct shear tests were finally compared, where the dilation angles obtained from multi-stage shear tests were found to be valid only for the first normal stress conditions.

• The Journal of Engineering Geology
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• v.2 no.1
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• pp.1-18
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• 1992

Rock mass having discontinuous plane almost appear roughness which have a great effect on shear strength. Rocks of studied object choose granites (15 samples), gneisses (7 samples), and andesites (1 sample). The purpose of this study was to clarify shear strength of discontinuous planes as value of shear strength angle (${\Phi}_p$), critical stress of roughness (${\sigma}_r$) and shear failure strength (${\tau}_o$). 1. Roughness decrease from ${\Phi}_i=38.03^{\circ}$ to $33.21^{\circ}$ that is, friction angle has the highest value at first stage and has the lowest value at the last stage. 2. Critical angle of roughness distribution within $45^{\circ}$ (test max. $angle=43^{\circ}$), JRC(Joint Roughness Coefficient) is less than 14 and lies distribution range of boundary is following: $JRC=-4.63Ln{\sigma}n+5.63$. 3. When the roughness critical stress(${\sigma}_T) is from 0.1 to 3 .56Mpa, shear failure strength of roughness (${\tau}_o$) is from 0.01 to 0.46Mpa, shear strength(${\tau}$) of discontinuous plane is from 3.65 to 39.11 Mpa. If loading is higher than these values, collapse and sliding will occur on the rock mass.

• Tunnel and Underground Space
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• v.29 no.5
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• pp.292-304
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• 2019

Limestone joint surfaces with smooth roughness were experimented by means of both the individual direct shear tests based on the KSRM standard test method and the multi-stage direct shear test to apply the stepwise vertical stresses. Changes in the roughness of the joint surfaces before and after the shear tests were examined and the difference between the two kinds of tests mentioned above was analyzed. In both tests, the shear resistance increased as the joint roughness increased and the maximum shear stress required for shearing the joint surface increased as the vertical stress increased. The peak friction angle obtained by the multi-stage direct shear tests was only 63% of that obtained by the individual direct shear tests. In the multi-stage direct shear test, the initial engagement of the concave-convex parts changes frequently during stepwise shearing process, which deforms the original roughness of a joint surface. Accordingly, the individual direct shear test is thought to be more effective when obtaining the friction angle of the rock joint surfaces. Limestone joint surfaces with smooth roughness of JRC value 4~8 were found to have peak friction angle of $47^{\circ}$, residual friction angle of $38^{\circ}$ and cohesion of 37 kPa.

• Tunnel and Underground Space
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• v.21 no.6
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• pp.494-507
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• 2011

Rock joint surface roughness is one of the most important parameters in shear behavior analysis of rock joint surface. Until now, estimation of joint surface roughness has been conducted by various statistical methods with two-dimensional analysis. In this study, standard roughness profile suggested by Barton and Choubey (1977) was expanded into a 3D surface and its surface roughness was analyzed by surface angularity parameter. And the validity of quantification based on surface angularity was secured through comparison with $Z_2$ and Ai parameter. Also the surface angularity parameter was compared with shear strength by joint shear test using the replicated specimen.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.229-238
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• 2002

This paper introduces the surface roughness parameter, Rs to the characterization of joint roughness and quantitatively illustrates the influence of joint roughness on the joint shear strength. A new peak shear strength criterion for rock joints using Rs is suggested. The results show that the surface roughness parameter, Rs can appropriately reflect the degree of roughness for the rock joint surfaces tested in this study A measuring interval of 2mm and profile length of 5cm can be used to characterize the joint roughness of the rock core size surfaces; however, the scale of fluctuation, $\delta_\alpha$ should be considered to extend the surface roughness parameter, Rs to the large-scale field rock joint surfaces. For the smooth joint roughness, sliding of the rock cores is the principal shear mechanism; however, the breakage of roughness from the rock cores is inferred for rougher joint roughness.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.383-392
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• 2016

This study is to evaluate the physical and mechanical properties on the Ipseok-dae columnar joints of Mt. Mudeung National Park. For these purposes, physical and mechanical properties as well as discontinuity property on the Mudeungsan tuff, measurement of vibration and local meteorology around columnar joints, and ground deformation by self-weight of columnar joints were examined. For the physical and mechanical properties, average values were respectively 0.65% for porosity, 2.69 for specific gravity, 2.68 g/cm³ for density, and 2411 m/s for primary velocity, 323 MPa for uniaxial compressive strength, 81 GPa Young's modulus, and 0.25 for Poisson's ratio. For the joint shear test, average values were respectively 3.15 GPa/m for normal stiffness, 0.38 GPa/m for shear stiffness, 0.50 MPa for cohesion, and 35° for internal friction angle. The JRC standard and JRC chart was in the range of 4~6, and 1~1.5, respectively. The rebound value Q of silver schmidt hammer was 57 (≒ 90 MPa). It corresponds 20% of the uniaxial compressive strength of intact rock. The maximum vibration value around the Ipseok=dae columnar joints was in the range of 0.57 PPV (mm/s)~2.35 PPV (mm/s). The local meteorology of surface temperature, air temperature, humidity, and wind on and around columnar joints appeared to have been greatly influenced the weather on the day of measurement. For the numerical analysis of ground deformation due to its self-weight of the Ipseok-dae columnar joints, the maximum displacement of the right ground shows when the ground distance is approximately 2 m, while drastically decreased by 2~4 m, thereafter was insignificant. The maximum displacement of the middle ground shows when the ground distance is approximately 0~2 m, while drastically decreased by 3~10 m, thereafter was insignificant. The maximum displacement of the left ground shows when the ground distance is approximately 5~6 m, while drastically decreased by 6~10 m, thereafter was insignificant.