• Tunnel and Underground Space
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• v.14 no.6 s.53
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• pp.391-398
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• 2004

An algebraic algorithm for predicting the joint trace distribution on the cut-face of rock slope based on the orientations and the locations of joints investigated in the borehole has been developed. Joint trace prediction is manipulated by utilizing the three dimensional plane equations of both joint planes and projection face, and the extent of trace within the projection area is calculated by considering the persistence of each joint plane. Joint trace prediction method is efficiently applied for analyzing the stability and the adequacy of support design of Gimhae Naesam cut-slope, which is structurally unstable due to slumping. Structural characteristics of rock mass is investigated by performing DOM drilling and the potential rock mass sliding inside slope face is analyzed by examining the orientations of joint planes which can induce the slope failure. Also, the efficiency of anchor support design is evaluated by considering the joint trace distribution on the anchor installation area and its sliding potential.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.449-458
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• 2001

In order to verify the numerical model, which was developed to simulate the behavior of the two-phase fluid flow in a single fracture, the characteristic equation of relative permeability was incorporated into the developed numerical model, and the computed results were compared with the experimental results of the model test. As results of the sensitivity analysis on the roughness and the aperture size of fracture, the gas velocity was inversely proportional to the fracture roughness, and not proportional to the square of aperture size which is usually observed in single phase flow in a single fracture. The numerical model was applied to the underground LPG storage terminal in order to check the field applicability. The simultaneous flow of water and gas in accordance with the operation pressures in a single fracture near cavern was simulated by the model. It was shown that the leaked gas was able to be controlled in a single fracture neither by the pressure of operation nor by that of groundwater in case the fracture became smoother in roughness and smaller in aperture size.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.321-328
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• 2009

A optimal reinforcement in the joint rock slope excavation adjacent to an existing tunnel would be influenced by excavation distance from the tunnel, slope angel, and joint conditions but has been empirically determined so far. In this study, large scale model tests were conducted to find out the relationship between load translation on the excavation surface and bebavior of the tunnel according to excavation steps of the jointed rock slope. Consequently, two main parameters, joint dip and sloped angle were investigated in those model tests. From the test results, it was found that tunnel deformation was the largest one when the excavation of joints located closer to the tunnel crown or invert. Stability of the slope and the tunnel were varied in a certain excavation stage related to the angle of slope. In the future, based on results of this study the reinforcement method for the tunnel and slope safety in a jointed rock mass will be demonstrated.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.183-196
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• 2006

Rock joint roughness obtained from the camera-type 3D scanner was classified into waviness and unevenness. The classification criteria were established in the previous study; digital filtering was used to distinguish one from another. The classified and original profiles were used to produce metal moulds. For accurate machining of the moulds, the WEDM(Wire-cut Electric Discharge Machining) was adopted. Specimens were cast using high strength gypsum, and joint shear tests were performed by varying normal stress from low value to high one. Roughness mobilization characteristics depending on the asperity scale and the applied normal stress were investigated. A new equation was proposed to predict shear strength of rock joint, which can consider the characteristics of roughness mobilization and roughness parameters. The roughness quantification composed of waviness and unevenness was found to be a useful method to predict the joint shear strength.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.4
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• pp.295-306
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• 2010

Contrary to an intact rock, the jointed rock mass shows strain-dependent deformation characteristics (elastic modulus and damping ratio). The maximum elastic modulus of a rock mass can be obtained from an elastic wave-based exploration in a small strain level and applied to seismic analyses. However, the assessment and application of the non-linear characteristics of rock masses in a small to medium strain level ($10^{-4}{\sim}0.5%$) have not been carried out yet. A non-linear dynamic analysis module is newly developed for FLAC3D to simulate strain-dependent shear modulus degradation and damping ratio amplification characteristics. The developed module is verified by analyzing the change of the Ricker wave propagation. Strain-dependent non-linear characteristics are obtained from disks of cored samples using a rock mass dynamic testing apparatus which can evaluate wave propagation characteristics in a jointed rock column. Using the experimental results and the developed non-linear dynamic module, seismic analyses are performed for the intersection of a shaft and an inclined tunnel. The numerical results show that vertical and horizontal displacements of non-linear analyses are larger than those of linear analyses. Also, non-linear analyses induce bigger bending compressive stresses acting on the lining. The bending compressive stress concentrates at the intersection part. The fundamental understanding of a strain-dependent jointed rock mass behavior is achieved in this study and the analytical procedure suggested can be effectively applied to field designs and analyses.

• Tunnel and Underground Space
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• v.10 no.2
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• pp.180-195
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• 2000

Grouting has been practiced as a reliable technique to improve the mechanical properties of rock mass. But, the study of ground improvement by greeting is rare especially in jointed rock mass. In this study, joint compression test and direct shear test were performed on pure rock joint and cement milk grouted rock joint to examine the grouting effect on the property of rock joint. In the pure rock joint compression test, joint closure varied non-linearly with normal stress. But after cement milk grouting, the normal deformation characteristics of the joint was linear at the low normal stress level. As normal stress increased. deformation of the sample rapidly increased due to the stress concentration at the joint asperities. Peak shear strength of the grouted joint in low normal stress was higher than that of non-grouted joint due to the cohesion, decreased exponetially as the grout thickness increased. Thus after cement milk grouting, the failure envelope modified to a curve that has cohesion due to grout material hydration with decreased friction angle. Shear stiffness and peak dilation angle of the grouted joint decreased as the grout thickness increased. The peak shear strength from the direct shear test on grouted rock joint was represented by an empirical equation as a fuction of grout thickness and roughness mean amplitude.

• Tunnel and Underground Space
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• v.16 no.2 s.61
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• pp.166-178
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• 2006

Recently, the frequency of occurring dynamic events such as earthquakes, explosives blasting and other types of vibration has been increasing. Besides, the chances of exposure for rock discontinuities to free faces get higher as the scale of rock mass structures become larger. For that reason, the frictional behavior of rock joints under dynamic conditions needs to be investigated. In this study, artificially fractured rock joint specimens were prepared in order to examine the dynamic frictional behavior of rough rock joint. Roughness of each specimen was characterized by measuring surface topography using a laser profilometer and a series of shaking table tests was carried out. For mated joints, the static friction angle back-calculated ken the yield acceleration was $2.7^{\circ}$ lower than the tilt angle on average. The averaged dynamic friction angle for unmated joints was $1.8^{\circ}$ lower than the tilt angle. Displacement patterns of sliding block were classified into 4 types and proved to be related to the first order asperity of rock joint. The tilt angle and the static friction angle for mated joints seem to be correlated to micro average inclination angle which represents the second order asperity. The tilt angle and the dynamic friction angle for unmated Joints, however, have no correlation with roughness parameters. Friction angles obtained by shaking table test were lower than those by direct shear test.

• Tunnel and Underground Space
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• v.13 no.2
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• pp.153-168
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• 2003

The objective of this present study is to understand long term(500 years) thermohydromechanical interaction behavior in the vicinity of a repository cavern on the joint location and repository depth variations. The model includes a saturated discontinuous granitic rock mass, PWR spent nuclear fuel in a disposal canister surrounded with compacted bentonite inside a deposition hole, and mixed bentonite backfilled in the rest of the space within a repository cavern. It is assumed that two joint sets exist within the model. Joint set 1 includes joints of 56$^{\circ}$ dip angle, spaced at 20 m, and joint set 2 is in the perpendicular direction to joint set 1 and includes joints of 34$^{\circ}$ dip angle, spaced at 20 m. In order to understand the behavior change on the joint location variations, 5 different models of 500m in depth are analyzed, and additional 3 different models of 1000 m in depth are analyzed to understand the effect of depth variation.

• The Journal of Engineering Geology
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• v.12 no.4
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• pp.421-437
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• 2002

In order to quantify the anisotropic properties of rock included joints and shear behavior in joint surface, the mold is Produced for rock joint surface using gypsum Plaster and Peformed for replicated joint models made of cement mortar. Rock sample is measured using mechanical profilometer before testing and their result is expressed quantitatively. The statistical parameters and the fractal dimension by fractal theory for roughness is investigated its coordinate value for numerical process. The shear strength to the shear displacement in low level normal stress ismaintained or increased in most joint models. Their results present that this relationship is depended several roughness properties in joint model for natural rock joint. The relationship between the shear strength and the Properties for profiles estimated by some statistical parameter in roughness has the low correlation and is not constant. The result between the data for direct shear test and using Barton's equation, Barton's equation has not the effectiveness for the effect of anisotropy and has not suitable to recognizing the properties for joint surface. It means that JRC has not the properties of anisotropic rock surface. The fractal dimension is well correlated with the data of direct shear test than those of JRC. New experimental formulae using fractal dimension is comported with the anisotropic properties for direct shear test.

• Economic and Environmental Geology
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• v.49 no.1
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• pp.31-41
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• 2016

A program code was developed to calculate block hydraulic conductivity of the 2-D DFN(discrete fracture network) system based on equivalent pipe network, and implemented to examine the effect of joint orientation distribution on the hydraulic characteristics of fractured rock masses through numerical experiments. A rock block of size $32m{\times}32m$ was used to generate the DFN systems using two joint sets with fixed input parameters of joint frequency and gamma distributed joint size, and various normal distributed joint trend. DFN blocks of size $20m{\times}20m$ were selected from center of the $32m{\times}32m$ blocks to avoid boundary effect. Twelve fluid flow directions were chosen every $30^{\circ}$ starting at $0^{\circ}$. The directional block conductivity including the theoretical block conductivity, principal conductivity tensor and average block conductivity were estimated for generated 180 2-D DFN blocks. The effect of joint orientation distribution on block hydraulic conductivity and chance for the equivalent continuum behavior of the 2-D DFN system were found to increase with the decrease of mean intersection angle of the two joint sets. The effect of variability of joint orientation on block hydraulic conductivity could not be ignored for the DFN having low intersection angle between two joint sets.