• Explosives and Blasting
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• v.35 no.4
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• pp.10-18
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• 2017

In this study, Rock deformation at the artificially advanced face was investigated by using the finite element code relating to the split blasting conducted in urban area. The maximum principal strain according to the detonation pattern and the detonation delay time at the rock surface was compared with the modeled blast section. As a result, it was found that the maximum principal strain was observed a difference depending on the detonation pattern at the rock surface, and the detonation delay time was an important parameter in split blasting.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.53-63
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• 2023

Rock disturbance caused by blasting and stress relaxation is commonly observed during excavation. As the distance from the source of disturbance increases, the degree of disturbance decreases, and rock at a large depth does not experience disturbance. However, in stability analyses, a single value of disturbance is often applied to the entire rock mass, which leads to underestimated results. In this study, this modeling mistake is addressed by considering realistically varying rock disturbance. The safety of infinite slopes in a disturbed rock mass with a strength governed by the Hoek-Brown failure criterion is investigated based on the kinematic approach of limit analysis. The maximum disturbance is assigned to the outermost slope face because it is directly exposed to blasting damage and dilation, and the disturbance progressively decays with distance in the rock mass. The safety analysis results indicate that the assumption of uniform disturbance in the entire rock mass leads to underestimation of the rock strength and safety on infinite rock slopes. A critical slip surface appears to be within the disturbed rock layer as well as the interface between the disturbed upper rock and undisturbed lower rock.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1016-1019
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• 2009

Detailed survey of the rock mass is essential for design, construction and maintenance of rock slope. However, geological survey of poor outcrops and various geophysical aids provides limited information for slope engineering. Remote measurement system for excavation surface (Surface Mapper) and projection s/w for borehole data (Fracjection) are developed for further support of slope surveying. The Surface Mapper measures orientation of joint, fault, foliation on excavated rock surface and database the measured data. The Fracjection projects measurements in boreholes, which are obtained by BIPS, Televideo and DOM operation, to any expected excavation space. These methods promise new approaches for surveying, designing, constructing and maintaining processes of slope.

• Proceedings of the Korean Geotechical Society Conference
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• 1993.10b
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• pp.235-247
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• 1993

The 62 m span Olympic lee Hockey cavern in Gjovik, Norway, is located in jointed gneiss of average RaD = 70% and has a rock cover of only 25 to 50m, thus posing challenging design p problems. The investigations prior to construction included two types of stress measurements, cross-hole seismic tomography, special coe logging, Q-system classification and numerical modelling with UDEC-BB. Predicted maximum deformations were 4 to 8 mm; surprisingly small due to the high horizontal stresses recorded. Extensometer (MPBX) installations from the surface prior to construction, precision surface levelling and MPBX installed from inside the cavern give a combined measure of maximum deformations in the range 7 to 8 mm with the 62 m span fully e excavated, and three adjacent caverns for the Postal Services also completed.

• Tunnel and Underground Space
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• v.5 no.2
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• pp.104-113
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• 1995

Shear strength of the discontinuity on which the pre-failure of rock slope was occurred during surface excavation was measured through the direct shear test using core samples obtained in-situ. Internal friction angle was increased as the roughness of discontinuity surface(JRC) was increased. Results of the tilt test using core samples of higher JRC also showed very similar trend as those of the direct shear test. When the samples replicated from natural cores were used int he tilt test, results of friction angles showed almost perfect continuation of the residual friction angles from the direct shear test. However, when the gouge material existed in the discontinuity the internal friction angle strongly depended upon the rate of filling thickness to the height of asperity irrespective of the JRC. Based on the results of both direct shear test and tilt test internal friction angle and cohesion of discontinuity, which reflect the in-situ conditions fo pre-sliding failure and also can be used for the optimum design of support system, were assessed. Two kinds of support measures which were expected to increase the stability of rock slope were considered; lowering of slope face angle and installation of rock cable. But, it was found that the first method might lead to more unstable conditions of rock slope when the cohesion of discontinuity plane was negligibly low and in that case the support systems of any kind which could exert actual resisting force were needed to ensure the permanent stability of rock slope.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.557-560
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• 2008

In this paper, it discusses about the stability of rock slope of pyroclastic rock, which can easily meet at construction site. Basically carry out the investigation about the development of a surface of discontinuity, too. With that, it refers to the basic groups of sedimentary rock, treats of general details about investigation of rock slope and stability analysis, and discusses general characteristics and stability analysis case study about rock slope of pyroclastic rock. Achieved basic geological investigation on rock slope of pyroclasic rock, and examine the stability of slope by doing limit equilibrium and geometric stability analysis due to the result of investigation. It is considered to be able to accumulate many data about slope design of pyroclastic rock hereafter estimating degrees of rock mass properties of pyroclastic rock quantitatively.

• Tunnel and Underground Space
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• v.5 no.3
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• pp.214-222
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• 1995

Geological events which are undetected by the surface geophysical or geological survey phase can cause many problems, especially when the tunnel is excavated by TBM. To detect the geological events ahead of tunnel face, a seismic method applied from VSP method is used. Generally uniaxial geophone has been used in surface seismic survey. But this time, triaxial geophone is used to reduce the noise of tunnel wave. DME(Dip moveout Enhancement) filter and diffraction stack method are used. Applying these techniques to the road tunnel in construction, it is proved that the geological events ahead of tunnel face is fairly well predicted. From the seismic trace, Vp and Vs which are related to the rock property can be also obtained. Rock property and proper support design can be dedced from these parameters.

• Tunnel and Underground Space
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• v.9 no.4
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• pp.350-363
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• 1999

The precision cyclic shear test system was established to investigate the mechanical characteristics of rough rock joints under cyclic loading conditions. Laboratory cyclic shear tests were conducted for saw-cut joints and artificial rough rock joints using Hwangdeung granite and Yeosan marble. Surface roughness and aperture characteristics of specimens were examined by measuring surface topography using the laser profilometer. Peak shear strength, phase difference during loading and unloading, and anisotropic shear behavior were investigated throughout the cyclic shear test results. These features and their subsequent variations in each loading cycle are significantly dependent upon the second order asperities and the strength of intact rock. It was observed that degradation of asperities for rough rock joints under cyclic shear loading followed the exponential degradation laws of asperity angle and that the mechanism for asperity degradation would be different depending upon the normal stress level, roughness of joint surface and the loading stage.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.45-51
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• 2003

Grouting materials in rock is grouted as vein type along the fault surface by the other way for soil and allow a change of characteristics in rock faults as a result of that. Therefore the deformation characteristics of rock faults after grouting differ as a direction and characteristic of grouted fault and stress condition of field rock. Thereby it must be analyzed the effect for deformation of rock according to characteristics of rock faults and characteristics of grouting materials to accurately evaluate the reinforced effect by grouting. But grouting method used in field until present depends on experience of workers, and inspection for those effects are evaluated by measurement of elastic wave velocity, permeability tests and etc. in field. In this study, it was investigated that the effects for shear characteristics of maximum shear strength, residual shear strength and etc. by comparison and analysis of test results which were worked by direct shear tests of rock faults with changing a type of grouting materials and the grouting depth(t) for average width(a) of fault surface roughness when OPC(Ordinary Portland Cement) and Micro cement was grouted in fault surface of field rock to evaluate characteristicsof the shear deformation for rock fault surface of dam by grouting.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.337-346
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• 2013

The characteristics of subsidence above a shallow tunnel excavated in weathered rock mass is analyzed. The tunnel is excavated minimum about 11m beneath some buildings and the width of the tunnel is 11m, too. Subsidence pins are installed at 23 locations on surface along the tunnel, 180m long, adjacent to the buildings. Subsidences are measured for about 2 years and they are optimized to analyze three dimensional deformed ground surface, trough width parameter K and sectional volume loss of unit tunnel length Vs of the surface deformation profile.