• Journal of the Korean Geotechnical Society
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• v.28 no.1
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• pp.29-39
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• 2012

The maximum unit point resistance ($q_{max}$) of rock socketed drilled shafts subjected to axial loads was investigated by a numerical analysis. A 3D Finite Difference Method (FDM) analysis and a Distinct Element Method (DEM) analysis were performed with varying rock elastic modulus (E), discontinuity spacing ($S_j$), discontinuity dip angle ($i_j$), and pile diameter (D). Based on the results of obtained, it was found that the ultimate point resistance ($q_{max}$) increased as rock elastic modulus (E) and rock discontinuity spacing ($S_j$) increased. But, it was found that $q_{max}$ decreased as pile diameter (D) increased. As for the influence of the dip angle of rock discontinuity ($i_j$), it was shown that $q_{max}$ decreased up to 50% of maximum value within the range of $0^{\circ}$ < $i_j$ < $60^{\circ}$ due to the shear failure at rock discontinuities. Furthermore, it was found that if $20^{\circ}{\leq}i_j{\leq}40^{\circ}$, influence of $i_j$ should be taken into account because $q_{max}$ tended to approach a minimum value as $i_j$ approached a value near the friction angle of the discontinuity (${\phi}_j$).

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.611-618
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• 2005

In this research, the effect of rock mass weathering on the side shear resistance of drilled shaft socketed into weathered rock was investigated. For that, a database of 23 cast-in-place concrete piles with diameters varying from 400mm to 1,500mm were socketed into weathered igneous/meta-igneous rock at four different sites. The static axial load tests were performed to examine the resistant behavior of the piles, and a comprehensive field/laboratory testing program at the field test site was also performed to describe the in situ rock mass conditions quantitatively. No correlation was found between the compressive strengths of intact rock and the side shear resistance of weathered/soft rock. The ground investigation data regarding the rock mass conditions (e.g. $E_m,\;E_{ur},\;_{plm}$, RMR, RQD, j) was found to be highly correlated with the side shear resistance, showing the coefficients of correlation greater than 0.7 in most cases. Additionally, the applicability of existing methods for the side shear resistance of piles in rock was verified by comparison with the field test data. The existing empirical relations between the compressive strength of intact rock and the side shear resistance(Horvath (1982), Rowe & Armitage(1987) etc.) appeared to overestimated the side shear resistance of all piles tested in this research unless additional consideration on the effect of rock mass weathering or fracturing was applied. The existing methods which consider the effect of rock mass condition were modified and/or extended for weathered rock mass where mass factor j is lower than 0.1, and RQD is below 50%.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4C
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• pp.205-212
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• 2008

In this research, the effect of rock mass weathering on the side shear resistance of drilled shaft socketed into igneous-metamorphic rock was investigated. For that, 23 cast-in-place concrete piles with diameters varying from 400mm to 1,500mm were constructed at four different sites, and the static axial load tests were performed to examine the resistant behavior of the piles. A comprehensive field/laboratory testing program at the field test site was also performed to describe the in situ rock mass conditions quantitatively. The side shear resistance of rock socketed piles was found to have no intimate correlation with the compressive strength of the intact rock. However, the global rock mass strength, which was calculated by the Hoek and Brown criteria, was found to closely correlate to the side shear resistance. The ground investigation data regarding the rock mass conditions (e.g. $E_m$, $E_{ur}$, $p_{lm}$, RMR, RQD, j) were also found to be highly correlated with the side shear resistance, showing the coefficients of correlation greater than 0.75 in most cases. Additionally, the applicability of existing methods for the side shear resistance of weathered granite-gneiss was verified by comparison with the field test data. The existing methods which consider the effect of rock mass condition were modified and/or extended for weathered rock mass where mass factor j is lower than 0.15, and RQD is below 50%.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.3
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• pp.129-135
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• 2021

Rock sheds are a type of rockfall protection facility that is installed on the road near steep slopes, where large amount of rockfall is expected. Rock sheds are generally designed to resist approximately 200 kJ to 3,000 kJ of rockfall energy. In a previous study, a new type rock shed structure having a concrete-filled tube (CFT) main frame was proposed. By using CFT as the main frame in a rock shed, rapid construction is possible. Additionally, high load carrying capacity and ductility can be achieved. The behavior of the proposed rock shed structure was studied via elastic analysis with the equivalent static load of rockfall energy as in a previous study. However, it is necessary to investigate the behavior of the proposed rock shed in more detail with a full 3D finite element (FE) model considering realistic rockfall load. The FE model for the CFT rock shed main frame was developed first in this study. Then, the resistance of the CFT rock shed main frame Under ultimate rockfall energy was investigated.

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.404-406
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• 2001

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.144-146
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• 2003

Techniques for rock slope management and assessment must be developed for the prevention and mitigation of rock fall hazards. To enable this, the rock discontinuity such as fault and joint data must be surveyed, analysed and managed. For this, the discontinuities were detected by automatic and semi-automatic method using DEM and ortho-rectified image of rock slope and the rock slope analysis and management system was developed using GIS. Using the system, slope locations and discontinuities data were constructed to spatial database. The system is consist of ‘Data Management’, ‘Rock Slope DB’, ‘Basic Information’, ‘Image Processing’, ‘Image Analys ing’, ‘Edit’, ‘View’, ‘Theme’, ‘Graphic’, ‘Window’ and ‘Help’. The system was developed using avenue of ArcView 3.2.

• Geomechanics and Engineering
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• v.23 no.6
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• pp.503-512
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• 2020

Mining activities focus on the production of mineral resources for energy generation and raw material requirements worldwide and it is a known fact that shallow reserves become scarce. For this reason, exploration of new resources proceeds consistently to meet the increasing energy and raw material demand of industrial activities. Rock mechanics has a vital role in underground mining and surface mining. Devices and instruments used in laboratory testing to determine rock mechanics related parameters might have limited sensing capability of the failure behavior. However, methodologies such as, thermal cameras, digital speckle correlation method and acoustic emission might enable to investigate the initial crack formation in detail. Regarding this, in this study, thermographic analysis was performed to analyze the failure behaviors of different types of rock specimens during uniaxial compressive strength experiments. The energy dissipation profiles of different types of rocks were characterized by the temperature difference recorded with an infrared thermal camera during experiments. The temperature increase at the failure moment was detected as 4.45℃ and 9.58℃ for andesite and gneiss-schist specimens, respectively. Higher temperature increase was observed with respect to higher UCS value. Besides, a temperature decreases of about 0.5-0.6℃ was recorded during the experiments of the marble specimens. The temperature change on the specimen is related to release of radiation energy. As a result of the porosity tests, it was observed that increase in the porosity rate from 5.65% to 20.97% can be associated to higher radiation energy released, from 12.68 kJ to 297.18 kJ.

• Journal of the Korean GEO-environmental Society
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• v.23 no.3
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• pp.5-13
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• 2022

In this study a test was conducted to identify weak section using 100kJ class rock energy to find out the protection performance of rockfall prevention fences in Korea. Performance rating of the rockfall protection fences is very low (48~61kJ) compared to that of foreign countries and it is necessary to determine whether it can function properly if high rock energy is generated. Furthermore, a reinforcing technology that can improve to 100kJ energy on the existing rockfall protection fences should be developed. Therefore, this study confirmed the protection performance using 100kJ rock energy in the existing rockfall protection fence system (for national road, for highway) and identified weak section of post, wire ropes and nets. Furthermore, it will be used as basic data for developing 100kJ class reinforcement technology without dismantling the existing rockfall protection fence (48-61kJ).

• Tunnel and Underground Space
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• v.10 no.2
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• pp.227-236
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• 2000

The fracture toughness can be measured by the two testing methods using chevron-notched specimen according to the ISRM Working Group of Commission of Testing Methods. They are chevron bend (CB) test and short rod (SR) test. In this study, the suggested methods (Level I tests) were conducted on the CB and SR specimens of Chuncheon granite. In addition. the J-integral analysis was combined with an acoustic emission technique to determine the fracture toughness. The results from two telling methods were analyzed in terms of the anisotropy and the acoustic emission characteristics.

• Geomechanics and Engineering
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• v.8 no.1
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• pp.97-111
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• 2015

The kinematical approach of limit analysis is used to estimate the three dimensional stability analysis of rock slopes with nonlinear Hoek-Brown criterion under earthquake forces. The generalized tangential technique is introduced, which makes limit analysis apply to rock slope problem possible. This technique formulates the three dimensional stability problem as a classical nonlinear programming problem. A nonlinear programming algorithm is coded to search for the least upper bound solution. To prove the validity of the present approach, static stability factors are compared with the previous solutions, using a linear failure criterion. Three dimensional seismic and static stability factors are calculated for rock slopes. Numerical results of indicate that the factors increase with the ratio of slope width and height, and are presented for practical use in rock engineering.