• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.447-450
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• 2005

The purpose of this study is to investigate properties of compressive strength of concrete using the shale rock as coarse aggregates. To evaluate properties of compressive strength of concrete using crushed shale rock, we performed the expriment according to the proportioning strength of $10MPa\~40MPa$ and the slupm of $12\%\~15\%$. The result of this study is as follow. The compressive strength of concrete using crushed shale rock is lower than those of granite aggregates. The proportioning strength is higher, the reduction of comperssive strength of concrete using the shale rock is higher.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.79-86
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• 2004

Interfacial properties between rock mass and shotcrete play a significant role in the transmission of loads from the ground to shotcrete. These properties have a major effect on the behaviours of rock mass and shotcrete. They, however, have merely been considered in most of numerical analyses, and little care has been taken in identifying them. This paper aimed to identify interfacial properties including cohesion, tension, friction angle, shear stiffness, and normal stiffness, through direct shear tests as well as interface normal compression tests for shotcrete/rock cores obtained from a tunnel sidewall. Mechanical properties such as compressive strength and elastic modulus were also measured to compare them with the time-dependent variation of interfacial properties. Based on the experiments, interfacial properties between rock and shotcrete showed a significant time-dependent variation similar to those of its mechanical properties. In addition, the time-dependent behaviours of interfacial properties could be well regressed through exponential and logarithmic functions of time.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.967-973
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• 2004

Rock socketed drilled shafts transfer significant portion of structural loads at the socketed part. Therefore, a proper design of side and base resistances of a shaft at the socket is a major concern for the geotechnical engineers. In this study, we modified the Hoek-Brown criterion to estimate side resistance of rock socketed drilled shafts. Earlier method to compute side resistance of a shaft is linear or power functions of intact rock masses. However, side resistance is mobilized like shearing which influenced by the mechanical properties of concrete and rock masses, adhesion of rock/concrete interface, roughness of rock socket. Therefore, a single coefficient or power of uniaxial compressive strength of intact rock cannot provide accurate values of side resistance in a wide range of the uniaxial compressive strength. A new approach proposed in this study can consider in situ rock mass condition (frequency or discontinuities, weathering condition), and rock types thus, it has a wider applicability than the earlier models.

• Journal of Conservation Science
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• v.28 no.4
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• pp.329-341
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• 2012

Magai Wareiishi Jizo (Buddhist statue carved on rock surface) is close to shoreline and a part of rock block is periodically immersed by seawater. Rock material of the Wareiishi-jizo statue is composed mainly of medium or coarse-grained biotite granite and very durable. However, physical properties of the rock have been changed according to the complex interactions of the salt solution and surrounding environment. Exfoliation of the rock surface is a serious condition by salt crystallization. Exfoliation (14.6%) is concentrated on the upper part of the rock block with mainly boundary of seawater as the center. On the other hand, lower part of the rock block show black layers by contaminants deposition. In addition, brown discoloration and biological contaminants is overlapped. Rock surface show high discoloration rate of 50.5% (black discoloration, 29.2% > yellow discoloration, 14.1% > brown discoloration, 4.4% > green discoloration, 2.9%). Upper part of the rock block had a lot of change in the physical properties than lower part that is immersed by seawater. In particular, surface properties of the rock block was very weak state at the boundary surface of seawater permeation.

• Tunnel and Underground Space
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• v.20 no.4
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• pp.241-251
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• 2010

The polar region is in the limelight for an academic worth as well as plenty of natural resources. The study on the polar region was reviewed for better understanding of the polar region and its rock properties. The antarctica has a windy and dry climate along with the lowest temperature on the earth. The thermal distribution according to depth in the area was reported: The freezing-thawing process was repeated in shallow depth, and the temperature falls down below zero under the specific depth. There is a great temperature difference between the atmosphere and rock. A research reported for the degree of weathering of the antarctic slope by using Schmidt hammer and Taffoni test. The rock specimens weathered by repeated freezing-thawing process were tested of the shore hardness and uniaxial compressive strength: The rock strength gradually decreased as the freezing-thawing process was repeated. The comprehensive mechanical properties of the polar region rocks and the relationship between the laboratory weathering test result and the real rock property change in the site remain as future research topics.

• Economic and Environmental Geology
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• v.39 no.4 s.179
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• pp.451-471
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• 2006

Major projects and research topics in the field of rock mechanics are analyzed to obtain the following results: $\cdot$ Rock mechanics deals with the behavior of deformation, failure and displacement of the rock and rock mass on the basis of geological basics. Discontinuities in the rock mass are the most important parameters to control the behavior of rock mass around underground openings. $\cdot$ The objective of site investigation and testing is to determine the strength properties of the rock mass and the in situ stress regime. Specimens for laboratory and in situ tests are to be selected in order that the results of the tests give the representative properties oi the rock mass of the site in question. $\cdot$ The result of a numerical model would be better evaluated not quantitatively but qualitatively. The displacement behavior of the rock mass has to be monitored properly for the NATM (New Austrian Tunneling Method) principles. $\cdot$ The stability of rock slope is to be evaluated preferably by back analysis with strength parameters, such as cohesion and friction angle.

• Geomechanics and Engineering
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• v.22 no.5
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• pp.461-473
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• 2020

Natural rock mass contains defects of different shapes, usually filled with inclusions such as clay or gravel. The presence of inclusions affects the failure characteristics and mechanical properties of rock mass. In this study, the strength and failure characteristics of rock with inclusions were studied using the particle flow code under uniaxial compression. The results show that the presence of inclusions not only improves the mechanical properties of rock with defects but also increases the bearing capacity of rock. Circular inclusion has the most obvious effect on improving model strength. The inclusions affect the stress distribution, development of initial crack, change in crack propagation characteristics, and failure mode of rock. In defect models, concentration area of the maximum tensile stress is generated at the top and bottom of defect, and the maximum compressive stress is distributed on the left and right sides of defect. In filled models, the tensile stress and compressive stress are uniformly distributed. Failing mode of defect models is mainly tensile failure, while that of filled models is mainly shear failure.

• Tunnel and Underground Space
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• v.28 no.5
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• pp.476-492
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• 2018

In this study, various laboratory experiments were conducted on tuff, basalt and diorite specimens, which were obtained in the southern part of Korean Peninsula. Experiments were performed under dry and water saturated conditions. Results showed that strength degradation and change of deformation characteristics were remarkable although the specimens had small porosity. Based on the results, regression models that are capable of predicting important mechanical rock properties, such as uniaxial compressive strength, Young's modulus, Brazilian tensile strength were proposed. P-wave velocity and Shore hardness were selected as independent variables and the results showed satisfactory prediction performance for the experimental data collected in this study.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.4
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• pp.337-348
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• 2003

The propagation mechanism of a detonation pressure with fully coupled charge is clarified and the blasting pressure propagated in rock mass is derived from the application of shock wave theory. The blasting pressure was a function of detonation velocity, isentropic exponent, explosive density, Hugoniot parameters, and rock density. Probabilistic distribution is obtained by using explosion tests on emulsion and rock property tests on granite in Seoul and then the probabilistic distribution of the blasting pressure is derived from the above mentioned properties. The probabilistic distributions of explosive properties and rock properties show a normal distribution so that the blasting pressure propagated in rock can be also regarded as a normal distribution. Parametric analysis was performed to pinpoint the most influential parameter that affects the blasting pressure and it was found that the detonation velocity is the most sensitive parameter. Moreover, uncertainty analysis was performed to figure out the effect of each parameter uncertainty on the uncertainty of blasting pressure. Its result showed that uncertainty of natural rock properties constitutes the main portion of blasting pressure uncertainty rather than that of explosive properties. In other words, since rock property uncertainty is much larger than detonation velocity uncertainty the blasting pressure uncertainty is more influenced by the former than by the latter even though the detonation velocity is found to be the most influencing parameter on the blasting pressure.

• Tunnel and Underground Space
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• v.19 no.4
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• pp.328-338
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• 2009

Schmidt hammer test as an indirect method has so far been widely applied for determining the physical properties of intact rock, and many researchers have developed procedures for its use on rock cores, blocks and in field. Though many methods have developed upto date for indirect using, the almost were single blow which has many errors. The purpose of this study was to evaluate the established as for ASTM, ISRM, BSI, Poole & Farmer and Hucka method and to suggest a new optimum test method and statistical analysis on rocks. The finding has indicated that succeeding blow has served as an optimal to predict physical properties of rocks. To conduct the experiment, researchers have examined 150 rock blocks, which include igneous, metamorphic and sedimentary rocks in Korea nation wide.