• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.3
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• pp.9-14
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• 2002

It is common that the soil layer is few meters below the earth surface and there are rock masses below the soil layer in the view of geological characteristics in Korea. The boundary between rock and soil is clearly divided. When dealing with the stability of rock masses, as in the case of rock slopes or dam foundations, the majority of the collapses is not within the soil layer, but within the soil-rock boundary. Therefore, it is important to identify the shear strength characteristics between soil-rock contacts. It has been common practice to assume that the strength of the soil or shale represents the minimum strength present. However, it has been suggested by Patton(1968) that such an assumption may not be valid and that lower shear strengths might be obtained along the soil-rock interface than for either material alone. Then, in this thesis, introduce rock and residual soil shear strength tests and the specimen preparation and testing procedures are described in detail and also the testing results are presented and discussed.

• Geomechanics and Engineering
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• v.9 no.3
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• pp.329-344
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• 2015

Cratering tests in rock are generally carried out to identify its fragmentation characteristics. The test results can be used to estimate the minimum amount of explosives required for the target volume of rock fragmentation. However, it is not easy to perform this type of test due to its high cost and difficulty in securing the test site with the same ground conditions as the site where blasting is to be performed. Consequently, this study investigates the characteristics of rock fragmentation by using the hydrocode in the platform of AUTODYN. The effectiveness of the numerical models adopted are validated against several cratering test results available in the literature, and the effects of rock mass classification and ground formation on crater size are examined. The numerical analysis shows that the dimension of a crater is increased with a decrease in rock quality, and the formation of a crater is highly dependent on a rock of lowest quality in the case of mixed ground. It is expected that the results of the present study can also be applied to the estimation of the level and extent of the damage induced by blasting in concrete structures.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2004.10a
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• pp.119-134
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• 2004

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2004.04a
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• pp.231-239
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• 2004

• Tunnel and Underground Space
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• v.4 no.1
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• pp.38-46
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• 1994

This paper concerns the design of blasts adjacent to structures and facilities. In order to investigate the site characteristics, measurements of in-situ wave propagation and laboratory tests of rock cores taken from the boreholes were carried out. Effects of rock media and delay intervals on ground vibration levels were identified from over sixty measurements of three times of test blasts. For practical use in the field, an empirical propagation equation was derived so as to reflect the characteristics of rock media and delay effects. Safe limits of vibration level for structures were conservatively established based on various suggested criteria. Safe limits for facilities were adopted so that vibration levels induced by blasting should not exceed the allowable limits specified in the manufacturer's installation condition. Suggested were blast pattern and operation to enhance the rock fracturing and to reduce the ground vibration levels under the restricted conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.711-716
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• 2002

When judging the ground by core-logging, depth of coring might be stopped by coming into view of the moderately weathered rock and also considered as bedrock line. However, highly weathered rock may appear again, if coring more, because there are core-stones in the residual soil and highly weathered rock by the effect of hydraulic-thermal differentiation and does the irregular rock weathering or metamorphic rock region. Therefore, there are room for misunderstanding of diagnosing the moderately weathered rock. Even though the irregular ground where the corestones were come out will show clear geotechnical differences between the ground and the gradually weathered bedrock, nowadays, the construction sites do not take into account the characteristic of core-stone region. In conclusion, to study the failure-strength characteristics of soil layers containing core-stones, we made artificial core-stones and varied percentage of corestones, and measured cohesion and friction factors to adjust them to construction sites containing corestones such as slope, tunnel, and underground.

• Tunnel and Underground Space
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• v.21 no.6
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• pp.460-470
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• 2011

Wave velocity was measured to define the weathering characteristics of rock and the strength evaluation of weathered rock on a target of the Aso gravestones with various sizes under the natural environment. As a result, the size correction method which was changed sample of the different size to one of the same size for evaluating wave velocity was proposed, and also suggested the NET (Normalized Elapsed Time) as a new weathering index of rock. In addition, the strength of the weathered rock was estimated from the weathering classification of rock using the NET. Wave velocity of welded tuff was high and didn't show velocity degradation, on the other hand, one of andesite was low and showed velocity degradation. The degree of weathering between rocks of the different size is considered to be comparable, applying the NET based on the on the $V_p/V_o$-NET curve. Furthermore, the classification of rock weathering stages using the NET based on the $S_c/S_o$-NET curve was available, and the estimation of strength for the weathered rock was also possible.

• Tunnel and Underground Space
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• v.7 no.2
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• pp.91-99
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• 1997

To stabilize the energy price, the more storage facilities of energy are required and among the storage methods of LPG and LNG, the method of storage at low temperature under normal confining pressure is considered. It is needed to understand the mechanical and thermal characteristics of rock under temperature variation so that the behaviors of rock can be predicted. In this paper, the variation of the rock charateristics of the Hwangdeung granite and the Boryung sandstone is studied at low temperature. The mechanical characteristics of rock under low temperatures are that as temperature decreased, unaxial compression strength and Young's modulus increased for Hwangdeung granite; strength and Young's modulus in wet condition were greater than those in dry condition. In the case of Boryung sandstone, as temperature decreases unaxial compression strength and Young's modulus increase but decrease below -10$0^{\circ}C$ in dry condition and below -16$0^{\circ}C$ in wet condtion. The mechanical characteristics of rock after cooling to previous temperature and thawing are that uniaxial compression strength and Young's modulus decrease as temperature decreases. Uniaxial compression strength and Young's modulus in wet conditon decrease more than those in dry condition. Brazilian tension strength decreases as temperature decreases.

• Tunnel and Underground Space
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• v.2 no.2
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• pp.224-236
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• 1992

It is very important to determine the thermo-mechanical characteristics of the rock mass surrounding the repository of radioctive waste and the LPG storage cavern. In this study, Hwasoon-Shist. Dado-Tuff adn Chunan-Tonalite were the selected rock types. Temperature dependence of the mechanical properteis such as uniaxial compressive strength, tensile strength, Young's modulus was investigated by measuring the behaviour of these properties due to the variation of temperature. Also, the characteristics of strength and deformation of these rocks were examined through high-temperature triaxial compression tests with varing temperatures and confining pressures. Important results obtained are as follows: In high temperature tests, the uniaxial compressive strength and Yong's modulus of Tonalite showed a sligth increase at a temperature up to 300$^{\circ}C$ and a sharp decrease beyond 300$^{\circ}C$, and the tensile strength showed a linear decrease with increasing heating-temperature. In high-temperature triaxial compression test, both the failure stress and Young's modulus of Tonalite increased with the increase of confining pressure at constant heating-temperature, and the failure stress decreased at 100$^{\circ}C$ but increased at 200$^{\circ}C$ under a constant confining pressure. In low temperature tests, the uniaxial compressive and tensile strengths and Young's modulus of these rocks increased as the cooling-temperature is reduced. Also, the uniaxial compressive and tensile strengths of wet rock specimens are less than those of dry rock specimens.

• Tunnel and Underground Space
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• v.34 no.3
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• pp.231-247
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• 2024

In the field of high-level radioactive waste disposal targeting deep rock environments, hydraulic characteristic information serves as the most important key factor in selecting relevant disposal sites, detailed design of disposal facilities, derivation of optimal construction plans, and safety evaluation during operation. Since various rock types are mixed and distributed in a small area in Korea, it is important to conduct preliminary work to analyze the hydrogeological characteristics of rock aquifers for various rock types and compile the resulting data into a database. In this paper, we obtained hydraulic conductivity data, which is the most representative field hydraulic characteristic of a high-depth volcanic bedrock aquifer, and also analyzed and evaluated the field data. To acquire field data, we used a high-performance hydraulic testing system developed in-house and applied standardized test methods and investigation procedures. In the process of hydraulic characteristic data analysis, hydraulic conductivity values were obtained for each depth, and the pattern of groundwater flow through permeable rock joints located in the test section was also evaluated. It is expected that the series of data acquisition methods, procedures, and analysis results proposed in this report can be used to build a database of hydraulic characteristics data for high-depth rock aquifers in Korea. In addition, it is expected that it will play a role in improving technical know-how to be applied to research on hydraulic characteristic according to various bedrock types in the future.