• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.353-360
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• 1998

Dynamic measurements are used rather sparingly to determine the elastic moduli of rock cores and modulus values are not much utilized in design practice. The reason seems to result from the general perception that values obtained by dynamic measurement are much higher (about 10 times) than those determined statically. This paper presents results from dynamic and static tests on rock cores. The findings are : 1) elastic moduli can be consistently determined by laboratory seismic testing. 2) nonlear deformation characteristic of rock cores was tentatively proposed with variation in elastic modulus with strain.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.4
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• pp.95-100
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• 1999

Dynamic measurements are used rather sparingly to determine the elastic modull of rock cores and modulus values are not much utilized in design practice. The reason seems to result from the general perception that values obtained by dynamic measurement are much higher (about 10 times) than those determined statically. This paper presents results from dynamic and static tests on rock cores. The findings are: 1) elastic modull can be consistently determined by laboratory seismic testing. 2) nonlinear deformation characteristics of rock cores was tentatively proposed with variation in elastic modulus with strain.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.75-80
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• 1998

Dynamic measurements are used rather sparingly to determine the elastic moduli of rock cores and modulus values are not much utilized in design practices. The reason seems to result from the general perception that values obtained by dynamic measurement are much higher (about 10 time) than those determined statically. This paper presents results from dynamic and static tests on rock cores. One of the findings is that both moduli determined by statically and dynamically on a solid rock core agrees well at the same-strain. At different strain levels, the ratio between dynamic and static modult widely varies depending upon micro-cracks and discontinuites of rock cores.

• Geophysics and Geophysical Exploration
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• v.19 no.3
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• pp.121-130
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• 2016

Several factors are discussed that should be considered in measuring thermal conductivity of rock cores with a PEDB (potable electronic divided bar) system, which is relatively accurate and easy to operate, and can measure the thermal conductivity of rock cores for various diameters. Then the system is applied to measure thermal conductivity of 70 rock cores from Ulleung Island. Air temperature affects most on the thermal conductivity measurements, so that it is very important to minimize the temperature change during the measurement. Other factors such as the temperature of heat source, averaging time window on the thermal conductivity measurements do not affect much compared to air temperature. Slightly higher thermal conductivity is measured when using the thermal contact paste between the sample and heat source or heat sink. Especially, rock cores with irregular surface showed bigger difference. Repeatability showed less than ${\pm}0.3%$ for standard samples and less than ${\pm}4%$ for rock samples, respectively, when the room temperature changes within $1^{\circ}C$ during the measurements. Thermal conductivity of the rock cores from Ulleung Island roughly increases as depth increases but does not show any dependency on the rock types.

• Geomechanics and Engineering
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• v.29 no.1
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• pp.65-77
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• 2022

Determination of strength properties of intact rock using artificial cores has been considered in recent years. In this study, some relationships for estimating the static properties of dolomudstone cores of the Asmari reservoir were presented using artificial cores prepared from cuttings of two wells, southwest of Iran. For this purpose, first natural cuttings (NC) and 33 cores including dolomite limestone (dolomudstone), anhydrite and anhydrite dolomite were prepared between depths of 1714 and 2208 meters. Petrographic, physical, mechanical and dynamic tests were performed on cores, NC and artificial cuttings (AC) which was prepared from the residuals of dolomudstone cores. For preparing the artificial cores, the average porosity of the dolomudstone cores was considered and determined using four methods. Artificial and natural cuttings were classified as dolomite limestone and dolomite limestone to calcareous dolomite, respectively. Using ordinary Portland cement (OPC), water, AC and NC artificial cores were prepared. Results of evaluating the proposed relationships using statistical criteria showed that the static properties of the artificial cores can be used to predict the static properties of the dolomudstone cores.

• Journal of the Korean Geotechnical Society
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• v.29 no.1
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• pp.149-159
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• 2013

This paper deals with behaviors of Poisson's ratio with water content through uniaxial compressive strength against 307 individual rock cores, which are classified into sedimentary, igneous and metamorphic rock. Poissons' ratio demonstrates independent behaviors and does not correlate with mechanical and physical parameter of rocks. The water content behavior of Poissson's ratio represents decrease, increase and random style. Rock samples with decreasing behavior demonstrate absolute preponderance above the 70% level. As Poisson' ratio shows independent behaviors, it should be considered based on experimental results of in-situ rock in the process of design, construction, and supervision.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.229-238
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• 2002

This paper introduces the surface roughness parameter, Rs to the characterization of joint roughness and quantitatively illustrates the influence of joint roughness on the joint shear strength. A new peak shear strength criterion for rock joints using Rs is suggested. The results show that the surface roughness parameter, Rs can appropriately reflect the degree of roughness for the rock joint surfaces tested in this study A measuring interval of 2mm and profile length of 5cm can be used to characterize the joint roughness of the rock core size surfaces; however, the scale of fluctuation, $\delta_\alpha$ should be considered to extend the surface roughness parameter, Rs to the large-scale field rock joint surfaces. For the smooth joint roughness, sliding of the rock cores is the principal shear mechanism; however, the breakage of roughness from the rock cores is inferred for rougher joint roughness.

• Economic and Environmental Geology
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• v.41 no.1
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• pp.93-113
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• 2008

This study presents petrochemistry and $^{40}Ar/^{39}Ar$ absolute ages of subsurface volcanic rock cores from twenty(20) boreholes in the eastern lowland (altitude loom below) of Jeju Island, Handeong-Jongdal-Udo-Susan-Samdal-Hacheon areas, and discusses topography and volcanism in the area. The subsurface volcanic rock cores are mainly basalts in composition with minor tholeiitic andesites and basaltic trachyandesites. Sequences of intercalated tholeiitic, transitional and alkalic lavas suggest that tholeiitic and transitional to alkalic lavas must have erupted contemporaneously. Especially, occurrences of trachybasalts and basaltic trachyandesites at the bases in the area imply that the volcanism in the area was initiated with slightly differentiated alkaline magma activity. The $^{40}Ar/^{39}Ar$ absolute ages of the subsurface volcanic rock cores range from $526{\pm}23ka\;to\;38{\pm}4Ka$. The lava-forming Hawaiian volcanic activities of the eastern lowland can be divided into five sequences on the basis of sediment distribution, whole rock geochemistry and $^{40}Ar/^{39}Ar$ absolute ages of the subsurface volcanic rock cores; stage I-U$(550{\sim}400Ka)$, stage II$(400{\sim}300Ka)$ and stage III$(300{\sim}200Ka)$ during syn-depositional stage of Seoguipo Formation, and stage IV$(200{\sim}100Ka)$ and stage V(younger than 100Ka) during post-depositional stage. In the eastern lowland of Jeju Island, compositional variations and local occurrences of the subsurface volcanic rocks as well as existences of various intercalated sediment layers (including hydrovolcanogenic clasts) suggest that the volcanism must have continued for long time intermittently and that the land has been progressively glowed from inland to coast by volcanic activities and sedimentation. It reveals that the subsurface volcanic rocks in the eastern lowland of Jeju Island must have erupted during relatively younger than 200Ka of stages IV and V. The results of this study are partly in contrast with those of previous studies. This study stresses the need that previous reported volcanic activities in Jeju Island based on K-Ar ages of volcanic rocks should be carefully reviewed, and that stratigraphic correlation from boreholes should be conducted by quantitative criteria combined with petrography and petrochemstry as well as radiometric studies of volcanic rock cores.

• Economic and Environmental Geology
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• v.27 no.3
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• pp.289-294
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• 1994

This paper describes an effective utilization method of well logging data and boring cores for understanding the geology of Keoje-do area. Six holes were drilled in 1988-1989, and all rock cores were recovered. Nevertheless, seven kinds of logs were carried out in each borehole. The geologic situations of the drilling sites are accurately evaluated from a comparison between core descriptions and well logging data. Porosities and clay contents of sedimentary rocks can be calculated using the data of density and gamma-ray logs. Fractured zones are easily detected from the change in inside diameter of borehole by caliper log. Sonic, density and gamma-ray logging data clearly indicate alternated and dyke zones; the former can be detceted from an acoustic wave attenuation and a decline of compaction by sonic and density logs, the latter can be detected from the amount of potassium contents of bed rock and dyke by gamma-ray log.

• Economic and Environmental Geology
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• v.27 no.6
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• pp.563-569
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• 1994

Resistivity Image Profiling has been applied to a geological survey in the Keoje-do area. Survey lines are located near the KD-02 and KD-06 wells in the area, where we have already sampled all rock cores and carried out several kinds of geophysical logs. In each site a resistivity cross-section is obtained by inverting pole-pole apparent resistivities. Comparing the reconstructed resistivity section with the rock cores and logging data obtained in the well provides a detailed picture of subsurface geology. The geology of KD-02 site is composed of conglomerate, sandstone and shale with fractures. The reconstructed resistivity image is useful for assessing the grade of weathering of these rocks. The KD-06 site is mainly underlain by granitic rocks, and its fresh basement can be delineated by resistivities over $1000{\Omega}{\cdot}m$.