• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.257-266
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• 2004

A three node triangular element with drilling rotations incorporating improved higher-order zig-zag theory(HZZT) is developed to accurately assess the stress distribution through thickness of the laminated plate and analyze the vibration of pretwisted composite plates with embedded damping layer. Shear force matching conditions are enforced along the interfaces between the embedded damping patch and the border patch. The natural frequencies and model loss factors are calculated for cantilevered pretwisted composite blade with damping core with the present triangular element, and compared to experiments and MSC/NASTRAN using a layered combination of plate and solid elements.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.197-202
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• 2007

Most of seismic reflection prospecting assumes subsurface formation to be homogeneous media. These models are not capable of estimating small scale heterogeneity which is verified by well log data or drilling core. And those synthetic seismograms by homogeneous media are limited to explain various changes at field data. So we developed a inhomogeneous velocity model which can estimate inhomogeneity of background medium to implement numerical modeling from homogeneous medium and inhomogeneous medium on the model. Background medium using three autocorrelation functions in order to generate inhomogeneous velocity media was according to dominant wavelength of background medium and correlation length of random medium. And then we compared shot gathers. The results show that numerical modeling implemented at inhomogeneous medium depicts complex wave propagation of field data.

• The Journal of Engineering Geology
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• v.11 no.3
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• pp.279-294
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• 2001

When constructing subsurface structures and drilling wells, the precise hydraulic parameters must be obtained for operating safety and for developing enough quantity of groundwater, respectively. In this study we conducted water injection test at different depths on six boreholes drilled in the granite of Mt. Geumjeong. Hydraulic conductivity was calculated using Moye and Hvorslev methods. The relation between hydraulic conductivity and fracture frequency data obtained from acoustic televiewer and core log was analyzed. From the result, though the correlation coefficient between the hydraulic conductivity and the fracture frequency from acoustic televiewer data is higher than that between the hydraulic conductivity and the fracture frequency from core log data on most of the test holes, the correlation coefficient between the hydraulic conductivity and the fracture frequency from the televiewer data is lower than 0.5. This suggests that the hydraulic conductivity of granite in the study area is influenced not only by the fracture frequency but also by various factors of fracture network such as fracture aperture and length, interconnectivity of fractures, fracture orientation and angle, filling material and so on.

• Journal of Energy Engineering
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• v.22 no.2
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• pp.156-168
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• 2013

Drilling expedition #1 in 2007 and drilling expedition #2 in 2010 were performed for gas hydrate resources evaluation and optimal site selection of pilot test in Ulleung basin, East Sea, Korea. This study presents to build the 3D spatial distribution models using the estimated sedimentary facies, porosity, and gas hydrate saturation derived by well logs and core analysis data from UBGH1-4, UBGH1-9, UBGH1-10, UBGH1-14, UBGH2-2-1, UBGH2-2-2, UBGH2-6, UBGH2-9, UBGH2-10 and UBGH2-11. The objective of 3D spatial distribution modeling is to build a geological representation of the gas hydrate-bearing sediment that honors the heterogeneity in 3D grid scale. The facies modeling is populating sedimentary facies into a geological grid using sequential indicator simulation. The porosity and gas hydrate saturation modeling used sequential Gaussian simulation to populate properties stochastically into grid cells.

• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.133-143
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• 2011

In Mujoo area, the granitic pegmatites are developed in the granitic gneiss complex with Jurassic gneissic granites, where Nb-Ta mineralization were reported. Pegmatites are mainly composed of large crystals of quartz, feldspars of end-member orthoclase and albite, and muscovite. Nb-Ta minerals in study area are columbite (Nb > Ta) in composition. Chemistry of muscovites shows post-magmatic in origin and they are closely related with columbite. Large columbite, in pegmatites occurred with quartz and feldspars, while microcrystalline columbite is associated with muscovite. The Nb contents in large columbite are relatively higher than those in microcrystalline ones. Two pegmatites, 4~15 m in width and 120 m, 250 m in extension respective1y, are developed. Five drilling cores with total 600 m in length are finally obtained and revealed no possible potential for economic rare metals of Na-Ta deposits.

• The Journal of the Petrological Society of Korea
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• v.24 no.3
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• pp.233-252
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• 2015

This research are systematic and scientific approaches to obtain the distribution, occurrence and quality of granite stone for building purposes. The process of dimension stone exploration must be carried out to know the underground potentiality of granitic body using the basic data collection and study, field mapping, detailed drilling survey, televiewer technique, and physical and chemical tests in the Geochang area. Televiewer data obtained in drilling boreholes can be accurately distinguished from the discontinuous face, strike and inclination, extension which is difficult to obtain in a core logging. 3D joint images will be helpful to establish a quarry exploitation plan because the 3D joint images give quite accurate information down to depth below the outcrop surface. Through the process of the quality estimation on the Geochang site, the proven reserve estimated as dimensional building stone are calculated with good quality in petrologic and physical properties.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.181-191
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• 2016

In geological storage of $CO_2$, the behavior of $CO_2$ is influenced by pore network of rock. In this study, the drilling cores from Pohang Basin were analyzed quantitatively using three-dimensional images acquired by X-ray micro computed tomography. The porosities of sandstone specimens around 740 m-depth (T1), 780 m-depth (T2) and 810 m-depth (T3) which were target strata were 25.22%, 23.97%, 6.28%, respectively. Equivalent diameter, volume, area, local thickness of pores inside the sandstone specimens were analyzed. As a result, the microstructural properties of T1 and T2 specimens were more suitable for geological storage of $CO_2$ than those of T3 specimens. The result of the study can be used as input data of the site for decision of injection condition, flow simulation and so on.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.92-97
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• 2018

Recently, the safety issue of high-rise concrete buildings damaged by fire, helicopter collisions, earthquakes, and faulty construction has attracted a great deal of interest. It is essential to know the strength of the concrete in order to accurately evaluate its safety for the reinforcement of these buildings. The core drilling method is considered to be the most effective method of assessing the compressive strength of concrete. However, it is very difficult to retrieve the core without the reinforcing bars, because buildings made with high-strength concrete are overcrowded with reinforcing bars. These reinforcing bars are often present in the core specimens, but there are few research studies and no regulations concerning the assessment of the strength of the concrete for high-strength core specimens within reinforcing bars. The purpose of this study is to investigate the effects of the reinforcement arrangement on the strength of the concrete and to present the quantitative values. To complete this research, the compressive strengths of different types of concrete with two different strengths (40 MPa and 60 MPa), two reinforcing bar diameters (10 mm and 12 mm), and 15 types of specimens with or without reinforcement arrangements were prepared and tested. As a result, the strength of the cylinders whose volume is less than or equal to the reinforcement volume of $53.1cm^3$ (about 4 - 13 mm) was predicted to have a low value of up to 60% of the strength of the cylinders without reinforcement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.552-558
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• 2016

Recently, the repair and reinforcement of deteriorated concrete buildings has attracted much interest. In order to accurately evaluate the safety of these existing structures, it is essential to know the strength of the concrete that they are composed of. The core drilling method is considered to be the most effective and common method of assessing the compressive strength of concrete. In general, the regulations do not permit the core specimens within reinforcing bars to be used to assess the strength of the concrete, even if the core specimens contain reinforcing bars in some cases. The purpose of this study is to investigate the effects of the reinforcement arrangement on the compressive strength of concrete, and to propose the quantitative specific standard of strength for core specimens containing reinforcements, in order to facilitate their safe inspection by repair or retrofit companies who want to evaluate the soundness of the structures. To complete this research, one type of cylinder specimen without reinforcement and 14 types of specimens with reinforcement arrangements were prepared and their compressive strength evaluated. It was found that the strength of the cylinders with reinforcement volumes of up to $50cm^3$ (about 4-ϕ13mm) was more than 80% of that of the cylinders without any reinforcement.

• Journal of the Korean earth science society
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• v.39 no.2
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• pp.154-163
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• 2018

Geoacoustic model comprises physical and acoustic properties of submarine bottom layers influencing sound transmission through sea water and underwater. This study suggested for the first time that we made a geoacoustic model of long-coring bottom layers at the SSDP-105 drilling site of the Ulsan coastal area, which is located in the southwestern inner shelf of the East Sea. The geoacoustic model of 52 m depth below seafloor with three-layer geoacoustic units was reconstructed in the coastal sedimentary strata at 79 m in water depth. The geoacoustic model was based on the data of a deep-drilled sediment core of SSDP-105 and sparker seismic profiles in the study area. For actual modeling, the geoacoustic property values of the models were compensated to in situ depth values below the sea floor using the Hamilton modeling method. We suggest that the geoacoustic model be used for geoacoustic and underwater acoustic experiments of mid- and low-frequency reflecting on the deep bottom layers in the Ulsan coastal area of the East Sea.