• Structural Engineering and Mechanics
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• v.38 no.1
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• pp.65-79
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• 2011

Concrete hydraulic structures such as: Dams, Intake Towers, Piers and dock are usually recognized as" Vital and Special Structures" that must have sufficient safety margin at critical conditions like when earthquake occurred as same as normal servicing time. Hence, to evaluate hydrodynamic pressures generated due to seismic forces and Fluid-Structure Interaction (FSI); introduction to fluid-structure domains and interaction between them are inevitable. For this purpose, first step is exact modeling of water-structure and their interaction conditions. In this paper, the basic equation involved the water-structure-foundation interaction and the effective factors are explained briefly for concrete hydraulic structure types. The finite element modeling of two concrete gravity dams with 5 m, 150 m height, reservoir water and foundation bed rock is idealized and then the effects of fluid domain and bed rock have been investigated on modal characteristic of dams. The analytical results obtained from numerical studies and modal analysis show that the accurate modeling of dam-reservoir-foundation and their interaction considerably affects the modal periods, mode shapes and modal hydrodynamic pressure distribution. The results show that the foundation bed rock modeling increases modal periods about 80%, where reservoir modeling changes modal shapes and increases the period of all modes up to 30%. Reservoir-dam-foundation interaction increases modal period from 30% to 100% for different cases.

• Tunnel and Underground Space
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• v.23 no.4
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• pp.271-279
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• 2013

This report introduced the types of drilling equipment and their operation mechanisms. The state of the art technologies of the Top-hammer drill equipment were investigated and the technology level of Korean drill industry was compared to that of the advanced country. Based on the investigation, the necessity of fusion research and development in the Korean drilling technology and industry was discussed, and the future strategy to catch up with the advanced technology was suggested.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.435-437
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• 2003

In order to investigate processes and factors controlling the chemical and isotopic compositions of the Han River, seasonal studies were carried out. The North Han River was much lower in the concentrations of total dissolved solids (TDS), dissolved inorganic carbon (DIC) and major ions than the South Han River, but higher in $SiO_2$ concentration, $\delta$$^{34}$ $S_{so4}$ value and $^{87}$ Sr/$^{86}$ Sr ratio. This indicates that the chemical and isotopic compositions of the Han River were strongly controlled by the geology of their drainage basins: silicate rocks in the North Han River and carbonate rocks in the South Han River. The $\delta$$^{34}$ $S_{so4}$ values were relatively higher in the North Han River (5.90$\pm$1.46$\textperthousand$)) than in the South Han River (3.48$\pm$0.73$\textperthousand$). This implies that dissolved S $O_{4}$$^{2-}$ in the North Han River might be mostly derived from deposition of atmospheric sulfates, whereas in the South Han River from oxidation of sulfide minerals in the abandoned poly-metallic deposits and the coal-bearing sedimentary rocks distributed over the upstream as well as deposition of atmospheric sulfates. The $^{87}$ S $r^{86}$ Sr ratios in the North Han River were distinctly higher than those in the South Han River, reflecting water-rock interaction with different rock types.pes.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.1
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• pp.3-9
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• 2001

The investigation of the fragmentation of blasted rocks is particularly important because it is a measure of the blast efficiency. The degree of fragmentation has a major effect on the efficiency of the loading and crushing operations. Getting such an information on the large pile of blasted rock is not an easy operation. This paper presents the results of case study to evaluate the performance of two types of tunnel blasting: V-cut and burn cut. The digital images of muckpiles were analyzed to produce size distribution and it was compared with those of predictive equations.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.1
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• pp.21-26
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• 2001

Till now a lot of studies has been performed to increase the efficiency of tunnel blasting. Nevertheless there are still uncertainties of input parameter to determine the specific charge. In order to solve this problem, the rock types and the charges of 17 road tunnel sites were analyzed. As a result of these analyses an empirical formula depending on rock type and charge was developed. Through this formula rational tunnel blasting will be designed by quantitative method rather than by assumption.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.15 no.3
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• pp.213-220
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• 2005

Penetration and health effect of fibers was related with their diameters and length. The purpose of this study is to characterize and compare the diameter and length of airborne man-made mineral fibers(MMMF) or synthetic vitreous fibers in the related industries. The average fiber length of the continuous filament glass, rock wool, refractory ceramic, and glass wool fibers production industries approximately 27, 28, 35, $50-105{\mu}m$. Airborne glass fibers were longest in all the type of MMMFs. The average diameters of airborne fibers generated from refractory ceramic, rock wool, glass wool, continuous filament glass fibers production industries were approximately 1.0, 1.6, 1.5-4 and $10{\mu}m$, respectively. The percentages of respirable fibers(<$3{\mu}m$) were 94% for RCFs, 73% for rock wool fibers, 61.0% for glass fibers, and 1.6% for filament glass fibers. The length of glass fibers were the longest in all types of fibers, and length of the others were similar. The refractory ceramic fibers were smallest in diameters and highest in fraction of respirable fibers.

• Journal of the Korean GEO-environmental Society
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• v.7 no.2
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• pp.43-53
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• 2006

Hydraulic fracturing is an important and abundant process in both industrial applications and natural environments. The formation of hydraulic fractures includes nucleation, growth, and termination in numerous rock types and stress regimes, at scales ranging from microns to many kilometers. As a result, fracture segmentation, commonly observed at all scales and in all geo-materials, contributes to this complexity in many ways. In particular, the mechanical interaction of fracture segments strongly affect almost all hydraulic fracturing processes. In this paper, the segmented fracture opening deformation in rock by hydraulic fracturing is quantified using boundary collocation method and is compared with non-interacting single fracture.

• Journal of Soil and Groundwater Environment
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• v.19 no.4
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• pp.12-22
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• 2014

This study evaluated the pattern of groundwater fluctuation in cyrstalline rock using time series and factor analyses. From the results, groundwater level for the 18 wells was classified into 4 types reflecting the hydrogeological properties and rainfall event. Type 1 (DB1-5, DB1-6, DB2-2, KB-10, KB-13) was significantly influenced by groundwater flow through water-conducting features, whereas type 2 (DB1-3, DB1-7, KB-1~KB-3, KB-7, KB-11, KB-14, KB-15) was affected by minor fracture network as well as rainfall event. Type 3 (DB1-1, DB1-2) was mainly influenced by surface infiltration of rainfall event. Type 4 (DB1-8, KB-9) was reflected by the irregular variation of groundwater level caused by anisotropy and heterogeneity of crystalline rock.

• Geomechanics and Engineering
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• v.33 no.4
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• pp.353-367
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• 2023

The construction of a protective embankment is a suitable strategy to stop and control high-energy rock blocks' impacts during the rockfall phenomenon. In this paper, based on the discrete element numerical method, by modeling an existing embankment reinforced with geogrid, its stability status under the impact of a rock block with two types of low and high kinetic energy, namely 2402 and 4180 kJ, respectively, has been investigated. The modeling results show that the use of geogrid has caused the displacement in the front and back of the embankment to decrease by more than 30%. In this case, the reinforced embankment has stopped the rock block earlier. The displacements obtained from the DEM modeling are compared with the displacements measured from an actual practical experiment to evaluate the results' validity. Comparison between the results shows that the displacement values are close together, while the maximum percentage error in previous studies by an analytical method and the finite element method was 76.4% and 36.6%, respectively. Therefore, the obtained results indicate the discrete numerical method's high ability compared to other numerical and analytical methods to simulate and design the geogrid-reinforced soil embankment under natural disasters such as rockfall with a minor error.

• Tunnel and Underground Space
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• v.7 no.4
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• pp.274-283
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• 1997

It is necessary to estimate the soundness of tunnel using non-destructive tests(NDT) for effective repairs and maintenances. But, the state of tunnel lining could not be investigated using previous non-destructive techniques, due to the various types of support and accessibility only from one side in tunnel lining. Recently, the various non-destructive techniques such as ground penetrating radar(GPR) have been researched and developed for inspection of tunnel lining. In this study, the usefulness and applicability of GPR test in tunnel lining inspection has been investigated through model tests and tunnel site application. This paper described the tunnel lining inspection for lining thickness, cavity and support using GPR test. From the results of tests, we have concluded that GPR test are very useful and effective techniques to look into the interior of lining and measure the lining thickness.