• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.611-620
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• 2019

The shield tunnel was mostly applied to cable tunnel with a diameter of 3~4 m, recently 7.8 m diameter shield tunnel was constructed in the lower section of the Incheon International Airport runway and is planning or under construction to roads and railway tunnels in the lower section of the Han River. Segments are also becoming larger as the shield tunnel cross-section increases, which causes a number of problems in the design, construction, and performance evaluation of segments. In this study, segment lining structural safety, criteria for serviceability check considering axial forces and quality control method for approximately 8 m in diameter shield tunnel were reviewed by field measurements and full scale bending test.

• Geomechanics and Engineering
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• v.30 no.4
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• pp.325-336
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• 2022

This paper analyzes the ground surface settlements induced by side-by-side twin shield tunnels bored in sedimentary soils, which primarily consist of sand with clay strata above the tunnel crown. The measurements were obtained during the construction of twin tunnels underneath the Incheon International Airport (IIA) located in Korea. The measured surface settlement troughs are approximated with Gaussian functions. The trough width parameters i and K of the settlement troughs produced by the first and second tunnel passings are determined, along with those for the total settlement trough. The surface settlement troughs produced by the first shield passing are reasonably represented by a symmetric Gaussian curve. The surface settlement troughs induced by the second shield tunnel display marginal asymmetric shapes at selected sections. The total settlement troughs are fitted both with a shifted symmetric Gaussian function and the superposition method utilizing an asymmetric function for the incremental trough produced by the second tunnel. It is revealed that the superposition method does not always produce better fits with the total settlement. Instead, the shifted symmetric Gaussian function is overall demonstrated to provide more favorable agreements with the recordings. Therefore, the shifted symmetric Gaussian function is recommended to be used in the design for the prediction of the settlement in clays caused by twin tunneling considering the simplicity of the procedure compared with the superposition method. The amount of increase in the width parameter K for the twin tunnel relative to that for the single tunnel is quantified, which can be used for a preliminary estimate of the surface settlement in clay induced by twin shield tunnels.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4146-4158
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• 2022

Ultra-high performance concrete (UHPC) has been widely utilized in military and civil protective structures to resist intensive loadings attributed to its excellent properties, e.g., high tensile/compressive strength, high dynamic toughness and impact resistance. At present, aiming to improve the defects of the traditional vertical concrete cask (VCC), i.e., the external storage facility of spent fuel, with normal strength concrete (NSC) shield, e.g., heavy weight and difficult to fabricate/transform, the feasibility of UHPC applied in the shield of VCC is numerically examined considering its high radiation and corrosion resistance. Firstly, the finite element (FE) analyses approach and material model parameters of NSC and UHPC are verified based on the 1/3 scaled VCC tip-over test and drop hammer test on UHPC members, respectively. Then, the refined FE model of prototypical VCC is established and utilized to examine its dynamic behaviors and damage distribution in accidental tip-over and end-drop events, in which the various influential factors, e.g., UHPC shield thickness, concrete ground thickness, and sealing methods of steel container are considered. In conclusion, by quantitatively evaluating the safety of VCC in terms of the shield damage and vibrations, it is found that adopting the 300 mm-thick UHPC shield instead of the conventional 650 mm-thick NSC shield can reduce about 1/3 of the total weight of VCC, i.e., about 50 t, and 37% floor space, as well as guarantee the structural integrity of VCC during the accidental drop simultaneously. Besides, based on the parametric analyses, the thickness of concrete ground in the VCC storage site is recommended as less than 500 mm, and the welded connection is recommended for the sealing method of steel containers.

• The Journal of Korean Society for Radiation Therapy
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• v.27 no.1
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• pp.87-95
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• 2015

Purpose : This study presents the usefulness assessment of secondary shield for the lens exposure dose reduction during radiation treatment of peripheral orbit. Materials and Methods : We accomplished IMRT treatment plan similar with a real one through the computed treatment planning system after CT simulation using human phantom. For the secondary shield, we used Pb plate (thickness 3mm, diameter 25mm) and 3 mm tungsten eye-shield block. And we compared lens dose using OSLD between on TPS and on simulation. Also, we irradiated 200 MU(6 MV, SPD(Source to Phantom Distance)=100 cm, $F{\cdot}S\;5{\times}5cm$) on a 5cm acrylic phantom using the secondary shielding material of same condition, 3mm Pb and tungsten eye-shield block. And we carried out the same experiment using 8cm Pb block to limit effect of leakage & transmitted radiation out of irradiation field. We attached OSLD with a 1cm away from the field at the side of phantom and applied a 3mm bolus equivalent to the thickness of eyelid. Results : Using human phantom, the Lens dose on IMRT treatment plan is 315.9cGy and the real measurement value is 216.7cGy. And after secondary shield using 3mm Pb plate and tungsten eye-shield block, each lens dose is 234.3, 224.1 cGy. The result of a experiment using acrylic phantom, each value is 5.24, 5.42 and 5.39 cGy in case of no block, 3mm Pb plate and tungsten eye-shield block. Applying O.S.B out of the field, each value is 1.79, 2.00 and 2.02 cGy in case of no block, 3mm Pb plate and tungsten eye-shield block. Conclusion : When secondary shielding material is used to protect critical organ while irradiating photon, high atomic number material (like metal) that is near by critical organ can be cause of dose increase according to treatment region and beam direction because head leakage and collimator & MLC transmitted radiation are exist even if it's out of the field. The attempt of secondary shield for the decrease of exposure dose was meaningful, but untested attempt can have a reverse effect. So, a preliminary inspection through Q.A must be necessary.

• Corrosion Science and Technology
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• v.6 no.3
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• pp.90-95
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• 2007

Cathodic protection technology has been widely used on ship's outer hull and inner side of ballast water tanks as a supplementary corrosion protection measure in combination with protective organic coatings. Impressed current cathodic protection system is typically opted for the ship's hull and, sacrificial anode system, for ballast water tanks. The anticipation and interest in cathodic protection system for ships has been surprisingly low-eyed to date in comparison with protective coatings. Computational analysis for the verification of cathodic protection design has been tried sometimes for offshore marine structures, however, in commercial shipbuilding section, decades old design practice is still applied, and no systematic or analytical verification work has been done for that. In this respect, over-rotection from un-erified initial design protocol has been also concerned by several experts. Especially, it was frequently reported in sacrificial anode system that even after full design life time, anode was remaining nearly intact. Another issue for impressed current system, for example, is that the anode shield area design for ship's outer hull should be compromised with actual application situation, because the state-of-the-art design equation is quite impractical from the applicator's stand. Besides that, in this study, some other critical design issues for sacrificial anode and impressed current cathodic protection system were discussed.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.277-280
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• 1991

We have developed 154kV OF cable accessories from 1987. 4 to 1990. 10 by doing assembly design, investing equipment, manufacturing inspecting parts, type testing in labortary, in our company, in KEPCO. The one of those accessories. Oil Stop Joint, has been developed by using Shield Metal Embeded Type Epoxy Unit. This is More reliable than old type.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.549-550
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• 2011

In this study simple formula of magnetic field in case of shield with finite-width infinite-length were deduced. By using these formula calculation is very fast and programing is easy. The formula are applicable to analysis of shielding effectiveness and the design for shield of distribution lines.

• Transactions of the Korean hydrogen and new energy society
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• v.8 no.2
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• pp.57-65
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• 1997

Thermal analysis has been performed to design a high-performance $LH_2$ vessel with about 1% per day evaporation loss. Analysis includes the combined insulations of MLI(Multi-Layer Insulation) and VCS (Vapor-Cooled Shield) under high vacuum. Combined insulation of MLI and VCS shows the existence of optimal location of VCS to minimize evaporation loss. Comparison of parallel-type DVCS (Double Vapor-Cooled Shield) and serial-type DVCS is also made to show the effectiveness of the system. The results indicate that the serial-type DVCS vessel is better than the parallel-type DVCS vessel with respect to overall evaporation loss. The combined insulation of SVCS (Single Vapor-Cooled Shield) with a partial MLI can give a similar performance characteristics compared to that with MLI and DVCS.

• Journal of Radiation Protection and Research
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• v.17 no.2
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• pp.37-48
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• 1992

It was carried out to analyze the nuclear energy deposition rates for the bulk shield components including materials of the primary end shield and side primary systems of Wolsong 2 during steady state operations at 100% full power using ANISN code. This paper has been prepared to support system design of Wolsong 2.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.1
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• pp.107-119
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• 1993

The objective of this study is to analyze the static and dynamic characteristics of automotive rubber components by computer simulation. Bush / rectangular type engine mounts and wind shield weather strip are analyzed by using the commercial code ABAQUS and the results are verified by experiments. Large deformation static response is analyzed in order to get the information about the deformation pattern and static stiffness of engine mounts, and about the seperation force of wind shield weather strip from body. The isothermal steady-state dynamic response of components which have been subjected to an initial static pre-load is analyzed for the dynamic stiffness of engine mount rubber components. There are good agreements between simulation and experiments. So it is possible to apply the computer simulation to the design of automotive rubber components.