• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1995.03a
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• pp.1-26
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• 1995

Key aspects of the Norwegian Method of Tunnelling (NMT) are reviewed. These include a predictive method of support design using the six-parameter Q-system of rock mass characterisation. The rock mass rating or Q-value is updated during tunnel driving. The designed tunnel support generally consists of wet process, steel fibre reinforced shotcrete combined with fully grouted, untensioned rock bolts, Even in poor rock conditions S(fr) + B usually acts as the final rock reinforcement and tunnel lining. Since it is a drained lining, it is very economic compared to cast concrete with membranes. Light, free-standing steel liners are used to prevent water affecting the runnel environment. Rock mass conditions, and hence lining design and cost estimation can be assessed by careful use of seismic surveys. Relationships between the P-wave velocity, the rock mass deformation modulus and the Q-value have recently been established, where tunnel depth, rock porosity and the uniaxial compression strength of the rock are important variables. The rock mass modulus estimate, and simple index testing of the joints, provide the key input which joints are discretely represented (either in two dimensions with the UDEC code or in three dimensions with the 3DEC code) is generally favoured compared to continuum analysis. The latter may give a misleading impression of uniformity and deformations tend to be understimated. Q-system NMT designs of S(fr) + B (fibre reinforced shotcrete and bolting) are numerically checked and adjustments made to bolt capacities and shotcrete thickness if overloading is evident around the modelled profile.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.789-792
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• 2004

This study aims to detect only voids and estimate the cross-sectional size and thickness of voids using radar. A new method based on radar image processing is carried out with various void sizes and depths. The regression relationship between void size which has different depth and the amplitude characteristics of the radar return is considered in a new method of this research. For the purpose of examining; this regression relationship, experiments with change of void depth, surface area and thickness were carried out. Finally, the threshold value for image processing which aims to represent only voids to be fitted size (width) can be obtained. As the results, a proposed method in this study has a possibility of detecting only voids and estimating void size and thickness with good accuracy.

• Fire Science and Engineering
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• v.32 no.1
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• pp.81-88
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• 2018

Air and ultra lightweight aerogels were used to lighten the weight of the firefighters' protective clothing. In order to lighten the firefighters' protective clothing composed of 3 layers (outer shell, mid-layer, lining), it was most effective to replace the lining which occupied the largest weight in the total weight with the new materials. Thermal protective performance tests were carried out on flame (ASTM D 4108), radiant heat (KS K ISO 6942) and mixing heat (KS K ISO 17492) of flame and radiation. When the lining felt was replaced with an air layer, the air layer must be at least 3 mm to meet the KFI and ISO standards for the thermal protective performance. However, even if the thickness of the air layer increased to 10 mm, the thermal protective performance was lower than that of the existing products. When the felt was replaced with aerogels, the TPP rating (ASTM D 4108) satisfied the KFI standard at the 2 mm thickness of the aerogels. When the thickness of the aerogels was 3 mm, the TPP rating was improved about 140% compared to the existing products. It was confirmed that not only weight reduction but also thermal protective performance was improved by use of aerogels. However, due to the fragile nature of aerogels, a method of fixing them to a constant thickness between layers constituting a firefighters' protective clothing should be considered in the future.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.512-517
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• 2008

The brake system is very important part of the machine working. If the machine can't be stopped, it would be serious accident. It is the same as the ship. The mooring winch brake hold the ship in harbor. But sometimes it appeared the excessive stress and brake lining would be broken. So it is necessary to change the shape of brake system with improve the braking power. This study carried out research on optimum design like as moved the position of link pin or modified the thickness of brake band and lining.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.363-366
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• 2005

The radar method based non-destruction inspection stands in the spotlight of concrete tunnel lining due to the advantages of less restrictions of applicability, simpleness and quickness. However, in the case of utilizing at constructions, the decomposition ability is decreased because the effect of damping and dispersion is potent and the utilization of high frequency is difficult. In particular, it is very difficult to investigate the size and thickness of tunnel using the low frequency radar with low decomposition ability In this work, to resolve the above problems, the effect of arrangement between adjacent tunnels is investigated utilizing the low frequency radar and results are reported

• Proceedings of the Korean Geotechical Society Conference
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• 1999.12a
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• pp.169-180
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• 1999

Ground penetrating radar(GPR) uses radio waves to detect buried objects in any non-metallic material. Initially it was used to detect structures in ice. GPR has evolved to include the penetration of soils, rocks and man-made structures. GPR uses a sensitive detector to record weak radio waves reflected from objects embedded in the material under investigation. In this study, the GPR is applied to outside plant telecommunication facilities such as cable tunnels, manholes and underground conduits and model experiments to obtain radar characteristics. The thickness and soundness of tunnel lining can be evaluated, and the location of rebars and steel ribs can also be found effectively. The location of underground conduits as well as manholes can be found and the results of GPR give good coincidence with design drawings. In order to investigate the tunnel lining, the GPR mounted vehicle is developed and it is proved that the vehicle can save time and manpower.

• Journal of the Korean Home Economics Association
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• v.11 no.1
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• pp.26-43
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• 1973

This study was carried out on the Sewbility of Urethane Foam usually used as coldproof lining. The Sewability was estimated with the Puckering Grade and Seam Efficiency according to the thicknes of urethane foam, fineness and material of sewing thread, and the sort of covering fabric. The result shows the following ; 1. The thick foam proportinally shows the low Puckering Grade. 2. Effect on the sewability is small in fineness of sewing thread but large in material. Especially silk thread shows the greatest sewability in foam sewing. When the material of covering fabric is same as that of sewing thread (for example ; p/c fabric and p/c thread) the sewability is excellent in special. 3. Taffeta in covering foam is not suitable to foam sewing, satin and twill show superior sewability without reagrd to the thickness of foam. 4. In case of sewing foam covered with tricot, optimum thickness of foam and fineness of sewing thread through pretest must determine. 5. The thicker foam is the better seam efficiency tends, and Seam Efficiency largely effects to the strength of the sewing thread itself. 6. The seam Efficiency can heighten with the strength of sewing thread in proportion to that of covering fabric.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.817-820
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• 2000

Existence of void or delamination inside building foundation or tunneling lining can cause serious problems in structural safety. Therefore, 0probing of such voids in architectural and civil structures is an important process in evaluating the overall integrity of the structures. In this study, the radar method has been examined in its use in detecting voids inside concrete specimens. The dimensions of the specimens are 1,000 mm(width) $\times$ 600 mm (height) $\times$ 140 mm (thickness). A void is embedded inside concrete specimens with the dimensions of 200 mm(width) $\times$ 600 mm (height) $\times$ 50 mm (thickness). Concrete cover depth of 30 mm, 60 mm is studied for comparison. In both cases, the voids is located with 1 GHz antenna.

• Journal of the Korean GEO-environmental Society
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• v.18 no.3
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• pp.15-23
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• 2017

Gangwon Province, located in the northeastern part of South Korea, is the coldest area in South Korea with 90% of the total area as mountainous. Therefore, tunnel damage has been reported continuously in winter. But there has been lack of researches on frost heave occurring behind tunnel lining. In this study, numerical analysis was conducted to investigate the frost depth in road tunnel constructed in Gangwon province. Based on the database on road tunnel and weather in Gangwon province, a standard tunnel shape and geotechnical properties of ground was determined. And then thermal analysis for the frost depth according to the temperature change and ground conditions were conducted. Analysis result showed that the sensitivity to frost heave of metamorphic rock and sedimentary rock is higher than sand. Lower initial ground temperature leads to deeper frost depth and consequently increases frost damage. In addition, lining thickness, specific heat capacity, and thermal conductivity also affect greatly on the variation of frost depth.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.3
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• pp.187-195
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• 2005

When a tunnel is excavated below groundwater table, the groundwater flow occurs towards the tunnel resulting in the seepage pressure. In this paper, the effect of groundwater flows on the behavior of shotcrete lining installed between ground-liner interfaces was studied considering permeability ratio between the ground and the shotcrete into account. Three-dimensional coupled finite element analysis was performed for this assessment. Seepage forces will seriously affect the shotcrete behavior since arching phenomena do not occur in seepage forces. A parametric study was conducted on the various tunnelling situations including interfacial properties between ground and shotcrete lining, the shape of tunnel cross-section and the thickness of liner, etc. Moreover, the convergence-confinement method (CCM) of a NATM tunnel considering seepage forces was proposed. The result showed that the more water tight is the shotcrete, the smaller is the convergence and the larger is the internal pressure. Therefore, the watertight fiber-reinforced shotcrete is found to be even more advantageous when used in under water tunnel.