• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.2
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• pp.143-153
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• 2002

Convergence Confinement Method (CCM) makes a more simple judgement in a ground-support reaction than numerical method. Also this method is good for the applicability of construction feedback and the analysis of field measurement. However, there has been little research with respect to the application of CCM in tunnel construction. One of the problems in CCM is a decision of the time to support installation. To decide a reasonable supporting installation time, support characteristic curve and displacement characteristic curve considering construction stage are proposed. In addition, to predict displacement distribution ratio and load distribution ratio, the time dependent support reaction curve is used. Finally, through a comparison of the result between CCM and numerical analysis, the trust of this study is proved and the practical application is proposed to control resonable tunnel construction management.

• Tunnel and Underground Space
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• v.8 no.4
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• pp.296-306
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• 1998

Ongoing huge Bakun Hydropower project is including the construction of a 210 m height hydroelectric rockfill dam with an installed capacity of 2,520 MW and a power transmission system connecting to the existing networks between Sarawak and peninsula Malaysia. In order to allow the main dam construction during the dry season, the Ballui river will have to be detoured through 3 concrete lined diversion tunnels with an internal diameter of 12 m and a length of 1,400 m each. The geology of Bakun site belongs to the several thousand meters thick Belaga formation deposited from the late Cteteceous to the early Teriary in the Northwest Borneo geosyncline. The orientation of the bedding plane, strike at N55$^{\circ}$E to N70$^{\circ}$E and dip at 50$^{\circ}$SE to 70$^{\circ}$SE, is developed uniformly in Bakun sedimentary rocks. Rock mechanical characteristics of Bakun site have been classified into 4 rock mass types(RMT) depending on the degree of weathering and the occurrence of rock jointing with RMR. Graywacke(Sandstone) as well as Shale can take place together in the same rock mass type if their rock mass properties are similar. It was summarized the rock support type and support system design of underground diversion tunnels in view of rock mechanics.

• Journal of the Korean GEO-environmental Society
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• v.12 no.9
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• pp.47-54
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• 2011

This study has analysed overbreaks, shotcrete rebound and the ratio between the actual quantity of shotcrete sprayed compared to designed quantity measured during a NATM tunnel construction. Based on the measurements of size of the excavated tunnel faces, an average overbreak was about 28.5 cm, which is about 260% of allowable overbreak. The measured shotcrete rebound was about 7.2% in average which is about half the allowable rebound(15%). In addition, due to overbreaks and rebound the actual quantity of shotcrete used in the tunnelling work was about 116.5 % of the designed value. It has been found from the field measurements that the quantity of shotcrete showed some relation with rock mass rating(RMR) and the standard guideline of tunnel supports, but the size of overbreak showed less correlation with RMR and the standard guideline of tunnel supports. Hence, the current tunnel design specifications stating the size of overbreak based entirely on the standard guideline for tunnel supports should perhaps be reestablished. The insight into the design guideline regarding overbreak and actual quantity of shotcrete will be reported and discussed.

• The Journal of Engineering Geology
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• v.30 no.1
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• pp.43-57
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• 2020

The objective of this study was to evaluate the performance of high-strength lattice girders as a possible superior alternative to conventional steel arch ribs. For this purpose, the structural characteristics of supports were analyzed using numerical analysis, and their performance was evaluated using maximum bending load tests and tensile tests of the welded joint. According to the results of structural analysis, the optimum size of the upper and lower members and plates is 50 mm × 31.8 mm × 25.4 mm, demonstrating excellent functionality and economic efficiency. High-strength lattice girders of dimensions 55 mm × 30 mm × 20 mm and 85 mm × 30 mm × 20 mm, determined from bending load tests, are found to meet both the reference values and the target values of H-profiles 100 and 125. A review of the ratio of theoretical deflection to actual deflection shows that the high-strength lattice girder developed during this study meets fewer than five of the evaluation criteria for lattice girder deflections proposed by the Federal Railway Department of Germany. Finally, tensile test results reveal that the welded joint of the high-strength lattice girder at the main steel bar-auxiliary steel bar-plate junction exceeds the target value, indicating that the welded joint has sufficient stability.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.5
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• pp.379-387
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• 2010

In this study, a case study was introduced for the design of a twin tunnel along high speed national highway Route 12 from Damyang to Sungsan. It was related to determine the optimal tunnel support pattern and excavation method based on a risk analysis in order to incorporate the uncertainty of ground properties. To this end, three alternatives with different amounts of support and excavation method were selected and risk analysis was performed by applying Monte Carlo simulation technique, respectively. Stability of the tunnel was quantified by the factor of safety. To improve the result, the 729 cases of the combination of ground properties (deformation modulus, cohesion, and internal friction angle) satisfying a Gaussian distribution were generated and applied. Also, stability of the tunnel was confirmed by analyzing the distribution of both displacement and shotcrete bending stress.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.1
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• pp.89-96
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• 2005

Due to fast development of digital equipments, various information techniques have been applied to the tunneling and a decision aid system based on IT has also been used during excavation stage. A PDA based informative tunneling method is, therefore, studied in this paper and the decision aids for tunneling using digital face mapping data as well as geologic information in terms of digital data is developed. For this, wireless network, mobile computer, CDMA and digital camera have been combined to generate the digital map of the tunnel face and reinforcement or excavation pattern can be estimated based on digitalized geologic conditions. Future studies will be concentrated on the enhancement of the PDA S/W so that reinforcement method as well as the amount of reinforcements can also be stored in the same DB. Furthermore, field application of the S/W will be undertaken and a virtual reality technique will also be introduced to visualize all the tunneling work on the computer monitor.

• Tunnel and Underground Space
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• v.23 no.2
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• pp.130-140
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• 2013

In this study, scaled model tests were performed to investigate the stability of twin tunnels with small clearance, where the pillar widths were 0.5D and 0.25D, respectively. The tunnels were supposed to be constructed in anisotropic weathered rocks with $30^{\circ}$ inclined bedding planes, and the model tests were conducted under the condition of lateral pressure ratio, 1. Six types of test models which had respectively different pillar widths and support conditions were experimented, where crack initiating pressures, maximum pressures, failure modes of pillar and deformation behaviors around tunnels were investigated. The models with wider pillar were cracked under higher pressure than the models with shallower pillar. The models with lining support were cracked under higher pressure and showed less tunnel convergence than the unsupported models. The models with both lining and pillar reinforcement were proved to be most stable among the tested models. In particular, as the model of 0.25D pillar width with only lining support showed shear failure of pillar according to the existing bedding planes, so both lining and pillar reinforcement were thought to be indispensable in that case of tunnel.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2003.05a
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• pp.324-325
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• 2003

스쿠티카충은 해산어류의 체표 등과 같은 외부기관 뿐만 아니라 뇌에까지 침입하여 양식산업에 심대한 경제적 손실을 야기시키는 기생충으로써(Cheung et al., 1980; Ototake and Matsusato, 1986; Dragesco et al., 1995; Munday et at.,1997; Jee et al., 2001), 이 기생충에 의한 국내의 양식 넙치 폐사량은 총 폐사량의 약 10 % 정도 내외에 이르고 있다. 본 연구는 체내에 감염된 스쿠티카충에 대한 케토코나졸의 치료효과를 검토하고 본 약물의 넙치에 대한 안전성을 분석코자 하였다. (중략)

• Journal of the Korean GEO-environmental Society
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• v.11 no.11
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• pp.37-45
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• 2010

In this study, the value of numerical analysis was compared to the measured value of horizontal displacement during construction. And also, the value was reviewed by comparing with numbers calculated by SUNEX program and EXCAV program. When comparing to suggested values of the maximum horizontal displacement in clayey layer, the displacement caused by the IPS system is larger than one by the Strut girder type system. When comparing the result of SUNEX program to that of EXCAV program, the SUNEX program interprets larger value. It could be concluded the result of SUNEX program is closer to the suggested value, 0.5%H, in clayey layer. The result also shows that the internal friction angle(${\Phi}$) is the key factor of developing horizontal displacement rather than type of supporting systems or materials. That means small horizontal displacement occurs in sandy layer having large value of the internal friction angle, whereas vice versa in clayey layer having small value of the internal friction angle. Therefore, the result of EXCAV program is larger in sandy layer and vice versa in clayey layer. When comparing the measured result during construction to the value of 0.5%H, the measured result is 1.4 times greater than the value of 0.5%H. In contrast, the result of SUNEX program is only 78.1% of the value of 0.5%H and the one of EXCAV program is just 18.1% of that. This result shows the calculated value by SUNEX or EXCAV program is smaller than the observed value by measuring during construction. In result, more careful attention is needed to determine the behavior of the ground. To better analyze the behavior of the ground, more precise finite element method is required.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.69-79
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• 2012

This pre-supported nail method is able to decrease ground displacements more than NATM because this method reinforces ground with grouted steels before tunnel excavation. Therefore this method has advantage of being able to increase the stability and workability. This study presents applicability of pre-supported nail method with case of site measurement for shallow tunnel composed with high groundwater level and unconsolidated soil, performs this research the mechanism of new supporting system is compared with the conventional existing supporting system in terms of soil reinforcement. NATM has characteristics that construction stage displacement of the apparent height difference is observed in the step of divided excavation processing. Otherwise it is analyzed that pre-supported nail method is not sensitive in the displacement problem of excavation processing in comparison to NATM. It is found that this method is very applicable in shallow depth tunnel such as portal area, tunnel in soil and weak zone without arching effect.