• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1518-1525
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• 2008

This paper concerns optimum design of 2-Arch tunnel. A 2-Arch tunnel adopted in a subway tunnel construction site is considered in this study. A calibrated 3D finite element model was adopted to conduct a parametric study on the lagged distance between left and right tunnel faces. The results of analysis were examined to determine optimum lagged distance for minimizing the interaction between the left and right tunnels. The results indicated that the shotcrete lining stress and the center pillar load are more influenced by the second tunnel excavation than the tunnel deformation. Also shown is that a lagged distance of 20m is sufficient to minimize the interaction between two tunnels. Fundamental mechanism of 2-arch tunnel was also investigated based on the results.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.161-176
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• 1999

A powerful numerical method that can be used for modeling rock-structure interaction is the Discontinuous Deformation Analysis (D D A) method developed by Shi in 1988. In this method, rock masses are treated as systems of finite and deformable blocks. Large rock mass deformations and block movements are allowed. Although various extensions of the D D A method have been proposed in the literature, the method is not capable of modeling water-block interaction, sequential loading or unloading and rock reinforcement; three features that are needed when modeling surface or underground excavation in fractured rock. This paper presents three new extensions to the D D A method. The extensions consist of hydro-mechanical coupling between rock blocks and steady water flow in fractures, sequential loading or unloading, and rock reinforcement by rockbolts, shotcrete or concrete lining. Examples of application of the D D A method with the new extensions are presented. Simulations of the underground excavation of the \ulcornerUnju Tunnel\ulcorner in Korea were carried out to evaluate the influence of fracture flow, excavation sequence and reinforcement on the tunnel stability. The results of the present study indicate that fracture flow and improper selection of excavation sequence could have a destabilizing effect on the tunnel stability. On the other hand, reinforcement by rockbolts and shotcrete can stabilize the tunnel. It is found that, in general, the D D A program with the three new extensions can now be used as a practical tool in the design of underground structures. In particular, phases of construction (excavation, reinforcement) can now be simulated more realistically.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.315-323
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• 2016

This study examined the durability and method for making a mockup of bobsled tracks for constructing a bobsled stadium, which is a sport in the Winter Olympics. As bobsleigh games are very fast and dangerous, a safety design for players and a precise construction using highly efficient shotcrete is necessary. Moreover, a general molding construction is difficult because bobsleigh tracks are composed of various curves and slopes, and it is necessary to construct them using high-strength and high durability materials. The developed method for making a mockup and performing durability evaluation of bobsleigh tracks through this research will be applied in the construction of the 2018 Pyeongchang Winter Olympics Sliding centre and bobsleigh tracks using domestic techniques.

• Geotechnical Engineering
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• v.14 no.6
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• pp.17-32
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• 1998

The Bakun hydroelectric project includes the construction of a hydroelectric power plant with an installed capacity of 2,520MW and a power transmission system connecting to the existing transmission networks in Sarawak and Western Malaysia, The power station will consist of a 210m height concrete faced rockfill dam. During the construction of the dam and the power facilities the Balui river has to be diverted by three diversion tunnels with a length of some 1,400m each. The inner diameter of the tunnels is 12m and the tunnel width is 16m at the portal area. This paper describes the stability analysis and design methods for the open cut rock slopes in the inlet and outlet area of the diversion tunnels. The geotechnical parameters employed in stability calculations were given as a function of four. defined Rock Mass Types (RMT) which were based on RMR system from Bieniawski. The stability calculations procedure of the rock slopes are divided into two stages. In the first stage, it is calculated for the stability of each 'global' slope without any rock support and shotcrete system. In the second stage, it is calculated for each 'local'slope stability with berms and supported with rock bolts and shotcrete. The monitoring instrumentation was performed continuously and some of the design modification was carried out in order to increase the safety of failed area based on the unforeseen geological risks during the open cut excavation.

• 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.

• 한국터널공학회:학술대회논문집
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• 2005.04a
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• pp.105-116
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• 2005

This study investigated the applicability of the Artificial Neural Network(ANN) technique for prediction of tunnel behavior. For training data collection, a series of finite element analyses were conducted for actual tunnel project site. Using the data, optimimzed ANNs were developed through a sensitivity study on internal parameters. The developed ANNs can make tunneling related predictions such as tunnel crown settlement, shotcrete lining stress, ground surface settlement, and groundwater inflow rate. The results indicated that the developed ANNs can be used as an effective and efficient tool for tunnelling related prediction in practical tunneling situations.

• Geomechanics and Engineering
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• v.9 no.2
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• pp.195-205
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• 2015

Barricade failures generally occur at the early times of paste backfill when it is fresh in the stopes. The backfill strength increases and need for barricading pressure decreases as a result of the hydration reactions. In this study, paste backfill barricades of Cayeli copper mine were investigated to design cemented mineral processing plant tailings as barricade body concrete. Paste backfill in sub-level caving stopes of the mine needs to be barricaded for only four or five days. Therefore, short term strength and workability tests were applied on several cemented tailings material designs. Barricade failure mechanisms, important points of barricade designing and details of the new concrete material are explained in this work. According to the results obtained with this experimental study, the tailings were assessed to be used in concrete applied as temporary supports such as cemented paste backfill barricades.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.860-865
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• 2005

In Korea, NATM (New Austrian Tunneling Method) has widely been used in order for constructing tunnels. The major support materials of the method are the shotcrete and rock bolt together with the arch-shaped tunnel section, which ensure the inherent strength of the rock masses. One of the most important features of the method is the feedback system between tunnel analyses and measurements, such as tunnel displacement and support stresses. This study, therefore, attempts to examine the difference in displacement and stresses between numerical results. and measurements in order for more practical design and construction of tunnels.

• Tunnel and Underground Space
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• v.7 no.3
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• pp.191-201
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• 1997

Geological and geotechnical surveys, in general, should precede the excavation to ensure the safety of the tunnel and should be followed up according to the various geological condition during the excavation. However actually the standard support patterns which were decided during the design step used be insisted for the whole excavation steps in spite of the various geological conditions. OO tunnel was excavated with NATM and a support pattern type-V in weak rocks. When the tunnel was excavated up to 25m long, the severe displacement was generated in the portal area and the shotcrete was damaged to make the cracks and the tunnel face was totally collapsed. It might happen owing to the one-day heavy rain, but the exact reason for that accident should be found out and the new optimal support patternt needed. Consequently three dimensional numerical analysis was applied for the evaluation of the cause of the tunnel collapse instead of two dimensional analysis, because three dimensional analysis can show better the real field phenomenon than two dimensional analysis in which the load distribution methods are adopted for the tunnel excavation. We could simulate the actual situations with three dimensional finite difference code and propose the new optimal support patterns.

• Geomechanics and Engineering
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• v.28 no.2
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• pp.145-155
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• 2022

Safety is a most important parameters in underground railway transportation; Also stability of underground tunnel is very important in tunneling engineering. Design of a reliable support system requires an evaluation of both ground demand and support capacity. Iran's traditional railway tunnels are mainly supported with masonry structures or unsupported in high quality rock masses. A decrease in rock mass quality due to changes in groundwater regime creep and fatigue in rock and similar phenomena causes tunnel safety to decrease during time. The case study is an old tunnel in Iran, called "Keshvar"; it is more than 50 years old railway organization. In operating this Tunnel, until the several problems came up based on stability and leaking water. The goal of study is evaluation of the various reinforcement systems for supporting of the tunnel. The optimal selection of the reinforcement system is examined using TOPSIS Fuzzy method in light of the looming and available uncertainties. Several factors such as; the tunnel span, maintenance, drainage, sealing, ventilation, cost and safety were based to choose the method and system of designing. Therefore, by identifying these parameters, an optimal reinforcement system was selected and introduced. Based on optimization system for analysis, it is revealed that the systematic rock bolts and shotcrete protection had a most appropriate result for these kind of tunnel in Iran.