• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.823-837
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• 2018

Congestion of the city with the rapid industrial development was accelerated to build complex social infrastructure. And numerous structures have been designed and constructed in accordance with these requirements. Recently, to solve complex urban traffic, many researches of large-diameter tunnel under construction downtown are in progress. The large-diameter tunnel has been developed with a versatile double-deck of deep depth tunnel. For the safe tunnel construction, ground reinforcement methods have been developed in the weakened pillar section like as junction of tunnel. This paper focuses on evaluation of the effects of new developed ground reinforcement methods in double-deck junction. The values of reinforcement determined from the existing and developed methods were compared to each other by numerical simulation.

• Tunnel and Underground Space
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• v.26 no.1
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• pp.32-45
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• 2016

For effective utilization of downtown area, many studies about underground have been performed around the world, and double-deck tunnel have being operated in USA, Europe and China, etc. (A86 East Duplex in France, M30 tunnel project in Spain, SR-99 in seattle, USA, Yangtze river tunnel in China) In Korea, the research about network type double-deck tunnel in deep underground space is in progress to solve the traffic jam and secure the ground space. In this study, a number of factors required for double-deck tunnel in deep underground are analyzed through the existing ventilation design outline and unique ventilation design factors for network type double-deck tunnel are established by reviewing design cases of overseas double-deck tunnel.

• Fire Science and Engineering
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• v.30 no.2
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• pp.81-86
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• 2016

Recently, frequent traffic congestion has occurred in domestic urban roads. As a solution for downtown traffic congestion in domestic urban roads, plans for great depth underground double-deck tunnels have been made. Great depth underground double-deck tunnels that have been planned for passenger cars, has the structure of a network type; the entry of vehicles is carried out in the underground space. In these network great depth underground double-deck tunnels, the cross section and the height of the tunnel are smaller than the general road tunnel, and the smoke of a fire will propagate faster than the evacuation of tunnel passengers by the action of the traffic-ventilation and casualties are expected. Therefore, in the present study, an attempt was made to prevent the delay system for fire smoke diffusion at the time of a fire in a domestic network great depth underground double-deck tunnel according to the area of the tunnel block during the operation of the delay system for fire smoke diffusion to analyze the effects of reducing the inflow velocity. When the area of the tunnel block was not less than 50%, the effect of reducing about 21% of the wind speed acting on the tunnel was significant. If the area is more than 50%, the diffusion rate of fire smoke was reduced by approximately 21%, which will be useful for a safe evacuation.

• Tunnel and Underground Space
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• v.27 no.1
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• pp.50-57
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• 2017

In this study, the experiment for determining shock loss at the branch is conducted for the design of network double-deck road tunnel ventilation. The shock loss coefficient that determines the quantity of shock loss has been considered only regarding the constant aspect ratio of circular or rectangular section. However the suggestion of shock loss coefficient is needed since the aspect ratio of double-deck road tunnel for small vehicle is considered around 1:3 with the low height in Korea. The experiment model was made with the scale of around 1:23 applying Reynolds similarity law, so that the shock loss coefficient on the branch of the large aspect ratio was measured. The result of the study showed that shock loss coefficients of both split branch and straight branch were measured two to three times higher than those calculated from the theoretical equation or design values of previous studies. Therefore the study resulted the effect of large aspect ratio on shock loss coefficient was huge, and it is expected that precise design value can be suggested for the design of network double-deck tunnel ventilation.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.132-145
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• 2017

Shock loss was not applied for the tunnel ventilation of road tunnel in the past. However, pressure losses due to the shock loss can be significant in network double-deck road tunnel in which combining and separating road structures exist. For the optimum ventilation design of network double-deck road tunnel, this study conducted 3D CFD numerical analysis for the shock loss at the combining and separating flows. The CFD model was made with the real-scale model that was the standard section of double-deck road tunnel. The shock loss coefficient of various combining and separating angles and road width was obtained and compared to the existing design values. As a result of the comparison, the shock loss coefficient of the $30^{\circ}$ separating flow model was higher and that of the two-lane combining flow model was lower. Since the combining and separating angles and road width can be important for the design of shock loss estimation, it is considered that this study can provide the accurate design factors for the calculation of ventilation system capacity. In addition, this study conducted 3D CFD analysis in order to calculate the shock loss coefficient of both combining and separating flows at flared intersection, and the result was compared with the design values of ASHRAE. The model that was not widened at the intersection showed three times higher at the most, and the other model that was widened at the intersection resulted two times higher shock loss coefficients.

• Tunnel and Underground Space
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• v.28 no.1
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• pp.111-124
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• 2018

The purpose of this study is to analyze ventilation design factor for network-type double-deck road tunnel that have been developed actively around the world. A numerical analysis was carried out through computational fluid dynamics (CFD) to derive shock loss coefficient that occurs due to the change in cross sectional area at both merging section and diverging section. The model used for the numerical analysis is real-scale model and the reliability of the result is secured by comparing with the coefficient of the previous studies. As a result of this study, shock loss coefficient was calculated depending on the change in cross-sectional area ratio and was higher than the result of previous studies in case of both merging section and diverging section. It is considered that the characteristics of the geometrical structure of network-type double-deck road tunnel have a great impact on shock loss coefficient. Therefore, the result of this study is expected to be helpful for more accurate ventilation design of network-type double-deck road tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.115-126
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• 2019

Recently, in order to solve the traffic congestion in urban areas and to improve the peripheral environment, research on the design and construction technology development of great depth underground double-deck tunnel is under way by using the underground space in the urban area. The network type double-deck tunnel is in the form of an intersection with a small cross section and a steep slope as per construction at the base of a flatland, so that the fire smoke spreads rapidly in case of fire, which is expected to cause damage of human life. Therefore, this study is analyzed the delay effect of fire smoke diffusion according to the installation and non - installation of delay system for fire smoke diffusion at the intersection. Fire fumes were delayed up to 270 seconds when the delay system for fire smoke diffusion was installed at the intersection and it is analyzed that the greater the operating area of the delay system for fire smoke diffusion, the more preventable the damage of human life of the intersection.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.675-687
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• 2019

In recent years, the needs for double deck-tunnels have increased in large cities due to the increase in traffic volume and high land compensation costs. In Korea, a network type tunnel which is smaller than general road tunnels and crosses another tunnel underground is planned. In the shield tunnel joints between the existing shield tunnel and the box-type enlargement section, a partial steel-concrete joint is proposed where the bending moment is large instead of the existing full-section steel joint. In order to analysis the enlargement section of the shield tunnel diverged section to reflect the three-dimensional effect, the two-dimensional analysis model is considered to consider the column effect and the stiffness effect of the longitudinal member. A two-dimensional analysis method is proposed to reflect the stiffness of the longitudinal member and the column effect of the longitudinal point by considering the rigidity of the longitudinal member as the elastic spring point of the connecting part in the lateral model. As a result of the analysis of the model using the longitudinal member, it was considered that the structural safety of the partial steel-concrete joint can be secured by reducing the bending moment of the joint and the box member by introducing the longitudinal member having the stiffness equal to or greater than a certain value.