• Proceedings of the KSR Conference
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• 2007.11a
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• pp.313-336
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• 2007

Unlike a conventional railway system, a high-speed rail system experiences various aerodynamic problems in tunnel sections. Trains running at a high speed in a small tunnel, when compared with the open field, face significant air pressure, resulting in reduced operating stability and fast change in pressure inside the tunnel. These phenomena further cause some unexpected problems such as the passengers onboard feeling an aural discomfort and an impulsive noise at the tunnel exit. To solve these problems, this paper introduces analysis of aerodynamic characteristics for determination of tunnel cross section. The optimum cross-section that satisfies the criteria of aural discomfort was reviewed through lots of numerical simulation analysis. Also, the pressure inside the passenger car of a train operating on Kyungbu HSR line was measured, and the pressure inside the tunnel and the micro-pressure waves at tunnel exit were measured at Hwashin 5 Tunnel. At the same time, a test of train operation model was performed and then the measurement results and test results were compared to verify that various parameters used as input conditions for the numerical simulations were appropriate.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.699-715
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• 2019

Recently, in urban areas, cavities and ground collapse adjacent to underground structures are frequently reported. Several studies on the cavity generation by structure cracks have been made, however they are focused on the cause of cracks and settlement of the ground. In this paper, soil particle and groundwater discharge through pipe cracks and cavity generation mechanism are investigated. The theoretical analysis of the groundwater, which is the main factor of the drainage of the soil particles, and the particle transport mechanism and flow characteristics were investigated. An experimental model test was carried out to identify the mechanism of cavity generation by underground buried pipe cracks. The soil particle weight of discharge through the cracks, and the movement characteristics of the particles were analyzed using PIV. In this study, it is clearly identified that soil particle movements, cavity generation and ground collapse that occur in the ground are basically caused by the movement of groundwater.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.1-8
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• 2012

The aim of this study is to evaluate fire-induced damage for shield tunnel linings. Full-scale fire test was conducted to evaluate fire-induced damage. Residual compressive strength was measured on the core samples of shield tunnel lining subjected to high temperatures. Heating temperature was predicted by XRD and TG analysis. As a result, Strength degradation of concrete with temperatures can be evaluated by residual compressive strength of core samples. In addition, residual compressive strength can be estimated by previous studies if heating temperature is exactly predicted. It is possible that heating temperature is predicted by XRD and TG analysis at $450^{\circ}C$. For more accurate prediction of heating temperature it should be performed both instrumental analysis and analytical methods with temperatures ranging from $400{\sim}600^{\circ}C$.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.4
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• pp.53-59
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• 2008

If fire is occurred in the subway, the train must be moved to the closest station and make passengers get off the train. As a matter of fact, the Fire of Dae-gu Subway was coped with this way. But, the fire smoke extraction system of real subway stations have not designed to deal with fire of trains yet. Therefore, we have to establish a plan of station railroad for preventing from unexpected damage when the fired train comes to the station. The purpose of this study is to establish the effective smoke extraction measure that is to prevent stations from damage by the scale-down experiment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.193-201
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• 2014

This paper presents the development of simulation system on EPB shield TBM Hood operation. In recent, EPB shield TBM is widely used in the tunnel construction. Since the hood system of the EPB shield TBM is most important to excavate the tunnel, it is necessary to perform the simulation of hood system to investigate the design and operation parameters prior to tunnel construction. In order to carry out this study, the scaled simulation system was designed and developed. The model tests were performed to verify the developed system. During the simulation, the earth pressures developed in the chamber during tunnelling were measured to evaluate the operation technique. The test results obtained by the developed simulation system show clearly the similar behaviour of TBM hood compared with the field data. It was also found that the ground loss during tunnelling is dependent on the change of earth pressure in chamber. Therefore, the simulation system developed in this study will be very useful to evaluate the operation technique of the TBM hood prior to tunnel construction. In addition, this system will be applied in a various condition of ground to get the operating information.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.5
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• pp.485-501
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• 2012

This study aims to experimentally investigate ground settlement and ground movement around the square pipe by its penetration in sandy ground. A series of laboratory model tests were carried out with a small-scale auger equipment for penetration of a square pipe as well as a newly designed test box with a sand raining equipment. From the experiments, it is shown that a square pipe induces ground movement evenly around it in a low overburden condition. However, as the overburden becomes higher, ground movement by a square pipe is concentrated mainly above it. Especially, horizontal strain above the square pipe was mainly dominated by its penetration. In addition, sand surface movement is the smallest in case of the dimensionless penetration rate equal to 0.2. When its penetration rate of the square pipe is fixed, the rotation speed of auger controls surface movement whether it is settlement or heaving. Therefore, the selection of an optimal dimensionless rate for the square pipe is a key design factor to minimize ground settlement in a trenchless construction.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.199-209
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• 2002

This research is experimental thesis to prepare the structural safety of the upper bridge for support type on tunnel and the effect of settlement. Unit weight test and uni-axial compression test have been performed to simulate the physical property of foundation on the tunnel. Tunnel model of slip form type for centrifuge model has been developed to performed the tunnel excavation while field stress is activated. And the support type of tunnel such as umbrella arch method and large diameter steel pipe reinforce method has been tested for the centrifuge model. After the analysis of experiment, results show that internal displacement of large diameter steel pipe reinforce method is smaller than that of the umbrella arch method.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.469-484
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• 2020

This study focused on shielding through inflatable structure in the event of sudden water inflow into the submerged floating tunnels. Currently, there is a lack of measures to deal with unexpected water in tunnels in Korea. Although water treatment facilities such as waterproofing and floodgates in tunnels are installed, there are limitations to the sudden inflow of large amounts of seawater or underground water. Also, floodgates cannot respond quickly to sudden damage due to slow blocking time. Accordingly, a study was conducted on the shielding rate and axial movement distance for inflatable structure. The results of the reduced model experiment confirmed that the number of inflatable structure and internal pneumatic pressure influence on the shielding rate. As the number of inflatable structure increased from one to two, the shielding rate increased by about 35 up to 40 percent. It was also confirmed that the shielding rate increased by about 4 percent as the internal pneumatic pressure increased from 0.2 bar to 0.3 bar. If we verify and further develop the results identified in this study through a real-size experiment, it will be able to be used as an effective waterproof measure for sudden water inflow into the undersea tunnels or underwater tunnels.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.221-234
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• 1999

This paper deals with the application of joint element in the finite element modeling of discontinuities encountered during rock tunneling. A nodal displacement joint element was implemented in a two dimensional finite element program GEOFE2D. The applicability of the joint element for modeling of discontinuities and the numerical stability of the implemented algorithm were examined by comparing the results of reduced small scale model tests as well as commercially available FEM program. The GEOFE2D was then used to analyze a tunnel crossed by a major discontinuity for the purpose of understanding the effect of discontinuity on the tunnel behavior. In addition, a modeling technique for the junction of discontinuity and shotcrete lining was presented. The results of analysis indicated that the stress-strain field around the tunnel is significantly altered by the presence of discontinuity, and that the stresses in the shotcrete lining considerably increase at the junction of the shotcrete lining and the discontinuity. It is therefore concluded that the major discontinuities must be carefully modeled in the finite element analysis of a tunneling problem in order to obtain more reliable results close to actual tunnel behavior.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.65-80
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• 2014

This study conducted Trapdoor tests with actual tunnel shape, investigated the mechanical behavior of ground and loosening load on tunnels, and evaluated the mechanism of progressive failure by numerical simulation. The loosening load sharply decreased initially, but it generally increased and reached the stabilized level exhibiting the arching effect, and loose sand showed relatively higher values than those of dense sand. The shear band started from the tunnel shoulder with $63^{\circ}$ (loose sand) to $69^{\circ}$ (dense sand), and gently curved inward to the ground surface. The widths of shear band formation above the tunnel showed a range from 1.8b to 1.9b (b=Tunnel width), which are similar to those values calculated from existing formular. The vertical height of this shear band for deep tunnel was turned out to be a bit lower than that from existing studies (3.0*Tunnel Height).