• Title/Summary/Keyword: 터널단면

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An Experimental Study on the Determination of Backlayering Distance in Tunnel Fires (터널 화재시 역기류의 위치 결정에 관한 실험적 연구)

  • 이성룡;유홍선
    • Tunnel and Underground Space
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    • v.14 no.4
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    • pp.269-274
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    • 2004
  • In this study reduced-scale experiments were conducted to determine the backlayering distance in tunnel fires. The 1/20 scale experiments were carried out under the Froude scaling using ethanol square pool fire ranging from 8 to 1km in each side with total heat release rate from 2.47 to 12.30 ㎾. It has been found that ventilation velocity increases with aspect ratio(tunnel height/tunnel width). At L$\_$B/$\^$*/ <5 the ventilation velocity increases proportional to the backlayering distance from 0.25 power of the heat release rate. However at L$\_$B/$\^$*/ $\geq$5 the ventilation velocity varies as the 0.3 power of the heat release rate.

The Smoke Propagating Distance in the Reduced-scale Model for a Subway Railroad Tunnel (축소 모형을 이용한 지하철터널에서의 연기전파거리 측정)

  • Kim, Myung-Bae;Choi, Byung-Il;Oh, Chang-Bo;Han, Yong-Shik
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.7 no.4
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    • pp.295-304
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    • 2005
  • The smoke propagating distances are measured in case that a fire occurs within the subway railroad tunnel. The tunnel is 800m long and the dimension of the cross-section is. Three vertical shafts exist for smoke ventilation. The experiments are performed using the 1/50 reduced-scale model. The smoke propagating distances are measured by thermocouples and by visualization for the accuracy. In order to understand the effect of a fire size and ventilation capacity of the shafts on the smoke propagating distance, 9 test scenarios are chosen. Based on the results, the smoke propagating distance is shown to be important criteria for the ventilation design of the tunnel.

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Stability analysis of a 2 arch tunnel considering excavation sequence (굴착단계를 고려한 2 아치 터널의 안정성 해석)

  • You, Kwang-Ho;Park, Yeon-Jun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.4 no.2
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    • pp.167-174
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    • 2002
  • In this study, a numerical stability analysis was performed for a large tunnel considering excavation sequence. In most cases, stability of a tunnel is analyzed based on the stability of the final excavation stage only. In this study, stability analysis of a tunnel was performed at each excavation stage. In summary, it can be inferred that there is no problem in stability of the tunnel. However, thorough and careful measurements are recommended. Also, it is found that the stability of the tunnel at the 5th excavation stage when the right half of the main tunnel is excavated is rather lower than that of the tunnel at the final excavation stage.

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A Study on the Stability of Twin Tunnels in Anisotropic Rocks Using Scaled Model Tests (이방성 암반내 쌍굴터널의 안정성에 대한 모형실험 연구)

  • Kim, Jong-Woo;Kim, Myeong-Kyun
    • Tunnel and Underground Space
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    • v.22 no.3
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    • pp.205-213
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    • 2012
  • In this study, scaled model tests were performed to investigate the stability of twin tunnels constructed in anisotropic rocks with $30^{\circ}$ inclined bedding planes under the condition of lateral pressure ratio, 2. Five types of test models which had respectively different pillar widths and shapes of tunnel sections were experimented, where both crack initiating pressures and deformation behaviors around tunnels were investigated. The models with shallower pillar width showed shear failure of pillar according to the existing bedding planes and they were cracked under lower pressure than the models with thicker pillar width. In order to find the effect of tunnel sectional shape on stability, the models with four centered arch section, circular section and semi-circular arch section were experimented. As results of the comparison of the crack initiating pressures and the deformation behaviors around tunnels, the semi-circular arched tunnel model was the most unstable whereas the circular tunnel model was the most stable among them. Furthermore, the results of FLAC analysis were qualitatively coincident with the experimental results.

The Effect of Seepage Forces on the Ground Reaction Curve of Tunnel (침투력이 터널의 지반반응곡선에 미치는 영향)

  • Lee Seok-Won;Jung Jong-Won;Nam Seok-Woo;Lee In-Mo
    • Journal of the Korean Geotechnical Society
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    • v.21 no.3
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    • pp.87-98
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    • 2005
  • When a tunnel is excavated below groundwater table, the groundwater flows into the excavated wall of tunnel and seepage forces are acting on the tunnel wall. The ground reaction curve is defined as the relationship between internal pressure and radial displacement of tunnel wall. Therefore, the ground reaction curve is significantly affected by seepage forces. In this study, the theoretical solutions of ground reaction curves were derived for both the dry condition and the seepage forces. The theoretical solutions derived were validated by numerical analysis. The ground reaction curves with the support characteristic curve were also analyzed in various conditions of groundwater table. Finally, the theoretical solutions of the ground reaction curve derived in this study can be utilized easily to determine the appropriate time of support systems, the stiffness of support system and so forth for the reasonable design.

Finite Element Analysis on the Ground Behavior for Tunnel with Pipe-roof (파이프루프공법이 적용된 터널의 지반거동 유한요소 해석)

  • Jo, Seon-Ah;Jin, Kyu-Nam;Sim, Young-Jong
    • Land and Housing Review
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    • v.7 no.4
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    • pp.261-269
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    • 2016
  • Pipe-roof method is one of the mostly used method to prevent the ground subsidence during the tunnel construction. As pipe-roof method has made technical advancement and performance improvement, it suggested to utilize pipe-roof to a permanent support system rather than a temporal pre-reinforcing method. Therefore, in this study, pipe-roof method is numerically simulated using finite element method to evaluate effects of pipe-roof on behavior of ground and structure. Analyses are performed considering two major conditions that are with and without the application of pipe-roof and the shape of tunnel cross section. The results are presented with respect to variation of settlement and vertical stress distribution. Based on this results, it is found that ground settlement above the shallow tunnel can be considerably reduced by application of pipe-roof system. Also, the shape of tunnel cross section can influence on the mechanical behavior of ground and structure.

A study on the optimal reinforcement area for excavation of a small cross-section shield TBM tunnel in fault fracture zone through parameter analysis (매개변수 분석을 통한 단층파쇄대의 소단면 쉴드 TBM 터널 굴착 시 최적 보강영역 연구)

  • Kang, Byung-Yun;Park, Hyung Keun;Cha, Jae-Hoon;Kim, Young-Jin
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.22 no.3
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    • pp.261-275
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    • 2020
  • When excavating a small cross-section tunnel in a fault fracture zone using the shield TBM method, there is a high possibility of excessive convergence and collapse. Appropriate ground reinforcement is required to minimize construction cost loss and trouble due to a fault fracture zone. In this study, the optimal reinforcement area was suggested and the surrounding ground behavior was investigated through numerical analysis using MIDAS GTS NX (Ver. 280). For the parameters, the width of the fault fracture zone, the existence of fault gouge, and the groundwater level and depth of cover were applied. As a result, when there is not fault gouge, the convergence and ground settlement are satisfied the standard when applying ground reinforcement by up to 0.5D. And, due to the high permeability coefficient, it is judged that it is necessary to apply 0.5D reinforcement. There is a fault gouge, it was possible to secure stability when applying ground reinforcement between the entire fault fracture zone from the top of the tunnel to 0.5D. And, because the groundwater discharge occurred within the standard value due to the fault gouge, reinforcement was unnecessary.