• Title/Summary/Keyword: tunnel support

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The Support Types of the Tunnel for Centrifuge Model (터널의 지보방법에 관한 원심모형실험(遠心模型實驗))

  • Yoo, Nam-Jae;Lee, Myung-Woog;Park, Byung-Soo
    • 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.

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An Assessment of Safety Zone for Mountain Tunnel Portal Using Strength Reduction Technique (강도감소법을 이용한 산악터널 갱구부의 안전영역 평가)

  • Hong, Chang-Soo;Hwang, Dae-Jin;Lee, Kang-Ho;You, Kwang-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.925-930
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    • 2006
  • During the excavation of a tunnel portal, failure zones around the tunnel heading occur and also the ground supports itself. In a portal, its location and the ground characteristic have a great influence on the stability of the tunnel. Therefore, the failure mechanism of a tunnel heading and how to assess the stability of the tunnel are very important. In this paper, the numerical analyses were executed to evaluate the safety factor using strength reduction technique. The influence area of an excavation was also predicted through a case study in which no-support case and support case with the Pattern P-6 were compared in terms of the ground class and the shear strain.

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Optimization of tunnel support patterns using DEA (차분진화 알고리즘을 적용한 터널 지보패턴 최적화)

  • Kang, Kyung-Nam;An, Joon-Sang;Kim, Byung-Chan;Song, Ki-Il
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.1
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    • pp.211-224
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    • 2018
  • It is important to design tunnel support system considering the various loads acting on the tunnel because they have a direct impact on the stability of tunnels. In Korea, standardized support patterns are defined based on the rock mass classification system depending on the project, and it is stated that it should be modified appropriately considering the behavior of tunnel during construction. In this study, the tunnel support pattern optimization method is suggested based on the convergence-confinement method, earth pressure, axial force of rock bolt, and moment acting on the shotcrete. The length and spacing of the rock bolts and the thickness of the shotcrete were optimized by using the differential evolution algorithm (DEA) and the results were compared to the standard support pattern III for railway tunnel. Rock bolt length can be reduced and the installation interval can be widened for shallow tunnel. As the depth of tunnel increases, the thickness of shotcrete increases linearly. Therefore, the thickness of shotcrete should be thicker than the standard support pattern as the depth of tunnel increases to secure the stability of tunnel.

A risk analysis for the determination of a tunnel support pattern (터널 지보패턴 결정을 위한 위험도 분석)

  • You, Kwang-Ho;Park, Yeon-Jun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.5 no.3
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    • pp.241-250
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    • 2003
  • Rock mass is very inhomogeneous in nature and data obtained by site investigations and tests are very limited. For this reason, many uncertainties are to be included in the process of constructing structures in rock mass. In the design of a tunnel, support pattern, advance rate, and excavation method, which are important design parameters, must be determined to be optimal. However, it is not easy to determine those parameters. Moreover if those parameters are determined incorrectly, unexpected risk occurs such as decrease in the stability of a tunnel or economic loss due to the excessive supports etc. In this study, how to determine an optimal support pattern and advance rate, which are the important tunnel design parameters, is introduced based on a risk analysis. It can be confirmed quantitatively that the more supported a tunnel is, the larger reliability index becomes and the more stable the tunnel becomes. Also an optimal support pattern and advance rate can be determined quantitatively by performing a risk analysis considering construction cost and the cost of loss which can be occurred due to the collapse of a tunnel.

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Non-Destructive Test for Tunnel Lining Using Ground Penetrating Radar (지하레이다(GPR)를 이용한 터널 라이닝 비파괴시험에 관한 연구)

  • 김영근;이용호;정한중;신상범;조철현
    • Tunnel and Underground Space
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    • v.7 no.4
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    • pp.274-283
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    • 1997
  • It is necessary to estimate the soundness of tunnel using non-destructive tests(NDT) for effective repairs and maintenances. But, the state of tunnel lining could not be investigated using previous non-destructive techniques, due to the various types of support and accessibility only from one side in tunnel lining. Recently, the various non-destructive techniques such as ground penetrating radar(GPR) have been researched and developed for inspection of tunnel lining. In this study, the usefulness and applicability of GPR test in tunnel lining inspection has been investigated through model tests and tunnel site application. This paper described the tunnel lining inspection for lining thickness, cavity and support using GPR test. From the results of tests, we have concluded that GPR test are very useful and effective techniques to look into the interior of lining and measure the lining thickness.

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Evaluation of Support Performance of Fiber-Net Integrated Shotcrete in Tunnel Support System (숏크리트용 섬유 그물망 일체형 터널 지보시스템의 지보 성능 평가)

  • Kim, Jiyoung;Choi, Seongcheol
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.4
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    • pp.545-552
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    • 2020
  • This study evaluated the support performance of fiber-net integrated shotcrete in tunnel support system developed for the purpose of improving constructability and stability while fully performing its mechanical performance as a tunnel support materials by four-point bending test, two-dimensional numerical analysis, and cross-sectional analysis. As a result of evaluating the flexural performance through a four-point bending test, in the case of fiber-net reinforced shotcrete, the tensile performance of fiber-net resulted in a continuous increase in load after crack occurrence, unlike steel fiber reinforced shotcrete. Also, the results of the tunnel cross-sectional structure analysis for ground conditions and the cross-sectional analysis of fiber-net and steel fiber reinforced shotcrete showed that sufficient support performance can be exhibited even if the thickness of fiber-net reinforced shotcrete was reduced compared to the previous one. Additionally, through these results, the support pattern of fiber-net integrated shotcrete in tunnel support system, which can be applied efficiently to the construction sections requiring higher stability among the rock mass class III, was proposed.

A study on Actual Quantity of Shotcrete Sprayed in a NATM tunnel (NATM 산악터널의 숏크리트 투입율에 관한 연구)

  • Lee, Cheol-Ju;Kim, Sung-Yun;Kim, Dong-Gun;Yoo, Nam-Jae
    • Journal of Industrial Technology
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    • v.29 no.B
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    • pp.57-64
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    • 2009
  • This study has analysed actual overbreak, shotcrete rebound and the ratio between the actual quantity of shotcrete to designed shotcrete measured during a NATM tunnel construction. The measured shotcrete rebound was about 7.2% in average which was about half the allowable rebound (15%), showing shotcrete spraying was performed well. Based on the measurement of excavated tunnel shape, average overbreak was about 28.5cm after tunnel excavation by drill and blasting method. This was about 260% of allowable overbreak. In addition, due to the rebound and overbreak actual amount of shotcrete used in the tunnelling work was about 116.5 % of the designed value. According to the field measurement the ratio of actual shotcrete to designed value showed some relation with standard support pattern, but the size of overbreak did not show the correlation with standard support pattern. Hence current design specifications stating the size of overbreak based entirely on standard support pattern should perhaps be reestablished. The insight into the design guideline regarding overbreak and shotcrete.

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Effect of the Rock Characteristics Condition on the Behavior of Tunnel by Numerical Analysis (수치해석에 의한 암반특성의 변화가 터널에 미치는 영향)

  • Kwon, Soon-Sub;Lee, Jong-Sun;Kim, Kyoung-Ho;Lee, Jun-Woo
    • Proceedings of the KSR Conference
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    • 2007.05a
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    • pp.375-378
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    • 2007
  • The selection of the support system is an important design parameter in design and construction of the tunnel using the new Australian tunnel method. It is a common practice to select the support based on the rock mass grade, in which the rock mass is classified into five rock groups. The method is applicable if the characteristics of the rock mass are uniform in the direction of tunnel excavation. However, such case is seldom encountered in practice and not applicable when the properties vary along the longitudinal direction. This study performs comprehensive three dimensional finite difference analyses to investigate the ground deformation pattern for cases in which the rock mass properties change in the direction of the tunnel axis. The numerically calculated displacements at the tunnel crown show that the displacement is highly dependent on the stiffness contrast of the rock masses. The results strongly indicate the need to select the support type $0.5\sim1.0D$ before the rock mass boundary. The paper proposes a new guideline for selecting the support type based the results of the analyses.

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Application on Cable bolt as Tunnel Support System (터널 보강재로서의 케이블 볼트의 적용성 평가)

  • Kim, Young-Ho;Yoo, Chan-Ho;Han, Beom-Seok;Kim, Seoung-Wook;Kim, Hong-Taek
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.1530-1535
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    • 2009
  • The cable bolt is useful underground space support system such as mining in Europe. In spite of favorable strength characteristics, past record of the cable bolt is rarely in Korea. In this study, to evaluate the mechanically characteristics the cable bolt on tunnel support system. To conduct the laboratory strength test in order to enquire material properties as reinforcement material and numerical analysis was performed considering laboratory test results. To estimate the behavior characteristics on tunnel system in which supported by the cable bolt system and compared the behavior characteristics with the rebar rock bolt system result.

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Effect of the support pressure modes on face stability during shield tunneling

  • Dalong Jin;Yinzun Yang;Rui Zhang;Dajun Yuan;Kang Zhang
    • Geomechanics and Engineering
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    • v.36 no.5
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    • pp.417-426
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    • 2024
  • Shield tunneling method is widely used to build tunnels in complex geological environment. Stability control of tunnel face is the key to the safety of projects. To improve the excavation efficiency or perform equipment maintenance, the excavation chamber sometimes is not fully filled with support medium, which can reduce the load and increase tunneling speed while easily lead to ground collapse. Due to the high risk of the face failure under non-fully support mode, the tunnel face stability should be carefully evaluated. Whether compressive air is required for compensation and how much air pressure should be provided need to be determined accurately. Based on the upper bound theorem of limit analysis, a non-fully support rotational failure model is developed in this study. The failure mechanism of the model is verified by numerical simulation. It shows that increasing the density of supporting medium could significantly improve the stability of tunnel face while the increase of tunnel diameter would be unfavorable for the face stability. The critical support ratio is used to evaluate the face failure under the nonfully support mode, which could be an important index to determine whether the specific unsupported height could be allowed during shield tunneling. To avoid of face failure under the non-fully support mode, several charts are provided for the assessment of compressed air pressure, which could help engineers to determine the required air pressure for face stability.