• Title/Summary/Keyword: Steel pipe multistep grouting

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Seepage-induced Face Stability of n Tunnel with Steel Pipe-reinforced Multistep Grouting (강관 다단 그라우팅으로 보강된 터널의 침투수력을 고려한 막장 안정성 검토)

  • 이인모;이재성;남석우;이형주
    • Journal of the Korean Geotechnical Society
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    • v.19 no.4
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    • pp.121-131
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    • 2003
  • Tunneling in difficult geological conditions is often inevitable especially in urban areas. Ground improvement and reinforcement techniques are often required to guarantee safe tunnel excavations and/or to prevent damage to adjacent structures. The steel pipe-reinforced multistep grouting method has been recently applied to tunnel sites in Korea as an auxiliary technique. In this study, the face stability with steel pipe-reinforced multistep grouting was evaluated emphasizing the effect of seepage forces. The study revealed that the influence of the steel pipe-reinforced multistep grouting on the support pressure in dry condition is not significant while there is relatively a large amount of reduction in seepage forces by adopting the technique in saturated condition. The effect of the anisotropy of permeability on the seepage force acting on the tunnel face was also estimated by conducting the coupled analysis. It was found that a higher horizontal permeability compared with the vertical one causes reduction in the seepage farce acting on the tunnel face.

Applicability Analysis of an Improved Multistep Steel Pipe Grouting Method in Shallow Depth Railway Tunnels in Considering Safety and Constructability (저토피 철도터널구간의 안전 및 시공성을 고려한 개선된 강관다단 그라우팅 공법 적용성 분석)

  • Kim, Nakseok;Choi, Gisung;Kim, Seokhyun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.40 no.1
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    • pp.97-103
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    • 2020
  • The newly improved multistep steel pipe grouting method was applied to an existing steel pipe-reinforced grouting method. It was applied in order to prevent a damage caused by ground failure from excessive grouting pressure in a tunnel construction. The tunnel goes under a highway and a ramp connected to a rest area on OO highway with 11.3~12.1 m depth cover and is a part of roadbed facility construction section ordered by OO public corporation. The improved grouting method provides pre-construction work condition assessment technique through new water injection limit test and grouting effect assessment technique by grouting type assessment. It also includes assessments on interval of joints, appropriate grouting pressure, and optimal operation time to be applied to current operations. Application of the grouting method allowed the smooth road management in shallow-depth grouting construction area located upper part of tunnel excavation. Moreover, the possibility of the application of the method not only to shallow-depth grouting construction but also to various steel pipe-reinforced grouting constructions was confirmed.

Evaluation of tunnel face stability based on upper bound theorem (상한치 이론에 근거한 터널 막장의 안정성 연구)

  • Lee, In-Mo;Lee, Jae-Sung;Nam, Seok-Woo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.5 no.1
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    • pp.3-11
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    • 2003
  • Face stability of a tunnel is a main concern during tunnel excavation. However, there has been only a few studies on this problem while a lot of researches on the support systems have been carried out. In addition, when tunneling is performed below the groundwater level, the groundwater flows into the tunnel so that the seepage forces generated on the tunnel face might give rise to a serious potential for the face instability. In this study, the face stability was evaluated by simultaneously considering two factors: one is the effective stress calculated by upper bound theorem; the other is the seepage forces acting on the tunnel face obtained by numerical analysis under the condition of steady-state groundwater flow. Tunneling in difficult geological conditions often requires auxiliary techniques to guarantee safe tunnel excavations and/or to prevent damage to structures and services around the tunnel. The steel pipe-reinforced multistep grouting has been recently applied to tunnel sites in Korea. Face stability of a tunnel with the steel pipe-reinforced multistep grouting was also analyzed in this study.

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A comparative analysis of prediction and measurement for reinforcement effect of face bolts (수치해석 및 계측자료 분석을 통한 막장볼트의 보강효과에 관한 연구)

  • Seo, Kyoung-Won;Kim, Woong-Ku;Baek, Ki-Hyun;Kim, Jin-Woung
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.12 no.5
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    • pp.359-368
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    • 2010
  • Unlike in Korea where steel pipe-reinforced multistep grouting is of commonly used methods for tunnel reinforcement, face bolt method is more widely used due to its better workability and lower construction cost in other countries. In this paper, the effects of both methods after tunnel failure were numerically analyzed and verified based on the oversea construction experiences. As a result it is concluded that the face bolt method may be effective to reinforcement especially when there are some fractured zones developed in the face of tunnel.