• Proceedings of the KSR Conference
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• 2006.05b
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• pp.1179-1187
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• 2006

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.6
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• pp.407-416
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• 2010

A new tunnel auxiliary method is proposed in this paper which utilizes the concept of cavity expansion for tuunel reinforcement by forming an umbrella arch on the roof of tunnel. When an inflatable pipe is inserted and expanded by pressure in the bore hole of umbrella arch, the ground around the bore hole can be compacted so that the stress condition above the tunnel perimeter is favorably changed. In order to verify the reinforcement effect of new concept, pilot-scale chamber test, trapdoor test and numerical analysis were performed and compared. In pilot-scale chamber test, three types of inflatable pipes are tested to verify the capability of expansion, and the results arc compared with analytical results obtained by applying cavity expansion theory and with results obtained from finite clement analysis, and the experimental results showed agreeable matches with analytical and numerical ones. Numerical analysis of a tunnel and trapdoor test applied with the inflatable pipes are also performed to figure out the reinforcement effect of the proposed techniques, and the results implied that the new method with 3 directional inflatable pipe (no pressure to downward direction) can contribute to reduce tunnel convergence and face settlement.

• Journal of the Korea Institute of Building Construction
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• v.9 no.6
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• pp.121-129
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• 2009

The construction sites of small and medium buildings have small scale groundwork and the depth of excavation is often shallow. In this case, if the groundwork, girders, and ground slabs are built simultaneously by embedded assisting form rather than the existing conventional method to place concrete twice using the general form, we can expect to reduce the frame duration of the basement, resulting in cost savings. The existing embedded assisting form is restricted from use because there are cost problems with materials, labor costs,and with quality depending on the form's type. Therefore, this study is to provide an improved suggestion of building the groundwork, girders, and ground slabs simultaneously with Polystyrene by using the embedded assisting form. It also will compare the technique with existing methods of construction, and will verify its usefulness by evaluating each method of construction.

• 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.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.1
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• pp.11-22
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• 2009

Tunnel excavation with several sections and appropriate auxiliary measures such as face bolt and pre-grouting are widely used in case of weak and less rigid ground for the stability of a tunnel face during excavation. This papers first described the evaluation methods proposed in technical literature to maintain the tunnel face stable, and then studied by FEM analysis whether face reinforcement is need in what degree of ground deformation and strength features for the stability of a tunnel face when excavating by full excavation with sub-bench. Lastly, a three dimensional FEM analysis was performed to study how the tunnel face itself and the ground around the tunnel behave depending on different bolt layouts, length of bolts, number of bolts. There were relative differences in comparison of results on the stability of a tunnel face by a theoretical evaluation methods and FEM analysis, but the same in reinforced effect of face. It was found that the stability of a tunnel face can be obtained with face bolt installed longer than 1.0D (tunnel width), bolt density of about 1 bolt per every $1.5\;m^2$ (layout of grid type), and reinforcement area of $120^{\circ}$ arch area of upper section.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.367-372
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• 2003

도심의 편리한 생활을 위해 초고속 데이터 통신, 상하수도, 가스등의 원할 한 공급이 요구되고 있으며 이러한 인프라 시설들은 지하터널을 통하여 공급이 되게 된다. 도심지의 교통혼잡과 소음, 진동으로 인한 사회비용의 증가와 민원으로 사실상 개착식 공법은 적용되기 어려운 실정에 있다. 특히 앞에 열거한 인프라 시설들은 2m이하의 중소형 크기로 마이크로터널링 공법이 널리 사용되고 있으며 최근에는 현실적인 현장의 요구와 공사비용의 절감을 위해 1m이하의 소형터널에 대한 요구가 늘어 나고 있으나 마이크로터널링 머신의 소형화에 따른 절삭력의 감소와 지하 장애물에 대한 대처가 어려워짐으로 이에 대한 해결책이 요구되고 있다. 이를 위해 워터젯이 장착된 마이크로터널링 머신이 소개된바 있지만 면판에 단순고정된 형태라 절삭면적 및 효율에 한계가 있다. 본 연구는 절삭면적의 확대 및 효율의 증가를 위해 공전하는 면판에 자전하는 워터젯 보조면판을 제안하였으며 워터젯에 가장 적합한 커터종류를 찾기 위해 절삭력을 고려한 성능계수를 제안하였다.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.97-106
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• 2004

In case of tunnel construction with a shallow soil cover in cohesionless soils or highly weathered rocks, reinforcement measures are required for a tunnel stability during the tunnel construction. Recent developments show that the use of Umbrella Arch Method(UAM) as tunnel reinforcement and water cut-off in domestic projects has increased. Unfortunately, guidelines for the design and construction of UAM have not been established, only empirical designs and applications in tunnel construction have been performed so far. In this study, behaviour of the steel pipes installed on the tunnel roof was analyzed through the monitoring of bending and axial stresses of the pipes with the advance of the tunnel face. The monitoring results were used in the establishment of the loading mechanism around the pipe. This paper suggests, the guidelines used in the determination of the total length, overlapping length and lateral spacing of the reinforcing pipes obtained from the established loading mechanism.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.4
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• pp.701-715
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• 2018

A reliability based design approach of the tunnel reinforcement with umbrella arch method was considered to better represent the uncertainties of the weak rock properties around the tunnel. For this, a machine learning approach called an Adaptive Support Vector Machine (ASVM) together with the limit equilibrium method were introduced to minimize the iteration numbers during the classification training of the tunnel stability. The proposed method was compared with the results of typical Monte Carlo simulations. It was concluded that the ASVM was very efficient and accurate to calculate the probability of failure having auxiliary umbrella arches and uncertain material properties of the tunnel. Future work will be concentrated on the refinement of the fast adaptation of the SVM classification so that the minimum number of numerical analyses can be used where the limit solution is not available.

• Geotechnical Engineering
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• v.23 no.6
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• pp.33-38
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• 2007

• Magazine of the Korea Concrete Institute
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• v.14 no.5
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• pp.47-53
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• 2002

근래 지구촌의 산업화가 가속됨에 따라 대지의 활용도가 급속하게 증가하고 있으며 아울러 인구의 증가 및 개개인 삶의 공간적 범주가 점점 확대되면서 지구상에 광범위하게 분포되어 있는 연약지반으로의 관심이 집중되고 있는 실정이다. 최근 국내에서도 고속철도, 인천국제공항, 도심지 지하철 및 서ㆍ남해안 항만공사 등 대규모 국가건설공사가 진행 중에 있으며 더더욱 임해시설의 확충이라든지 인공섬 등의 건설이 활발해지면서 연약지반에 대한 관심이 고조되고 있다. 하지만 연약지반의 특성을 경시한 나머지 터널의 붕락, 주변지반 및 인접건물의 부등침하, 측방유동에 의한 구조물변위 등 대형 안전사고가 빈발하게 발생되어 왔다. 이러한 안전사고의 대책으로서 지반보강을 위한 여러 가지 신공법이 개발되었고, 새로운 터널보조공법이 국내 지하철건설현장에서 널리 쓰여지고 있으며 이러한 공법 등을 통한 성과도 적지 않게 보고되고 있다.(중략)