• Title/Summary/Keyword: Bored tunnel

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Preliminary study on the ground behavior at shore connection of submerged floating tunnel using numerical analysis

  • Kang, Seok-Jun;Kim, Jung-Tae;Cho, Gye-Chun
    • Geomechanics and Engineering
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    • v.21 no.2
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    • pp.133-142
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    • 2020
  • Submerged floating tunnel (SFT) is a type of tunnel which causes the tunnel segments to float in the water. When the SFTs are connected to the ground, the connection between the SFT and the subsea bored tunnel is fragile due to the difference in behavioral characteristics between the two types of tunnels. Therefore, special design and construction methods are needed to ensure the stability of the area around the connection. However, since previous research on the stability of the connection site has not been undertaken enough, the basic step necessitates the evaluation of ground behavior at the shore connection. In this study, the numerical analysis targeting the shore connection between the subsea bored tunnel and the SFT was simulated. The strain concentration at the shore connection was analyzed by numerical simulation and the effects of several factors were examined. The results showed the instability in the ground close to the shore connection due to the imbalance in the behavior of the two types of tunnels; the location of the strain concentration varies with different environmental and structural conditions. It is expected that the results from this study can be utilized in future studies to determine weak points in the shore connection between the submerged floating tunnel and the subsea bored tunnel, and devise methods to mitigate the risks.

Numerical study on tunnel design for securing stability at connection between submerged floating tunnel and bored tunnel (수중터널 지반 접속부 안정성 확보를 위한 터널 설계에 대한 수치해석적 연구)

  • Kang, Seok-Jun;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.22 no.1
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    • pp.77-89
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    • 2020
  • Submerged floating tunnel (SFT) is a type of tunnel that allows tunnel segments to float underwater by buoyancy, and is being actively studied in recent years. When the submerged floating tunnel is connected to the ground, the tunnel and the bored tunnel inside the ground must be connected. There is risk that the stress will be concentrated at the connection between the two tunnels due to the different constraints and behavior of the two tunnels. Therefore, special design and construction methods should be applied to ensure the stability around the connection. However, previous studies on the stability at the connection site have not been sufficiently carried out, so study on the basic stage of the stability at connection site are necessary. In this study, numerical analysis simulating the connection between submerged floating tunnel and the bored tunnel confirmed that the shear strain concentration occurred in the ground around the connection, and it was analyzed that the structural factors can be handled during construction to have effects on the stability of the ground around the connection. Numerical results show that the risks from disproportionate displacements in the two tunnels can be mitigated through the construction of grouting material and joint design. Although the results from this study are qualitative results, it is expected that it will contribute to the determination of structural factors and risk areas that should be considered in the design of connections between the submerged floating tunnel and bored tunnel in the future studies.

Development of optimal cross-section design methods for bored utility tunnels: case study of overseas typical cross-sections and design criteria (터널식 공동구 최적단면 설계기술 개발: 해외 표준단면 사례 및 설계기준 분석)

  • Park, Kwang-Joon;Yun, Kyoung-Yeol
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.6
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    • pp.1073-1090
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    • 2018
  • Since the domestic utility tunnels were built mainly in the development project of the new city, they are all in the form of cut-and-cover box tunnel. But, in the case of overseas construction of utility tunnels for existing urban areas, the bored tunnel types are mainly adopted. It is reasonable to install bored tunnels in a downtown area because it is difficult to block the roads or install bypass roads due to heavy traffic and civil complaints. In order to activate the utility tunnels in bored type, it is necessary to secure optimized cross-sectional design technology considering the optimal supplying capacity and mutual influencing factors (Thermal Interference, electrolytic corrosion, efficiency of the maintenance, etc.) of utilities (power cables, telecommunication cables, water pipes, etc.). The optimal cross-section design method for bored utility tunnels is ultimately to derive the optimal arrangement technique for the utilities. In order to develop the design methods, firstly, the cases of tunnel cross-section (Shield TBM, Conventional Tunneling) in overseas shall be investigated to analyze the characteristics of the installation of utilities in the section and installation of auxiliary facilities, It is necessary to sort out and analyze the criteria related to the inner cross-section design (arrangement) presented in the standards and guidelines.

A Study of Proper Escape way interval by QRA on Single bored double track tunnel (정량적 위험도 분석을 이용한 복선철도터널에서의 적정 대피통로 간격 산정을 위한 연구)

  • Roh, Byoung-Kuk;Lee, Ho-Suk;Song, Myung-Kyu;Choo, Seok-Yeon
    • Proceedings of the KSR Conference
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    • 2007.11a
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    • pp.371-376
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    • 2007
  • This paper describes a study to determine proper escape way interval for the design phase of single bored double track tunnel. Among many methods which determine escape way interval, we choose a QRA(Quantitative Risk Analysis) method. But a different method must be chosen differ from other country because of special design situation of Korea. So, it is necessary to develop a method which considers a special design condition of Korea. Because fire accidents of railway tunnel are a rare event, simulated situation can be produced by CFD simulation and evacuation analysis simulation. However, it is generally difficult to estimate of fatalities from these methods, so a concept of FED is introduced to estimate of fatalities. Quantification process provides effective results for practical design stage and the result were employed in design.

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Numerical analysis on stability of express railway tunnel portal

  • Zhou, Xiaojun;Hu, Hongyun;Jiang, Bo;Zhou, Yuefeng;Zhu, Yong
    • Structural Engineering and Mechanics
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    • v.57 no.1
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    • pp.1-20
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    • 2016
  • On the basis of the geological conditions of high and steep mountainous slope on which an exit portal of an express railway tunnel with a bridge-tunnel combination is to be built, the composite structure of the exit portal with a bridge abutment of the bridge-tunnel combination is presented and the stability of the slope on which the express railway portal is to be built is analyzed using three dimensional (3D) numerical simulation in the paper. Comparison of the practicability for the reinforcement of slope with in-situ bored piles and diaphragm walls are performed so as to enhance the stability of the high and steep slope. The safety factor of the slope due to rockmass excavation both inside the exit portal and beneath the bridge abutment of the bridge-tunnel combination has been also derived using strength reduction technique. The obtained results show that post tunnel portal is a preferred structure to fit high and steep slope, and the surrounding rock around the exit portal of the tunnel on the high and steep mountainous slope remains stable when rockmass is excavated both from the inside of the exit portal and underneath the bridge abutment after the slope is reinforced with both bored piles and diaphragm walls. The stability of the high and steep slope is principally dominated by the shear stress state of the rockmass at the toe of the slope; the procedure of excavating rockmass in the foundation pit of the bridge abutment does not obviously affect the slope stability. In-situ bored piles are more effective in controlling the deformation of the abutment foundation pit in comparison with diaphragm walls and are used as a preferred retaining structure to uphold the stability of slope in respect of the lesser time, easier procedure and lower cost in the construction of the exit portal with bridge-tunnel combination on the high and steep mountainous slope. The results obtained from the numerical analysis in the paper can be used to guide the structural design and construction of express railway tunnel portal with bridge-tunnel combination on high and abrupt mountainous slope under similar situations.

Applicability Analysis of Empirical Methods for the Calculation of TBM Advance Rate (국내 TBM굴진속도 산정을 위한 경험적 방법들의 적용성 분석)

  • 조만섭;우동찬;김경곤;이진무
    • Tunnel and Underground Space
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    • v.13 no.4
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    • pp.260-269
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    • 2003
  • In order to introduce to engineers the suitable calculation techniques of TBM advance rate (ad.) and ultimately promote to understand the designing process, this study was carried out. We analyzed the 17 bored data of TBM which applied to the roadway and water supply tunnels in Korea. From this analysis, it was able to how that the average utilization is 30.83% md the correlation equation of Ad and TBM´s diameter (D) is Ad(m/month) = 506.05ㆍ $e^{-0.1162}$$\times$D than the correlation coefficient ($R^2$) is 0.76. In the object of the W tunnel of Seoul-Busan highspeed railway, the Ad of TBM 5.0mø was analyzed by the variety of empirical models and upper correlation equation. Average Ad of the empirical models was calculated to be larger than one of the upper equations. But considering only the results of 3.0~5.0mø TBM in the 17 bored data, the average Ad by the models belongs to the similar range of bored data. Therefore, when the reliability and representative of parameters are decreased, a reliability test should be carried out through the comparison a variety of empirical models with the upper correlation equation.

Tunnelling in Bangkok - Two Case Studies (방콕의 터널공사 - 두 개의 사례연구)

  • Teparaksa, Wanchai;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.7 no.2
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    • pp.153-163
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    • 2005
  • This paper presents two case studies for tunnelling in Bangkok: a subway tunnel site and a flood diversion tunnel site. The first case study is related to ground displacement response for dual tunnel Bangkok MRT subway. The MRT subway project of Bangkok city consists of dual tunnels about 20 km long with 18 subway stations. The tunnels are seated in the firm first stiff silty clay layer between 15-22 m in depth below ground surface. The behavior of ground deformation response based on instrumentation is presented. The back analysis based on plain strain FEM analysis is also presented and agrees with field performance. The shear strain of FEM analysis is in the range of 0.1-1% and in accordance with the results of self boring pressuremeter tests. Meanwhile, the second case study is related to the EPB tunnelling bored underneath through underground obstruction. The Premprachakorn flood diversion tunnel is the shortcut tunnel to divert the flood water in rainy season into the Choapraya river. The tunnel was bored by means of EPB shield tunnelling in very stiff silty clay layer at about 20-24 m in depth. During flood diversion tunnel bored underneath the existing Bangkok main water supply tunnel and pile foundation of the bridge, instrumentation was monitored and compared with predicted FEM analysis. The prevention risk potential by means of predicting damage assessment is also presented and discussed.

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Evaluation of pre-developed seismic fragility models of bored tunnels (기 개발된 굴착식 터널의 지진취약도 모델 적용성 평가)

  • Seunghoon Yang;Dongyoup Kwak
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.25 no.3
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    • pp.187-200
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    • 2023
  • This study analyzed the seismic fragility of bored tunnels based on their surrounding conditions and suggested a representative seismic fragility model. By analyzing the existed seismic fragility models developed for bored tunnels, we developed weighted combination models for each surrounding conditions, such as ground conditions and depth of the tunnel. The seismic fragility curves use the peak ground acceleration (PGA) as a parameter. When the PGA was 0.3 g, the probability of damage exceeding minor or slight damage was 20% for depth of 50 m or less, 10% for depth between 50 m and 100 m, and 3% for depth of 100 m or more. It was also found that the probability of damage was higher for the same PGA and depth when the surrounding ground was rock rather than soil. The probability of damage decreases as the depth increase. This study is expected to be used for developing a comprehensive seismic fragility function for tunnels in the future.

A Case Study for the 1st Double-level Tunnel for Light vehicle in Urban Area in Korea (국내 최초 소형차 전용 도심지 대심도 복층터널 설계 사례)

  • Kim, Gyoung-Hun;Choi, Jun-Dong;Jun, Duk-Chan;Shin, Il-Jae;Sim, Dong-Hyun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09a
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    • pp.1302-1313
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    • 2010
  • The west express way is notorious for extremely heavy traffic area in the west of Seoul, South Korea. Hence, the city government recently initiated a new underground BTO (Build-Transfer-Operate) road project to solve traffic congestion and a high construction cost. The proposed underground express road being designed is the first double-level tunnel ever designed in South Korea and using Conventional tunnelling method (NATM). A total length of tunnel for light vehicles is 10.91km long including both open cut structures and concrete lining with middle-deck in bored tunnel. There are also 4 ventilation shafts for ventilation and evacuation on emergency. Many design issues had been aroused during the preliminary design phase and detail design phase is currently going on. This paper discusses design focuses including excavation methods, ground water issues, a deck slab installation, and a construction cost etc. for the double level road tunnel design of urban area.

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A Case Study on M & E Design for Double-Deck Tunnel in Urban Area (도심지 대심도 복층터널의 환기 및 방재계획)

  • Byun, Sang-Hun;Jeong, Jae-Ho;Jun, Duk-Chan;Shin, Il-Jae;Sim, Dong-Hyun
    • Tunnel and Underground Space
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    • v.21 no.4
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    • pp.281-286
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    • 2011
  • The west underground express way is a recent initiated BTO (Build-Transfer-Operate) project for releasing heavy traffic of the existing west express way which is notorious on-ground road for extremely traffic stuck area in the west of Seoul, South Korea. The new express way for light vehicles is the first double-deck tunnel ever designed in South Korea and 10.91 km long including both open cut structures and concrete lining with middle-deck in bored tunnel. Because the new express way is going through underground of heavily populated area, mechanical & electrical design for the safety of drivers in tunnel is one of the most important parts among many design issues. This paper discusses M & E design focuses including ventilation-evacuation plan and various safety facilities.