• Title/Summary/Keyword: Tunnel pressure

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A Intercomparison on the estimating shield TBM tunnel face pressure through analytical and numerical analysis (이론해와 수치해석적 검토를 통한 쉴드TBM 막장압 산정 결과 상호비교)

  • Jun, Gy-Chan;Kim, Dong-Hyun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.18 no.3
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    • pp.273-282
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    • 2016
  • This study estimates tunnel face pressure through existing 8 analytical equations and 3D numerical analysis, and compares and examines it. In general, the estimating tunnel face pressure of domestic shield TBM has been examined by a method according to analytical equation and empirical method, but numerical analysis is combined in a section passing complicated stratigraphic condition and special soil condition. Therefore, the researcher is to find a reliable method to examine of tunnel face pressure by confirming a correlation between tunnel face pressure estimated by equation and tunnel face pressure estimated by numerical analysis program. When tunnel face pressure is estimated, both analytical equation and numerical analysis were identically examined in soil conditions such as sandy soil and cohesive soil. In addition, existing analytical equation is used as equation, and 3D analysis copying construction process and shield tunnel as numerical analysis.

Flow characteristics after water inrush from the working face in karst tunneling

  • Wu, J.;Li, S.C.;Xu, Z.H.;Pan, D.D.;He, S.J.
    • Geomechanics and Engineering
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    • v.14 no.5
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    • pp.407-419
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    • 2018
  • In order to investigate flow characteristics after water inrush from the working face in process of karst tunnel construction, numerical calculation for two class case studies of water inrush is carried out by using the FLUENT software on the background of Qiyueshan tunnel. For each class water inrush from the tunnel face, five cases under different water-inrush velocity are simulated and researched. Three probing lines are selected respectively in the left tunnel, cross passage, right tunnel and in the height direction of the tunnel centerline. The variation characteristics of velocity and pressure on each probing line under the five water-inrush velocities are analyzed. As for the selected four groups probing lines in the tunnels, the change rules of velocity and pressure on each group probing lines under the same water-inrush velocity are discussed. Finally, the water flow characteristics after inrush from the tunnel face are summarized by comparing the case studies. The results indicate that: (1) The velocity and pressure change greatly at the intersection area of the cross passage and the tunnels. (2) The velocity nearby the tunnel side wall is the minimum, while it is the maximum in the middle position. (3) The pressure value of every cross section in the tunnels is basically fixed. (4) As water-inrush velocity increases, the flow velocity and pressure in the tunnels also increase. The former is approximately proportional to their respective water-inrush velocity, while the latter is not. The research results provide a theoretical basis for making scientific and rational escape routes.

Analysis on the Field Measurements with the Construction of Cut and Cover Tunnel (복개 터널구조물의 현장 시공에 따른 계측 분석 사례)

  • 이석원;박시현;최순욱;배규진
    • Tunnel and Underground Space
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    • v.13 no.2
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    • pp.125-137
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    • 2003
  • Field measurements were carried out in this study to investigate the behavior of cut and cover tunnel such as the distribution and the magnitude of the earth pressure during back fill process. Three kinds of measuring instruments, such as the earth pressure load cell, the concrete strain gauge and the reinforcing bar meter of embedded type in concrete structure were installed and measured. Earth pressure load cells measured the outside forces acting on the tunnel lining with radial directions. Three load cells were installed at the crown, the right and the left shoulder of the tunnel, respectively. Three sets of reinforcing bar meter were installed in the double reinforcements of the tunnel lining and their locations were the same with the position of the earth pressure load cells. Concrete strain gauge was installed only one site of the upper compressive part at the tunnel crown. Based on the measurements, the deformation and the earth pressure acting on the tunnel lining were investigated with the back fill process. Considerations on the validity of the field measurements were paid.

Aerodynamic analysis on the step types of a railway tunnel with non-uniform cross-section

  • Li, Wenhui;Liu, Tanghong;Huo, Xiaoshuai;Guo, Zijian;Xia, Yutao
    • Wind and Structures
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    • v.35 no.4
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    • pp.269-285
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    • 2022
  • The pressure-mitigating effects of a high-speed train passing through a tunnel with a partially reduced cross-section are investigated via the numerical approach. A compressible, three-dimensional RNG k-ε turbulence model and a hybrid mesh strategy are adopted to reproduce that event, which is validated by the moving model test. Three step-like tunnel forms and two additional transitions at the tunnel junction are proposed and their aerodynamic performance is compared and scrutinized with a constant cross-sectional tunnel as the benchmark. The results show that the tunnel step is unrelated to the pressure mitigation effects since the case of a double-step tunnel has no advantage in comparison to a single-step tunnel, but the excavated volume is an essential matter. The pressure peaks are reduced at different levels along with the increase of the excavated earth volume and the peaks are either fitted with power or logarithmic function relationships. In addition, the Arc and Oblique-transitions have very limited gaps, and their pressure curves are identical to each other, whereas the Rec-transition leads to relatively lower pressure peaks in CPmax, CPmin, and ΔCP, with 5.2%, 4.0%, and 4.1% relieved compared with Oblique-transition. This study could provide guidance for the design of the novel railway tunnel.

Effect of a Frontal Impermeable Layer on the Excess Slurry Pressure during the Shield Tunnelling (전방 차수층이 쉴드터널 초과 이수압에 미치는 영향)

  • Lee, Yong-Jun;Lee, Sang-Duk
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.1199-1213
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    • 2011
  • Slurry type shield would be very effective for the tunnelling in a sandy ground, but low slurry pressure could cause a tunnel face failure or a ground settlement in front of the tunnel face. Thus, the stability of tunnel face could be maintained by applying an excess slurry pressure that is larger than the active earth pressure. However, the slurry pressure should increase properly because an excessively high slurry pressure could cause the slurry flow out or the passive failure of the frontal ground. It is possible to apply the high slurry pressure without passive failure if a horizontal impermeable layer is located in the ground in front of the tunnel face, but its location, size, and effects are not clearly known yet. In this research, two-dimensional model tests were carried out in order to find out the effect of a horizontal impermeable layer for the slurry shield tunnelling in a saturated sandy ground. As results, larger slurry pressure could be applied to increase the stability of the tunnel face when the impermeable layer was located in the ground above the crown in front of the tunnel face. The most effective length of the impermeable grouting layer was 1.0~1.5D, and the location was 1.0D above the crown level. The safety factor could be suggested as the ratio of the maximum slurry pressure to the active earth pressure at the tunnel face. It could also be suggested that the slurry pressure in the magnitude of 3.5~4.0 times larger than the active earth pressure at the initial tunnel face could be applied if the impermeable layer was constructed at the optimal location.

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Study on deformation law of surrounding rock of super long and deep buried sandstone tunnel

  • Ding, Lujun;Liu, Yuhong
    • Geomechanics and Engineering
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    • v.16 no.1
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    • pp.97-104
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    • 2018
  • The finite difference software Flac3D is used to study the influence of tunnel burial depth, tunnel diameter and lateral pressure coefficient of original rock stress on the stress and deformation of tunnel surrounding rock under sandstone condition. The results show that the maximum shear stress, the radius of the plastic zone and the maximum displacement in the surrounding rock increase with the increase of the diameter of the tunnel. When the lateral pressure coefficient is 1, it is most favorable for surrounding rock and lining structure, with the increase or decrease of lateral pressure coefficient, the maximum principal stress, surrounding displacement and plastic zone range of surrounding rock and lining show a sharp increase trend, the plastic zone on the lining increases with the increase of buried depth.

A Numerical Study on the Compression Wave Generated by the Train Entering a Tunnel (열차가 터널에 진입할 때 발생하는 압축파에 대한 수치해석)

  • Kim, Sa-Ryang
    • The KSFM Journal of Fluid Machinery
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    • v.9 no.6 s.39
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    • pp.17-21
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    • 2006
  • The numerical simulations on the train entering a tunnel were performed by solving unsteady axi-symmetric problems. In the case that 5th order velocity profile is used to reduce the effects of the pressure wave generated by the train starting abruptly, the effect of the initial distance between the train and the tunnel were examined. The impulsive start gives undesired pressure disturbances to the flow field including inside the tunnel. But 5th order velocity profile with initial distance more than 80 m gives much stable pressure variance in time, and pressure distribution inside the tunnel in space. The distance to the train reaches the highest running velocity from the start should be more than 80 m when the train speed is 350 km/h.

Experimental Study on the Slit Cover Hood for Reducing the Micro Pressure Waves in High-Speed Train-Tunnel Interfaces (고속철도에서 슬릿커버 완충공의 터널 미기압파 저감성능)

  • Kim, Dong-Hyeon;Min, Dong-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.6
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    • pp.758-765
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    • 2001
  • Purpose of the present is to investigate the food configuration at a tunnel entrance for reducing the micro pressure wave that is generated according to train speed. Two configurations were examined for tunnel of 0.5 km length. The experimental results show that a slit cover hood installed at the entrance of the tunnel reduces the maximum micro pressure wave by 41.2%, and a configuration with a slit cover hood installed at the entrance and a 45$^{\circ}$slanted portal at the exit of the tunnel suppresses it by 47.7%.

An experimental study on the reduction method of earth pressure acting on the cut-and-cover tunnel lining (개착식 터널의 라이닝에 작용하는 토압경감대책에 관한 실험적 연구)

  • Kim, Sang-Yoon;Im, Jong-Chul;Park, Lee-Keun;Bautista, Ferdinand E.
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.952-957
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    • 2004
  • Cut and Cover Method is generally used in shallow tunnels and tunnel entrances with thin soil cover. In this type of cons0truction, backfilling is considered to be the most important process. In this process even though the backfill material is thoroughly compacted, compaction and self-weight due to vehicular vibration and pressure exerted by the soil cause the backfill material to undergo self-compression which leads to settlement. The settlement of the backfill material subjects the tunnel lining under excessive earth pressure which cause cracking and deformation. In the model test performed installation of geotextile on the sides and top of the tunnel was able to reduce the earth pressure acting on the tunnel lining.

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NUMERICAL STUDY ON WIND TUNNEL GROUND PLATE WITH A PRESSURE CONTROL DEVICE (압력 조절 장치를 갖는 풍동 지면판에 관한 수치해석적 연구)

  • Lee, M.J.;Kim, C.W.
    • Journal of computational fluids engineering
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    • v.15 no.4
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    • pp.53-59
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    • 2010
  • Preliminary design of a ground plate, a device installed close to the aircraft model for wind tunnel test to simulate the ground effect, was performed by a numerical simulation. A two-dimensional numerical study was performed initially to decide the optimal leading edge and flap configurations. Then, three-dimensional studies were conducted to decide the optimal flap deflection angle for pressure distribution reduction since the plate and the plate supporting system generate static pressure difference between the upper and lower flow regions. Three-dimensional simulation additionally studied the effect of the clearance between the plate and the wind tunnel side wall. For the efficiency of computation, half model was simulated and a symmetric boundary condition was applied on the center plane. Based on the preliminary design, a ground plate was designed, manufactured and tested at the Korea Aerospace Research Institute(KARI) wind tunnel. The measured pressure differences versus flap deflection angle agreed well with the predicted results.