• Title/Summary/Keyword: tunnel behavior

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Behaviour Analysis of Crown Collapse under Tunnel Construction After Completing Reinforcement (보강완료 후 시공 중 터널 천단부 붕락 거동 분석)

  • Kim, Nagyoung;Baek, Seungchol;Min, Kyungjun;Kim, Bongsu;Heo, Yol
    • Journal of the Korean GEO-environmental Society
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    • v.17 no.4
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    • pp.39-46
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    • 2016
  • The final stability analysis of the tunnel structure is generally evaluated by performing site monitoring to determine whether or not the measured value through the convergence after the completion of excavation in the face. When the ground conditions are so poor, the reinforcement around the tunnel was applied for enhancing the stability of tunnels. For the additional tunnel crown collapse or excessive displacement have occurred under construction, correlation analysis were performed for the comparison construction and numeric analyses. In this paper, we investigated the collapse types, tunnel collapse were mostly occurs at the crown and they were analyzed because of the geological conditions in the collapse zone. And also, it was analyzed as being correlated in the crown of tunnel exists a fault fracture zone which extends to the surface part. Thus, in case of ground conditions such as fault fracture zone with a tunnel extending from the crown to the surface, the behavior is larger than the behavior predicted by numerical method.

Effect of orientation of fracture zone on tunnel behavior - Numerical Investigation (파쇄대의 공간적 분포가 터널 거동에 미치는 영향 - 수치해석 연구)

  • Yoo, Chung-Sik;Cho, Yoon-Gyu;Park, Jung-Gyu
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.15 no.3
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    • pp.253-270
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    • 2013
  • This paper concerns the effect of orientation and geometric characteristics of a fracture zone on the tunnel behavior using a numerical investigation. A parametric study was executed on a number of drill and blast tunnelling cases representing different fracture and tunnelling conditions using two and three dimensional finite element analyses. The variables considered include the strike and dip angle of fracture zone relative to the longitudinal tunnel axis, the width and the clearance of the fracture zone, the tunnel depth, and the initial lateral stress coefficient. The results of the analyses were examined in terms of the tunnel deformation including crown settlement, convergence, and invert heave as well as shotcrete lining stresses. The results indicate that the tunnel deformation as well as the shotcrete lining stress are strongly influenced by the orientation of the fracture zone, and that such a trend becomes more pronounced for tunnels with greater depths.

Ground Behavior around Tunnel Using Tunnel-shaped Trapdoor Model Test (터널형상의 Trapdoor 모형실험을 통한 지반 거동에 관한 연구)

  • Han, Young-Chul;Kim, Sang-Hwan;Jeong, Sang-Seom
    • Journal of the Korean Geotechnical Society
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    • v.30 no.4
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    • pp.65-80
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    • 2014
  • This study conducted Trapdoor tests with actual tunnel shape, investigated the mechanical behavior of ground and loosening load on tunnels, and evaluated the mechanism of progressive failure by numerical simulation. The loosening load sharply decreased initially, but it generally increased and reached the stabilized level exhibiting the arching effect, and loose sand showed relatively higher values than those of dense sand. The shear band started from the tunnel shoulder with 63 (loose sand) to 69 (dense sand), and gently curved inward to the ground surface. The widths of shear band formation above the tunnel showed a range from 1.8b to 1.9b (b=Tunnel width), which are similar to those values calculated from existing formular. The vertical height of this shear band for deep tunnel was turned out to be a bit lower than that from existing studies (3.0*Tunnel Height).

Effect of Spatial Distribution of Geotechnical Parameters on Tunnel Deformation (지반 물성치의 공간적 분포에 따른 터널 변위 특성 분석)

  • Song, Ki-Il;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.8 no.3
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    • pp.249-257
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    • 2006
  • The spatial distribution of design parameters greatly affects tunnel behavior during and after construction, as well as in the long-term temporal responses. However, the tunnel design parameters commonly used in numerical modeling tend to be representative or average values of global-scale properties. Furthermore, the uncertainty and spatial variation of the design parameters increase as the tunnel scale increases. Consequently, the probability of failure also increases. In order to achieve structural stability in large-section tunnels, the design framework must take into consideration the quantitative effect of design parameter variations on tunnel behavior. Therefore, this paper suggests a statistical approach to numerical modeling to explore the effect of spatially distributed design parameters in a circular tunnel. Also, the effect of spatial variation in the lining strength is studied in this paper. The numerical results suggest that the deformation around the tunnel increases with an increase in the variation of the design parameters.

Behavior of 2 Arch Tunnel in Sand (사질토지반에서 2 Arch 터널의 거동)

  • Lee, Sang-Duk;Cheon, Eun-Sook
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.6 no.2
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    • pp.171-182
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    • 2004
  • This study is focused on finding out the mechanical behavior of pillars and the ground adjacent to the tunnel depending on the central tunnel size and the invert during the construction of 2 arch tunnels in the sandy ground. Model tests were performed in the trap door system, which was composed of 3 separately movable plates. Central pillar was installed on the central movable plate to measure the pillar loads during the excavation of pilot tunnel and the main tunnel. The load-transfer and the loosening load were measured at the bottom plates adjacent to the 2 arch tunnels. The ground settlement and displacement of the tunnel lining were also measured. As results, not only pillar load but also the load transfer mechanism was influenced by the construction sequences, central tunnel size, and the invert.

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Study on the Effective Method of Fire Protection Technology in Railway Tunnel Fire (철도터널 내화성능 기술개발을 위한 내화성능 확보방안에 관한 연구)

  • Park, Kyung-Hoon;Kim, Heung-Yeol;Kim, Hyung-Jun
    • Fire Science and Engineering
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    • v.24 no.4
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    • pp.86-91
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    • 2010
  • In event of a tunnel fire, all kinds of equipment can be destroyed in high temperature that can exceed 1300C, fatal structural demage can be caused by spalling of concrete structural elements. To make matters worse, there is a high possibility of the secondary damage which can lead to the collapse of the shear resisting structure. Accordingly, it is time that we developed the technology to counter fires in connection with the fire-resistant design of a tunnel structure. To secure the reliability of the fire-resistance performance of a tunnel structure, it is necessary to assess the fire's behavior on every structural element exposed to the fire as well as to calculate the tunnel fire intensity and the quantity of heat released. In this study, we drew out the fire damage range of each structural element of a tunnel and the minimum thickness of concrete cover for each fire-resistant material through some actual experiments of fire behavior on the structural elements of a tunnel.

Numerical investigation on 3D behavior of 2-Arch tunnel (2-Arch 터널의 3차원 거동 특성 - 수치해석 연구)

  • Yoo, Chung-Sik;Kim, Joo-Mi;Kim, Hee-Chul
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.3
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    • pp.255-264
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    • 2009
  • This paper concerns the behavior of 2-Arch tunnel constructed under various conditions. A 2-Arch tunnel section adopted in a subway tunnel construction site is considered in this study. A calibrated 3D finite element model was adopted to conduct parametric studies on a variety of construction scenarios including lagged distance between left and right tunnels, overburden, and geological condition. The results of analyses were examined in terms of crown settlement, shotcrete lining stress, and load on center column in relation to the lagged distance, cover depth, and the ground condition. The results indicate that the shotcrete lining stress and the center pillar load are more influenced by the second tunnel excavation than the tunnel deformation. Also shown is that a greater lagged distance is required to minimize the interaction between two tunnels when the ground condition becomes weaker. Fundamental mechanisms of 2-arch tunnel were also discussed based on the results.

Three Dimensional Behavior or Square Footing and Bnlined Solt Ground Tunnel (정방형 기초와 Unlined Soft Ground터널의 3차원적 거동)

  • 유충식
    • Geotechnical Engineering
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    • v.10 no.3
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    • pp.97-110
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    • 1994
  • Interaction between an unlined tunnel may cause a serious stability both the tunnel and the overlying and unli Red tunnel interaction meta study on the three dimensional bets a three dimensional elasto plastic the program, a wide range of blur puter analysis such as stress distr menu and tunnel deformation were footing and unlined tunnel. The yes traces the ultimate bearing capacity only on the tunnel size and location revealed is that an unlined tunnel under a square footing is subjected to three dimensional stress pattern along the tunnel axis, and that the magnitudes of stresses in the foundation soil and around tunnel perimeter are considerably smaller when loaded with a square than with a strip footings and the difference varies with the location and the type of stress. It is also revealed that the footing failure mechanism varies with the degree of footing and tunnel interaction.

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Experimental study on behavior of the existing tunnel due to adjacent slope excavation in a jointed rock mass (절리암반에서의 근접사면굴착에 의한 기존터널 거동에 대한 실험적 연구)

  • Lee, Jin-Wook;Lee, Sang-Duk
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.1
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    • pp.1-9
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    • 2009
  • When a rock slope is excavated adjacent to a existing tunnel, the behavior of the existing tunnel in the jointed rock masses is greatly influenced by the joint conditions and slope status. In this study, the effects of joint dip and slope angle close to a tunnel are investigated through a large scale model using a biaxial test equipment (3.1m×3.1m×0.50m (width × height × length)). The jointed rock masses were built by concrete blocks. The diameter of the modeled tunnel is 0.6 m and the dip angles of joint vary in the range of 090. In addition, the excavated slope angle varies within 3090. Deformational behaviors of the tunnel were analyzed in consideration of joint dip and slope angle. With increase of the joint dip and slope angle, the magnitude of tunnel distortion and the moment of tunnel lining were increased. Rock mass displacement in horizontal was also dependent on the joint dip and the excavated slope angle, which indicated the optimal slope reinforcement for a specific rock mass conditions.

Evaluation of Cave-in Possibility of a Shallow Depth Rock Tunnel by Rock Engineering Systems and Uumerical Analyses (암반공학시스템과 수치해석을 이용한 저심도 암반터널에서의 붕락 발생 가능성 평가)

  • Kim, Man-Kwang;Yoo, Young-Il;Song, Jae-Joon
    • Tunnel and Underground Space
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    • v.19 no.3
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    • pp.236-247
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    • 2009
  • Overpopulation has significantly increased the use of underground spaces in urban areas, and led to the developments of shallow-depth underground space. Due to unexpected rock fall, however, it is very necessary to understand and categorize the rock mass behaviors prior to the tunnel excavation, by which unnecessary casualties and economic loss could be prevented. In case of cave-in, special attention should be drawn since it occurs faster and greater in magnitude compared to rock fall and plastic deformation. Types of cave-in behavior are explained and categorized using seven parameters - Uniaxial Compressive Strength (UCS), Rock Quality Designation (RQD), joint surface condition, in-situ stress condition, ground water condition, earthquake & ground vibration, tunnel span. This study eventually introduces a new index called Cave-in Behavior Index (CBI) which explains the behavior of cave-in under given in-situ conditions expressed by the seven parameters. In order to assess the mutual interactions of the seven parameters and to evaluate the weighting factors for all the interactions, survey data of the experts' opinions and Rock Engineering Systems (RES) were used due to lack of field observations. CBI was applied to the tunnel site of Seoul Metro Line No. 9. UDEC analyses on 288 cases were done and occurrences of cave-in in every simulation were examined. Analyses on the results of 288 cases of simulations revealed that the average CBI for the cases when cave-in for different patterns of tunnel support was estimated by a logistic regression analysis.