• Title/Summary/Keyword: tunnel behavior

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Stability of A Surcharged Tunnel under the Effect of Pre-Loading on the Adjacent Braced Wall (근접한 흙막이벽체에 가하는 선행하중의 영향을 받는 상재하중 재하 터널의 안정)

  • Kim, IL;Lee, Sang Duk
    • Journal of the Society of Disaster Information
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    • v.4 no.2
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    • pp.10-27
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    • 2008
  • When the ground is excavated adjacent to the existing tunnel, which is loaded by the surcharge on the ground surface, the tunnel stability would be very sensitive to the deformation of the ground induced by the horizontal displacement of braced wall. The stability of the existing surcharged tunnel could be controlled by pre-loading on the braced wall. In this paper, it was investigated, if it would be possible to keep the existing surcharged tunnel stable by preventing the horizontal displacement of a braced wall by imposing the pre-loading during the ground excavation. For this purpose, large scale model tests were performed in a scale 1/10 at the test pit which was 2.0m in width and 6.0m in height and 4.0m in length. Isotropic test ground was constructed homogeneously by wet sand. Model tunnel was constructed in the test ground. Surcharge was loaded on the ground surface above the tunnel. During the tests, the behavior of model tunnel and model braced wall was measured. Numerical analyses were also performed in the same condition as the tests. And their results were compared to that of the model tests. Consequently, the effect of a surcharge could be compensated by imposing the pre-loading on the braced wall. The existing tunnel and the braced wall could be kept stable by preventing the horizontal displacement of the braced wall through pre-loading, although the tunnel is surcharged.

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Stability Analysis of Tunnels Excavated in Squeezing Rock Masses (압출 암반내 굴착된 터널의 안정성해석)

  • 정소걸
    • Tunnel and Underground Space
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    • v.13 no.4
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    • pp.245-259
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    • 2003
  • Refering to the articles "Squeezing rocks in tunnels(Barla, 1995)" and "Tunnelling under squeezing rock conditions(Barla 2002)" this article deals with technologies for design, stability analysis and construction of the tunnel being driven in the squeezing rock mass. The definition of this type of behavior was proposed by ISRM(1994). The identification and quantification of squeezing is given according to both the empirical and semi-empirical methods available to anticipate the potential of squeezing problems in tunnelling. Based on the experiences and lessons learned in recent years, the state of the art in modem construction methods was reported, when dealing with squeezing rock masses by either conventional or mechanical excavation methods. The closed-form solutions available for the analysis of the rock mass response during tunnel excavation are described in terms of the ground characteristic line and with reference to some elasto-plastic models for the given rock mass. Finally numerical methods were used for the simulation of different models and for design analysis of complex excavation and support systems, including three-dimensional conditions in order to quantify the influence of the advancing tunnel face to the deformation behavior of the tunnel.

Behavior of shallow 2-Arch tunnel due to excavation under horizontal discontinuity plane (수평 불연속변 하부에 굴착한 얄은 심도의 2-Arch 터널의 거동)

  • Cheon, Eun-Sook;Kim, Hong-Moon;Lee, Sang-Duk
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.7 no.3
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    • pp.227-237
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    • 2005
  • In this study, the behavior of shallow 2-Arch tunnel due to excavation under horizontal discontinuity plane was verified experimentally. The model tests were carried out by varying the overburden height and the location of the discontinuity plane. The model tests followed exactly the real 2-Arch tunnel construction stages. As a result, it is discovered that stress-transfer mechanism and loosening area around the 2-Arch tunnel depends on the overburden heights and the location of the discontinuity plane. And central pillar load is also dependent on overburden height, location of discontinuity plane and construction stages.

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A Study on the Earth Pressure Characteristic of Cut-and-Cover Tunnel Lining by Centrifuge Model Experiment (원심모형시험에 의한 복개터널 복공의 토압특성에 관한 연구)

  • Lee, Myung-Woog;Park, Byung-Soo;Jung, Gil-Soo;Yoo, Nam-Jae
    • Journal of Industrial Technology
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    • v.24 no.B
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    • pp.107-116
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    • 2004
  • This thesis is results of experimental works on the behavior of the cut-and-cover tunnel. Centrifuge model tests were performed to simulate the behavior of the cut-and-cover tunnels having cross sections of national road and subway tunnels. Model experiments were carried out with changing the cut slope and the slope of filling ground surface. Displacements of tunnel lining resulted from artificially accelerated gravitational force up to 40g of covered material used in model tests, were measured during centrifuge model tests. In model tests, Jumunjin Standard Sand with the relative density of 80 % and the zinc plates were used for the covered material and the flexible tunnel lining, respectively. Basic soil property tests were performed to obtain it's the property of Jumumjin Standard Sand. Shear strength parameters of Jumunjin Standard Sand were obtained by performing the triaxial compression tests. Direct shear tests were also carried out to find the mechanical properties of the interface between the lining and the covered material. Compared results model tests estimation with respect to displacements of the lining.

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Behavior of a tunnel face reinforced with longitudinal pipes - laboratory investigation (실내실험에 의한 수평보강재로 보강된 터널막장의 거동)

  • Yoo, Chung-Sik;Yang, Ki-Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.4 no.2
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    • pp.91-100
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    • 2002
  • This paper presents the results of laboratory investigation on the deformation behavior of tunnel face reinforced with longitudinal pipes. A series of reduced-scale model tests was carried out to investigate the effect of reinforcement layout on the tunnel face axial displacement as well as the surface settlement. Among other things, the results of the model tests indicate that the axial displacement of tunnel face as well as the ground surface settlement can significantly be reduced by pre-reinforcing the tunnel face with longitudinal pipes, suggesting that the pre-reinforcing technique may effectively be used as a positive ground control method in the urban environments. Also illustrated is that the reinforcing effect is significantly influenced by the reinforcement layout. The implications of the findings from this study are discussed in a great detail.

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A study on the behavior of cut and cover tunnel by numerical analysis (수치해석 기법을 이용한 복개 터널구조물의 거동에 관한 연구)

  • Lee, Seok-Won;Lee, Gyu-Phil;Bae, Gyu-Jin
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.5 no.1
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    • pp.43-54
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    • 2003
  • In the deign of cut and cover tunnel, the structural analysis such as rigid frame analysis has been used for its simplicity and convenience. The structural analysis, however, can not consider the geological and geotechnical factors such as soil arching effect. In this study, the dominant factors influencing the behavior of cut and cover tunnel such as interface element, slope of excavation plane, distance between slope and tunnel lining, and location of slope of covered soil, were investigated by the numerical analysis to develop the analysis technique and design technology. Based on the results, the variation of bending moment, shear stress, axial force and displacements were evaluated and analyzed for each factor.

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Behavior of braced wall due to distance between tunnel and wall in excavation of braced wall nearby tunnel (터널에 인접한 흙막이굴착 시 터널 이격거리에 따른 거동특성)

  • Ahn, Sung Joo;Lee, Sang Duk
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.4
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    • pp.657-669
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    • 2018
  • In recent years, the development of complex urban areas has become saturated and much attention has been focused on the development of underground space, and deep excavation is frequently performed in order to increase the utilization of underground space due to the enlargement of buildings and the high rise of buildings. Therefore, in this study, we tried to understand the behavior of the braced wall and the behavior of the tunnel adjacent to the wall according to the stiffness of the wall and the distance between the tunnel and wall. As a result of the study, the deformation of the braced wall tended to decrease with increasing the stiffness of the wall, and the axial force acting on the struts was also different according to the stiffness of braced wall. When the stiffness of the braced wall is small (2 mm), the point at which the axial force of the braces maximizes is near 0.3H of the wall. When the stiffness of the braced wall is large (5 mm), the axial force is maximum at around 0.7H of the wall. Also, the tunnel convergence occurred more clearly when the separation distance from the braced wall was closer, the stiffness of the wall was smaller, and the tunnel convergence was concentrated to the lower right part. The ground settlement due to the excavation of the ground tended to decrease as the distance between tunnel and braced wall was closer to that of the tunnel, which is considered to be influenced by the stiffness of the tunnel.

Ground Behavior and Reinforcing Methods of NATM Tunnel through Deep Weathered Zone (NATM 터널의 대심도 풍화대층에서의 지반거동 및 보강방법)

  • Sung, Hwa-Don;An, Jung-Whan;Chun, Byung-Sik
    • Proceedings of the KSR Conference
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    • 2007.05a
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    • pp.1782-1788
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    • 2007
  • This study analyzed ground settlement and ground stress depending on tunnel excavation and the ground reinforcing grouting methods for double line road tunnel through deep weathered zone. Diameter of double line road tunnel was approximately 12m and umbrella arch method and side wall reinforcing grouting were applied. The ring-cut split excavation method and CD-cut excavation method for excavation method were applied. Analysis of failure rate and vertical stress ratio show that the tunnel for which the height of the cover(H) was higher than four times the diameter, it can be considered a deep tunnel. Comparisons of various excavation and ground reinforcement methods were showed that CD-cut method results in lower surface and crown settlement, and lower failure rate than where using Ring-cut split method. In addition the side wall reinforcing grouting resulted in reduction of tunnel displacement and settlement.

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Dynamic interaction analysis of submerged floating tunnel and vehicle (튜브형 수중교량의 교량-차량 동적상호작용 해석방법)

  • Kim, Moon-Young;Kwark, Jong-Won;Min, Dong-Ju
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2013.04a
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    • pp.83-88
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    • 2013
  • The purpose of this study is to develop the algorithm for dynamic interaction analysis of submerged floating tunnel and vehicles. The dynamic behavior characteristic of submerged floating tunnel is certainly different with general structures, because the submerged floating tunnel is floating in the middle of water, and subjected to constant buoyance. Therefore the analyses in various aspects should be carried out to secure structural stability and practicality of structures. To conduct the dynamic interaction analysis, the structure is modeled by commercial FEM program ABAQUS to investigate modal characteristic. Also the added mass concept is applied to represent the inertial force by a fluid, and then dynamic interaction analyses are conducted with superposition method when the KTX is moving along the submerged floating tunnel. And the time histories are presented for vertical and lateral displacement at the center of the tunnel.

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Dynamic Analysis of Tunnel Structures Considering Soil-Structure Interaction (지반-구조물 상호작용을 고려한 터널 구조물의 동적 해석)

  • Kim, Hyon-Jung;Park, Jang-Ho;Shin, Yung-Seok
    • Journal of the Korean Society of Safety
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    • v.20 no.1 s.69
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    • pp.101-106
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    • 2005
  • When a underground structure is constructed at the site composed of soft soil, the behavior of a underground structure Is much affected by the motion of soft soil. Therefore, the effect of soil-structure interaction is an important consideration in the design of a underground structure such as tunnel at the site composed of soft soil. This paper presents the results of the study on dynamic response of tunnel structures and soil-structure interaction effects. The computer program SASSI was used in seismic analysis of tunnel structures because it is more capable of analyzing dynamic response or structures considering soil-structure interaction. As regards the results, the flexibility of surrounding soil affects dynamic response characteristics of tunnel structures and response of tunnel structures can be amplified.