• Title/Summary/Keyword: Tunnel Displacement

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An Analysis for the Stress Redistribution around Tunnel Face Using Three-Dimensional Finite Element Method (3차원 유한요소법을 이용한 터널 막장 주위에서의 응력 재분배 해석에 관한 연구)

  • 문선경;이희근
    • Tunnel and Underground Space
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    • v.5 no.2
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    • pp.95-103
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    • 1995
  • In this paper the stress redistribution around tunnel face was analyzed by using a three-dimensional finite element model. The effects of in-situ stress levels, excavation sequences, stiffness difference between the hard ground and the weak zone on the stress redistributions were considered. Displacement and stress changes at tunnel crown, side wall, and invert were investigated throughout the sequential excavation. To show ground response, percentage of the displacement and stress variations are used as a function of normalized distance that is between the face and monitoring section. Preceding displacements and stress variations were presented to be adopted in the two-dimensional tunnel analysis.

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The Characteristics of Stress and Displacement due to the Diagonal Parallel Tunnel Excavation (대각선 병설터널 굴착에 따른 응력과 변위특성)

  • Kim, Youngsu;Pack, Songja
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.11
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    • pp.39-49
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    • 2011
  • In this paper it was focused on the characteristics of displacement and stress due to the construction of diagonal twin tunnel. In this research, the characteristics have been analyzed with the presumption that the tunnel's diameter (D) is 13m and the ground was formed by weathered rock. In analysis, the width of pillar is 2.0D, 2.5D, 3.0D, the height of soil cover is 3D, 4D, 5D, and the installation angle of diagonal twin tunnel has been changed into $15^{\circ}$, $30^{\circ}$, $45^{\circ}$. And the program used in this analysis is FLAC which is widely used in solution problems of ground engineering in order to gain and analyze occurring shotcrete and rockbolt stress and nearby ground displacement according to pillar width, the height of soil cover and installation angle of diagonal twin tunnel. As a result, in the weathered rock grounds, when the width of pillar is more than 2.0D, the height of soil cover is over 5.0D, and the installation angle of diagonal twin tunnel is lower, they lessen effects on the ground and favorable on the stability of tunnel.

The Pre-Evaluation of Stability during Tunnel Excavation using Unconfined Compression Strength of Intact Rock or Rock Mass and Crown Settlement Data (터널천단변위와 암석 또는 암반의 일축압축강도를 이용한 시공 중인 터널의 예비 안정성 평가)

  • Park, Young Hwa;Moon, Hong Duk;Ha, Man Bok
    • International Journal of Highway Engineering
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    • v.17 no.6
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    • pp.27-32
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    • 2015
  • PURPOSES : It is difficult to estimate tunnel stability because of lack of timely information during tunnel excavation. Tunnel deformability refers to the capacity of rock to strain under applied loads or unloads during tunnel excavation. This study was conducted to analyze a methods of pre-evaluation of stability during tunnel construction using the critical strain concept, which is applied to the results of tunnel settlement data and unconfined compression strength of intact rock or rock mass at the tunnel construction site. METHODS : Based on the critical strain concept, the pre-evaluation of stability of a tunnel was performed in the Daegu region, at a tunnel through andesite and granite rock. The critical strain concept is a method of predicting tunnel behavior from tunnel crown settlement data using the critical strain chart that is obtained from the relationship between strain and the unconfined compression strength of intact rock in a laboratory. RESULTS : In a pre-evaluation of stability of a tunnel, only actually measured crown settlement data is plotted on the lower position of the critical strain chart, to be compared with the total displacement of crown settlement, including precedent settlement and displacement data from before the settlement measurement. However, both cases show almost the same tunnel behavior. In an evaluation using rock mass instead of intact rock, the data for the rock mass strength is plotted on the lower portion of the critical strain chart, as a way to compare to the data for intact rock strength. CONCLUSIONS : From the results of the pre-evaluation of stability of the tunnel using the critical strain chart, we reaffirmed that it is possible to promptly evaluate the stability of a tunnel under construction. Moreover, this research shows that a safety evaluation using the actual instrumented crown settlement data with the unconfined compression strength of intact rock, rather than with the unconfined compression strength of a rock mass in the tunnel working face, is more conservative.

Numerical Analysis on the Behavior of the Earth Tunnel due to Supporting Methods (지보공법에 따른 토사터널의 거동에 관한 수치해석)

  • Kim, Jin-Tae;Park, Byung-Soo;Jeong, Gil-Soo;Yoo, Nam-Jea
    • Journal of Industrial Technology
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    • v.24 no.A
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    • pp.239-250
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    • 2004
  • Numerical analysis were performed to investigate the stability and internal movement of tunnel located beneath the base of abutment of bridge according to the method of supporting tunnel. Two supporting methods of the multi-staged grouting method with steel pipes and the large diameter of pipe supporting method were used in the centrifuge model tests. The slip form of model lining, specially built to simulate the process of tunnel excavating under the condition of accelerated g-level, was used in the centrifuge model tests. Four centrifuge model tests were performed, changing the supporting methods of the multi-staged grouting method with steel pipes and the large diameter of pipe supporting method and the location of model abutment base of bridge. For internal displacement of tunnel, movements of the crown. The left and the right sides of spring line were measured during the proceeds of excavating tunnel in centrifuge model tests. Test results were compared with numerically estimated values of internal displacement of tunnel by using the commercially available FEM software of PENTAGON-3D. It was found that they were in good agreements and the large diameter of pipe supporting method was more stable than the multi-staged grouting method with steel pipes with respect to the internal movement of tunnel.

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A numerical study on the analysis of behavior characteristics of inclined tunnel considering the optimum direction of steel rib (강지보재 최적 설치방향을 고려한 경사터널의 거동특성에 대한 수치해석적 연구)

  • Park, Sang-Chan;Kim, Sung-Soo;Shin, Young-Wan;Shin, Hyu-Soung;Kim, Young-Geun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.10 no.3
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    • pp.245-256
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    • 2008
  • The steel rib, one of the main support of tunnel, plays a very important role to stabilize tunnel excavation surface until shotcrete or rockbolt starts to perform a supporting function. In general, a steel rib at the horizontal funnel is being installed in the direction of gravity which is known favorable in terms of constructability and stability. However, as the direction of principal stress at the inclined tunnel wall is different from that of gravity, the optimum direction of steel rib could be different from that at the horizontal tunnel. In this study, a numerical method was used to analyze the direction of force that would develope displacement at the inclined tunnel surface, and that direction could be the optimum direction of steel rib. The support efficiency of steel rib could be maximized when the steel rib was installed to resist the displacement of the tunnel. Three directions which were recommended for the inclined tunnels in the Korea Tunnel Design Standard were used for the numerical models of steel rib direction. In conclusion, the results show that all displacement angle of the models are almost perpendicular to the tunnel surface regardless of face angle. So if the steel rib would be installed perpendicular to the inclined tunnel surface, the support efficiency of steel rib could be maximized.

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Aeroelastic model test of a 610 m-high TV tower with complex shape and structure

  • Ding, Quanshun;Zhu, Ledong
    • Wind and Structures
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    • v.25 no.4
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    • pp.361-379
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    • 2017
  • In view of the importance of the wind-structure interaction for tall and slender structures, an aeroelastic model test of the 610m-high TV tower with a complex and unique structural configuration and appearance carried out successfully. The assembled aeroelastic model of the TV tower with complex shape and structure was designed and made to ensure the similarities of the major natural frequencies and the corresponding mode shapes. The simulation of the atmospheric boundary layer with higher turbulent intensity is presented. Since the displacement and acceleration responses at several measurement sections were directly measured in the wind tunnel test, a multi-mode approach was presented to indirectly estimate the displacement and acceleration responses at arbitrary structural floors based on the measured ones. It can be seen that it is remarkable for the displacement and acceleration responses of the TV tower in the two horizontal directions under wind loads and is small for the dynamic response of the torsional displacement and acceleration.

On Monitoring of Induced Stress and Displacement for Support Design around Tunnel in Weak Rock (연약 암반내 터널 보갱법 설계를 위한 2차 응력 및 변위 계측에 관한 연구)

  • 임한욱;이상은
    • Tunnel and Underground Space
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    • v.4 no.3
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    • pp.297-304
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    • 1994
  • This study aimed at analysis of induced stress and deformation behavior in rock mass around coal seams of Sam Chuck coal mine. For this study Vibrating Wire Stressmeters and Multi-point Borehole Extensometers were installed in the area of coal shale near coal seams. Induced stress and displacement in this area were coutinuously increased for 6 days from the begining of measurement, and then converged. But induced stress and displacement occurred when there were another openings by tunnelling and mining. The value of final induced stress was 21.8kgf/$\textrm{cm}^2$, displacement of rod extensometer was 1.3 mm at arch. Especially, over 1 mm of displacement between E2 and E3 in rod extensometer was measured.

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Numerical Analysis on the Effect of Heterogeneous/Anisotropic Nature of Rock Masses on Displacement Behavior of Tunnel (비균질/이방성 암반에서의 터널 거동 분석을 위한 수치해석적 연구)

  • Baek, Seung-Han;Kim, Chang-Yong;Kim, Kwang-Yeom;Hong, Sung-Wan;Moon, Hyun-Koo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.939-948
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    • 2006
  • The structural anisotropy and heterogeneity of rock mass, caused by discontinuities and weak zones, have a great influence on the deformation behavior of tunnel. Tunnel construction in these complex ground conditions is very difficult. No matter how excellent a geological investigation is, local uncertainties of rock mass conditions still remain. Under these uncertain circumstances, an accurate forecast of the ground conditions ahead of the advancing tunnel face is indispensable to safe and economic tunnel construction. This paper presents the effect of anisotropy and heterogeneity of the rock masses to be excavated by numerical analysis. The influences of distance from weak zone, the size or dimension, the different stiffness and the orientation of weak zones are analysedby 2-D and 3-D finite element analysis. By analysing these numerical results, the tunnel behavior due to excavation can be well understood and the prediction of rock mass condition ahead of tunnel face can be possible.

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A Study on Behavior of 2-Arch Tunnel by Numerical Approach (수치해석적 접근을 통한 2Arch 터널의 거동양상 고찰)

  • 김상균;박동욱
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.225-232
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    • 2003
  • The behaviour of ground induced by tunneling of 2arch tunnels may differ from the one caused by usual type tunnels. This paper describe the behaviour created by the size of pilot tunnel and the condition on the construction method of center piller Also, loads acting on the supports of the first tunnel and the center pillar during the excavation of second tunnel is investigated by numerical analyses. The results of numerical analyses are compared to the data records of measurement results, i.e. force on the support system and ground displacement.

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