• Title, Summary, Keyword: 최종천단침하

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Relations between Initial Displacement Rate and Final Displacement of Arch Settlement and Convergence of a Shallow Tunnel (저심도 터널의 천단침하 및 내공변위의 초기변위속도와 최종변위의 관계)

  • Kim, Cheehwan
    • Tunnel and Underground Space
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    • v.23 no.2
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    • pp.110-119
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    • 2013
  • It is generalized to measure the arch settlement and convergence during tunnel construction for monitoring its mechanical stability. The initial convergence rate a day is defined from the first convergence measurement and the final convergence defined as the convergence measured lastly. The initial and the final tunnel arch settlement are defined like the preceding convergence. In the study, the relations between the initial and final displacements of a shallow tunnel are analyzed. The measurements were performed in the tunnel of subway 906 construction site in Seoul. The overburden is 10-20 m and the tunnel goes through weathered soil/rock. The width and height of the tunnel are about 11.5 m, 10m, respectively. So this is a shallow tunnel in weak rock. The length of tunnel is about 1,820 m and the tunnel was constructed in 2 stages, dividing upper and lower half. The numbers of measurement locations of arch settlement and convergence are 184 and 258, respectively. As a result, the initial displacement rate and the final displacement are comparatively larger in the section of weathered soil.

Forecasting Final Displacement With Displacement Functions Using Deformation Measurements While Constructing a Tunnel (계측치와 변위함수에 의한 시공 중인 터널의 최종변위 예측)

  • Kim, Chee-Hwan
    • Tunnel and Underground Space
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    • v.20 no.6
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    • pp.408-420
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    • 2010
  • It is important to forecast the final deformation of a tunnel during construction for evaluating its mechanical stability. In this study, the final deformation of a tunnel is forecasted by fitting tunnel deformations measured while excavating to a displacement function and exterpolating it. The tunnel for the study was built in two stages divided into an upper and a lower part. During the lower part construction of the tunnel, the displacement function forecasts the final incremental displacement well compared to the increment measured after completion of the tunnel. It is because the critical initial displacement occurred on passing the measurement pins can be adequately measured during excavating the lower part, which can not be measured during the upper part excavation of the tunnel.

A study on hydraulic back analysis for an urban tunnel site and stability analysis based on hydro-mechanical coupling analysis (도심지 터널 용출수 발생구간에서의 수리 역해석 및 수리-역학 연계해석을 통한 안정성 해석 연구)

  • Park, Inn-Joon;Song, Myung-Gyu;Shin, Uyu-Soung;Park, Yong-Su
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.10 no.4
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    • pp.397-404
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    • 2008
  • Excessive amount of groundwater flowed into tunnel, while constructing Incheon international airport railway. Tunnel passes under subway line no. 2 with only 1.76 m below. To protect the existing structure, TRcM excavation method was applied. As station and construction shaft are already constructed, which are located back and forth of TRcM section, 86.4 ton per day of groundwater inflow is against expectation. To identify mechanism of excessive water inflow, hydraulic back analyses were performed. Then, hydro-mechanical coupled analysis were also performed with the hydrogeologic parameters identified, whose results are investigated for checking the stability of adjacent structures to the tunnel under construction. And a number of mechanical analyses were also performed to check the hydro-mechanical coupling effect. The result from the mechanical analysis shows that subsidence and tunnel ceiling displacement will be 0.85 mm and 1.32 mm. The result of hydro-mechanical couple analysis shows that subsidence and maximum tunnel ceiling displacement will be 1.2 mm and 1.72 mm. Additional displacements caused by groundwater draw down were identified, however, displacement is minute.

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The effects of the face reinforcement at shallow tunnels in fractured rock masses (파쇄대 암반에서 얕은 심도의 터널 굴착시 막장보강효과에 관한 연구)

  • Nam, Kee-Chun;Heo, Young;You, Kwang-Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.5 no.4
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    • pp.323-336
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    • 2003
  • Recently, the development of tunnel reinforcement method has been required relating to the shallow tunnelling in soft ground. In this study, the improvement method on tunnel stability is proposed by evaluating the efficiency of face reinforcement which enables to control extrusion of advance core, however, it is often neglected in urban tunnelling under the poor ground conditions. Systematic pre-confinement ahead of the face improves the tunnel stability, subsequently, displacement of the crown and surface settlement can be restrained by proper method. 3-dimensional numerical analysis including horizontal reinforcement modelling on a face is applied to estimate the behaviour of a tunnel in relation to the ground and reinforcement conditions. Consequently, extrusion at the face decreases significantly after using the horizontal reinforcement and the effect of reinforcement is much increased in case of applying the supplemental reinforcement ahead of the face together. Especially, confinement effect around the tunnel and the core is proved by means of the core reinforcement in poor ground conditions.

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Back Analysis of Field Measurements Around the Tunnel with the Application of Genetic Algorithms (유전자 알고리즘을 이용한 터널 현장 계측 결과의 역해석)

  • Kim Sun-Myung;Yoon Ji-Sun;Jun Duk-Chan;Yoon Sang-Gil
    • Journal of the Korean Geotechnical Society
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    • v.20 no.7
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    • pp.69-78
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    • 2004
  • In this study, the back analysis program was developed by applying the genetic algorithm, one of artificial intelligence fields, to the direct method. The optimization process which has influence on the efficiency of the direct method was modulated with genetic algorithm. On conditions that the displacement computed by forward analysis for a certain rock mass model was the same as the displacement measured at the tunnel section, back analysis was executed to verify the validity of the program. Usefulness of the program was confirmed by comparing relative errors calculated by back analysis, which is carried out under the same rock mass conditions as analysis model of Gens et at (1987), one of back analysis case in the past. We estimated the total displacement occurring by tunnelling with the crown settlement and convergence measured at the working faces in three tunnel sites of Kyungbu Express railway. Those data measured at the working face are used for back analysis as the input data after confidence test. As the results of the back analysis, we comprehended the tendency of tunnel behaviors with comparing the respective deformation characteristics obtained by the measurement at the working face and by back analysis. Also the usefulness and applicability of the back analysis program developed in this study were verified.

Stability Analysis on the Intersection Area of Subway Tunnels by Observational Method (계측에 의한 지하철터널 교차부의 안정성 검토)

  • Kim Chee-Hwan
    • Tunnel and Underground Space
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    • v.15 no.1
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    • pp.71-79
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    • 2005
  • The stability of the intersection area of two tunnels is analyzed by observational method. The depth from ground surface to the intersected area is shallow and the geology around the area consists of soil and/or weathered rock. The tunnel is supported by reinforced protective umbrella method with 12 m long 3-layer steel-pipes and the intersected area is additionally reinforced with 6 m long rockbolts. The measured displacements are converged and mechanical stability of the intersected area of two tunnels is confirmed; tunnel arch settles to 6-7 mm at the crown and the sidewalls converges to about 5 mm. So based on the displacement measurements, the supporting system for the tunnel intersection proves to be effective to not only reduce the deformation of tunnels but also maintain the stability of tunnels.