Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Experimental Study on the Ground Behavior around a Tunnel due to the Sidewall Deformation of Shallow Tunnel in Longitudinal Direction Excavated under the Slope

사면 하부지반에 종단 방향으로 굴착한 얕은 터널에서 측벽변형에 따른 터널 주변지반의 거동에 대한 실험적 연구

  • Na, Yong Soo (Dept. of Civil and Transportation Sys. Eng., Ajou Univ.) ;
  • Lee, Sang Duk (Dept. of Civil and Transportation Sys. Eng., Ajou Univ.)
  • 나용수 (아주대학교 건설교통공학과) ;
  • 이상덕 (아주대학교 건설교통공학과)
  • Received : 2019.03.23
  • Accepted : 2019.04.24
  • Published : 2019.05.31
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Abstract

While the study of the shallow tunnel has been mainly on the longitudinal load transfer and horizontal surface conditions, the study of the ground behavior of shallow tunnel under the slope is not sufficient. Therefore, in this study on the ground behavior around a tunnel due to the sidewall deformation of shallow tunnel under the slope that is excavated in longitudinal direction, a scale-down model test has been performed. The model tunnel has the dimension of 320 mm wide, 210 mm high and 55 mm long with enough material strength in aluminum and the model ground has the uniform ground conditions by 3 types of carbon rods. The model test has been performed with the variables of slopes and the cover depths by controlling the tunnel sidewall deformation, and the change of sidewall-load, load transfer, ground subsidence was monitored and analyzed. According to the increase of the slope, the maximum ground subsidence increased by 20~39% compared to the horizontal surface. The load ratio increased by maximum 20% in the tunnel crown and decreased in sidewall according to the surface slope. The load transfer shows maximum 128% of increase at the cover depth of 1.0D, while at the 1.5D cover depth it shows non-critical difference from horizontal surface. The slope has major effects on load transfer at the cover depth of 1.0D.

얕은 터널에 대한 연구는 종방향 하중전이와 수평지반에 대한 연구가 주를 이루었으며 사면 하부에 위치한 얕은 터널 주변지반의 거동연구는 미흡한 실정이다. 따라서 본 연구에서는 사면 하부에 위치한 터널의 종방향 굴진에 따른 터널 주변지반의 거동을 규명하기 위해 변위제어방식으로 모형시험을 실시하였다. 모형터널은 폭 320mm, 높이 210mm, 길이 55mm 규격의 강성이 큰 알루미늄 강체로 제작하였고, 모형지반은 3가지 규격의 탄소봉을 혼합하여 균질한 모형지반을 조성하였다. 모형시험은 사면 경사와 토피고를 변수로 측벽변형을 발생시키는 변위제어방식으로 실시하였으며, 터널 벽체의 하중변화, 터널 주변지반의 하중전이와 지표침하 변화를 측정하고 분석하였다. 지표침하의 변화는 경사가 증가할수록 수평지반보다 20~39%의 증가가 나타났다. 터널 천단부 및 측벽부의 하중 변화는 사면 경사가 증가할수록 천단부는 최대 20%가 증가하고, 측벽부는 사면 경사의 영향으로 하중비가 감소하는 것을 확인하였다. 연직하중은 토피고가 1.0D 이하에서는 최대 128%의 하중증가가 나타났지만, 토피고가 1.5D 이상에서는 수평지반과 큰 차이가 나타나지 않았다. 이것으로 사면 경사는 토피고 1.0D에서 가장 큰 영향이 나타나는 것을 확인하였다.

Keywords

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Fig. 1. Deformation modes for shallow tunnel (Pinto et al., 2014)

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Fig. 2. Trapdoor test (Terzaghi, 1936)

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Fig. 3. Lateral ground subsidence (Lee, 2013)

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Fig. 4. Shape, slope and curvature of lateral ground subsidence (Attewell, 1978)

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Fig. 5. Model tunnel

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Fig. 6. Ground conditions of tunnel model tests

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Fig. 7. Instrument for measurement

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Fig. 9. Ground settlement distribution of inclined surface condition

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Fig. 8. Ground settlement distribution (A00 case)

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Fig. 10. Load ratio of tunnel according to tunnel displacement (A00 case)

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Fig. 11. Load ratio of tunnel according to tunnel displacement (A10 case)

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Fig. 12. Load ratio of tunnel according to tunnel displacement (A20 case)

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Fig. 14. Load ratio of around tunnel of inclined surface condition

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Fig. 13. Load ratio of around tunnel (A00 case)

Table 1. List of the tunnel model tests

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Table 3. Max. ground settlement and location of inclined surface condition

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Table 2. Ground settlement and location (A00 case)

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Table 4. Max. Load ratio according to slope

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