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A comparative study on the stability evaluation of double deck tunnel in terms of excavation

대심도 복층터널에 대한 굴착 안정성 평가 비교 연구

  • Jang, Namju (Geotechnical Department, Sambo Engineering Co., Ltd.) ;
  • Gang, Han-gil (Geotechnical Department, Sambo Engineering Co., Ltd.) ;
  • Kim, Kihwan (Geotechnical Department, Sambo Engineering Co., Ltd.) ;
  • Choi, Chang-rim (Geotechnical Department, Sambo Engineering Co., Ltd.)
  • 장남주 (삼보기술단 지반사업부) ;
  • 강한길 (삼보기술단 지반사업부) ;
  • 김기환 (삼보기술단 지반사업부) ;
  • 최창림 (삼보기술단 지반사업부)
  • Received : 2018.12.01
  • Accepted : 2018.12.14
  • Published : 2019.01.31

Abstract

It is necessary to construct underground in the metropolis. Road traffic has reached saturation point. The city has several underground road construction projects. In abroad, double deck tunnels are planned and constructed. It is attained a high level of underground development technology. In case the double deck tunnel (2 lane) is planed instead of the bidirectional tunnel (2 lane), excavation area is similar. But tunnel width is decreased. The reduced width can cut cost for the tunnel reinforcement. This study evaluates the stability of excavation on double deck tunnel. By the assessment of the strength-stress ratio and strength reduction method, quantitative analysis is conducted between double deck tunnel and the bidirectional tunnel.

주요 도심지 도로건설은 포화상태로 지하공간의 개발이 필요하며 이를 위해 지하철도와 지하 도로 터널의 건설은 활발히 진행되어 왔다. 국외의 경우 지하 도로터널을 2층구조로 활용하는 복층터널 시공이 이루어 졌으며 이에 따른 지하공간 개발 기술이 높은 수준에 이르고 있다. 2차로 병설터널을 2차로 복층터널로 계획하는 경우 굴착 면적은 크게 차이가 나지 않으며, 터널 통과구간이 차지하는 폭을 대폭 줄일 수 있다. 이를 통해 터널 통과구간이 차지하는 폭을 대폭 감소시킬 수 있으므로 지반조건이 불량한 경우 필요한 상부 보강 비용을 절감할 수 있다. 본 연구에서는 복층터널 굴착에 따른 영향에 대해 알아봄으로써 지하공간 활용 기술을 높이고 단층터널 굴착영향과 비교를 통해 향후 복층터널 설계 및 안정성 평가에 도움이 될 수 있을 것으로 기대된다.

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Fig. 1. Calculation of local factor of safety (You et al., 2000)

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Fig. 2. Shear strength and trial shear strength (Park and You, 1998)

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Fig. 3. Road alignment plan in branch section (Seoul ○○○ tunnel)

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Fig. 4. Road alignment plan in branch section– reduced speed section (up), raised speed section (down)

Table 1. Tunnel in branch section (Seoul ○○○ tunnel)

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Table 2. Double deck tunnel in branch section

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Table 3. Analysis condition

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Table 4. Properties of rock mass

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Table 5. Load relaxation factors

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Table 6. Rock support pattern

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Table 7. Plastic failure zone in single tunnel

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Table 8. Plastic failure zone in double deck tunnel

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Table 9. Local factor of safety in single tunnel and double deck tunnel

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Table 10. Global factor of safety in single tunnel and double deck tunnel

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Acknowledgement

Grant : 대심도 복층터널 설계기술 및 시공기술개발

Supported by : 국토교통과학기술진흥원

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