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2020 Vol.22, Issue 4 Preview Page

Research Paper

Effect of widening excavation in divergence section of a double-deck tunnel on its stability

복층터널 분기구 확폭구간 굴착에 따른 안정성 영향

You-Sung La1
,
Yunhee Kim2
,
Kangil Lee3
,
Yongseong Kim4
,
Bumjoo Kim5*
나 유성1
,
김 윤희2
,
이 강일3
,
김 용성4
,
김 범주5*
1General Manager, Dept. of Geotech and Tunnel, SEOHA Engineering Co., Ltd.
2Ph.D. Student, Dept. of Civil and Environmental Engineering, Dongguk University
3Professor, Dept. of Civil Engineering, Daejin University
4Professor, Dept. of Regional Infrastructure Engineering, Kangwon National University
5Professor, Dept. of Civil and Environmental Engineering, Dongguk University
1정회원, (주)서하기술단 차장
2비회원, 동국대학교 건설환경공학과 박사과정
3정회원, 대진대학교 건설시스템공학과 교수
4비회원, 강원대학교 지역건설공학과 교수
5정회원, 동국대학교 건설환경공학과 교수
* Corresponding Author
31 July 2020. pp. 435-450
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Abstract

The divergence section of a double-deck tunnel can be divided into a ‘widening pre-divergence section’, a large cross-section with a cap shape and a ‘post-divergence section’ where the separation between the main and the branch tunnel is made. Since the cross-section of the widening pre-divergence section is considerably larger than that of the post-divergence section, the influence of excavation due to the different sizes and shapes in the cross-section should be considered in the examination of the tunnel stability. In this study, the effect of the preceding excavation, that is the excavation of the widening pre-divergence section, on excavation stability of the post-divergence section was examined by varying the excavation methods and bench lengths through 3D finite element analysis. The results showed that although the effects of the excavation methods and the bench lengths are not significant on the variation of principal stresses, the preceding excavation causes a relatively large variation on the stresses which may have an impact on the stability of the post-divergence section from the comparison of Stress-Strength Ratio (SSR) between the cases with and without the consideration of the preceding excavation effect by 2D finite element analysis.

Keywords
Double-deck tunnel
Divergence section
Excavation stability
Excavation method
Bench length

복층터널의 분기구간은 터널 형상이 모자 모양의 대단면 구간인 ‘분기 전 확폭구간’과 본선과 분기터널 간 이격이 생기는 ‘분기 후 구간’으로 나눌 수 있으며, 분기 전 확폭구간의 터널 단면이 분기 후 구간의 단면에 비해 매우 크기 때문에 이러한 차이에 따른 굴착 영향이 분기구의 전체적인 굴착 안정성 검토 시 고려되어야 한다. 본 연구에서는 암반에서 시공되는 NATM 방식의 2차로 대심도(40 m) 본선 복층터널에서 1차로 단층터널로 분기가 되는 조건을 대상으로 3차원 유한요소해석을 통해 분기 전 확폭구간 굴착(선행굴착) 시 굴착공법과 벤치길이 변화에 따라 선행굴착이 분기 후 구간의 굴착 안정성에 미치는 영향을 검토하였다. 그 결과, 굴착공법과 벤치길이 변화에 따른 차이는 상대적으로 작은 편이었으나, 2차원 수치해석에 의한 선행굴착을 고려하지 않은 경우와 강도응력비 비교를 통해 선행굴착이 분기 후 구간의 굴착 안정성에 영향을 미칠 정도로 큰 응력의 변화를 유발함을 확인하였다.

키워드
복층터널
분기구간
굴착 안정성
굴착공법
벤치길이
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Information
  • Publisher :Korean Tunneling and Underground Space Association
  • Publisher(Ko) :한국터널지하공간학회
  • Journal Title :Journal of Korean Tunnelling and Underground Space Association
  • Journal Title(Ko) :한국터널지하공간학회 논문집
  • Volume : 22
  • No :4
  • Pages :435-450
  • Received Date : 2020-06-12
  • Revised Date : 2020-07-13
  • Accepted Date : 2020-07-14
  • DOI :https://doi.org/10.9711/KTAJ.2020.22.4.435
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