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Stability analysis of an existing utility tunnel due to the excavation of a divergence tunnel emerging from double-deck tunnel

복층터널의 분기터널 굴착에 따른 지하 공동구의 안정성 분석

Kyoung-Min Nam1
,
Min-ki Choi2
,
Jung-Joo Kim3
,
Turab H. Jafri4
,
Han-Kyu Yoo5*
남 경민1
,
최 민기2
,
김 정주3
,
Jafri Turab H.4
,
유 한규5*
1Graduate student, Department of Civil Engineering, Hanyang University
2Master, Department of Civil Engineering, Hanyang University
3PhD student, Department of Civil Engineering, Hanyang University
4PhD student, Department of Civil Engineering, Hanyang University
5Professor, Department of Civil Engineering, Hanyang University
1한양대학교 건설환경공학과 석·박사통합과정
2한양대학교 건설환경공학과 석사
3한양대학교 건설환경공학과 박사수료
4한양대학교 건설환경공학과 박사수료
5한양대학교 건설환경공학과 교수
*교신저자. *Corresponding Author. 
31 March 2017. pp. 231-248
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Abstract

Government plans to construct a double-deck tunnel under a portion of Gyeongbu Expressway that will solve traffic problems and could also be used as a flood storage facility. Divergence tunnels connect the main tunnel to the urban areas and their construction effects on adjacent structures at shallow depth need to be analyzed. This study primarily includes the numerical analysis of construction effects of divergence tunnels on utility tunnels. The utility tunnel was analyzed for three cases of volume loss applied to the divergence tunnel and two cases of the angle between main tunnel and divergence tunnel (36° and 45°). The results show that the more the volume loss was applied and the shorter the distance was between utility tunnel and divergence tunnel, the more the utility tunnel was affected in terms of induced displacements, angular displacement and stability. The worst scenario was found out to be the one where the angle between main tunnel and divergence tunnel was 36° and the distance between divergence tunnel and utility tunnel was 10 m, resulting in the largest displacement and differential settlement at the bottom of the utility tunnel. A relationship between the angular displacement and the distance to diameter ratio was also established.

Keywords
분기터널
공동구
지반손실률
각변위
안정성 평가

서울시는 도심지 교통체증을 해결하기 위해 최근 경부고속도로의 일부 구간을 복층터널로 계획하는 방안을 검토하고 있다. 도심지에 복층터널을 건설할 경우, 교통난 해소뿐만 아니라 말레이시아 스마트 터널과 같이 홍수 시 침수방지를 위한 저류시설로도 활용할 수 있을 것으로 본다. 그러나 도로터널을 복층터널로 계획할 경우에는 각 지역을 연결하는 분기터널이 필요하며, 분기터널은 토피가 낮은 구간에 편평율이 큰 대단면 또는 복잡한 터널 단면형상으로 이루어지게 된다. 이때 토피가 낮은 지역에서는 지하 공동구나 건물 기초 등에 인접하여 위치하게 되며 터널 건설로 인해 지장물에 미치는 영향에 대해 반드시 검토해야 한다. 본 연구에서는 복층터널에서 분기되는 터널 굴착 시, 지하 공동구에 미치는 영향을 수치해석을 통해 분석하였다. 변위조절모델(Displacement Controlled Model)을 이용하여 터널 주변의 지반손실률을 1.0%, 3.0%, 그리고 5.0%까지 모사하였다. 복층터널에서 분기되는 각도를 45°와 36°로 다르게 설정하여 공동구 측면 및 하부로의 접근을 고려할 수 있도록 하였다. 그 결과, 일반적으로 분기터널이 공동구에 근접할수록 그리고 지반손실률이 클수록 변위, 각변위 그리고 안정성에 미치는 영향이 큰 것으로 타나났다. 공동구 바닥부의 침하와 공동구 부재의 안정성에는 이격거리 보다는 공동구의 하부에 근접하여 큰 변위와 부등침하를 유발할 수 있는 각도 36°, 이격거리 10 m가 가장 취약한 것으로 나타났다. 본 연구를 통해 근접시공 시 구조물의 안정성 평가를 위한 각변위-거리/직경 관계를 제시하였으며, 지하 공동구 안정성에 영향을 미치는 한계 임계 지반손실률을 산정하였다.

키워드
Divergence tunnel
Utility tunnel
Volume loss
Angular distortion
Stability analysis
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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 : 19
  • No :2
  • Pages :231-248
  • Received Date : 2017-03-10
  • Revised Date : 2017-03-21
  • Accepted Date : 2017-03-23
  • DOI :https://doi.org/10.9711/KTAJ.2017.19.2.231
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