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A study on the risk and settlement evaluation of a shield TBM excavated in soft marine sedimentary soils

해저 연약 퇴적층 지반 쉴드 TBM 위험요인 평가 및 장비 침하에 관한 연구

Kwang-Ho You1
,
Chi-Myeon Park2*
유 광호1
,
박 치면2*
1The Unuversity of Suwon, Dept. of Civil Engineering, Professor
2The University of Suwon, Dept. of Civil Engineering, Ph. D. Student, ESCO Consultant & Engineers Co., Ltd., Director
1수원대학교 토목공학과 교수
2수원대학교 토목공학과 박사과정, (주)에스코컨설턴트 전무이사
*교신저자. *Corresponding Author. 
31 July 2016. pp. 355-364
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Abstract

Recently, a 3,250 meter-long tunnel was constructed beneath the sea bed formed of composite sedimentary soils to transport reusable waste heat gas of industrial complex in the west coast of Korea. Some risks such as machine settlement always exist due to the uncertainties of geological and construction factors during the subsea shield TBM tunnelling. In this construction site, the deviation of tunnel alignment caused by shield TBM settlement was occurred during excavation. It was examined that the lack of bearing capacity of soft clay was a main cause. This paper evaluates the risk of shield TBM tunnelling considering the ground conditions. Correlation between machine settlement and its advance rate was evaluated through the analytical equation in which bearing capacity is considered and a 3-D numerical analysis which can simulate the TBM advance condition (in other words, the dynamic condition). It was found out that a shield TBM could settle due to the insufficient bearing capacity of soft clay layers. In order to prevent such the problem, the best advance rate proper to the ground characteristics is needed to be applied. In the ground conditions of the section of interest, it was turned out that if the shield TBM advance rate was maintained between 35 mm/min and 40 mm/min, the machine settlement could be avoided.

Keywords
Risk evaluation
Marine sedimentary soils
Subsea shield TBM tunnelling
Settlement

최근 우리나라 서해안 산업단지의 폐열과 증기의 재활용을 위한 운송관로 수용목적으로 해저 퇴적층 지반에 3.25km의 해저터널이 쉴드 TBM으로 시공 완료되었다. 쉴드 TBM 터널은 지반조건 및 시공요인에 기인한 불확실성으로 인해 장비 침하 등 많은 위험요인을 겪게 되는데 터널 시공 중 쉴드 TBM 장비 침하로 인한 선형이탈이 발생하였으며 원인 분석결과 지지력이 부족한 연약한 점토층 지반조건이 주원인으로 작용한 것으로 검토되었다. 본 연구에서는 지반조건을 고려한 위험요인을 평가하고, 지지력을 고려한 이론식과 TBM 굴진조건 즉, 동적조건을 구현할 수 있는 3차원 수치해석을 통해 장비 침하 및 쉴드 TBM 굴진속도와의 상관관계에 대한 검토를 수행하였다. 연약한 점토층 지반에서 지지력 부족으로 쉴드 TBM 장비 침하가 발생할 수 있으며, 이를 방지하기 위해서는 지반특성에 적합한 최적 굴진속도의 적용이 필요한 것으로 검토되었으며 본 검토 대상구간 지반조건에서는 쉴드 TBM 굴진속도를 35~40 mm/min로 유지하는 경우에 장비 침하를 방지할 수 있는 것으로 검토되었다.

키워드
위험요인 평가
해성 퇴적토
해저 쉴드 TBM 터널
침하
References
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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 : 18
  • No :4
  • Pages :355-364
  • Received Date : 2016-07-08
  • Revised Date : 2016-07-21
  • Accepted Date : 2016-07-25
  • DOI :https://doi.org/10.9711/KTAJ.2016.18.4.355
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