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2026 Vol.28, Issue 2 Preview Page

Research Paper

Probabilistic assessment of settlement behavior induced by shield TBM excavation of power cable tunnels in weathered soil

풍화토 지반에서 전력구 쉴드 TBM 터널 굴착에 따른 침하 거동의 확률론적 평가

So-Yi Lee1
,
Yun-Hee Kim2
,
Bumjoo Kim3*
이 소이1
,
김 윤희2
,
김 범주3*
1Master’s Researcher, Dept. of Civil and Environmental Engineering, Dongguk University
2Postdoctoral Researcher, Dept. of Civil and Environmental Engineering, Dongguk University
3Professor, Dept. of Civil and Environmental Engineering, Dongguk University
1학생회원, 동국대학교 건설환경공학과 석사 후 연구원
2정회원, 동국대학교 건설환경공학과 박사 후 연구원
3정회원, 동국대학교 건설환경공학과 교수
*Corresponding Author
31 March 2026. pp. 127-147
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Abstract

Urban power cable tunnels constructed using shield TBM methods are often located beneath roadways and near buried utilities, where excavation-induced ground settlement may cause significant social and economic risks. Weathered soil exhibits high spatial variability and uncertainty in mechanical properties, making deterministic evaluations based on mean values insufficient to represent settlement risks. To address this, we probabilistically evaluated ground surface and tunnel crown settlement induced by shield TBM excavation in weathered soil using Monte Carlo simulation and three-dimensional finite difference analysis under different cover depths (20, 30, and 40 m). The results show that surface settlement decreases with increasing cover depth, and the exceedance probability of settlement also decreases. The exceedance probabilities for cover depths of 20, 30, and 40 m were estimated as 9%, 3%, and 1%, respectively, while the corresponding reliability indices increased to 1.34, 1.88, and 2.33. In contrast, crown settlement showed an opposite trend, where both mean settlement and the probability of exceeding the allowable limit increased with increasing cover depth. The failure probabilities were estimated as 2%, 8%, and 25%, and the corresponding reliability indices decreased to 2.05, 1.41, and 0.67. By presenting settlement responses as probability distributions and risk levels rather than a single deterministic value, this study complements limitations of conventional deterministic approaches and proposes a quantitative risk assessment framework based on exceedance probability and reliability index for shield TBM tunnels in weathered soil.

Keywords
Shield TBM tunnel
Settlement
Weathered soil
Probabilistic analysis
Monte Carlo simulation (MCS)

도심지 전력구 쉴드 TBM 터널은 도로 하부 및 각종 매설물 인근에 시공되는 경우가 많아, 굴착 과정에서 발생하는 지반침하가 사회·경제적 위험으로 확대될 수 있다. 특히 풍화토 지반은 물성의 공간적 변동성과 불확실성이 커서 평균값 기반의 결정론적 평가만으로는 잠재적 침하 리스크를 충분히 설명하기 어렵다. 이에 본 연구에서는 풍화토 지반의 불확실성을 명시적으로 반영하기 위해 몬테카를로 시뮬레이션과 3차원 유한차분해석을 결합하여 토피고가 다른 조건(20, 30, 40 m)에서 전력구 쉴드 TBM 터널 굴착 시 지표침하 및 천단침하 거동을 확률론적으로 평가하였다. 해석 결과, 지표침하는 토피고 증가에 따라 평균값과 이론값 초과확률(Pex)이 감소하여 토피고 20, 30, 40 m에서 초과확률이 각각 9%, 3%, 1%로 나타났고 신뢰도 지수(𝛽)는 1.34, 1.88, 2.33으로 증가하였다. 반면 천단침하는 토피고 증가에 따라 평균 침하 및 허용기준 초과 가능성이 증가하여 파괴확률(Pf)이 2%, 8%, 25%로 증가하고 𝛽는 2.05, 1.41, 0.67로 감소하였다. 본 연구는 풍화토 지반 쉴드 TBM 터널의 침하를 단일 값이 아닌 분포 및 위험도로 제시함으로써 결정론적 접근의 한계를 보완하고, 초과확률–신뢰도지수 기반의 정량적 리스크 평가 틀을 제안하였다.

키워드
쉴드 TBM 터널
침하
풍화토
확률론적 해석
몬테카를로 시뮬레이션(MCS)
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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 : 28
  • No :2
  • Pages :127-147
  • Received Date : 2026-03-06
  • Revised Date : 2026-03-23
  • Accepted Date : 2026-03-23
  • DOI :https://doi.org/10.9711/KTAJ.2026.28.2.127
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