Journal of the Korean GEO-environmental Society (한국지반환경공학회 논문집)

Korean Geo-Environmental Society (한국지반환경공학회)
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A Study on the Behavior of Surface Settlement due to the Excavation of Twin TBM Tunnels in the Clay Grounds

점토지반에서 TBM 병렬터널 굴진 시 지표침하거동에 대한 연구

  • You, Kwangho (Department of Civil and Environmental Engineering, University of Suwon) ;
  • Jung, Suntae (Department of Civil and Environmental Engineering, University of Suwon / Dongah Geological Engineering Co. Ltd.)
  • Received : 2018.11.16
  • Accepted : 2019.01.07
  • Published : 2019.02.01
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Abstract

Mechanized constructions have been frequently increased in soft ground below sea bed or river bed, for urban tunnel construction, and for underpinning the lower part of major structures in order to construct a safer tunnel considering various risk factors during the tunnel construction. However, it is difficult to estimate the subsidence behavior of the ground surface due to excavation and needs to be easily predicted. Thus, in this study, when a twin tunnel is constructed in the soft ground, it is proposed a simpler equation relating to the settlement behavior and a corrected formula applicable to soft ground and large diameter shield tunnels based on the previously proposed theory by Peck (1969). For this purpose, it was analyzed to long-term measurement values such as the amount of maximum settlement, the subsidence range by ground conditions, and interference volume loss due to the parallel construction, etc. As a result, a equation was suggested to predict the amount of maximum settlement in the soft sediment clay ground where is located at the upper part of the excavation site. It is turned out that the proposed equation is more suitable for measurement data in Korea than Peck (1969)'s.

최근 터널 시공 시 여러 위험요인을 감안하여 보다 안전한 터널의 시공을 위하여 해상이나 하상 밑의 연약지반에서, 도심터널공사나 주요 구조물 하부 통과를 위해서 기계화 시공의 빈도가 높아지고 있다. 그러나 굴착으로 인한 지표면의 침하거동 산정이 어려워 간편하게 예측하는 식이 필요한 실정이다. 따라서 본 연구에서는 연약지반에 병렬로 터널이 시공되어지는 경우 침하거동에 대해 보다 간단한 식과 기존에 Peck(1969)이 제안한 이론을 근거로 연약지반 및 대구경 shield 터널에서 적용 가능한 수정식을 제안하고자 하였다. 이를 위해 최대 침하량, 지반조건에 따른 침하범위, 병렬시공에 따른 간섭 체적손실 등의 장기간의 계측값을 분석하였다. 그 결과 굴착면 상부가 퇴적점토인 연약지반에서 간편하게 최대 침하량을 산정할 수 있는 식을 제시하였는데, Peck(1969)의 식보다 국내 계측데이터에 더 적합한 것으로 나타났다.

Keywords

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Fig. 1. Five phases of settlement occurrence according to TBM construction

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Fig. 2. Definition of gap (Lee et al., 1992)

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Fig. 3. Transverse settlement trough (Peck, 1969)

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Fig. 4. Site investigation (longitudinal section)

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Fig. 5. Characteristics of clay

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Fig. 6. Characteristics of sand and soil

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Fig. 7. Grain size distributions

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Fig. 8. The schematic diagram of a shield TBM

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Fig. 9. Instrumentation locations

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Fig. 10. Surface settlement monitoring data

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Fig. 11. Ground surface settlement in the longitudinal direction of tunnel against time

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Fig. 12. Surface settlement by various depth tunnels

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Fig. 13. Volume loss of interference

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Fig. 14. Volume loss vs. rock cover of tunnel

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Fig. 15. Volume of interference vs. separation distance of tunnels

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Fig. 16. Comparison of settlement range and monitoring data by excavation diameter

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Fig. 17. Comparison of 1.0 D and 1.5 D settlement data and monitoring data

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Fig. 18. Settlement proposal model

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Fig. 19. Theoretical settlement by Peck vs. Modification

Table 1. Specifications of a shield TBM

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Table 2. Volume loss by monitoring data

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Table 3. Settlement measurement results

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Table 4. Proposed equations for the estimation of 𝒾 (Kim, 2013)

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References

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  2. Attewell, P. B. and Woodman, J. P. (1982), "Predicting the dynamics of ground settlement and its derivatives caused by tunnelling in soil", Ground Engineering, Vol. 15, No. 8, pp. 13-20.
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Cited by

  1. Prediction of Subsidence during TBM Operation in Mixed-Face Ground Conditions from Realtime Monitoring Data vol.11, pp.24, 2019, https://doi.org/10.3390/app112412130