Journal of Korean Tunnelling and Underground Space Association (한국터널지하공간학회 논문집)

Korean Tunnelling and Underground Space Association (한국터널지하공간학회)
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A study on the optimal reinforcement area for excavation of a small cross-section shield TBM tunnel in fault fracture zone through parameter analysis

매개변수 분석을 통한 단층파쇄대의 소단면 쉴드 TBM 터널 굴착 시 최적 보강영역 연구

  • 강병윤 ((주)수성엔지니어링) ;
  • 박형근 (충북대학교 토목공학부) ;
  • 차재훈 ((주)수성엔지니어링 지반부) ;
  • 김영진 ((주)수성엔지니어링 지반부)
  • Received : 2020.03.23
  • Accepted : 2020.04.23
  • Published : 2020.05.31
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Abstract

When excavating a small cross-section tunnel in a fault fracture zone using the shield TBM method, there is a high possibility of excessive convergence and collapse. Appropriate ground reinforcement is required to minimize construction cost loss and trouble due to a fault fracture zone. In this study, the optimal reinforcement area was suggested and the surrounding ground behavior was investigated through numerical analysis using MIDAS GTS NX (Ver. 280). For the parameters, the width of the fault fracture zone, the existence of fault gouge, and the groundwater level and depth of cover were applied. As a result, when there is not fault gouge, the convergence and ground settlement are satisfied the standard when applying ground reinforcement by up to 0.5D. And, due to the high permeability coefficient, it is judged that it is necessary to apply 0.5D reinforcement. There is a fault gouge, it was possible to secure stability when applying ground reinforcement between the entire fault fracture zone from the top of the tunnel to 0.5D. And, because the groundwater discharge occurred within the standard value due to the fault gouge, reinforcement was unnecessary.

쉴드 TBM 공법을 사용해 단층파쇄대에 소단면 공동구 터널을 굴착 시 과다한 내공변위 및 붕락 발생 가능성이 높다. 단층파쇄대로 인한 트러블 및 공기증가로 인한 공사비 손실을 최소화하기 위해 적절한 지반보강이 요구된다. 본 연구에서는 단층파쇄대의 폭, 단층점토의 존재여부, 토피고 지하수위를 매개변수로 하여 MIDAS GTS NX (Ver. 280)을 이용한 수치해석을 통해 최적보강영역을 제시하고 주변지반 거동을 알아보았다. 그 결과 단층점토가 없는 경우 최대 0.5D 만큼 지반보강 적용 시 내공변위 및 지표침하 기준을 만족하였으며, 높은 투수계수로 인해 0.5D의 차수보강 적용이 필요하다고 판단된다. 단층점토가 존재할 때 내공변위 및 지표침하는 최소 0.5D에서 최대 터널 상부 단층파쇄대 전체에 지반보강 적용 시 안정성확보가 가능하였으며, 단층점토로 인해 지하수 유출량이 기준치 이내로 발생하여 차수보강이 불필요하였다.

Keywords

References

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