Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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Behaviour of Ground Anchor According to Period Characteristic of Seismic Load Using Numerical Analysis

수치해석을 통한 지진하중의 주기특성에 따른 그라운드 앵커의 거동

  • Oh, Dong-Wook (Department of Civil Engineering, Seoul National University of Science and Technology) ;
  • Jung, Hyuk-Sang (Department of Railroad Construction and Safety Engineering, Dongyang University) ;
  • Yoon, Hwan-Hee (Department of Railroad and Civil Engineering, Dongyang University) ;
  • Lee, Yong-Joo (Department of Civil Engineering, Seoul National University of Science and Technology)
  • 오동욱 (서울과학기술대학교 건설시스템공학과) ;
  • 정혁상 (동양대학교 철도대학 철도건설안전공학과) ;
  • 윤환희 (동양대학교 일반대학원 철도토목학과) ;
  • 이용주 (서울과학기술대학교 건설시스템공학과)
  • Received : 2018.11.29
  • Accepted : 2018.12.24
  • Published : 2018.12.31
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Abstract

Many people have been recognized that the Korean Peninsula is no longer safe area from the earthquake by the recent earthquakes occurred in the country. The earthquakes that occurred at Pohang and Gyeongju appeared differently from them considered in the seismic design and researches on the seismic design method have been also conducted by many researchers. Studies on seismic loads are mainly focused on existing superstructures, and research involving them has been actively carried out in reality. However, paper regarding structural stability of reinforcement from seismic load such as soil-nails, rock-bolts, ground anchors which were constructed to ensure stability of serviced structure have been published rarely. In this study, ground anchor been effected by static load and seismic load which is settled in the weathered rock is analyzed. Results for static load are obtained from field test and seismic load is from numerical analysis. In this study, the behavioral characteristics of the ground anchor were analyzed by numerical analysis in case of seismic loading based on the result of the in-situ tensile test of the ground anchor settled weathered rock. As a result, settlement of concrete block due to application of tension force for ground anchor occurred as well as following loss of axial force for ground anchor. Also, as bond length and period of seismic load are longer, increasement of displacement is greater.

최근 국내에 발생된 지진으로 인해 더 이상 한반도가 지진으로부터 안전지대가 아니라는 것이 많은 사람들에게 각인되었다. 경주와 포항에서 발생된 지진은 그 동안 국내에서 내진설계에 기준으로 고려한 지진의 특성과 상이하게 나타났고, 그에 따른 내진설계 방법에 대한 연구 또한 많은 연구자들에 의해 수행되어 지고 있다. 이러한 지진하중에 대한 고려는 주로 기존 상부 구조물에 초점이 맞춰져 있으며, 그에 따른 연구 또한 활발히 이루어지고 있는 실정이다. 하지만, 지반의 구조적 안정성을 확보하기 위해 시공된 네일, 록볼트, 그라운드 앵커 등과 같은 지중구조물에 대한 지진하중으로부터의 구조적 안정성에 대한 고려는 많이 이루어지지 않고 있는 실정이다. 본 연구에서는 풍화암에 정착된 그라운드 앵커에 대해 정하중이 작용할 때와 지진하중이 앵커에 미치는 영향을 분석하였다. 정하중에 의한 영향은 현장 인장시험 결과로, 지진하중 영향은 수치해석을 통해 파악하였다. 그 결과, 앵커에 긴장력 도입으로 인한 반력판의 침하가 발생하는 것으로 나타났으며, 그로 인한 앵커의 축력 감소가 발생하였다. 또한 지진하중에 의해 앵커 정착부의 변위가 증가하였으며, 정착부 길이가 길수록 장주기 지진에 의한 영향이 큰 것으로 나타났다.

Keywords

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Fig. 1. N value with depth

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Fig. 2. Ground anchor construction phase

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Fig. 3. Result and overview of performance test for ground anchor

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Fig. 4. Earthquake wave propagation

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Fig. 5. Mesh generation for numerical analysis

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Fig. 6. Dynamic curve

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Fig. 7. Settlement of concrete block

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Fig. 8. δv for T step depending on Lb

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Fig. 9. Increasement vertical displacement (Δδv)

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Fig. 10. Vertical displacement rate of change

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Fig. 11. Normalized δv rate of change

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Fig. 12. δH of bond length

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Fig. 13. Change of axial force due to earthquake

Table 1. Material properties

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Table 2. Rayleigh damping coefficient

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