Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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Estimation of the Characteristics of Delayed Failure and Long-term Strength of Granite by Brazilian Disc Test

압열인장시험을 이용한 화강암의 지연파괴특성 및 장기안정성 평가

  • 정용복 (한국지질자원연구원 지구환경연 구본부 심지층활용연구센터 지하공간 연구팀) ;
  • 천대성 (한국지질자원연구원 지구환경연 구본부 심지층활용연구센터 지하공간 연구팀) ;
  • 박의섭 (한국지질자원연구원 지구환경연 구본부 심지층활용연구센터 지하공간 연구팀) ;
  • 박찬 (한국지질자원연구원 지구환경연 구본부 심지층활용연구센터 지하공간 연구팀) ;
  • 이윤수 (경북대학교 지질학과 대학원) ;
  • 박철환 (한국지질자원연구원 지구환경연구본부) ;
  • 최병희 (한국지질자원연구원 지구환경연구본부)
  • Received : 2014.01.10
  • Accepted : 2014.01.27
  • Published : 2014.02.28
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Abstract

Long-term stability and delayed failure of granite were evaluated through the laboratory test based on Wilkins method and Brazilian disc test (BDT) which yields tensile strength, mode I fracture toughness and subcritical crack growth parameters. Then, the long-term strength of granite was estimated by using analytical models and long-term stability of compressed air-energy storage (CAES) pilot cavern pressurized up to 5 ~ 6 MPa was evaluated using numerical code, FRACOD with the determined subcritical crack growth parameters. The results of test and analyses showed that the subcritical crack growth index, n was determined as 29.39 and the inner pressure of 5 ~ 6 MPa had an insignificant effect on the long-term stability of pilot cavern. It was also found that the measurement and analysis of acoustic emission events can describe the accumulation of damage due to subcritical crack growth quantitatively. That is, AE monitoring can provide the current status of rock under loading if we make an identical installation condition in the field with that of the laboratory test.

본 연구에서는 임계하균열성장 변수를 구하기 위해 제안된 Wilkins의 시험법을 압열인장시험과 결합하여 화강암의 인장강도, Mode I 파괴인성과 임계하균열성장지수를 동시에 구하였으며 이를 사용하여 암석의 장기거동을 평가하였다. 또한 내부압력을 받는 압축공기저장(CAES) 공동에 대한 장기안정성을 수치해석코드인 FRACOD를 사용하여 해석하였다. 시험 결과 화강암의 임계하균열성장지수(n)는 29.39로 결정되었으며 5 ~ 6 MPa의 내압은 저장공동의 장기안정성에 큰 영향을 미치지 않는 것으로 나타났다. 또한 시험 과정에서 측정한 미소파괴음을 분석한 결과 암석내의 미소균열 생성 및 전파에 따른 암석의 손상을 정량적으로 기술할 수 있었다. 만약, 실내와 동일한 조건으로 현장에서 AE 모니터링을 수행할 경우 AE 모니터링을 통해서 하중을 받는 암석의 현재 상태를 정량적으로 평가하는 것이 가능할 것으로 판단된다.

Keywords

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