Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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A Basic Study on Borehole Breakout under Room Temperature and High Temperature True Triaxial Compression

상온 및 고온 하 진삼축압축실험을 이용한 시추공의 파괴 거동 기초 연구

  • Yoon, Jeonghwan (Department of Energy Systems Engineering, Seoul National University) ;
  • Min, Ki-Bok (Department of Energy Systems Engineering, Seoul National University) ;
  • Park, Eui-Seob (Deep Subsurface Research Center, Geologic Environment Division, Korea Institute of Geoscience of Mineral Resources) ;
  • Jung, Yong-Bok (Deep Subsurface Research Center, Geologic Environment Division, Korea Institute of Geoscience of Mineral Resources)
  • 윤정환 (서울대학교 에너지시스템공학부) ;
  • 민기복 (서울대학교 에너지시스템공학부) ;
  • 박의섭 (한국지질자원연구원 지질환경연구본부 심지층연구센터) ;
  • 정용복 (한국지질자원연구원 지질환경연구본부 심지층연구센터)
  • Received : 2020.12.10
  • Accepted : 2020.12.23
  • Published : 2020.12.31
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Abstract

This paper performs laboratory experiments for borehole stability considering temperature and true triaxial stress condition, and observes a thermo-mechanical behavior of the rock under stress and temperature conditions of deep underground. China yellow sandstone and Hwangdeung granite specimens were used to perform a true triaxial compression test. Mechanical tests were carried out under nine confining pressure conditions, and thermo-mechanical tests using granite samples were carried out under six confining pressure conditions at 60-100℃. In the mechanical tests, maximum principal stress at borehole breakout was proportional to intermediate principal stress. In the thermo-mechanical tests, it was confirmed that thermal stress is added to the stress field of the borehole with the increase in temperature, resulting in additional breakout progress. To analyze the results of the laboratory experiment, Mogi-Coulomb failure criterion was used. The results of traditional triaxial compression test on cylindrical specimens and borehole breakout under true triaxial compressions matched well with Mogi-Coulomb failure criterion.

본 연구에서는 현지 암반의 진삼축 응력 조건과 온도 변화를 고려한 공벽 안정성 실험을 수행하고, 심부 지하의 응력 조건과 압력 조건에서 암석의 열역학적 거동을 관찰하였다. 중국 황색 사암과 국내 황등 화강암 시료를 이용하여 진삼축압축실험을 진행하였다. 역학 실험은 각각 9가지 구속압 조건에서 수행되었고 열역학 실험은 화강암 시료를 이용하여 6가지 구속압 조건에서 시료를 60℃~100℃로 가열하여 수행하였다. 역학 실험 결과 공벽 파괴가 발생하는 최대 주응력은 중간 주응력에 비례하는 것을 확인하였다. 열역학 실험에서는 온도 증가에 따라 공벽의 응력장에 열응력이 추가되어 공벽 파괴가 추가적으로 발생하는 것을 확인하였다. 실내 실험 결과를 분석하기 위해 모기쿨롱 파괴 기준식을 사용하여 분석하였다. 원통형 시료에 대한 전통적인 삼축압축시험 결과와 진삼축 조건 하의 공벽 파괴 실험 결과가 모두 진삼축 파괴 기준식인 모기쿨롱 파괴 기준식에 잘 부합됨을 확인하였다.

Keywords

Acknowledgement

본 논문은 한국지질자원연구원(KIGAM)의 지원을 받아 수행한 연구 과제입니다(GP2020-010). 논문 작성을 위한 서울대학교 공학연구원의 지원에 감사드립니다.

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