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

Korean Tunnelling and Underground Space Association (한국터널지하공간학회)
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Evaluation of mechanical properties of KURT granite under simulated coupled condition of a geological repository

복합 처분환경 모사조건에서의 KURT 화강암의 역학적 물성 변화 평가

  • Park, Seunghun (Radioactive Waste Disposal Research Division, Korea Atomic Energy Research Institute) ;
  • Kim, Jin-Seop (Radioactive Waste Disposal Research Division, Korea Atomic Energy Research Institute) ;
  • Kim, Geon Young (Radioactive Waste Disposal Research Division, Korea Atomic Energy Research Institute) ;
  • Kwon, Sangki (Dept. of Energy Resource Engineering, Inha University)
  • 박승훈 (한국원자력연구원 방사성폐기물처분연구부) ;
  • 김진섭 (한국원자력연구원 방사성폐기물처분연구부) ;
  • 김건영 (한국원자력연구원 방사성폐기물처분연구부) ;
  • 권상기 (인하대학교 에너지자원공학과)
  • Received : 2019.04.30
  • Accepted : 2019.06.21
  • Published : 2019.07.31
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Abstract

The rock properties measured under in-situ geological condition can be used to increase the reliability in numerical simulations with regard to the long-term performance of a high-level waste repository. In this study, the change in mechanical properties of KURT (Korea atomic energy research institute Underground Research Tunnel) granite was evaluated under the simulated THM (Thermo-Hydro-Mechanical) coupled condition due to a deep geological formation in the disposal repository. The rock properties such as uniaxial compression strength, indirect tensile strength, elastic modulus and Poisson's ratio were measured under the coupled test conditions (M, HM, TM, THM). It was found that the mechanical properties of KURT granite is more susceptible to the change in saturation rather than temperature within the test condition of this study. The changes in uniaxial compression strength and indirect tensile strength from the rock samples of dried or saturated conditions showed the maximum relative error of about 20% and 13% respectively under the constant temperature condition. Therefore, it is necessary to use the material properties of rock measured under the coupled THM condition as input parameters for the numerical simulation of long-term performance assessment of a disposal repository

심부 지하환경 조건에서 측정된 암석물성의 사용은 고준위폐기물처분장의 장기 안전성 평가 측면에서 해석의 신뢰성을 향상시킬 수 있다. 본 연구는 지하처분연구시설(Korea atomic energy research institute Underground Research Tunnel, KURT)의 화강암(한국원자력연구원, 대전)을 대상으로 고준위폐기물 처분장에서 예상되는 복합환경 조건을 구현한 후 암석의 역학적 물성 변화를 측정하였다. 실험은 심지층 처분환경이 모사되도록 열-수리-역학적 복합 환경(Thermo-Hydro-Mechanical, THM)이 조절될 수 있는 실험장치를 제작하였다. 다양한 복합 실험조건(M, HM, TM, THM)을 구현하여 일축압축강도와 간접인장강도, 탄성계수, 포와송비 등의 암석물성을 측정한 후 그 결과를 분석하였다. 실험결과, 처분장 근계암반 예상 온도범위 내에서는 KURT 화강암의 역학적 물성이 온도의 영향 보다 포화유무에 따른 변화가 더 큰 것을 확인할 수 있었다. 또한, 동일한 온도 조건에서 포화 유무에 따른 일축압축시험 결과는 최대 약 20%의 상대적인 차이를 보였으며, 간접인장시험 결과는 최대 13%의 차이가 발생하였다. 따라서 처분장의 장기거동에 따른 성능평가 및 안전성 예측을 위해서는 기존의 상온 실내시험을 통해 도출된 암석물성을 사용하기보다 심부 지하환경을 반영한 암석의 복합물성을 활용하는 것이 해석의 신뢰도 향상에 기여할 수 있을 것이다.

Keywords

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Fig. 1. THM interactions of rock

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Fig. 2. Geological features and KURT of area of collected rock specimen (Lee et al., 2019)

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Fig. 3. Specimens for experiment

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Fig. 4. Test device for measuring rock strengths

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Fig. 5. Layout of Thermo-Hydro-Mechanical test condition

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Fig. 6. Analysis results of collected rock specimens

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Fig. 7. Stress-stain curve under uniaxial compressive test

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Fig. 8. The changes of uniaxial compressive strength, elastic modulus, poisson’s ratio

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Fig. 9. Stress-stain curve under indirect tensile test

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Fig. 10. The changes of indirect tensile strength, splitting elastic modulus, tensile elastic modulus

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Fig. 11. Difference of saturated and dried properties on rock types (modified from Choi et al., 2018)

Table 1. Test conditions of rock specimens

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Table 2. The results of density, specific gravity, porosity, water absorption of granite

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Table 3. Dynamic rock properties of granite

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Table 4. The results of uniaxial compressive strength, elastic modulus, poisson’s ratio of granite

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Table 5. Differences in rock properties under various conditions of uniaxial compressive test

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Table 6. The results of indirect tensile strength, splitting elastic modulus, tensile elastic modulus of granite

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Table 7. Differences in rock properties under various conditions of indirect tensile test

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