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

Korean Tunnelling and Underground Space Association (한국터널지하공간학회)
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Numerical simulation for variations of water saturation in bentonite buffer under the effect of a rock joint using the TOUGH2 code

TOUGH2 code를 이용한 처분장 절리암반 내 벤토나이트 완충재의 포화도 변화

  • 김진섭 (한국원자력연구원 방사성폐기물처분연구부) ;
  • 조원진 (한국원자력연구원 방사성폐기물처분연구부) ;
  • 이경수 (한국원자력연구원 방사성폐기물처분연구부) ;
  • 최희주 (한국원자력연구원 방사성폐기물처분연구부) ;
  • 조계춘 (한국과학기술원 건설및환경공학과)
  • Received : 2012.08.28
  • Accepted : 2012.10.28
  • Published : 2012.11.30
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Abstract

This paper briefly introduces the scope and objectives of SKB Task 8, which is an international cooperative research project. In addition, the hydraulic behaviors of bentonite buffer focusing on the interactions between bentonite and a rock mass with a joint were investigated using TOUGH2 code as part of a sub-mission of Task 8a. The effects of a rock joint and high capillary pressure of bentonite on the re-saturation properties and pressure distribution in a buffer were identified and successfully incorporated in the TOUGH2 code. Based on the numerical results, it was found that the speed of re-saturation in bentonite surrounded by a rock mass with a joint is 2.5 to 12 times faster than that in a condition without a rock joint, while the degree of saturation in the lower part of the buffer material is generally higher than in the upper part in both the cases of with and without a joint. It can be anticipated that the results obtained from this study can be applied to an estimation of the full saturation time and a determination of optimum thickness with regard to the design of the bentonite buffer in a high level waste disposal system.

본 연구는 국제공동연구인 SKB Task 8에 대한 간단한 소개와 더불어, Task 8a 모델문제를 중심으로 유한차분과 유한체적법의 복합적 해석코드(integrated finite difference method)인 TOUGH2를 이용하여 벤토나이트 완충재와 현장암반의 수리학적 거동특성을 살펴보았다. 이를 위해 벤토나이트-암반의 상호작용을 중심으로 현장암반의 절리유무에 따른 완충재 내의 압력분포 변화 및 재포화 특성을 분석하였고, 벤토나이트 고유 특성인 높은 모세관 압력과 현장암반 내 절리영향을 TOUGH2 코드를 통해 성공적으로 구현하였다. 연구결과, 현장암반 내 절리를 고려함으로써 완충재의 포화속도는 약 2.5~12배 가량 차이가 발생하였으며, 무결암 및 절리암반 모두 완충재의 하단부가 상단부에 비해 포화속도가 상대적으로 빠르게 진행되었음을 확인할 수 있었다. 본 연구결과는 고준위폐기물 처분공 내의 완충재 설계와 관련하여, 완충재 포화 시기예측 및 최적 소요두께 결정 등에 중요한 자료로 활용될 수 있을 것으로 예상된다.

Keywords

References

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