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2025 Vol.27, Issue 6 Preview Page

Research Paper

Mechanical properties of bentonite-based backfill in deep disposal tunnel according to kaolinite infiltration

카올리나이트 침투에 따른 심층 처분 터널 내 벤토나이트 기반 혼합 뒤채움재의 역학적 물성 평가

Jun Sang Yu1
,
Tae-Min Oh2*
,
Yohan Cha3
,
Jin-Seop Kim4
유 준상1
,
오 태민2*
,
차 요한3
,
김 진섭4
1Master Student, Dept. of Civil and Environmental Engineering, Pusan National University
2Associate Professor, Dept. of Civil and Environmental Engineering, Pusan National University
3Senior Researcher, Disposal Performance Demonstration R&D Division, Korea Atomic Energy Research Institute
4Principal Researcher, Disposal Performance Demonstration R&D Division, Korea Atomic Energy Research Institute
1학생회원, 부산대학교 사회환경시스템공학과 석사과정
2정회원, 부산대학교 사회환경시스템공학과 부교수
3정회원, 한국원자력연구원 처분성능실증연구부 선임연구원
4정회원, 한국원자력연구원 처분성능실증연구부 책임연구원
*Corresponding Author
30 November 2025. pp. 623-639
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Abstract

Deep disposal tunnel that excavated a 500 m tunnel is considered for the high-level radioactive waste. Bentonite-sand mixture is considered as a backfill material in the deep disposal tunnel. Due to the long-term operation of the deep disposal tunnel, it is essential to understand the thermo-hydro-mechanical-chemical behavior of the backfill material. However, mechanical properties such as elastic modulus and uniaxial compressive strength have been less investigated compared to thermal, hydraulic, and chemical properties. During the operation of the deep disposal tunnel, kaolinite formed by groundwater-induced erosion in granite joints may infiltrate the backfill tunnel and degrade its long-term behavior. In addition, wetting-drying cycles caused by groundwater infiltration and decay heat from radionuclides within the waste can change the density of the backfill, thereby affecting the properties of the bentonite-sand mixture. Kaolinite infiltration and wetting-drying cycles should be considered factors in predicting the long-term behavior of the backfill. Therefore, this study evaluated the liquid and plastic limits of bentonite-kaolinite materials and investigated the elastic modulus and uniaxial compressive strength according to the kaolinite infiltration ratio. The mechanical properties obtained in this study can provide basic data for modeling the long-term behavior of engineered barrier backfills considering mineral infiltration and wetting-drying cycles.

Keywords
Bentonite
Backfill
Kaolinite
Mechanical properties

원자력 발전소 가동 후 발생하는 고준위 방사성 폐기물의 처분 방안으로 500 m 대심도 터널을 굴착하여 폐기물을 격납 및 밀봉하는 심층 처분 터널이 고려되고 있다. 심층 처분 터널의 공학적 방벽 중 하나인 뒤채움재의 후보 재료로 벤토나이트에 규사를 혼합하여 활용하는 방안이 채택되어 연구되고 있다. 장기간 운영되는 심층 처분 터널의 특성상, 뒤채움재의 열-수리-역학-화학적 장기 거동 특성에 대한 이해는 필수적이다. 그러나 열-수리-화학적 물성과는 달리, 탄성계수(영률), 일축압축강도 등의 역학적 물성에 대한 연구는 상대적으로 부족한 실정이다. 한편, 심층 처분 터널이 운영되는 동안, 주변 화강암 근계암반 절리 내부에서 지하수의 유동에 의해 발생하는 풍화광물인 카올리나이트가 뒤채움 터널 내부로 침투하여 뒤채움재의 장기 건전성을 저해할 가능성이 있다. 또한, 뒤채움재의 지하수 침투에 의한 포화 및 처분 용기 내부 방사성 핵종에서 발생하는 붕괴열에 의한 건조 과정의 반복은 뒤채움재의 밀도를 변화시켜 역학적 물성 거동에 영향을 미칠 수 있다. 이러한 카올리나이트의 침투 및 포화-건조 과정의 반복은 뒤채움재의 장기 거동 예측에 필수적으로 반영되어야 한다. 따라서, 본 연구에서는 뒤채움재의 벤토나이트 및 카올리나이트 비율에 따른 액·소성한계, 그리고 카올리나이트 침투 질량 분율에 따른 탄성계수 및 일축압축강도에 대한 평가 및 분석을 수행하였다. 본 연구에서 측정한 역학적 물성은 추후 공학적 방벽 뒤채움재의 풍화 광물 침투 및 포화-건조 반복 현상을 반영한 수치해석 모델 개발 시 기초 물성 데이터로 활용될 것으로 기대된다.

키워드
벤토나이트
뒤채움재
카올리나이트
역학적 물성
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Information
  • Publisher :Korean Tunneling and Underground Space Association
  • Publisher(Ko) :한국터널지하공간학회
  • Journal Title :Journal of Korean Tunnelling and Underground Space Association
  • Journal Title(Ko) :한국터널지하공간학회 논문집
  • Volume : 27
  • No :6
  • Pages :623-639
  • Received Date : 2025-11-03
  • Revised Date : 2025-11-10
  • Accepted Date : 2025-11-10
  • DOI :https://doi.org/10.9711/KTAJ.2025.27.6.623
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