한국지반공학회논문집 (Journal of the Korean Geotechnical Society)

  • 제40권2호
  • /
  • Pages.29-40
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  • 2024
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  • 1229-2427(pISSN)
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  • 2288-646X(eISSN)
한국지반공학회 (Korean Geotechnical Society)
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다양한 실험조건에 따른 경주 벤토나이트 완충재 블록의 팽윤 거동 해석

Swelling behavior Simulation Study of KJ-II Bentonite Buffer Blocks under Various Experimental Conditions

  • 이득환 (한국원자력연구원 저장처분기술개발부) ;
  • 고규현 (국립금오공과대학교 토목공학과) ;
  • 이기준 (한국원자력연구원 저장처분기술개발부 ) ;
  • 윤석 (한국원자력연구원 저장처분기술개발부)
  • Lee, Deuk-Hwan (Disposal Safety Evaluation R&D Division, KAERI) ;
  • Go, Gyu-Hyun (Dept. of Civil Engrg., Kumoh National Institute of Technology) ;
  • Lee, Gi-Jun (Disposal Safety Evaluation R&D Division, KAERI) ;
  • Yoon, Seok (Disposal Safety Evaluation R&D Division, KAERI)
  • 투고 : 2023.12.08
  • 심사 : 2024.02.02
  • 발행 : 2024.04.30
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초록

본 연구에서는 완충재 블록의 팽윤 거동 특성을 파악하고자 COMSOL Multiphysics의 비선형 탄성모델을 활용하여 완충재 팽윤압 측정실험에 대한 수치해석을 수행하였다. 수치해석에서는 실험 조건과 동일하게 사방 구속조건 및 물 주입압을 경계조건으로 설정하였으며, 실험값과 수치해석 결과를 비교하여 수치해석 모델을 검증하였다. 이후 해당 수치해석 모델을 활용하여 비구속 조건에서의 팽윤변형, 건조밀도별 팽윤압, 그리고 완충재의 기하학 형태에 따른 팽윤압을 모사하였다. 해석결과, 모델은 포화 과정에 따른 팽윤변형 현상과 건조밀도가 높아질수록 팽윤압이 증가하는 현상을 적절히 모사하였다. 또한, 완충재 기하학 형태에 따른 팽윤압 모사 결과에서는 팽윤압이 증가하는 속도가 원통형 시료보다 U자형 시료에서 훨씬 빠르게 나타났고, 포화 과정에 따라 U자형 시료의 내부 모서리에서 선제적으로 응력이 발현되는 것으로 분석되었다. 다만, 완충재의 실제 거동을 보다 정확하게 모사하기 위해서는 비선형 탄소성 모델을 적용하여 해석모델의 수준을 고도화해야 할 것으로 판단된다.

This study aimed to evaluate the swelling behavior characteristics of KJ-II buffer blocks by performing numerical analysis of swelling pressure measurement experiments using the nonlinear elasticity model of COMSOL Multiphysics. The analysis was conducted under boundary conditions that included isotropic constraints and water injection pressure, mirroring the experimental settings. Validation of the numerical model was achieved by comparing its outputs with experimental results. The validated model was then used to simulate swelling deformations under unconfined conditions and to analyze swelling pressure as influenced by dry density and the geometric shape of the buffer material. The results accurately represented the swelling deformation observed during the saturation process and demonstrated that swelling pressure increases with higher dry density. Moreover, simulations concerning the geometric shape of the buffer material indicated a markedly faster rate of pressure increase in U-shaped samples compared to cylindrical ones. Analysis suggested that stress manifested preemptively near the internal edges of U-shaped samples during saturation. To enhance the simulation's fidelity to actual buffer material behavior, further refinement of the analysis model using a nonlinear elasticity model is recommended.

키워드

과제정보

This work was supported by the Innovative Technology Development Program for High-Level Waste Management (No. 2021M2E3A2041351) and by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2022R1C1C1006507).

참고문헌

  1. Abed, A. A. and Solowski, W. T. (2017), A Study on How to Couple Thermo-hydro-mechanical behaviour of Unsaturated Soils: Physical Equations, Numerical Implementation and Examples, Computers and Geotechnics, Vol.92, pp.132-155.  https://doi.org/10.1016/j.compgeo.2017.07.021
  2. Bag, R. and Jadda, K. (2021), Influence of Water Content and Dry Density on Pore Size Distribution and Swelling Pressure of Two Indian Bentonites, Bulletin of Engineering Geology and the Environment, Vol.80, pp.8597-8614.  https://doi.org/10.1007/s10064-021-02459-0
  3. Bengtsson, A. and Pedersen, K. (2017), Microbial Sulphide-producing Activity in Water Saturated Wyoming MX-80, Asha and Calcigel Bentonites at Wet Densities from 1500 to 2000 kg m- 3, Applied Clay Science, Vol.137, pp.203-212.  https://doi.org/10.1016/j.clay.2016.12.024
  4. Kim, K. I., Lee, C., and Kim, J. S. (2021), A Numerical Study of the Performance Assessment of Coupled Thermo-hydro-mechanical (THM) Processes in Improved Korean Reference Disposal System (KRS+) for High-level Radioactive Waste, Tunnel and Underground Space, Vol.31, No.4, pp.221-242.  https://doi.org/10.7474/TUS.2021.31.4.221
  5. Komine, H. (2004), Simplified Evaluation for Swelling Characteristics of Bentonites, Engineering Geology, Vol.71, No.3-4, pp.265-279.  https://doi.org/10.1016/S0013-7952(03)00140-6
  6. Lee, C., Lee, J. W., and Kim, G. Y. (2020), Numerical Simulations of Coupled Thermo-hydro-mechanical (THM) behavior of FEBEX Bentonite, Korea Atomic Energy Research Institute. 
  7. Lu, N., Godt, J. W., and Wu, D. T. (2010), A Closed-form Equation for Effective Stress in Unsaturated Soil, Water Resources Research, Vol.46, No.5. 
  8. Lu, P. H., He, Y., Ye, W. M., Chen, Y. G., and Zhang, K. N. (2022), Experimental Investigations and Microscopic Analyses of Chemical Effects and Dry Density on the Swelling behavior of Compacted Bentonite, Bulletin of Engineering Geology and the Environment, Vol.81, No.6, p.243. 
  9. Narkuniene, A., Poskas, P., and Justinavicius, D. (2021), The Modeling of Laboratory Experiments with COMSOL Multiphysics Using Simplified Hydromechanical Model, Minerals, Vol.11, No.7, p.754. 
  10. Narkuniene, A., Justinavicius, D., Poskas, P., Grigaliuniene, D., and Ragaisis, V. (2022), The Modeling of Laboratory Experiments on Granular MX-80 Bentonite with COMSOL Multiphysics, Minerals, Vol.12, No.3, p.277. 
  11. Richard, L. A. (1931), Capillary Conduction of Liquids through Porous Mediums, Physics, Vol.1, No.5, pp.318-333.  https://doi.org/10.1063/1.1745010
  12. Rutqvist, J., Zheng, L., Chen, F., Liu, H. H., and Birkholzer, J. (2014), Modeling of Coupled Thermo-hydro-mechanical Processes with Links to Geochemistry Associated with Bentonite-backfilled Repository Tunnels in Clay Formations, Rock Mechanics and Rock Engineering, Vol.47, pp.167-186.  https://doi.org/10.1007/s00603-013-0375-x
  13. Schanz, T. and Al-Badran, Y. (2014), Swelling Pressure Characteristics of Compacted Chinese Gaomiaozi Bentonite GMZ01, Soils and Foundations, Vol.54, No.4, 748-759.  https://doi.org/10.1016/j.sandf.2014.06.026
  14. SKB (2010), "Buffer, Backfill and Closure Process Report for the Safety Assessment SR-Site" TR-10-47, Svensk Karnbranslehantering, A.B. 
  15. Van Genuchten, M. T. (1980), A Closed-form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils, Soil Science Society of America Journal, Vol.44, No.5, pp.892-898.  https://doi.org/10.2136/sssaj1980.03615995004400050002x
  16. Villar, M. V. (2004), Thermo-Hydro Mechanical Characteristics and Processes in the Clay Barrier of a High Level Radioactive Waste Repository, State of the Art Report. 
  17. Yong, R. N. (1999), Soil Suction and Soil-water Potentials in Swelling Clays in Engineered Clay Barriers, Engineering Geology, Vol.54, No.1-2, pp.3-13.  https://doi.org/10.1016/S0013-7952(99)00056-3
  18. Yoon, S., Chang, S., and Park, D. (2022), Investigation of Soil-water Characteristic Curves for Compacted Bentonite Considering Dry Density, Progress in Nuclear Energy, Vol.151, 104318. 
  19. Yoon, S., Jeong, H., Lee, H. L., Kim, T., Hong, C. H., and Kim, J. S. (2023), Evaluation of Uniaxial Compression and Point Load Tests for Compacted Bentonites, Acta Geotechnica, pp.1-12.