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2025 Vol.35, Issue 5 Preview Page

Original Article

Development of a Numerical Simulator for Swelling Behavior of the Buffer Material in the Engineered Barrier Induced by the Alteration under Hydro-Mechanical-Chemical Conditions

수리-역학-화학적 조건을 고려한 변질에 따른 공학적방벽 내 완충재 팽윤 거동 모사를 위한 해석 시뮬레이터 개발

Taehyun Kim1*
,
Jeonghwan Hwang1
,
Changsoo Lee2
,
Jin-Seop Kim2
김 태현1*
,
황 정환1
,
이 창수2
,
김 진섭2
1Senior Researcher, Korea Atomic Energy Research Institute
2Principal Researcher, Korea Atomic Energy Research Institute
1한국원자력연구원 선임연구원
2한국원자력연구원 책임연구원
*Corresponding Author
31 October 2025. pp. 584-601
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Abstract

A buffer material, a key component of the engineered barrier in a geological disposal system, exhibits swelling behavior when saturated. The chemical composition of groundwater can significantly influence its swelling capacity. Therefore, numerical analysis of the buffer’s swelling behavior, incorporating chemical effects, is essential to ensure the long-term stability of the disposal system over hundreds of thousands of years. In this study, we developed the OGSPHREEQC-FLAC3D simulator, which enables coupled Hydro-Mechanical-Chemical (HMC) analysis. OGSPHREEQC-FLAC3D integrates OGS-FLAC3D for thermal-hydro-mechanical (THM) simulation with PHREEQC for chemical analysis using a sequential coupling approach. The Barcelona Basic Model was employed to simulate swelling behavior induced by suction pressure. Chemical effects were incorporated by considering changes in ion concentration in the solute, and a coefficient reflecting montmorillonite concentration variation was applied. A series of numerical simulations were conducted to evaluate the swelling behavior of Na-type bentonite under one-directional flow conditions. To investigate the effect of potassium ion (K+) concentration in the injection water, K+ concentration was increased in the sample through advection and diffusion. As K+ concentration rose, the amount of illite produced by chemical alteration also increased, leading to a reduction in swelling pressure. These results demonstrate the capability of the developed simulator and provide a foundation for future research aimed at advancing fully coupled thermal-hydro-mechanical-chemical (THMC) numerical simulation for geological disposal systems.

Keywords
OGSPHREEQC-FLAC3D
Buffer material
Illitization
Swelling behavior
Hydro- Mechanical-Chemical coupled behavior

처분시스템 내 공학적방벽의 핵심 요소인 완충재는 포화 시 팽윤하는 특성을 지니고 있으며, 지하수의 화학 조성에 따라 팽윤하는 특성 또한 영향을 받게 된다. 따라서 수십만 년에 이르는 기간 동안 처분시스템의 장기 안정성 확보를 위해서는 화학적 영향을 고려한 완충재 팽윤 거동에 대한 수치해석적 연구가 필요하다. 본 연구에서는 수리-역학-화학 해석이 가능한 OGSPHREEQC-FLAC3D 해석 시뮬레이터를 개발하였다. OGSPHREEQC-FLAC3D 해석 시뮬레이터는 순차적 연동해석 기법을 적용하였으며, 열-수리-역학 복합거동 해석이 가능한 OGS-FLAC3D와 화학 거동 해석이 가능한 PHREEQC를 연동하였다. 흡입력에 따른 팽윤은 Barcelona Basic Model을 적용하였으며, 용질 내 이온 농도 변화에 따른 영향을 반영하였고, 몬모릴로나이트 함량 변화에 따른 영향 계수를 적용하였다. 개발된 해석 시뮬레이터의 적용성을 확인하기 위해 Na-벤토나이트를 대상으로 일차원 유동 시 팽윤 해석을 수행하였다. 주입수의 K+ 이온 농도에 따른 변질 영향을 평가하고자 하였으며, 이류 및 확산에 따라 시료 내 K+ 이온 농도가 증가함을 확인하였다. K+ 이온 농도 증가 시 변질에 따라 생성되는 일라이트 양이 증가하였으며, 일라이트화에 따라 팽윤압이 감소함을 확인하였다. 해석 결과는 향후 열-수리-역학-화학 복합거동을 고려한 심층 처분 해석 시뮬레이터 개발의 기반으로 활용할 수 있을 것으로 기대된다.

키워드
OGSPHREEQC-FLAC3D
완충재
일라이트화
팽윤 거동
수리-역학-화학 복합거동
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Information
  • Publisher :Korean Society for Rock Mechanics and Rock Engineering
  • Publisher(Ko) :한국암반공학회
  • Journal Title :Tunnel and Underground Space
  • Journal Title(Ko) :터널과 지하공간
  • Volume : 35
  • No :5
  • Pages :584-601
  • Received Date : 2025-08-25
  • Revised Date : 2025-09-23
  • Accepted Date : 2025-09-23
  • DOI :https://doi.org/10.7474/TUS.2025.35.5.584
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