[논문]입자기반 개별요소모델을 이용한 암석 균열의 수리역학 거동해석: 국제공동연구 DECOVALEX-2023 Task G (Benchmark Simulation)

박정욱; 박찬희; 이창수

doi:10.7474/tus.2021.31.4.270

입자기반 개별요소모델을 이용한 암석 균열의 수리역학 거동해석: 국제공동연구 DECOVALEX-2023 Task G (Benchmark Simulation)
Hydro-Mechanical Modeling of Fracture Opening and Slip using Grain-Based Distinct Element Model: DECOVALEX-2023 Task G (Benchmark Simulation) 원문보기

터널과 지하공간: 한국암반공학회지 = Tunnel and underground space, v.31 no.4, 2021년, pp.270 - 288

박정욱 (한국지질자원연구원) , 박찬희 (한국지질자원연구원) , 이창수 (한국원자력연구원)

초록
AI-Helper

본 연구에서는 입자기반 개별요소모델(grain-based distinct element model, GBDEM)을 이용하여 암석 균열의 역학적, 수리적 거동을 평가할 수 있는 수치해석기법을 제시하고 해석해와의 비교를 통해 검증하였다. 이는 DECOVALEX-2023 프로젝트 Task G의 일환으로 수행된 벤치마크 모델링 연구로, Task G는 결정질 암반 내 균열의 열-수리-역학적 복합거동을 해석하기 위한 수치해석기법을 개발하는 데에 목표가 있다. 본 연구에서는 사면체 개별 입자들을 이용하여 해석모델을 생성하고 3DEC을 이용하여 입자와 접촉에서의 거동을 해석하였다. 이 과정에서 등가연속체 개념을 적용해 입자기반모델의 미시물성을 산정할 수 있는 새로운 기법을 제시하였다. 한편, 균열 경사각과 거칠기, 경계응력조건 및 압력 조건에 따른 해석을 실시하여 각 해석조건이 균열의 수직, 전단방향 거동에 미치는 영향을 살펴보았다. 해석 결과, 제안된 수치모델은 경계응력에 따른 균열의 미끄러짐(fracture slip)과 유체 압력에 따른 균열의 개방(fracture opening), 균열 경사에 따른 응력 분포, 거칠기로 인한 전단변위의 구속 등을 합리적으로 재현하고 있음을 확인하였다. 수치해석을 통해 계산된 균열의 수직방향, 전단방향 변위는 모두 해석해를 통해 계산된 값과 거의 일치하는 결과를 보였다. 본 연구의 해석모델은 Task G에 참여하는 국외 연구팀들과의 의견 교류와 워크숍을 통해 지속적으로 개선하는 한편, 향후 다양한 조건의 실내시험에 적용하여 타당성을 검증할 예정이다.

Abstract ▼ AI-Helper

We proposed a numerical method to simulate the hydro-mechanical behavior of rock fracture using a grain-based distinct element model (GBDEM) in the paper. As a part of DECOVALEX-2023 Task G, we verified the method via benchmarks with analytical solutions. DECOVALEX-2023 Task G aims to develop a numerical method to estimate the coupled thermo-hydro-mechanical processes within the crystalline rock fracture network. We represented the rock sample as a group of tetrahedral grains and calculated the interaction of the grains and their interfaces using 3DEC. The micro-parameters of the grains and interfaces were determined by a new methodology based on an equivalent continuum approach. In benchmark modeling, a single fracture embedded in the rock was examined for the effects of fracture inclination and roughness, the boundary stress condition and the applied pressure. The simulation results showed that the developed numerical model reasonably reproduced the fracture slip induced by boundary stress condition, the fracture opening induced by fluid injection, the stress distribution variation with fracture inclination, and the fracture roughness effect. In addition, the fracture displacements associated with the opening and slip showed good agreement with the analytical solutions. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study experiments.

주제어

표/그림 (16)

그림 Fig. 1. Grain-based distinct element model: (a) micro-mechanisms for compression-induced tensile stress at the contacts between the particles (polygonal grain vs. circular grain, after Ghazvinkin et al., 2014) and (b) cylindrical model in 3DEC
표 Table 1. Mechanics benchmark model condition
그림 Fig. 2. Model generation for mechanics benchmark simulation
그림 Fig. 3. Results of uniaxial compression test on GBDEM (Case 1 in Table 2): stress-strain curve (unit of stress: Pa) and displacement vector (unit of displacement: m)
표 Table 2. Determination of micro-parameters of GBDEM by equivalent continuum approach
$Fig. 4. Rock displacement magnitude (unit: m) and maximum fracture shear displacement (at fracture center): (a) α = 0°, (b) α =30°, (c) α = 45°, (d) α = 60°, (e) α = 90°$ 그림 Fig. 4. Rock displacement magnitude (unit: m) and maximum fracture shear displacement (at fracture center): (a) α = 0°, (b) α =30°, (c) α = 45°, (d) α = 60°, (e) α = 90°
그림 Fig. 5. Rock shear stress (σ_xy) distribution (unit: Pa): (a) α = 0°, (b) α = 30°, (c) α = 45°, (d) α = 60°, and (e) α = 90°
$Fig. 6. Comparison of analytically and numerically calculated fracture shear displacements: (a) α = 30°, (b) α = 45°, and (c) α = 60°$ 그림 Fig. 6. Comparison of analytically and numerically calculated fracture shear displacements: (a) α = 30°, (b) α = 45°, and (c) α = 60°
$Table 3. Theoretical shear stress and shear displacement of inclined rock fracture$ 표 Table 3. Theoretical shear stress and shear displacement of inclined rock fracture
$Fig. 7. Representation of rough fracture (profile 1) with different resolutions of (a) 2 mm (b) 5 mm and (c) 10 mm$ 그림 Fig. 7. Representation of rough fracture (profile 1) with different resolutions of (a) 2 mm (b) 5 mm and (c) 10 mm
$Fig. 8. Shear displacement of rough fracture - profile 1 (unit: m): roughness resolutions of (a) 2 mm (b) 5 mm and (c) 10 mm$ 그림 Fig. 8. Shear displacement of rough fracture - profile 1 (unit: m): roughness resolutions of (a) 2 mm (b) 5 mm and (c) 10 mm
$Fig. 9. Comparison of numerically estimated rough fracture shear displacements (roughness resolutions of (a) 2 mm, (b) 5 mm, and (c) 10 mm) and analytical solution for planar fracture$ 그림 Fig. 9. Comparison of numerically estimated rough fracture shear displacements (roughness resolutions of (a) 2 mm, (b) 5 mm, and (c) 10 mm) and analytical solution for planar fracture
$Fig. 10. Shear stress (σ<sub>xy</sub>) of rock around fracture (unit: Pa): rough fracture models (profile 1) with different resolutions of (a) 2 mm (b) 5 mm and (c) 10 mm and (d) planar fracture model$ 그림 Fig. 10. Shear stress (σ_xy) of rock around fracture (unit: Pa): rough fracture models (profile 1) with different resolutions of (a) 2 mm (b) 5 mm and (c) 10 mm and (d) planar fracture model
표 Table 4. Hydro-mechanics benchmark model condition
$Fig. 11. Contour plot of displacement (at block center, unit: m) and maximum fracture shear displacement (at fracture center, unit: μm): (a) HM-1, (b) HM-2, and (c) HM-3$ 그림 Fig. 11. Contour plot of displacement (at block center, unit: m) and maximum fracture shear displacement (at fracture center, unit: μm): (a) HM-1, (b) HM-2, and (c) HM-3
$Fig. 12. Comparison of analytically and numerically calculated fracture shear displacements: (a) HM-1, (b) HM-2 and (c) HM-3$ 그림 Fig. 12. Comparison of analytically and numerically calculated fracture shear displacements: (a) HM-1, (b) HM-2 and (c) HM-3

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