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2025 Vol.27, Issue 5 Preview Page

Research Paper

Influence of grain bulk modulus on thermal-hydraulic-mechanical (THM) coupled behavior of rock in deep geological repositories

심층처분시스템 근계암반의 열-수리-역학적 연계거동 평가를 위한 입자 체적계수 영향 분석

Jong-Won Lee1
,
Junhyung Choi2
,
Byung-Gon Chae3
,
Eui-Seob Park4
,
Min-Jun Kim5*
이 종원1
,
최 준형2
,
채 병곤3
,
박 의섭4
,
김 민준5*
1Post-Doctoral Researcher, Deep Geological Disposal & Energy Storage Research Center, Korea Institute of Geoscience and Mineral Resources
2Senior Engineer, Deep Geological Disposal & Energy Storage Research Center, Korea Institute of Geoscience and Mineral Resources
3Principal Researcher, Deep Geological Disposal & Energy Storage Research Center, Korea Institute of Geoscience and Mineral Resources
4Head, Deep Geological Disposal & Energy Storage Research Center, Korea Institute of Geoscience and Mineral Resources
5Senior Researcher, Deep Geological Disposal & Energy Storage Research Center, Korea Institute of Geoscience and Mineral Resources
1정회원, 한국지질자원연구원 방폐물심층처분연구센터 박사후연수자
2비회원, 한국지질자원연구원 방폐물심층처분연구센터 선임기술원
3비회원, 한국지질자원연구원 방폐물심층처분연구센터 책임연구원
4정회원, 한국지질자원연구원 방폐물심층처분연구센터 센터장
5비회원, 한국지질자원연구원 방폐물심층처분연구센터 선임연구원
*Corresponding Author
30 September 2025. pp. 455-476
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Abstract

This study examines the effect of grain bulk modulus on the thermal-hydraulic-mechanical (THM) behavior of rock in deep geological repositories. The grain bulk modulus was obtained from unjacketed tests on Hwangdeung granite, where volumetric strain was measured under increasing confining pressure. Mineralogical compositions from X-ray diffraction analysis were also used to calculate theoretical values through a volume-fraction-weighted average, and elastic parameters were employed to derive additional estimates. Three cases were analyzed: (i) experimental values, (ii) elastic parameter-based estimates, and (iii) mineral fraction-based theoretical values. These parameters were applied in a numerical model to simulate the THM response of near-field crystalline rock around a KBS-3 type repository. Results showed that changes in grain bulk modulus had insignificant effects on temperature and pore pressure distributions. In contrast, clear differences appeared in mechanical responses, especially in maximum principal stress and volumetric strain. Theoretical estimates overpredicted stress-strain responses compared with experimental data. Therefore, using experimentally derived parameters is essential to improve the reliability of THM simulations and to ensure accurate long-term stability assessments of deep geological repositories. The findings of this study provide a scientific basis for applying experimentally measured parameters in future THM coupling analyses of underground rock.

Keywords
Deep geological repositories
Rock
Thermal-Hydraulic-Mechanical (THM) coupled behavior
Grain bulk modulus
Unjacketed test

본 연구에서는 심층처분시스템 근계암반의 열-수리-역학(thermal-hydraulic-mechanical, THM) 연계거동에 대한 입자 체적계수의 영향을 평가하였다. 황등화강암 시편을 대상으로 무자켓 실험을 수행하여 구속압 증가에 따른 체적변형률을 측정하고, 이를 통해 실험 기반 입자 체적계수를 산정하였다. 또한 X-선 회절분석을 통해 산출된 광물 체적분율을 활용하여 체적분율 가중평균 기법으로 이론값을 계산하였으며, 기존 문헌의 탄성계수를 적용하여 추가적인 이론값을 도출하였다. 세 가지 경우에서 산정된 입자 체적계수를 수치해석에 반영하여 KBS-3 방식 심층처분시스템의 근계암반을 모사하고, 시간에 따른 온도, 간극수압, 최대 주응력, 체적변형률, 수리응력 및 열응력의 거동을 평가하였다. 해석 결과, 입자 체적계수 변화는 온도와 간극수압 거동에 미치는 영향은 미미한 것으로 분석되었으나, 최대 주응력과 체적변형률은 명확한 차이를 보이는 것으로 파악되었다. 특히 이론값 기반 해석은 응력-변형 반응을 과대평가하는 경향을 보여, 장기 안정성 평가의 신뢰성을 저하시킬 수 있는 가능성이 확인되었다. 이러한 결과에서 실험 기반 입자 체적계수의 확보와 이를 활용한 THM 연계해석이 중요하게 고려되어야 할 것으로 판단된다. 본 연구의 결과는 향후 심층처분시스템의 안정성 평가를 위하여 유용하게 활용될 수 있을 것으로 기대된다.

키워드
심층처분시스템
근계암반
열-수리-역학적 연계거동
입자 체적계수
무자켓 실험
References
1

ASTM (1986), ASTM D2938 Standard test method for unconfined compressive strength of intact rock core specimens, ASTM International, West Conshohocken, Philadelphia.

2

Bieniawski, Z.T., Bernede, M.J. (1979), “Suggested methods for determining the uniaxial compressive strength and deformability of rock materials, Part 1. Suggested method for determining deformability of rock materials in uniaxial compression”, International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts, Vol. 16, No. 2, pp. 138-140.

10.1016/0148-9062(79)91451-7
3

Biot, M.A. (1941), “General theory of three-dimensional consolidation”, Journal of Applied Physics, Vol. 12, No. 2, pp. 155-164.

10.1063/1.1712886
4

Blanco-Martín, L., Wolters, R., Rutqvist, J., Lux, K.H., Birkholzer, J.T. (2016), “Thermal–hydraulic–mechanical modeling of a large-scale heater test to investigate rock salt and crushed salt behavior under repository conditions for heat-generating nuclear waste”, Computers and Geotechnics, Vol. 77, pp. 120-133.

10.1016/j.compgeo.2016.04.008
5

Cha, Y., Lee, C., Kim, J.S., Lee, M. (2023), “Evaluation of thermal-hydro-mechanical behavior of bentonite buffer under heating-hydration condition at disposal hole”, Journal of Korean Tunnelling and Underground Space Association, Vol. 25, No. 2, pp. 175-186.

10.9711/KTAJ.2023.25.2.175
6

Choens II, R.C., Ilgen, A.G., Espinoza, D.N., Aman, M., Wilson, J., Dewers, T.A. (2020), “Impacts on mechanical strength of chemical reactions induced by hydrous supercritical CO2 in Boise Sandstone”, International Journal of Greenhouse Gas Control, Vol. 95, 102982.

10.1016/j.ijggc.2020.102982
7

COMSOL Multiphysics reference manual, https://doc.comsol.com/6.3/doc/com.comsol.help.comsol/COMSOL_ReferenceManual.pdf (August 2, 2025).

8

Dudley, J.W., Brignoli, M., Crawford, B.R., Ewy, R.T., Love, D.K., McLennan, J.D., Ramos, G.G., Shafer, J.L., Sharf-Aldin, M.H., Siebrits, E., Boyer, J., Chertov, M.A. (2016), “ISRM suggested method for uniaxial-strain compressibility testing for reservoir geomechanics”, Rock Mechanics and Rock Engineering, Vol. 49, pp. 4153-4178.

10.1007/s00603-016-1055-4
9

Franklin, J.A. (1979), “Suggested methods for determining water content, porosity, density, absorption and related properties and swelling and slake-durability index properties”, International Journal of Rock Mechanics and Mining Science & Geomechanics Abstracts, Vol. 16, pp. 141-156.

10.1016/0148-9062(79)91453-0
10

Hart, D.J., Wang, H.F. (2010), “Variation of unjacketed pore compressibility using Gassmann’s equation and an overdetermined set of volumetric poroelastic measurements”, Geophysics, Vol. 75, No. 1, pp. N9-N18.

10.1190/1.3277664
11

Jaeger, J.C., Cook, N.G.W., Zimmerman, R.W. (2007), Fundamentals of Rock Mechanics (Fourth Edition), Blackwell Publishing, Oxford, pp. 106-137.

12

Kim, H.M., Kwon, S. (2017), “Deep geological disposal of high-level radioactive wastes and coupled thermal-hydraulic-mechanical-chemical analysis”, Journal of the Korean Society of Mineral and Energy Resources Engineers, Vol. 54, No. 4, pp. 319-327.

10.12972/ksmer.2017.54.4.319
13

Kim, K.Y., Zhuang, L., Yang, H., Kim, H., Min, K.B. (2016), “Strength anisotropy of Berea sandstone: Results of X-ray computed tomography, compression tests, and discrete modeling”, Rock Mechanics and Rock Engineering, Vol. 49, No. 4, pp. 1201-1210.

10.1007/s00603-015-0820-0
14

Kim, M.J., Lee, S.R., Jeon, J.S., Yoon, S. (2019), “Sensitivity analysis of bentonite buffer peak temperature in a high-level waste repository”, Annals of Nuclear Energy, Vol. 123, pp. 190-199.

10.1016/j.anucene.2018.09.020
15

Kim, M.J., Lee, S.R., Yoon, S., Jeon, J.S., Kim, M.S. (2018), “Optimal initial condition of a bentonite buffer with regard to thermal behavior in a high-level radioactive waste repository”, Computers and Geotechnics, Vol. 104, pp. 109-117.

10.1016/j.compgeo.2018.08.011
16

Kim, M.J., Park, E.S., Park, C., Choi, J. (2023), “An experimental study on measurement method for grain bulk modulus of sandstone”, Tunnel and Underground Space, Vol. 33, No. 2, pp. 71-82.

10.7474/TUS.2023.33.2.071
17

Kim, T., Park, C.H., Lee, C., Kim, J.S. (2022), “A thermo-hydro-mechanical coupled numerical simulation on the FE experiment: Step 1 Simulation in Task C of DECOVALEX-2023”, Tunnel and Underground Space, Vol. 32, No. 6, pp. 518-529.

10.7474/TUS.2022.32.6.518
18

Kwon, S., Cho, W.J., Lee, J.O. (2013), “An analysis of the thermal and mechanical behavior of engineered barriers in a high-level radioactive waste repository”, Nuclear Engineering and Technology, Vol. 45, No. 1, pp. 41-52.

10.5516/NET.06.2012.015
19

Lau, J.S.O., Chandler, N.A. (2004), “Innovative laboratory testing”, International Journal of Rock Mechanics and Mining Sciences, Vol. 41, No. 8, pp. 1427-1445.

10.1016/j.ijrmms.2004.09.008
20

Lee, J.O., Birch, K., Choi, H.J. (2014), “Coupled thermal-hydro analysis of unsaturated buffer and backfill in a high-level waste repository”, Annals of Nuclear Energy, Vol. 72, pp. 63-75.

10.1016/j.anucene.2014.04.027
21

Luo, Y. (2022), “Isotropized Voigt-Reuss model for prediction of elastic properties of particulate composites”, Mechanics of Advanced Materials and Structures, Vol. 29, No. 25, pp. 3934-3941.

10.1080/15376494.2021.1913772
22

Makhnenko, R.Y., Labuz, J.F. (2016), “Elastic and inelastic deformation of fluid-saturated rock”, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 374, No. 2078, 20150422.

10.1098/rsta.2015.042227597783PMC5014295
23

Mavko, G., Mukerji, T., Dvorkin, J. (2020), The Rock Physics Handbook, Cambridge University Press, Cambridge, pp. 169-228.

10.1017/9781108333016
24

NSSC (2024), General criteria for deep geological repositories for high-level radioactive waste, Nuclear Safety and Security Commission, Korea.

25

Nwonodi, R.I., Dosunmu, A., Okoro, E.E. (2022), “An equation for the bulk modulus of composites derived from the effective medium theory”, ASME Open Journal of Engineering, Vol. 1, 011044.

10.1115/1.4055628
26

Pandey, S.N., Vishal, V. (2017), “Sensitivity analysis of coupled processes and parameters on the performance of enhanced geothermal systems”, Scientific Reports, Vol. 7, No. 1, 17057.

10.1038/s41598-017-14273-429213070PMC5719037
27

Park, B.Y., Bae, D.S., Kim, C.S., Kim, K.S., Koh, Y.K., Jeon, S.W. (2001), Evaluation of the basic mechanical and thermal properties of deep crystalline rocks, KAERI/TR-1828/2001, Korea Atomic Energy Research Institute, pp. 14-46.

28

Park, J.W., Lee, Y.K., Park, C., Kim, C.M. (2022), “Crack initiation and propagation thresholds of Hwangdeung granite under elevated temperature”, Geosciences Journal, Vol. 26, No. 6, pp. 715-729.

10.1007/s12303-022-0015-0
29

Park, S., Kim, J.S., Kim, G.Y., Kwon, S. (2019), “Evaluation of mechanical properties of KURT granite under simulated coupled condition of a geological repository”, Journal of Korean Tunnelling and Underground Space Association, Vol. 21, No. 4, pp. 501-518.

10.9711/KTAJ.2019.21.4.501
30

Qin, X., Han, D.H., Zhao, L. (2022), “Measurement of grain bulk modulus on sandstone samples from the Norwegian continental shelf”, Journal of Geophysical Research: Solid Earth, Vol. 127, No. 9, e2022JB024550.

10.1029/2022JB024550
31

Rutqvist, J., Wu, Y.S., Tsang, C.F., Bodvarsson, G. (2002), “A modeling approach for analysis of coupled multiphase fluid flow, heat transfer, and deformation in fractured porous rock”, International Journal of Rock Mechanics and Mining Sciences, Vol. 39, No. 4, pp. 429-442.

10.1016/S1365-1609(02)00022-9
32

Selvadurai, A.P.S. (2021), “On the poroelastic Biot coefficient for a granitic rock”, Geosciences, Vol. 11, No. 5, 219.

10.3390/geosciences11050219
33

SKB (2010), Choice of method–evaluation of strategies and systems for disposal of spent nuclear fuel, SKB P-10-47, Swedish Nuclear Fuel and Waste Management Co., pp. 15-87.

34

Tarokh, A., Detournay, E., Labuz, J. (2018), “Direct measurement of the unjacketed pore modulus of porous solids”, Proceedings of the Royal Society A, Vol. 474, No. 2219, 20180602.

10.1098/rspa.2018.0602PMC6283901
35

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.

10.2136/sssaj1980.03615995004400050002x
36

Wang, H. (2000), Theory of Linear Poroelasticity with Applications to Geomechanics and Hydrogeology (Vol. 2), Princeton University Press, Princeton, New Jersey, pp. 47-69.

37

Wang, Y.P., Wang, Z., Yi, F.C., Fu, L., Luo, Y. (2025), “Numerical simulation of thermo-hydro-mechanical coupling of model test for nuclear waste disposal”, Applied Sciences, Vol. 15, No. 2, 930.

10.3390/app15020930
38

Zhang, J., Chen, J., Zhao, Z., Chen, S., Liu, G., Zhao, X., Wang, J., Lin, T., Liu, B. (2023), “Numerical modeling on nuclide transport around a nuclear waste repository under coupled thermo-hydro-mechanical condition”, Computers and Geotechnics, Vol. 164, 105776.

10.1016/j.compgeo.2023.105776
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 :5
  • Pages :455-476
  • Received Date : 2025-09-02
  • Revised Date : 2025-09-08
  • Accepted Date : 2025-09-08
  • DOI :https://doi.org/10.9711/KTAJ.2025.27.5.455
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