Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
권호 표지
DOI QR코드

DOI QR Code

Stability Analysis of Multiple Thermal Energy Storage Caverns Using a Coupled Thermal-Mechanical Model

열-역학적 연계해석 모델을 이용한 다중 열저장공동 안정성 분석

  • 김현우 (한국지질자원연구원 지구환경연구본부) ;
  • 박도현 (한국지질자원연구원 지구환경연구본부) ;
  • 박의섭 (한국지질자원연구원 지구환경연구본부) ;
  • 선우춘 (한국지질자원연구원 지구환경연구본부)
  • Received : 2014.08.05
  • Accepted : 2014.08.27
  • Published : 2014.08.31
Download PDF
⟨ Previous Next ⟩

Abstract

Cavern Thermal Energy Storage system stores thermal energy in caverns to recover industrial waste heat or avoid the sporadic characteristics of renewable-energy resources, and its advantages include high injection-and-extraction powers and the flexibility in selecting a storage medium. In the present study, the structural stability of rock mass pillar between these silo-type storage caverns was assessed using a coupled thermal-mechanical model in $FLAC^{3D}$. The results of numerical simulations showed that thermal stresses due to long-term storage depended on pillar width and had significant effect on the pillar stability. A sensitivity analysis of main factors indicated that the influence on the pillar stability increased in the order cavern depth < pillar width < in situ condition. It was suggested that two identical caverns should be separated by at least one diameter of the cavern and small-diameter shaft neighboring the cavern should be separated by more than half of the cavern diameter. Meanwhile, when the line of centers of two caverns was parallel to the direction of maximum horizontal principal stress, the shielding effect of the caverns could minimize an adverse effect caused by a large horizontal stress.

암반공동을 이용한 열에너지 저장은 대용량 저장이 가능하며 열저장매체를 선택할 수 있는 장점이 있다. 본 연구에서는 사일로 형태의 열저장공동이 지반 내 두 개 이상 배치될 때 공동 사이에 형성되는 암반 필라의 안정성에 대해 3차원 유한차분해석 프로그램인 $FLAC^{3D}$를 이용하여 분석하였으며, 저장된 열에너지로 인해 암반에 발생하는 열응력을 반영할 수 있도록 열-역학적 연계모델을 사용하였다. 해석 결과, 열에너지 장기 저장으로 인해 암반 필라에 작용하는 최대주응력이 상당량 증가하였으며, 필라 폭이 좁아질수록 근접한 열원 때문에 열응력 증가량도 커짐을 확인하였다. 필라 안정성에 영향을 미치는 주요인자로서 저장공동 간격, 측압계수, 심도를 선정하고 민감도 분석을 실시한 결과, 측압계수, 저장공동 간격, 심도 순서로 영향력이 크게 평가되었다. 저장공동 간격의 경우 동일한 크기의 공동 건설 시 필라 폭을 최소 저장공동 직경 이상 확보해야 할 것으로 판단되었다. 큰 규모의 저장공동 주변에 소규모 수직갱이 설치될 때는 최소한 저장공동 직경의 0.5배 이상 이격함으로써 크기 차이로 인해 수직갱에 응력이 집중되는 현상을 해소할 수 있었다. 또한 최대수평주응력 작용방향과 공동 중심을 잇는 축이 평행하도록 배치하여 저장공동에 의한 방패효과가 발휘될 수 있게 함으로써 현지응력이 공동 사이 암반 필라에 미치는 영향을 최소화할 수 있었다.

Keywords

References

  1. Andersson, J.C., 2007, Rock mass response to coupled mechanical thermal loading: Aspo Pillar Stability Experiment, Sweden, Doctoral thesis, Royal Institute of Technology, Sweden.
  2. Bauer, S.J. and B. Johnson, 1979, Effects of slow uniform heating on the physical properties of the Westerly and Charcoal granites, Proceedings of the 20th symposium on rock mechanics, Austin, TX, 7-18.
  3. Birch, F. and H. Clark, 1940, The thermal conductivity of rocks and its dependence upon temperature and composition, American Journal of Science 238.8, 529-558. https://doi.org/10.2475/ajs.238.8.529
  4. Choi, S.O., C. Park, J.H. Synn and H.S. Shin, 2008, A decade's experiences on the hydrofracturing in-situ stress measurement for tunnel construction in Korea, Proceedings of the Korean Society for Rock Mechanics 2008 Spring Conference, 79-88.
  5. Heuze, F.E., 1983, High-temperature mechanical, physical and thermal properties of granitic rocks-A review, International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 20.1, 3-10. https://doi.org/10.1016/0148-9062(83)91609-1
  6. Hoek, E., C. Carranza-Torres and B. Corkum, 2002, Hoek-Brown failure criterion-2002 edition, Proceedings of the 5th North American Rock Mechanics Symposium, Toronto, Canada, 267-273.
  7. Itasca Consulting Group, Inc., 2009, $FLAC^{3D}$ Manual-Thermal Analysis.
  8. KIGAM, 2012, Development of core technology for underground thermal energy storage in rock cavern, Research report GP2011-003-2012(1) Part. III, Ministry of Knowledge Economy.
  9. Lee, H.W. and C.I. Lee, 1996, A study on temperature dependency of strength and deformation behavior of rocks, Tunnel & Underground Space 6.2, 101-121.
  10. Lunder, P.J., 1994, Hard rock pillar strength estimation-An applied empirical approach, M.S. thesis, University of British Columbia, Canada.
  11. Martin, C.D. and W.G. Maybee, 2000, The strength of hard-rock pillars, International Journal of Rock Mechanics and Mining Sciences 37, 1239-1246. https://doi.org/10.1016/S1365-1609(00)00032-0
  12. Nordell, B., M. Grein and M. Kharseh, 2007, Large-scale utilization of renewable energy requires energy storage, Proceedings of International Conference for Renewable Energies and Sustainable Development, Algeria.
  13. Obert, L. and W.I. Duvall, 1967, Rock mechanics and the design of structures in rock, John Willey & Sons.
  14. Park, D., H.M. Kim, D. Ryu, B.H. Choi, C. Sunwoo and K.C. Han, 2013a, The effect of aspect ratio on the thermal stratification and heat loss in rock caverns for underground thermal energy storage, International Journal of Rock Mechanics and Mining Sciences 64, 201-209. https://doi.org/10.1016/j.ijrmms.2013.09.004
  15. Park, D., D. Ryu, B.H. Choi, C. Sunwoo and K.C. Han, 2013b, Mechanical stability analysis to determine the optimum aspect ratio of rock caverns for thermal energy storage, Tunnel & Underground Space 23.2, 150-159. https://doi.org/10.7474/TUS.2013.23.2.150
  16. Park, D., D. Ryu, B.H. Choi, C. Sunwoo and K.C. Han, 2013c, Thermal stratification and heat loss in underground thermal storage caverns with different aspect ratios and storage volumes, Tunnel & Underground Space 23.4, 308-318. https://doi.org/10.7474/TUS.2013.23.4.308
  17. Park, S.H., 2009, Design of experiment, Minyoungsa.
  18. Pariseau, W.G., 2007, Design analysis in rock mechanics, Taylor & Francis.
  19. Pavlov, G.K. and B.W. Olesen, 2011, Seasonal ground solar thermal energy storage review of systems and applications, Proceedings of ISES Solar World Congress, Kassel, Germany, 515-525.
  20. Robertson, E.C. and B.S. Hemingway, 1995, Estimating heat capacity and heat content of rocks, U.S. Geological Survey Open-file Report 95-622.
  21. Shim, B.O. and C.W. Lee, 2010, Status of underground thermal energy storage as shallow geothermal energy, Economic and Environmental Geology 43.2, 197-205.
  22. Van der Molen, I., 1981, The shift of the ${\alpha}-{\beta}$ transition temperature of quartz associated with the thermal expansion of granite at high pressure, Tectonophysics 73.4, 323-342. https://doi.org/10.1016/0040-1951(81)90221-3