Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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Mechanical Stability Analysis to Determine the Optimum Aspect Ratio of Rock Caverns for Thermal Energy Storage

열에너지 저장용 암반 공동의 최적 종횡비 결정을 위한 역학적 안정성 해석

  • 박도현 (한국지질자원연구원 지구환경연구본부) ;
  • 류동우 (한국지질자원연구원 지구환경연구본부) ;
  • 최병희 (한국지질자원연구원 지구환경연구본부) ;
  • 선우춘 (한국지질자원연구원 지구환경연구본부) ;
  • 한공창 (한국지질자원연구원 지구환경연구본부)
  • Received : 2013.03.20
  • Accepted : 2013.04.08
  • Published : 2013.04.30
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Abstract

It is generally well known that the stratification of thermal energy in heat stores can be improved by increasing the aspect ratio (the height-to-width ratio) of the stores. Accordingly, it will be desirable to apply a high aspect ratio so as to demonstrate the good thermal performance of heat stores. However, as the aspect ratio of a store increases, the height of the store become larger compared to its width, which may be unfavorable for the structural stability of the store. Therefore, to determine an optimum aspect ratio of heat stores, a quantitative mechanical stability assessment should be performed in addition to thermal performance evaluations. In the present study, we numerically investigated the mechanical stability of silo-shaped rock caverns for underground thermal energy storage at different aspect ratios. The applied aspect ratios ranged from 1 to 6 and the mechanical stability was examined based on factor of safety using a shear strength reduction method. The results from the present study showed that the factor of safety of rock caverns tended to decrease with the increase in aspect ratio and the stress ratio of the surrounding rock mass was influential to the stability of the caverns. In addition, the numerical results demonstrated that under the same conditions of rock mass properties and aspect ratio, mechanical stability could be improved by the reduction in cavern size (storage volume), which indicates that one can design high-aspect-ratio rock caverns by dividing a single large cavern into multiple small caverns.

일반적으로 열저장소의 종횡비(폭에 대한 높이의 비)가 커짐에 따라 저장된 열에너지의 성층화가 높게 유지될 수 있는 것으로 알려져 있다. 따라서 열저장소의 열적 성능을 높이기 위해서는 저장소 종횡비를 크게 설정하는 것이 유리할 것이다. 그러나 종횡비의 증가에 따라 저장소의 폭에 비해 높이가 커지고, 이는 열저장소의 구조적 안정성 측면에서 불리하게 작용할 수 있으므로 저장소의 최적 종횡비 결정시 열적 성능 분석과 더불어 역학적 안정성에 대한 정량적인 분석이 수행되어야 할 것이다. 본 연구에서는 지하 열에너지 저장을 위한 사일로형 암반공동의 종횡비 변화에 따른 역학적 안정성을 수치해석적으로 조사하였다. 적용한 종횡비는 1-6의 범위이었고, 전단강도 감소기법에 의한 안전율을 토대로 암반공동의 역학적 안정성을 평가하였다. 종횡비별 안정성 분석 결과, 암반공동의 종횡비가 증가함에 따라 안전율이 감소하는 경향을 보였으며, 주변 암반의 측압계수가 안정성에 미치는 영향이 큰 것으로 분석되었다. 또한 동일한 암반특성 및 종횡비 조건에서 암반공동의 규모(저장 용량)가 줄어듦에 따라 안정성이 향상되는 것으로 나타나, 큰 규모의 단일 암반공동을 소규모의 다중 암반공동으로 분할함으로써 높은 종횡비의 암반공동 설계가 가능한 것을 알 수 있었다.

Keywords

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  2. Analysis of the Optimal Separation Distance between Multiple Thermal Energy Storage (TES) Caverns Based on Probabilistic Analysis vol.24, pp.2, 2014, https://doi.org/10.7474/TUS.2014.24.2.155
  3. Stability Analysis of Multiple Thermal Energy Storage Caverns Using a Coupled Thermal-Mechanical Model vol.24, pp.4, 2014, https://doi.org/10.7474/TUS.2014.24.4.297
  4. Guidelines for Designing the Shape and Layout of Thermal Energy Storage (TES) Rock Caverns vol.25, pp.2, 2015, https://doi.org/10.7474/TUS.2015.25.2.115