Stresses and deformations induced by geothermal operations of energy tunnels

Alessandro F. Rotta Loria*, Alice Di Donna, Manlu Zhang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Underground tunnels used as heat exchangers in the form of energy tunnels can sustainably meet the thermal energy needs of buildings across city districts. Recently, a considerable understanding of the energy performance of such earth-contact structures has been achieved. However, knowledge of the geotechnical and structural performance of energy tunnels associated with their geothermal operation has remained limited, despite its key role for reliable tunnel applications. This paper focuses on the geotechnical and structural performance of energy tunnels by providing a comprehensive analysis of their mechanics in the context of geothermal operations. Attention is devoted to the stresses and deformations that develop within and around energy tunnels due to the influence of temperature variations. Through 3-D thermo-hydro-mechanical finite element simulations, the following results are unraveled: (i) the mechanics of tunnels operating as heat exchangers is governed by the internal airflow conditions to such structures, the air-tunnel-soil temperature differential, and the tunnel-soil stiffness ratio; (ii) thermally induced stresses in energy tunnels can be significant, while thermally induced displacements are negligible; (iii) the conventional belief that heat extraction operations dominantly involve tensile stresses and heat injection operations pervasively cause compressive stresses is not always valid for energy tunnels due to the influence of internal airflows.

Original languageEnglish (US)
Article number104438
JournalTunnelling and Underground Space Technology
Volume124
DOIs
StatePublished - Jun 2022

Keywords

  • Energy tunnel
  • Geotechnical effects
  • Structural effects
  • Thermally induced displacement
  • Thermally induced stress
  • Thermo-mechanics

ASJC Scopus subject areas

  • Building and Construction
  • Geotechnical Engineering and Engineering Geology

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