Thermo-active structures are underground facilities that enable the exchange of thermal energy between the ground and the overlying buildings, thus providing renewable means of space heating and cooling. Although this technology is becoming increasingly popular, the behaviour of geotechnical structures under additional thermal loading is still not fully understood. This paper focuses on the use of underground tunnels as thermo-active structures and explains their behaviour through a series of finite-element analyses based on an existing case study of isothermal tunnels in London Clay. The bespoke finite-element code adopted – the Imperial College Finite Element Program (ICFEP) – is capable of simulating the fully coupled thermo-hydro-mechanical behaviour of porous materials. The complex coupled interactions between the tunnel and the surrounding soil are explored by comparing results from selected types of coupled and uncoupled simulations. It is demonstrated that: (a) the thermally induced deformation of the tunnel and the ground are more critical design aspects than the thermally induced forces in the tunnel lining, and (b) the modelling approach in terms of the type of analysis, as well as the assumed permeability of the tunnel lining, has a significant effect on the computed tunnel response and, hence, must be chosen carefully.

中文翻译：

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伦敦粘土热活性隧道的预测建模

热活性结构是地下设施，能够在地面和上覆建筑物之间进行热能交换，从而提供可再生的空间供暖和制冷方式。尽管这项技术正变得越来越流行，但在额外热载荷下岩土结构的行为仍未完全了解。本文重点介绍地下隧道作为热活性结构的使用，并基于伦敦粘土等温隧道的现有案例研究，通过一系列有限元分析来解释它们的行为。采用的定制有限元代码——帝国理工学院有限元程序 (ICFEP)——能够模拟多孔材料的完全耦合的热-水-力学行为。通过比较选定类型的耦合和非耦合模拟的结果，探索隧道与周围土壤之间复杂的耦合相互作用。证明：（a ) 隧道和地面的热致变形是比隧道衬砌中的热致力更重要的设计方面，以及 ( b ) 就分析类型以及假设渗透率而言的建模方法隧道衬砌对计算的隧道响应有显着影响，因此必须谨慎选择。