Energy tunnels: concept and design aspects

Geotechnical structures are increasingly employed as energy geostructures in Europe and worldwide. Besides being constructed for their primary structural role, they are equipped to exchange heat with the ground and supply thermal energy for heating and cooling of buildings and de-icing of infrastructures. This technology can play a fundamental role in the current challenge of addressing the increasing need for clean and renewable sources of energy. This study investigates the possibility of thermal activation of tunnel linings. Particularly, attention will be paid on a new energy segment, which can be used together with tunnel boring machine tunneling to create so-called energy tunnels. Thermal and mechanical designs need to be developed by making effective use of computational methods to quantify the exploitable heat and assess the possible consequences on the surrounding ground and the structure itself. Guidance on how to proceed in this direction will be provided in this study, showing how thermo-hydro and thermo-mechanical numerical analyses can be used to achieve a proper and effective design of energy tunnels. Two examples of possible applications will also be presented.