Energy tunnel linings thermo-mechanical performance: comparison between field observations and numerical modelling

Energy linings are receiving great interest due to their potential to transform a tunnel into a smart energy system for enhancing thermal comfort of buildings and metro stations, as well as to absorb waste heat from the tunnel environment. Yet, besides their thermal performance, the impacts of equipping segments with a net of pipes are still challenging in the framework of energy tunnels structural design. Indeed, the thermal regime of the concrete members is altered due to heat carrier fluid circulation. Hence, the need to shed some light on the possible limit states attainment arises. In this paper, field monitoring of stresses and strains are presented for the first time in relation to a full scale monitored prototype of Enertun energy tunnel lining installed in Turin, Italy. Experimental data are compared to the results of a coupled thermo-mechanical numerical model, showing to be in good agreement. Criticalities from the ultimate limit state do not emerge, although a deeper analysis of serviceability limit states attainment should be performed.