Fire Modelling and Structural Assessment of Concrete Linings of Underground Structures

The structural fire safety of tunnels is a highly debated theme at international level. Car accidents in road tunnels, failures on the power lines in railway tunnels [1,2] and electrical related issues of technological installations in underground research infrastructures can lead to trigger a fire. Fire due to cars, trains and combustion of cable insulations can be considerably dangerous. Fire in such infrastructures causes the stress increases and the losses of bearing capacity in the exposed concrete linings. Thus, in presence of a relevant fire risk, both new and existing underground structures need to be assessed. This paper shows the analyses carried out on the cavern UX15 of the ATLAS experiment, located at the Point 1 of the Large Hadron Collider (LHC) of CERN – Meyrin, Switzerland. The structural fire assessment of tunnels requires to model the lining restrain conditions, the related structural resistance and the spalling phenomena. This modelling is done by Finite Element Method (FEM) code taking into account the spalling in advanced thermo‐mechanical analyses. The shell elements have been used due to their relatively conservative temperature distribution predictions, the acceptable accuracy of the displacement estimates, and a reasonable computational burden.