ABSTRACT
The new High Speed Rail 2 (HS2) connects London (UK) with West Midlands and in its central section includes 3No. twin Cut and Cover precast concrete tunnels (‘Green Tunnels’), totaling 6.7km in length with up to 16m of cover. This Paper presents the design methodology adopted to evaluate specifically the Green Tunnels response to the design situation of the accidental fire load. The design approach required firstly a simplified fire assessment, followed by an advanced numerical analysis. The non-linear numerical analysis adopts a transient semi-coupled thermal-mechanical numerical analysis with temperature dependent thermal and structural properties. The results of the two approaches are presented and compared. Finally, the fire test results, conducted at CERIB, France, are presented and validated against the design requirements drawing useful comparisons and conclusions.
