Full-scale fire tests of RC metro shield TBM tunnel linings

This paper presents the full-scale experimental test results of actual RC (reinforced concrete) metro shield TBM (tunnel boring machine) tunnel linings that are exposed to a standard ISO834 curve with 45 min and 90 min heating durations. The purpose of this work is to investigate fire damage to the actual RC metro shield TBM tunnel linings and to develop a feasible method to improve the fire safety of existing metro shield TBM tunnel linings. The experimental test results indicate that severe concrete explosive spalling as well as property deterioration occurs under high temperatures. Because of coupled thermo-mechanical actions, the opening angles and gaps of the tunnel lining joints significantly increase. Due to deterioration in the elastic modulus and the strength of the joint bolt induced by high temperatures, the flexural stiffness of the tunnel lining joints notably deteriorates as well. The rubber waterstop almost remains intact during the fire tests, but the flexible gasket close to the heating surface is severely damaged by high temperatures. The experimental test outcomes also reveal that the newly developed filling material performs well under high temperatures, and it greatly decreases the temperature of the joint bolt and the rubber waterstop.