Load and resistance characterization of tunnels under explosive threat scenarios
Tunnels are key elements in modern traffic networks, often crossing rivers and city regions with a high traffic density and important, highly frequented buildings and infrastructures in close proximity. Against this background, economical and societal consequences of large scale accidents and malicious threats such as fires, explosions, etc. are potentially very high. Furthermore, a comparatively small initial damage to the structure might lead to a disproportionate effect for the tunnel itself, the whole urban infrastructure system, or structures which are founded above or beneath the tunnel. In order to evaluate how critical and vulnerable a structure or its elements are, many stages of analysis have to be carried out to lead to an evaluation of the object under consideration. Explosions in tunnels have an extremely low probability of occurrence in comparison to other statistically certain events (wind, live loads), but at the same time, an enormous damage potential for structure, life and environment. The scenario of explosions with a criminal, terrorist background is additionally subject to further, sometimes subjective criteria so that the probability of occurrence has to be combined with a plausibility check Therefore, a method categorized as deterministic has been chosen for the investigation and evaluation of the possible extent of damage. The paper presents combined with the scheme explained in  important elements for such an evaluation procedure. Within this context, the paper will focus on the local and global structural integrity of tunnel constructions in the event of explosions. In order to assess this local and global structural integrity, it is of high importance to quantify the loading on and the resistance of the different tunnel types adequately. Therefore, methods will be presented to capture the dynamic loading and the structural resistance, especially taking the dynamic soil response under large stresses and strains into account.