On the blast resistance of high performance tunnel segments

This paper presents the main findings of an experimental study that focuses on the response of fibre reinforced concrete used in underground tunnel linings in case of internal explosion. Two situations are explored: (a) the effectiveness of thin high performance fibre reinforced cementitious composite (HPFRCC) plates applied to the intrados of new or existing tunnels as a protection panel and (b) the behaviour of a layered tunnel segment solution made of steel fibre reinforced concrete and HPFRCC when a void is present in the mortar filling layer injected between the lining and the excavated surface, thus amplifying the in–service internal actions (bending moment and shear force). Shock tube experiments are carried out to investigate the two situations. These conditions are experimentally achieved by means of a proper arrangement of an existing shock tube designed for soil–structure interaction at Politecnico di Milano. A small portion of a tunnel segment is investigated by using circular layered specimens subjected to two different levels of reflected pressure. Simplified models are proposed for assessing the overall response of the two situations explored under blast loading.