EXPERIMENTAL INVESTIGATION OF TSUNAMI IMPACT ON FREE STANDING STRUCTURES

As tsunami waves propagate towards the shoreline, they break where the water depth is approximately equal to the incident wave height. Following breaking, waves run up the shore in form of a hydraulic bore. Video footage of the 26 December 2004 Indian Ocean Tsunami shows that, upon reaching the shoreline, tsunami waves broke and transformed into a hydraulic bore that propagated onshore with considerably high velocity. However, mechanisms of hydraulic bore impact on structures are not yet well understood. Analogies between a tsunami-induced hydraulic bore and a dam-break induced wave have been previously demonstrated and published by various researchers. In order to advance the existing understanding of the complex interaction between hydraulic forces and the impacted structures, an experimental approach was taken where a dam-break induced flow, generated by the fast opening of a gate, impacted various free standing structures of different shapes located downstream of the gate. The pressures exerted on the upstream and lateral sides of a cylindrical structure, together with the bore height and the flow velocities in the flume were measured. In addition, the time history of the total force exerted on the cylindrical structure was also recorded. For the square structure, local forces on the upstream side were recorded. The effects of upstream obstacles and flow constrictions on flow velocities and on local forces exerted on a square structure were also investigated. In addition, to further understand the impact of debris during tsunami-induced flooding, wooden logs were added to the bore in order to act as water-borne missiles, while the structure's reaction was measured.