IMPACT OF A DRY BED SURGE AGAINST STRUCTURES WITH AND WITHOUT OPENINGS

Tsunamis, Impulse waves and the sudden collapse of dams are rare phenomena, but highly destructive. Nevertheless recent events showed that structures with openings can effectively reduce impact forces, ensuring people’s safety and limiting reconstruction costs. The present experimental study systematically investigates the impact of a dry bed surge against a free standing structure with various degrees of porosity, measuring forces and moments in all directions. For the impervious scenario, results showed the absence of an initial overshot and a good agreement with the classical hydrodynamic force computed as a function of the momentum flux. Structures with openings showed lower upstream water levels resulting in a reduced horizontal load. This was proved to be linearly proportional to the porosity value and the application point of the force was between 75 and 100 % of the maximum wave height, independently from the geometry. Vertical forces are given as the sum of buoyancy and the weight of water, presenting the highest values for porosities between 17 and 34 %.