Experimental study of dam-break-like tsunami loads on the vertical structure with overhanging horizontal slab: Flat slab

Tsunamis present a significant risk to coastal infrastructure. This study conducts a comprehensive experimental investigation into the effects of tsunami impacts on a vertical structure equipped with an overhanging horizontal slab. Dam-break waves were generated in the laboratory to simulate tsunami bore. The uplift pressure of the tsunami bore on the horizontal suspended slab and the horizontal pressure on the vertical wall were analyzed by combining experimental data with water flow patterns. The results revealed that the impact process could be categorized into four stages: initial impact, run-up, quasi-steady, and recession. Two characteristic pressures were identified: a maximum pressure during the initial impact stage and a quasi-steady pressure with a longer duration. The maximum uplift pressure was found to increase with the relative position and tsunami bore height. However, this trend was influenced by the slab height and gravity, particularly on the side of the slab closest to the wall. As the slab height increased, the water flow reflection area expanded, diminishing the focusing effect caused by the slab and decreasing the quasi-steady uplift pressure. The uplift coefficient was observed to decrease with an increase in the relative slab height, and a new uplift coefficient envelope was proposed based on experimental data and published articles. Equations for the uplift pressure distribution and a novel conversion method between uplift pressure and horizontal pressure were introduced. Furthermore, based on the measured data and existing theories, equations for estimating the maximum and quasi-steady uplift pressures are presented and validated using published data. These findings provide valuable insights into understanding and estimating the impact of tsunami on structures.