Protective effect of ecological embankment on a building subjected to tsunami bores

Abstract

The mangrove has a remarkable wave reducing effect, and it is arranged around the embankment to form an ecological embankment (eco-embankment), which complement each other's strengths. The tsunami wave simulated by the dam breaking wave is used in the flume to impact the test models. By measuring the tsunami bore height, transmission coefficient and impact pressure, and observing the flow state during the impact process, the wave elimination effect and protection effect of the eco-embankment are studied. The results show that the bore height is related to the initial water depth and the reservoir water level. The change of water level in the eco-embankment setting area (front, top, and behind of embankment) is related to the bore height, the location and the distribution density of mangroves. The transmission coefficient increases linearly with the relative water depth, but the magnitude of the increase is different for each eco-embankment model. Based on the experimental data, the equations for estimating the transmission coefficient are proposed. When tsunami waves impact buildings protected by embankments or eco-embankments, the pressure decreases and the time history of pressure appear a reflection stage compared to an unprotected building, this stage will change with the initial water depth and the distribution density of mangroves. Finally, based on the measured pressure data, the equations for estimating the dimensionless quasi-steady pressure for different models and different mangrove distribution densities are proposed as functions of relative height and Froude number, the calculated value is in good agreement with the measured value.