Experimental Study on Sand Dike Breaching by Wave Overtopping

A series of large-scale experiments are conducted to investigate the breaching process of sand dikes under wave overtopping. The dikes are constructed with uniform sand, covered with a thin clay layer on the upstream slope to prevent seepage during breaching. Wave height, wave period and dike slopes are systematically varied to examine their effects on the breaching process. Morphological development of the breach is recorded using a 3D laser scanner. The results indicate that erosion starts at the downstream edge of dike crest and the downstream dike slope gradually flattens. The breach cross-section is observed to be of a trapezoidal shape. Breach flow increases at an accelerating rate after initial overtopping until a peak flow is attained. The breach dimension and peak flow rate increase with increasing wave height, wave period, and upstream and downstream dike slopes. A dimensionless dike breach parameter is proposed to establish regression relations for the breach geometry and flow characteristics.