Numerical simulation for overtopping-induced break process of concrete-faced sandy gravel dams

On the basis of the break mechanism of concrete-faced sandy gravel dams, a numerical method is proposed to simulate the overtopping-induced break processes of the concrete-faced sandy gravel dams. In this method, based on the characteristics of dam materials, such as wide gradation and particle size variation, additional force which is perpendicular to water flow direction is brought into the model to consider the drag and bridging effects of coarse particles on fine particles and the effects of fine particles surrounding and filling coarse particles so as to derive reasonable critical incipient velocity of sandy gravel materials. An erosion formula for sandy gravel materials is proposed as an expression of the relationship between the rupture time of the concrete face and the erosion quantity of the dam materials. Thus a fairly rational determination of the rupture time of the concrete face is realized. The proposed method is applied in the numerical simulation of the overtopping-induced break processes of the concrete-faced sandy gravel dam of Gouhou Reservoir in Qinghai Province. The results show a fairly good agreement between the calculated and observed data of break processes and discharge hydrographs, hence its reasonability is proved.