Experimental investigation of failure modes and breaching characteristics of natural dams

The failure mode and breaching time of a natural dam are affected by many factors. To comprehensively analyse the effects of these factors on dam failure modes, 159 runs of laboratory experiments were performed with 11 channel bed slopes, 4 dam geometric shapes, 3 construction materials, and 8 inflow rates. Through these experiments, two types of failure modes were identified. The results show that for lower permeability coefficients of the dam material, the overtopping failure mode will more likely occur. When the permeability coefficient and angle between the downstream slope and the horizontal plane are both high, slope failure occurs. When other conditions are unchanged, an increase in the channel bed slope and a decrease in the inflow discharge will result in slope failure. As the channel bed slope increases, the failure mode will change from the overtopping failure mode to the slope failure mode and back to the overtopping failure mode. A new parameter, Cig, (an abbreviation corresponding to channel, inflow, and geometric) is defined to reflect the influences of these factors on breaching time. Under the two types of failure modes, breaching time is an exponential function of the lake volume and is a power function of Cig.