Abstract: Based on the physical model experiment and the design data of Xiaoda?e tailings impoundment, the course of tailings dam gravitational collapse in flood was modeled with the field tailings. The water system is controlled to model the tailings impoundment to suffer the flood situation, through the technique of side displacement points, water level measurement pipes, stress transducers and digital photography measurement, a series of important test data are obtained; such as displacements, saturation line, stresses and the broken processes, The mechanism and mode of tailings dam failure in flood are explored. The results indicate that: (1) the character of saturation line change has a time lag of the water level of tailings impoundment; (2) in the processes of the flood into tailings impoundment to the maximum water level of tailings impoundment design data in flood, the horizontal stress increment is larger than that of vertical beside dam slope center, and it is one of the important cause of dam failure; (3) the seepage force, buoyant force, gravity and pore pressure are increased by flood; then the cohesion of tailings dam is weakened and the load of dam is augment; then the stability of tailings dam is reduced; (4) the broken mode of tailings dam performs progressive failure; the failure of tailings dam happened in the toe of the dam and evolved from toe to upstream; it is shown pull-typed behavior, the failure slippage faces are composed of multi-arc faces. The model experiment results can provide significant data for deep study the mechanism of collapse and broken mode of such tailings dam in flood, so as to provide useful information for the prevention and control measures in flood disaster.

Key words: geotechnical engineering, tailings impoundment, mechanism of collapse, broken mode, model experiment