Abstract: The flow law of flood overtopping dam-break slurry in valley-type tailings reservoir is significantly affected by
valley topography. At present,most of the research focuses on V-type valleys,while there are few studies on U-type valleys. In
order to explore the flow law of overtopping dam-break slurry in valley-type tailings reservoir with U-shaped valley,a refined
three-dimensional dam-break finite element model was established based on a practical project,and the influence of dam-break
location and size on the flow law of dam-break slurry was studied. The results show that the discharge process of dam-break
slurry under the condition of U-shaped gully can be divided into three stages:start-up,circulation and gradual flow. Compared
with V-shaped gully,the lateral expansion ability of slurry is significantly enhanced,and the submerged range shows a fanshaped
trend. When the breach size of the U type gully tailings reservoir is constant,the breach is located in the riverbed position,
and the kinetic energy of the slurry is greater,which is the most unfavorable working condition of the dam break. When the
breach position is fixed,with the increase of the breach width,the impact on the downstream has a significant increasing trend.
The research results provide a theoretical reference for risk prevention and control and emergency plan preparation of similar
tailings reservoirs.

Key words: tailings reservoir,overtopping dam-break,U-type gully,numerical simulation,flow law