Abstract: In order to study the influence range of dam-break in the third phase of the tailings dam， the dam-break model is established considering the objective conditions such as the geographical location of the tailings dam site，the stability of the current dam height，the downstream topography，facilities and rainstorm. The influence range of dam-break is simulated by FLUENT fluid calculation software. The re⁃ sults show that the third-stage dam-adding scheme is feasible. After dam-break，the tail-discharge mortar body mainly evolves along the mountains and valleys in the downstream of the reservoir area，and a large number of tail sand will accumulate in the valleys in the downstream. Excavation of sand drains is adopted locally to ensure that there is no impact on residential houses on half-hill slopes.

Key words: tailings dam, dam-break model, tailings discharge