3.2.1. Flow Depth of Leaked Tailings

As presented in Figure 7, the leaked tailings flow evolves downstream along the topographically lowest point in the passage zone in all three different conditions. The tailings inundated area is larger for the upstream and downstream sections of passage zone than for the midstream section. Under three dam distance conditions, the maximum inundated ranges are 2.7 <sup>×</sup> 105 m2, 2.5 <sup>×</sup> <sup>10</sup><sup>5</sup> <sup>m</sup><sup>2</sup> and 2.37 <sup>×</sup> 105 <sup>m</sup>2, respectively. Consequently, the downstream inundated area shrinks with the narrowing distance between debris blocking and initial dams.

From Figure 8, it can be found that the deposition thicknesses of tailings crossing over the debris blocking dams decrease slightly compared with the case without such dams. The maximum sedimentation thicknesses are all found in front of the debris blocking dams, which increase with the shortening distance between initial and debris blocking dams and are all located in the valley near Village I. After flowing over the debris blocking dams, the tailings are deposited primarily in the valley near Village III, and the inundated height increases with the increasing of the distance between the debris blocking dam and the initial dam.

**Figure 7.** The maximum influence scope of leaked tailings flow with debris blocking dams at different distances. (**a**) 1000 m away from initial dam; (**b**) 600 m away from initial dam; (**c**) 400 m away from initial dam. g

**Figure 8.** Schematic diagram of the maximum impact height along the valley bottom.
