Abstract: In view of the large output of fine-grained waste rock in open-pit mines，it is easy to form a water-proof weak layer and aggravate the hidden danger of landslide in the waste dump by stacking alone. Taking the high-bench wastedump of a zinc-indium mine in Yunnan as the research object，through on-site particle size screening，indoor penetration and direct shear test and Geo-Slope numerical simula⁃ tion，the hydraulic mechanical response law of waste rock mixture with different fine-grained content and its influence mechanism on slope stability are explored. The unsaturated samples are prepared according to the natural moisture content of 5% in the field. The results show that with the increase of the content of fine-grained waste rock，the pores filled by particles lead to the shrinkage of the seepage channel，and the permeability coefficient of the mixture continues to decay. The permeability coefficient of the high-fine�grained ratio material is 72.3% lower than that of the original broken waste rock. The fine-grained compo⁃ nents have the effect of increasing viscosity and reducing friction. The cohesion increases slightly and the internal friction angle decreases gradually. The simplified Bishop method is used to calculate the safety fac⁃ tor of the slope under natural，rainfall and earthquake conditions. It is found that the higher the fine parti⁃cle content is，the lower the safety reserve of the slope is，and the deterioration of the rainfall condition is the most prominent. The safety factor of the downstream slope of the high-fine mixture is reduced to 1.193， which does not meet the stability requirements of specification 1.20. The study clarified the disaster-caus⁃ ing path of " pore siltation-strength attenuation-slope instability " caused by the change of fine-grained content. Based on this，the graded storage control standard is formulated，and the disposal scheme of low�medium fine-grained mixture global stacking and high-fine-grained material limited to the local filling of non-goaf area at the foot of the slope is proposed，and the layered compaction，interception and drainage， and displacement-pore water pressure dynamic monitoring measures are matched. The research results can provide theoretical support and engineering guidance for the mixed discharge of wide -graded waste rock and the prevention and control of geological disasters in wastedumps in similar mines.

Key words: fine-grained waste rock, waste dump, slope stability, numerical simulation, graded stor? age