Abstract: To reveal the evolution of static stability of upstream tailings dams under the combined effects of construction rate, fine-grained interlayers, and drainage facilities, this paper employs FLAC3D, integrating the Duncan-Chang constitutive model with the Van Genuchten-Mualem seepage model, to simulate the stability response of the dam during incremental construction. The results indicate that the landslide mode of the dam evolves through three stages: the unsaturated zone stage, the partially saturated zone stage, and the saturated zone stage. The shape of the most dangerous sliding surface is governed by the internal structure: it remains circular in homogeneous dams, whereas in dams containing fine-grained interlayers, it gradually transitions from circular to a non-circular shape controlled by the interlayers. The horizontal displacement at the crest of the starter dam exhibits three stages: initial deformation, uniform deformation, and accelerated deformation. The accelerated deformation stage is triggered by fine-grained interlayers and can be effectively suppressed by improving drainage. The safety factor evolution follows a two-stage pattern: the unsaturated-partially saturated zone landslide stage and the saturated zone landslide stage. The controlling effect of fine-grained interlayers on the sliding surface morphology only becomes apparent during the saturated zone landslide stage. The findings of this paper can provide a reference for the safety management of upstream tailings dams and help reduce the risk of static instability.

Key words: upstream tailings dams, static stability, dam construction rate, fine-grained interlayer, drainage facilities