Particle characteristics and gradation evolution of fine-grained molybdenum tailings considering loading modes

With the widespread adoption of fine-grained mineral processing technologies and increasing constraints on land resources, tailings have become progressively finer, while tailing dams have generally increased in height. The use of fine-grained tailings for dam construction presents several challenges, including poor drainage performance and reduced stability. Under extreme weather conditions, these deficiencies may significantly increase the risk of dam failure, thereby threatening the lives and property of nearby residents. Therefore, clarifying the particle characteristics and gradation evolution behavior of fine-grained tailings is of great significance for addressing the technical challenges associated with the construction of tailing dams using fine-grained materials. In this study, field investigations, theoretical analyses, and macro- and micro-scale experiments were conducted to systematically investigate the particle-size distribution and morphological characteristics of fine-grained tailings. On this basis, a gradation evolution model for tailing particles under different loading conditions was established. The results indicate that (1) the particle-size distribution of fine-grained tailings can be well described by the Rosin–Rammler function, with coefficients of determination ranging from 0.96 to 0.98; (2) sandy tailings, powdery tailings, and sticky tailings in fine-grained tailings exhibit considerable differences in particle-size distribution and particle morphology; as particle size decreases, the particle flatness increases from 1.37 to 2.96, whereas the convexity decreases from 0.107 to 0.023, indicating that the particle surfaces gradually become smoother and the particle shapes become increasingly flattened; (3) under different loading conditions, the breakage rate of tailings particles increases with increasing moisture content. Impact loading mainly induces brittle breakage of coarse particles through instantaneous high stresses, resulting in a significant reduction in the coarse-particle content. In contrast, grinding loading significantly increases the fine-particle content and improves particle morphology through continuous shearing and abrasion, thereby promoting the effective filling of voids between coarse particles by fine particles. These findings contribute to addressing the challenges associated with the storage of fine-grained tailings and may help reduce the risk of severe environmental pollution and property losses resulting from tailing dam failures.