Synergistic Effects of Slurry Concentration and Binder Reactivity on the Hydraulic Transport of Unclassified Tailings Backfill

To address the safety and environmental challenges associated with deep mining, this study investigates the rheological behaviors and pipeline transport characteristics of cemented paste backfill (CPB) using unclassified tailings from a lead-zinc mine. Through the characterization of basic physicochemical properties-including chemical composition, particle size distribution, and specific surface area-combined with L-shaped pipeline simulation tests, the effects of slurry concentration and pipe diameter on rheological parameters and transport resistance were quantitatively analyzed. Furthermore, the mechanical performance and cost-effectiveness of four different cementitious binders were evaluated to identify the optimal material. The results indicate that the unclassified tailings possess a favorable particle size distribution with a significant fine-particle filling effect, making them suitable as backfill aggregates. Slurry concentration was identified as the critical factor influencing rheological performance; a concentration range of 68% to 72% was determined to be optimal, exhibiting superior fluidity and low pipeline resistance conducive to gravity flow. Additionally, increasing the pipe diameter was found to effectively reduce transport difficulty. Based on a comprehensive technical and economic analysis, Kunlun Mountain PO42.5 cement was selected as the optimal binder, achieving the required backfill strength with controlled costs. This study provides a theoretical basis and practical engineering guidance for the design and optimization of deep-well backfill pipeline systems.