Preparation and Optimization of Backfill Slurry from Ultrafine Tailings in Tianxing Iron Mine and Its Engineering Application

Subsequent backfilling mining methods are critical technologies for the safe exploitation of deep metal mines, while the resource utilization of ultrafine tailings is a core component of green mining practices. This study focuses on the ultrafine tailings from the Tianxing iron mine to investigate the preparation and optimization of backfill slurry. The goal is to develop a low-cost, high-strength slurry suitable for large-scale preparation and long-distance pipeline transportation. The main findings are as follows: the 6920-type anionic flocculant was identified as the optimal agent, with an optimal dosage of 20 g/t, achieving an underflow concentration of 70.1% under dynamic testing conditions; a novel cementitious material (NCM) exhibited a 28-day uniaxial compressive strength of 3.14 MPa at a low binder-to-tailings ratio of 1:10, outperforming ordinary Portland cement and Slag Micro-powder; and the optimal slurry concentration was determined to be 70%, which provides a favorable balance between mechanical strength and flowability. Furthermore, economic analysis indicates that adopting NCM can reduce annual backfilling costs by approximately 13 million RMB. By establishing an integrated technical framework that includes “property characterization–flocculation optimization–binder selection–rheological regulation,” this study addresses key technical challenges associated with ultrafine tailings backfilling, significantly reduces binder consumption and overall backfilling costs, and provides precise parameter guidance for industrial-scale applications. The proposed approach demonstrates significant practical value for promoting green and sustainable mining development.