Eco-Friendly Mining Practices: Field Test of Phosphogypsum Filling Based on Slag Powder in Dayukou Phosphate Mine

Filling with phosphogypsum is one of the important ways to realize the sustainability development of phosphate mines. This study is based on the extensive on-site experiments conducted at the Dayukou phosphate mine. Over a period of 60 days, different proportions of phosphogypsum, cement, and mineral powder were used to fill the voids in the No. 1 and No. 2 test ore pillars. The results of strength testing during the experimental process indicate that the strength development of the filling material at various stages is normal, meeting all the requirements for mining production. The environmental protection monitoring station in the city conducted water quality analysis during the filling process, indicating that the concentrations of major elements such as Cu, Zn, Mn, Pb, Cd, and Hg in the water samples meet the industrial wastewater discharge standards. The fluoride content ranges from 3.28 to 6.90 mg/L, which is below the first-level standard of 10 mg/L specified in the “Comprehensive Wastewater Discharge Standards” (GB8978-1996). This suggests that the filling process has a minimal impact on the groundwater environment. After the completion of the filling, the pre-embedded pressure boxes function normally, and the data are generally stable, experiencing pressures ranging from 0.11 to 2.53 MPa. This on-site expanded trial indicates the feasibility of using cement, mineral powder, and phosphogypsum for underground filling. It demonstrates the potential for reutilizing the solid waste phosphogypsum as filling aggregate.