Experimental research on eco-friendly restoration of mining metallurgical waste rock sites using soil solidification technology

• ISS–cement synergy improves soil strength and reduces permeability. • Optimal ISS–cement mix achieved 1.44 MPa UCS with good workability. • Rainfall tests confirmed slope stability, low seepage, and vegetation growth. Mining and metallurgical waste rock yards occupy large areas and pose persistent ecological risks. This study evaluates a soil solidification approach using an ionic soil stabilizer (ISS) combined with cement to form layered cover systems for slope stabilization and revegetation. Mixes with varying solid–liquid ratios (40:30, 40:25, 40:20, 40:15, 40:10) and ISS:water ratios (1:10, 1:13) were assessed for flowability and mechanical performance (flexural and unconfined compressive strength, UCS). Microstructural and phase characterizations (XRD, SEM, EDS) were used to elucidate mechanisms, and laboratory slope models were tested under simulated rainfall intensities of 5.232 mm · d -1 (light rain) and 353.472 mm · d -1 (extremely heavy rain) for 14 days. Results show that the ISS–cement synergy promotes formation of C–S–H, C–A–S–H, ettringite, and CaCO₃, which bridge particles, fill pores, and reduce permeability. Flowability decreased as the solid–liquid ratio increased; at 6% cement, mixes of 40:20, 40:15, and 40:10 exhibited free-flow diameters of ∼180, ∼160, and ∼100 mm, suitable for base, middle, and surface layers, respectively. UCS reached up to 1.44 MPa at 40:15, while at 40:20 the UCS was 0.604 MPa (ISS:water 1:10) and 0.497 MPa (1:13). Model slopes showed excellent stability, low seepage, and healthy vegetation under both rainfall regimes. The proposed layered mix design offers a cost-efficient, mechanistically supported solution for ecological restoration of waste rock yards.