Erosion resistance and regional applicability of a solid-waste-based ecological slope-protection substrate

Conventional ecological slope-protection substrates rely heavily on planting soil, limiting the large-scale utilization of industrial solid waste. This study developed a solid-waste-based substrate using fly ash as the principal substitute for peat soil and a composite binder of flue gas desulfurization gypsum (FGDG) and cement. An L16 orthogonal design and the entropy weight method were used to evaluate the effects of mixture proportions on physicochemical, vegetation-related, and mechanical performance. The optimal formulation contained 30% fly ash, 12% cement, 15% FGDG, and 43% peat soil, with 2% water-retaining agent and 2% biochar. The total solid-waste content exceeded 50% while maintaining satisfactory vegetation growth and mechanical stability. Simulated rainfall tests showed that runoff increased with rainfall intensity and slope gradient, whereas infiltration was limited by the substrate infiltration-capacity threshold. Under identical rainfall and slope conditions, soil loss from the solid-waste substrate was approximately 60% lower than that from the peat-soil substrate. Regional assessment using the Chinese Soil Loss Equation classified 30°–50° slopes in Dalian as having very slight or slight erosion. The developed substrate can therefore reduce planting-soil consumption while providing adequate erosion resistance for ecological slope protection.