Research on sediment reduction benefits of engineering measures on waste rock slope under different rainfall intensities

The dump slope of open-pit coal mines is characterized by steep gradients, loose structure, and poor stability, leading to severe soil erosion under heavy rainfall. While past methods like vegetative hedges have shown some effectiveness in erosion control, soil erosion remains significant before vegetation reaches the desired coverage. In contrast, soil and water conservation engineering measures (SWCEMs) require shorter construction time and achieve immediate maximum benefits upon completion, enabling rapid erosion mitigation.To investigate the influence of SWCEMs (horizontal ditches, geotextile bags) on runoff and sediment yield under varying rainfall intensities, a dump slope model was constructed based on the geometric parameters of Haizhou open-pit mine’s dump slope. Rainfall intensities of 60, 90, and 120 mm/h were set according to the local storm intensity formula in Fuxin (50-year return period, 45-minute duration). Indoor artificial rainfall simulations were conducted, and factors including runoff rate, sediment yield, flow reduction benefit, and sediment reduction benefit were analyzed to evaluate erosion control efficacy. ① Under varying rainfall intensities, SWCEMs significantly reduced slope runoff generation and enhanced erosion resistance. The maximum reductions in runoff rate and sediment yield compared to the control group were 65.18% and 92.23%, respectively. Low-density geotextile bag cover outperformed other measures in both flow and sediment reduction. ② At 60 mm/h rainfall intensity, the runoff rate and sediment yield of narrow-ridge horizontal ditches, low-density geotextile bags, and high-density geotextile bags increased proportionally with rainfall intensity, using the control group’s baseline values as reference. ③ The relationship between sediment yield and runoff power varied across measures, but runoff power provided a more robust predictor of sediment yield overall. Under no measures or wide-ridge horizontal ditches, runoff rate and sediment yield exhibited a strong linear proportionality, indicating direct causality. However, narrow-ridge horizontal ditches and geotextile bags weakened this relationship, demonstrating their efficacy in decoupling runoff from sediment transport. By dispersing flow and reducing velocity, SWCEMs lowered runoff shear stress and power, thereby mitigating sediment yield.The findings underscore the critical role of appropriate selection and design of SWCEMs in dump slope erosion control, offering a scientific basis for deploying targeted mitigation strategies.