Abstract: This study aims to explore the runoff and sediment yield characteristics on loose engineering accumulations under different rainfall conditions. Based on field investigations, we developed models of accumulation test tanks for simulated rainfall experiments to examine the runoff and sediment yield disparities between pure accumulation and accumulation with 20% gravel content under varied rainfall conditions. The findings revealed the following: 1) Gravel effectively delayed runoff initiation on accumulation slopes, exhibiting an average delay benefit of 299.56%. Throughout the rainfall process, both pure and mixed soil and gravel accumulations demonstrated a similar increasing trend in runoff rate with prolonged runoff generation duration. The average runoff rate escalated by 34.48%-244.83% with rising rainfall intensity. In comparison to pure accumulation, mixed soil and gravel accumulation displayed a decrease in average runoff rate by 6.54%-45.83%, along with a reduction in average flow velocity by 13.76%-30.54%. 2) The erosion rate of both pure and mixed soil and gravel accumulations generally exhibited a gradual increase or tended to stabilize with runoff generation duration under rainfall intensities below 1.5 mm/min. The average erosion rate of mixed soil and gravel accumulation was 80.39%-84.95% lower than that of pure accumulation. However, under heavy rainfall conditions (2.0 mm/min), the erosion rate of pure soil accumulation experienced rapid escalation followed by a decline, while that of mixed soil and gravel accumulation increased in a fluctuating manner, with the average erosion rate 20.04% higher than the former. 3) Both rainfall intensity and gravel content significantly influenced runoff, sediment yield, and flow velocity on accumulation slopes, indicating notable differences overall (P<0.05). The overall trend displayed an increase in both water and sediment. These results offer scientific guidance for implementing measures against soil erosion in production and construction projects involving accumulations, and provide fundamental data for establishing soil erosion prediction models for accumulation engineering.

Key words: red soil accumulation, simulated rainfall, runoff and sediment yield, runoff velocity, mixed soil and gravel