Soil erosion characteristics of three-dimensional overburdened stockpiles

Overburdened stockpiles, a kind of typical loose mixture composed of different proportions of soil and gravel that are created by various production and construction projects, are one of the main sources of man-made accelerated erosion. Because of their specific source of production and unique three-dimensional shape, overburdened stockpiles often present a peculiar erosion process given rainfall conditions. To study this erosion process, a stockpile platform device was designed and used to simulate three-dimensional overburdened stockpiles. A series of indoor artificially simulated rainfall experiments at different precipitation intensities were conducted using loessial soil with different gravel contents. The following key results were obtained: (a) the runoff rate and flow velocity had the same trend over time – that is, a rapid increase, followed by a slower increase and stabilization, while the three-dimensional shape resulted in smaller numerical values of the Reynolds number and Froude number than a rectangular slope; (b) the sediment yield increased exponentially in response to the increasing rainfall intensity and decreased with increasing gravel content in a logarithmic manner; and (c) stream power could be the optimal factor describing soil erosion because it produced the strongest correlation and fitting degree for soil detachment rate. These findings improve our understanding of the hydraulic characteristics and erosion processes of overburdened stockpiles and also have implications for predictive soil and water loss models.