Runoff-sediment relationship and erosion dynamic characteristics for two types of engineering deposits under rainfall condition

Abstract

The engineering deposits produced by the increasing frequency of production and construction activities are the main source of man-made soil erosion. In this study, we examined the change of runoff-sediment relationship and erosion hydrodynamic characteristics with the engineering deposits of aeolian sandy soil and red soil, based on simulated rainfall experiments with different gravel contents (0, 10%, 20%, 30%) and rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min-1). The results showed that the sediment yield rate of the aeolian sandy soil deposits gradually increased with the duration of rainfall. The sediment yield rate of red soil deposits under 1.0 mm·min-1 rainfall intensity increased first and then gradually stabilized. Under other rainfall densities, there was a trend of fluctuation after rapid decline, the greater the rainfall intensity and the smaller the gravel content, the more intense the fluctuation. When the gravel content was 0 and 10%, there were rills erosion on the slope surface of aeolian sandy soil accumulation, and the sediment yield rate of rill development stage was 6.74-57.40 times of that of the sheet erosion stage. The erosion process of red soil deposits could be divided into two stages: the loose particle erosion and the soil-rock erosion stage. The sediment yield rate of the loose particle erosion stage was 1.05-3.49 times that of the soil-rock erosion stage. In general, the sediment yield rate of two soil deposits increased with increasing rainfall intensity. The sediment yield rate fluctuated with the increases of gravel content at 1.0 and 1.5 mm·min-1, with a decreasing trend under >1.5 mm·min-1. The sediment yield rate of aeolian sandy soil deposits was 1.45-4.14 times of that of red soil deposits under the same rainfall and gravel content conditions. During the erosion process of aeolian sandy soil deposits, the runoff-sediment relationship changed from low sediment concentration to high sediment concentration, while there was a reverse relationship for red soil deposits. During the high sediment concentration period, the increasing rate of the sediment yield rate of aeolian sandy soil deposits was 1.94-37.60 times of that of red soil deposits. For low sediment concentration period, the decreasing rate of the sediment yield rate of red soil deposits was 1.40-21.30 times of that of aeolian sandy soil deposits. In general, the runoff power was better than the runoff shear force in describing the erosion dyna-mics of these two types of deposits. The critical runoff power increased with increasing gravel content. The critical runoff power of aeolian sandy soil deposits during the rill erosion stage (0.02-0.04 W·m-2) was two times of that of the sheet erosion stage, while the critical stream power was lower than that of the red soil deposits. These results provide a scientific reference for modelling soil erosion processes for engineering deposits.