Retention and transport behavior of silicon micropowder in sand under periodical water level fluctuations

Due to the regulation of large-scale water conservancy projects and the influence of seasonal precipitation, groundwater levels along the banks of rivers and lakes undergo periodic changes. Water level fluctuation is an important factor affecting the particle migration and sedimentation characteristics in the sand layer in groundwater recharge and other projects. In this study, a self-developed sand test system was used to evaluate particle migration and sedimentation characteristics, under water level fluctuation conditions. The results showed that for the same fluctuation range, the continuous rise in water level caused the number of suspended particles undergoing migration in the pore channels to increase. Horizontal diffusion became increasingly obvious, which drove the suspended particles to roll or move in the pore channels and increased their contact with the porous media, making it easier for the suspended particles to deposit on the surfaces of the porous media or in the corners of the pore channels. For different fluctuation amplitudes, when smaller particles were injected, the overall concentration and peak value of the effluent also increased with increasing fluctuation amplitude. Larger and smaller particles showed opposite trends.