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 influences of seasonal precipitation, the groundwater levels along the banks of rivers and lakes undergo periodic changes. The 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 is used to evaluate the migration and sedimentation characteristics of particles under water level fluctuations. The results show that for the same fluctuation range, the continuous rise in the water level causes the number of suspended particles undergoing migration in the pore channels to increase. The horizontal diffusion becomes increasingly obvious, which drives the suspended particles to roll or move in the pore channels and increases 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 the smaller particles are injected, the overall concentration and peak value of the effluent also increase with the increasing fluctuation amplitude. Larger and smaller particles show opposite trends.