水位波动下砂层中颗粒运移及沉积特性试验研究

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

受大型水利工程调控及季节性降水影响,江河湖沿岸地下水位呈现出周期性变化规律,水位波动是地下水回灌等工程中影响砂层中颗粒运移及沉积特性的重要因素。通过砂层迁移-沉积试验系统开展了颗粒迁移-沉积特性试验,并采用浊度-浓度关系、穿透曲线、颗粒粒径、沉积量、流出液颗粒粒径分布、孔隙水压力及细观观测等方式实现了从宏观到细观、从定性到定量分析颗粒的迁移-沉积规律。结果表明:在相同的波动幅度下,随着水位的不断升高,悬浮颗粒横向上扩散的趋势愈加显著且渗透力作用逐渐增强,颗粒更容易沉积在多孔介质表面或孔隙通道角落中;在不同波动幅度下,注入小粒径颗粒时,随着波动幅度增加流出液浓度及峰值增大,大粒径颗粒与小粒径颗粒呈现相反规律;在相同尺寸的多孔介质中,悬浮颗粒粒径越大相对浓度峰值越低,大颗粒在孔隙中更容易由于筛滤作用发生沉积,从而造成多孔介质孔隙率和渗透性降低。

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.