渗透作用下多孔介质中悬浮颗粒的迁移过程研究

Transport processes of suspended particles in saturated porous media by column seepage tests

对天然硅粉悬浮颗粒在饱和的石英多孔介质中的渗透迁移特性进行圆柱穿透试验,得到6种不同颗粒粒径(10,15,20,25,33,47μm)、3种不同颗粒浓度(0.2,0.5,0.8 mg/ml)、3种不同渗透速度(0.087,0.173,0.260 cm/s)和3种不同渗透方向(即自上向下,水平,自下向上)的颗粒穿透曲线,重点研究这些因素对悬浮颗粒迁移的水动力学过程、弥散效应、沉积效应等物理机制的影响。研究表明,当渗透速度相同时,颗粒穿透过程中的浓度峰值一般随颗粒粒径的增大而减小。而随渗透速度的增大,水动力学作用对颗粒迁移的影响越来越大,此时颗粒粒径大小的影响则逐渐减小。此外,存在一个临界浓度值,当注入的悬浮颗粒浓度大于该值时,随着注入悬浮颗粒浓度的增大,出流液中的颗粒相对浓度反而有减小的趋势,这与大量的悬浮颗粒进入多孔介质造成多孔介质孔隙的堵塞有关。

The penetration processes of a typical silica powder in saturated porous media composed of quartz sands are studied by column seepage tests. The tests consider 6 kinds of particle sizes（i.e., 10, 15, 20, 25, 33, 47 μm）, 3 particle concentrations（i.e., 0.2, 0.5, 0.8 mg/m L）, 3 flow velocities（i.e., 0.087, 0.173, 0.260 cm/s）, and different flow directions（i.e., downward, horizontal, upward）, etc. According to the test results, the physical mechanisms of suspended particle migration such as hydrodynamics, dispersion and deposition are discussed. The studies show that for the same seepage velocity, the peak concentrations of penetration process decrease generally with the increase of particles size. On the other hand, the effect of hydrodynamic processes on particle transport is increased obviously with the increase of flow velocity while the effect of particle size is degenerated correspondingly. Besides, there exists a critical injected concentration, and beyond this value the relative concentration in the effluent begins to decrease, which is related to the logging of pores of porous media due to a large number of deposited particles.