不同浓度悬浮物颗粒在多孔介质中迁移特性研究

多孔介质中悬浮物迁移特性的研究,有利于减缓实际回灌工程中的堵塞问题,对地下水人工回灌技术的推广具有重要理论意义。采用室内砂柱试验,研究不同悬浮物浓度条件下多孔介质渗透性的变化、悬浮物颗粒在饱和多孔介质中的运移-沉积规律,并分析堵塞发生的机理。本次试验以中位粒径224.2μm的石英砂作为入渗介质并在砂柱中分别连续注入由中位粒径3.24μm的悬浮物颗粒配制而成的三组不同浓度溶液(100 mg·L~(-1)、300 mg·L~(-1)、500 mg·L~(-1))。研究结果表明,在不同的回灌浓度条件下,砂柱内均发生了表面-内部双重堵塞;且随着悬浮物溶液浓度的增加,悬浮颗粒在多孔介质内的迁移量减少,而滞留量却明显增多,但悬浮物浓度对沉积量的影响随着入渗深度的增加而减小;堵塞速率也会随着回灌液浓度的增加而加快;在回灌的初始阶段,多孔介质的渗透性随时间下降幅度很大,随着试验的进行,最终会趋于稳定状态,且越靠近砂柱表层,悬浮物堵塞的程度越为严重。在实际的人工回灌工程中,要尽可能降低回灌液中悬浮物颗粒的浓度,以降低堵塞的风险,保证回灌工程更为长久地运行。

Study on the migration characteristics of suspended particles in porous media during different concentration of suspension

The study of the characteristics of suspended particles’migration in porous media is helpful to reduce the occurrence of clogging in practical recharge engineering and it is of great theoretical significance to the popularization of managed aquifer recharge. In this study，indoor sand column experiment is used to study the change of permeability coefficient of porous media and the migration and deposition law of suspended particles in saturated porous media under the condition of different concentration of suspension，and to analyze the mechanism of suspension clogging. In this experiment，quartz sand with median particle size of 224. 2 μm is used as the infiltration medium and three groups of different concentration solutions ( 100 mg·L － 1，300 mg·L － 1 and 500 mg·L － 1 ) are injected into the sand column respectively，which are prepared by suspension particles with a median particle size of 3. 24 μm. The research results show that under the condition of different injection concentration，blockage occurs both within the surface and inside the sand column. With the increase of the concentration of suspended particles，the migration of suspended particles in porous media decreases，but the retention increases obviously. However，the influence of suspended concentration on the deposition amount decreases with the increase of the depth of infiltration，and the clogging rate also increases with the increase of the recharge concentration. In the initial stage of recharge，the permeability of saturated porous media decreases greatly with time flying，and eventually tends to be stable with the conduct of experiments. Moreover，the closer to the surface of sand column，the more serious the clogging becomes. In the actual artificial recharge engineering，the concentration of suspended particles in the recharge solution should be reduced as much as possible to reduce the risk of clogging and ensure the long- term operation of the recharge engineering.