渗流作用下多孔介质内颗粒迁移与堵塞规律研究

渗流作用下细颗粒在多孔介质中的迁移穿透与堵塞规律对于防止岩土内部侵蚀、提高人工渗滤设施性能具有重要意义。为此,以砾石为填料,基于X-CT技术开展了多孔介质内颗粒在渗流作用下的迁移与堵塞规律研究。研究结果表明,颗粒在多孔介质中的穿透率总体上随着渗流流速的增大而增大,但不同粒径比工况下,渗流流速对穿透率影响呈现出较大差异。通过X-CT扫描发现,小粒径比(d_ss/d_fs)下,颗粒在后期呈现稳定的竖向分布,呈现堵塞状态,而在大d_ss/d_fs条件下,竖向累积截留曲线呈直线分布且持续变化,表明颗粒发生持续穿透。在此基础上,分析了粒径比与渗流流速对颗粒迁移的影响规律与物理堵塞形成阈值,确定了堵塞形成的上下阈值线。进一步通过量纲分析发现,耦合参量(d_ss/d_fs)^2.1Re^~*1.8(tu~*/H)^0.2是预测颗粒穿透率m~*的最佳无量纲参量,并确定了计算穿透率的表达式。

Particle migration and clogging in porous media with seepage

The migration and clogging of fine particles in porous media with seepage are of great significance for preventing the internal erosion of soils and improving the performance of artificial filtration facilities.The migration and clogging in the gravel substrate under the seepage are studied based on the X-CT technology.The results indicate that the migration of particles in porous media generally increases with the increase of seepage velocity,and its influence is significantly different under different particle size ratios.The X-CT results indicate that the particles present a stable vertical distribution in the column and clogging formed under the smaller d_ss/d_fs.However,the vertical accumulative interception curve of particles presents a linear distribution and changes continuously,indicating that the particles penetrate continuously under the higher d_ss/d_fs.On this basis,the threshold whether particles penetrating or clogging is determined.Moreover,the factor of (d_ss/d_fs)^2.1Re^*1.8(tu^*/H)^0.2 is the best dimensionless parameter for calculating the penetration rate of particles,and the relevant formula is developed.