Investigation of suspended particle size effects on clogging of soil filters under laminar flow

Soil filters that are commonly used to stabilize base soils in infrastructures are gradually prone to microparticle accumulation. Sequestration and accumulation of suspended solid particles in fluid on the media surfaces of the filter lead to porosity and permeability reduction through the porous medium and cause physical clogging. This reduces hydraulic conductivity and eventually filters drainage capacity. This study evaluated the reduction in hydraulic conductivity and porosity of a soil filter with sand bed (average diameter 3.55 mm) affected by suspended particles in the fluid of silica and with the average sizes of 4, 20 and 40 microns with a concentration 1 g/L. Results show input suspended particle size has been effective on the reduction rate of the hydraulic conductivity and larger microsilica particles reduce hydraulic conductivity and porosity particularly in early days of filtration more rapidly. For the 4, 20 and 40-micron microparticles, the pressure drop is stabilized after 14, 10 and 7 days, respectively. The average stabilized values are 540, 1460 and 1200 Pascal, respectively. Pressure drop increase during the operation of the soil filter shows that hydraulic conductivity and porosity in porous media is reduced under different circumstances of input microsilica particle size.