Effect of physical-chemical combined clogging on the permeability of geotextile envelopes for subsurface drainage systems in arid regions

This study conducted particle flow and chemical precipitation experiments to investigate the effect of physical-chemical combined clogging on the permeability of geotextile envelope. The results show that there is a synergistic effect between physical clogging caused by soil particle accumulation and chemical clogging due to salt precipitation. Chemical precipitation exacerbates physical clogging, while physical clogging promotes the formation of chemical precipitation. The chemical precipitates on the upstream of the geotextile envelope binds the particles to each other and to the fibers of the geotextile envelope, while on the downstream, precipitates tends to encapsulate the fibers, with less physical clogging. After combined clogging, the permeability coefficient of the geotextile envelope decreases rapidly with the increasing of the clogging material, and then decreases slowly. When the area density of the clogging material is less than 91.02 g/m², it shows a linear decrease, and then followed by a logarithmic decrease. Physical-chemical combined clogging is more severe than single physical or chemical clogging. After the permeability stabilizes, for the same clogging mass, the decrease in permeability caused by combined clogging is 1.2 times and 2 times greater than that caused by physical and chemical clogging, respectively.