Evaluating Spatial-Temporal Clogging Evolution in a Meso-Scale Lysimeter

When surface water infiltrates soil, the fine soil particles carried in water gradually clog soil pores and form a low-permeability soil layer. Clogging impacts the variations in pore water pressure heads in soil and effective hydraulic conductivity. However, few studies have connected field measurements of pore water pressure heads to clogging in soil. This study proposed a diagram to demonstrate the relationship between the normalized pore water pressure head (lambda) and effective hydraulic conductivity (K-eff) based on a conceptual 1-D vertical infiltration model. The coevolution of lambda and K-eff indicated the occurrence of clogging and its location relative to the pore-pressure measurement point. We validated the lambda-K-eff diagram based on a series of numerical simulations of infiltration experiments in a lysimeter. The simulation results showed that the proposed diagram not only indicated the occurrence of clogging but also the development of the unsaturated zone beneath the upper clogging layer. Furthermore, we used a diagram to analyze the spatiotemporal changes in permeability in a lysimeter during three cycles of physical infiltration experiments. The experimental data presented with lambda-K-eff diagram indicated cracking on the soil surface, and clogging gradually developed at the bottom of the lysimeter.