The model tests of rainfall infiltration in two-layer unsaturated soil slopes

Rainfall infiltration experiments were conducted on an unsaturated slope consisting of two-layer soils. The water content and the pore-water pressure in the slope were monitored. The monitored data are analysed and discussed in the paper. The analysis indicates that the water content and the pore-water pressure in the model slope change with the depth and that their change conditions are related with the physical properties of soils. These characteristics are different from single-layer slope significantly. The response time of the water content and the pore-water pressure increases with the slope depth. The water content and the pore-water pressure of the lower layer decrease faster than those of the upper layer. Under the same rainfall intensity, the water content and the pore-water pressure develop with the duration of rainfall until the steady seepage. The response time is quicker when the rainfall intensity is higher. However, the time effect is not significant near the slope surface. The pore-water pressure and water content in the upper layer of the model slope show more marked changes than those in the lower layer. Antecedent rainfall greatly affects the pore-water pressure and water content profiles before the steady seepage state, especially at early stage of rainfall infiltration in unsaturated regions.