Rainfall Infiltration Test and Numerical Simulation Analysis of a Large Unsaturated Soil Slope

Rainfall infiltration is the primary factor affecting slope stability, which may lead to geological hazards such as landslides, collapses, and debris flows. Thus, it is crucial to investigate the rainfall infiltration patterns of unsaturated soil slopes. During a natural rainstorm, the soil volumetric water content at various depths of a significant unsaturated soil slope model was monitored onsite. The soil-water characteristic curve parameters and saturated permeability coefficient of remolded soil were quantified, and the Van Genuchten (VG) model was utilized to forecast the unsaturated permeability coefficient. The numerical simulation method was used to simulate the field rainfall experiment. Based on the mutual verification of the field measurement and numerical simulation, rainfall simulation with different rainfall intensities was added, and its influence on rainfall infiltration depth, pore water pressure, and transient saturated zone was analyzed. The findings revealed that under the rainstorm intensity of the field rainfall test, the rainfall infiltration depth ranged from 0.2 to 0.4 m after a continuous 9-h rainfall period. As the rainfall intensity increased, the range of soil pore water pressure variations expanded, with a maximum value ranging from 9 to 140 kPa under the rainstorm rainfall intensity. By extending the duration of rainstorm rainfall intensity to 14 h, the depth of the transient saturated zone reached 0.2 m. With a duration of 20 h, it reached 0.4 m. The depth reached 0.6 m after 27 h and 1.5 m after 36 h. The research findings of this paper can provide scientific guidance for revealing the hydrological characteristics of slopes during rainfall and for the protection and reinforcement of slopes.