Effects of the Rainfall-Triggered Lisse Effect on the Stability of Loess Slopes

This paper coupled a water-air two-phase hydrodynamic (WATPH) model with the Iverson’s method to analyze the influence of the Lisse effect on the fast groundwater pressure (P_w) response and the slope stability. Furthermore, the sensitivities of the driving force and loess soil parameters were investigated. Results showed that the WATPH model simulated the height and rise of the depth to the water table reasonably well. The depth to water table before rainfall (H₀) had a significant impact on the Lisse effect and the slope stability. When the H₀ was less than approximately 1 m, the rainfall triggered a significant Lisse effect and decreased the slope factor of safety (F_s). When the rainfall intensity (R_i) was higher than the saturated hydraulic conductivity (K_s), the Lisse effect and the Fs slightly changed with the increase of the R_i, and the slope tended to be unstable with continuous rainfall. With increasing K_s, the Lisse effect noticeably increased, and the minimum F_s quickly decreases. The analysis of the normalized sensitivity coefficient revealed that H₀ had a dramatic impact on the Lisse effect and loess slope stability. The different R_i and K_s values had prominent influences on the Lisse effect and slight impacts on F_s.