Experimental Study on Failure Mechanisms of Steep Loess Fill Slopes with Large Gradient

To explore the influence of steep slopes on the deformation and failure mechanisms as well as instability modes of loess-filled slopes under rainfall conditions, this study conducted indoor simulated rainfall experiments, combined with matrix suction sensors, moisture content sensors and 3D laser scanning technology for research. The results showed that under rainfall, the water movement rate of steep fill slopes follows the pattern of shoulder > toe > middle of the slope, and the moisture content exhibits a "stable-rapid increase-stable" trend. The slope destabilization induced by rainfall exhibits hysteretic nature. Under the same rainfall intensity, the steeper the slope, the shallower the slide surface, the smaller the critical rainfall amount for landslide initiation, the quicker the landslide onset, the smaller the landslide volume, and the higher the landslide probability. The failure mode of the 45° slope is "toe collapse-deep-seated creeping cracking failure", while that of the 60° slope is "slope shoulder collapse-multi-stage retrusive failure". This study provides theoretical references for the engineering construction and landslide disaster prevention of steep loess-filled slopes.