**6. Results and Analysis**

## *6.1. Speed Analysis*

Using the DAN-W software and the Frictional–Voellmy–Frictional model, the total time of the Panjinbulake loess landslide movement was 22 s. It is assumed that the speed of the landslide was 0 m/s when starting in the sliding source area. The sliding body started from the shear exit (i.e., the leading edge of landslide). Due to the steep slope of the landslide, the speed was very fast, reaching 5 m/s very quickly (Figure 7). Under the action of gravitational potential energy, the speed of the sliding body increased rapidly and reached 21.5 m/s at X = 200 m. This process lasted 7 s, and the average acceleration reached 2.3 m/s2. The sliding body moved from X = 200 m to X = 320 m in debris flow area. This area has exposed spring water (Figure 5), which provides suitable hydrogeological conditions for high speed movement of the sliding body. Thus, the sliding body was always in a high speed state. This phase lasted 8 s. The average speed reached 20 m/s and the sliding body entered the river terrace. Due to the friction of sandy gravel and gradual decrease of the slope, the moving speed of the sliding body dropped sharply, and the speed relative to the opposite mountain was 17.5 m/s. Due to the blocking of the opposite mountain, the sliding body stopped at a horizontal distance of X = 370 m, and the average acceleration in the deceleration phase reached <sup>−</sup>3.6 m/s2, which lasted for 7 s.
