Study on movement characteristics and occurrence mechanism of seismic-induced high-position landslide debris flows

High-position landslide debris flows triggered by earthquakes frequently occur in the southwest mountainous areas of China. The research on the high-speed and long-distance movement characteristics and mechanisms of such landslide debris flows is crucial for disaster early warning and prevention. This study focuses on the high-position rockfall-landslide debris flow in Luding County, Sichuan Province, and uses a combination of field investigation, rheological testing, and numerical simulation to reveal the rheological properties and catastrophic mechanisms of landslide debris flows under seismic loading. The results show that with increasing water content, the storage modulus (G′) and loss modulus (G′′) of the debris-flow soil significantly decrease, and shear-thinning is more pronounced at low water contents. High-frequency vibration (>10 Hz) suppresses the solid–liquid transformation of the soil, while low-frequency vibration (<1 Hz) accelerates its liquefaction. As frequency increases, the dependence of yield shear strain on water content decreases significantly. Also, as water content decreases, the dependence of yield shear strain on frequency lessens. Numerical simulation using RAMMS (Rapid mass movement simulation) shows a high overlap rate of 92.3% between the simulated debris-flow movement and the actual disaster-affected area, confirming the model′s reliability. The study indicates that seismic loading reduces the shear strength of the soil, increases pore-water pressure, and causes particle rearrangement, thus lowering the critical conditions for debris-flow initiation. The findings provide a theoretical basis for early warning and prevention of high-position landslide debris flows triggered by earthquakes.