Impact liquefaction mechanism of sandy silt with a change in impact energy

The impact liquefaction of sediments in the path of a landslide would reduce the friction of the sliding surface, leading to an increase in the speed and distance of the landslide. In this study, a self-designed impact-liquefaction test was used to explore the pressure development of soil under the effect of different impact energies. The microscopic mechanisms were unravelled by using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) methods. The results show that soil at the middle depth shows a higher porewater pressure than at the top and bottom of the layer. Furthermore, the variation in the porewater pressure in these parts is relatively stable, and the peak pressure linearly increases with impact energy. The collapse of large pores in sandy silt is the primary reason for the generation of high porewater pressures in sandy silt. But when the soils are high-energy impacted, the mesopores and small pores are compressed and blocked, which also stimulates the porewater pressure. The results also demonstrate weak drainage behaviour of sandy silt under conditions of rapid impact. If the impact energy is sufficient, the porewater pressure in sandy silt suppresses dissipation, causing quick liquefaction in the interior of the sandy silt.