4.3. The effect of permeability and viscosity
The permeability coefficient and liquid viscosity can significantly affect the frictional behavior of geomaterials as they determine water distribution and flow characteristics in geological disasters.
Figure 5 shows the effect of permeability coefficient and fluid viscosity on friction coefficient at different velocities. The coefficient of friction decreases as the permeability coefficient increases. This is because the larger permeability makes the water flow more easily and widely in granular materials, such as loess, which enhances the lubrication effect and reduces the force between asperities. Similarly, fluid viscosity can hinder its flow and widespread distribution in granular materials. Therefore, the coefficient of friction increases with the coefficient of fluid viscosity.