Transmission Characteristics of the Macropore Flow in Vegetated Slope Soils and Its Implication for Slope Stability

Macropores in the soil of vegetated slopes greatly affect the rainfall infiltration process. In this paper, a realistic 3D macropore network model of a soil column sample is established by CT scanning. Then, the transmission process of the macropore flow is simulated based on MODFLOW. The results show that (1) the shapes of macropores in the soil contain not only the dominant proportion of the circular tube but also a small proportion of the flake. (2) The velocity of macropore flow has a maximum of up to 0.2~0.3 m/s, which is much higher than that of matrix flow. In every single macropore, the flow velocity is the greatest at the central axis perpendicular to the extension and at the throat along the extension. (3) Due to the development of the macropore network system, rainwater can quickly pass through the soil profile in the form of preferential flow or pipe flow, which shortens the lag time of the peak discharge response to rainfall. This process can free up space for the next recharge, but reduce the overall quality of the soil, laying the foundation for the slope failure. Our work helps to unravel the mechanism of rainfall-induced landslides and promote harmony and sustainable development between humans and nature.