Influence of permeation effect on the microfabric of the slip zone soils: A case study from the Huangtupo landslide

This study aims to investigate the correlation between the permeation effect and microfabric of the slip zone soils with Huangtupo landslide in the Three Gorges Reservoir as the study case. Based on the permeability test and scanning electron microscope (SEM) images analysis, the fractal theory and probability entropy are used to quantify the characteristics of the remodeling specimens. First, the relationships between initial moisture content (IMC) and microstructure of the soil (percentage of particle area (PPA), pore roundness (Rp)) before and after permeability test are summarized. Then, the fractal dimension of the soil (pore distribution (Dpd), pore size (Dps)) are analyzed under the permeation effect. Based on the probability entropy, the entropy of pore (Ep) is used to characterize the porosity orientation, and the rose diagrams are used to show the particle orientation under the permeation effect. Finally, the relationship between the microstructure of the soil and its mechanical property is discussed. Results show that under the permeation effect, the microstructure of the soil has undergone tremendous changes. A flat long pore channel is formed. The order of the pore arrangement is enhanced, and soil particles switch the long axis to parallel infiltration direction to reach a new steady state. It can be inferred that the strength of soil would be weakened if the fractal dimension of soil pore decreases under any external environment.