The erosion of cohesive soils is regarded as one of the major threats to the failure of earth structures. The current evaluation of clay erodibility is primarily based on empirical correlations with other physical and mechanical soil properties, which lack a fundamental understanding of multiscale resistance formation under complicated environmental conditions. In this study, the hole erosion test (HET) was conducted using our augmented testing system, which includes sample preparation equipment and a temperature control unit. The kaolinite specimen is prepared following the saturated preconsolidation approach under defined stresses, which significantly improves the test repeatability. In total, 33 specimens are prepared and tested using the enhanced HET system under varying preconsolidation pressures, temperatures, and fines contents with triplicates for each case. The erosion resistance of clay increases with the preconsolidation pressure, and macropores are destructed into micropores, as revealed by the mercury intrusion porosimetry (MIP) test and the specific surface area analyzer. The scanning electron microscopy (SEM) images indicate an anisotropic aggregate structure prepared using the preconsolidation approach, which possesses different erodibility indices in different flow directions. With the increase in temperature from 10 degrees C to 40 degrees C, the critical shear stress decreases from 292 to 131 Pa (or by 55.1%). The addition of quartz sands in the kaolinite clay undermines the soil erosion resistance.

The erodibility of clay exhibits significant variability across different influencing factors. The existing research using compaction approach for specimen preparation neglected the non-uniformity in soil specimens and is unsuitable for high plasticity clay. In this study, the saturated preconsolidation approach was used to prepare uniform kaolinite specimens to simulate natural consolidating conditions. The prepared specimens were then analyzed using a hole erosion analyzer, and the surface morphology of the eroded hole was quantified using a 3D scanner. A total of 18 hole erosion tests were conducted under various preconsolidation pressures and erosion directions. The erosion resistances were found to increase with higher prestress, and the variation of critical shear stress across different erosion directions reached 29%. The SEM images reveal a stack-packing microstructure in the consolidated specimens, with a denser clay aggregate packing observed under higher pre-stress conditions. The anisotropic erosion property is properly described by the radial anisotropic coefficient kr and the roughness anisotropic coefficient k(pr), and the critical shear stress tau(c) is negatively correlated with k(r), while its correlation with k(pr) is not obvious.