Multiscale Investigation on Erodibility Characteristics of Cohesive Soils through Enhanced Hole Erosion Tests

Abstract

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°C to 40°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.