Meso-Structural evolution and erosion mechanisms of soil-structure interface explored via In-Situ CT scanning

Abstract

Compared with the surrounding soil matrix, the soil-structure interface (SSI) serves as a preferential seepage pathway, exhibiting heightened erosion characteristics. Despite its importance, the mechanisms underlying seepage and the meso-structural changes during SSI erosion are inadequately understood. In this study, a miniature triaxial permeameter is integrated with in-situ computed tomography (CT) scanning to investigate the erosion mechanisms and critical hydraulic criterion across various confining pressures, fine-grain contents, and interface roughnesses. We analyse meso-structural evolution through pore geometric, morphological, and topological parameters, providing direct visualization and quantification of particle erosion and clogging. Our findings reveal three distinct erosion patterns influenced by the confining pressure and fine-grain content. Notably, increases in hydraulic conductivity correlate with increased pore size, fractal dimension, and coordination number, alongside reductions in the sphericity index and aspect ratio of pore throats. This study provides mesoscopic structural evidence, obtained through in-situ CT scanning, that demonstrates that temporary clogging significant contributes to fluctuations in hydraulic conductivity. Furthermore, we propose a progressive four-stage mechanistic model with governing equations for SSI seepage erosion failure, including particle detachment, fluidized particle transport, localized temporary clogging, and dominant seepage channel formation until failure.