A new approach to evaluation of loess collapsibility based on quantitative analyses of colloid-clay coating with statistical methods

Collapsibility is of critical concern to mechanical properties of loess. It is fully characterised by its micro-structural features and determined by contents and locations of colloid-clay components. However, previous researches on collapsibility are mostly limited to qualitative descriptions when it comes to the colloid-clay effects over loess properties. The very few quantitative studies only consider the overall colloid-clay content as covariate in simple linear regressions. This leaves the research area of quantification of colloid-clay contents and spatial locations based on image analysis blank. This paper made novel application of a robust statistical method to extract the microstructural parameters from SEM scans where silt, colloid-clay and pore structures are satisfyingly segmented. Correlations between collapsibility and each of the microstructural parameters are discussed with the collapsibility behaviour further evaluated based on the spatial distribution of colloid-clay components. Colloid-clay components have the tendency to either fill in the gaps between sharp edges of particles or attach to flat and concave edges to round the particles; this is referred to as shape-surface selective fillings and attachments phenomenon. A simple circularity measurement is novelly introduced to justify such phenomenon with support of statistical hypothesis testings. The results showed robust estimates based on such statistical method in comparison to both experimental outcomes and previous researches. Both pore area ratios and circularity of particles have positive effects over loess collapsibility. The colloid-clay ratio act as a good indicator when describing collapsibility but it should be looked at combing with their spatial distribution. Despite the colloid-clay ratio presented adverse effect on collapsibility, more evenly distributed colloid-clay components prove the reasonableness in mechanism of loess collapsibility. This paper successfully provides a image segmentation method which allows one to draw connections between loess microstructural properties to collapsibility. It reveals the loess macro-behaviours from the internal structural perspective. Such application is also easily adaptable to other properties in future studies.

Automated summary

The critical concern of collapsibility in loess lies in its micro-structural features, particularly the colloid-clay components. Previous research has been mainly qualitative with limited quantitative analysis, leaving the area of quantification of colloid-clay contents and spatial locations blank. This paper introduces a robust statistical method to extract microstructural parameters from SEM scans and explores correlations between collapsibility and these parameters, revealing positive effects of pore area ratios and particle circularity on loess collapsibility, as well as the importance of colloid-clay ratio and spatial distribution in describing collapsibility.