Correlation between soil-water characteristic curve and collapsibility in undisturbed loess

This study investigates the correlation between the soil-water characteristic curve (SWCC) of undisturbed loess and its collapsibility. Undisturbed loess soil samples, obtained from depths up to 30 meters below the surface in Chang’an District, Xi’an City, Shaanxi Province, were taken for basic physical index tests and collapsibility assessments. SWCC analyses of loess-paleosol samples from different typical strata were conducted and analyzed using scanning electron microscope. The findings reveal a positive correlation between the number of macropores and saturated volumetric water content. Additionaly, the number of pores is positively correlated with the slope of the transition zone, indicating that a higher pore count accelerates the soil's water loss rate. The number of tiny voids and the plasticity index of soil affect the residual moisture content. For different soil layers, saturated volumetric water content and slope of transition zone exhibit a positive correlation with collapsible coefficient. The influence of collapsible coefficient of plastic index close to soil layer on residual volumetric water content is not obvious. The study also indicates a positive correlation between SWCC and the collapsibility coefficient of the loess layer. By approaching loess collapsibility from the direction of unsaturated soil mechanics, this paper introduces a novel research angle for the study of collapsibility.