Multiscale characteristics of the wetting deformation of Malan loess in the Yan’an area, China

Abstract

Loess is prone to collapse upon wetting due to its open metastable structure, which poses a considerable threat to the environment, construction processes and human life. In this study, double oedometer tests and scanning electron microscopy and mercury intrusion porosimetry analyses were conducted on loess from Yan’an to study the macroscopic and microscopic characteristics of loess wetting deformation and the underlying mechanism. The wetting collapse of loess under loading depends on the changes in different microstructure levels and elements. This collapse chain reaction is manifested by the dissipation, scattering and recombination of the cementation, deformation and reorganization of the particles, blocking of the pore channels, decrease in the dominant size and volume of unstable macropores (>14 µm) and abundant mesopores (2.5–14 µm), increase in the volume of small pores (0.05–2.5 µm), and volume contraction at the macroscale. This process is dependent on the initial water content, stress level and wetting degree. These findings can facilitate collapsible loess hazard prevention and geological engineering construction.