Microstructure change of loess soil during wet collapsing

Loess soil is a problematic soil which exhibits collapse property when saturated with water. This paper tends to provide direct evidence quantitatively describing the microstructure change in loess soil during different stages of collapse. Malan loess soil (Q3) was sampled and compacted to various densities to poses different collapsibilities. Elevated volumes of water were added to the specimens with the same density to establish the correlation between wetting deformation and saturation degree. All specimens were tested by Scanning Electron Microscope (SEM) and Mercury Intrusion Porosimetry (MIP) to investigate the microsturcture change during different collapsing stages. Test results indicate that under certain pressure the void ratio of loess soils specimens, even though with different initial densities, decreases exponentially with the increase of saturation degree, and finally become to be almost the same. The specimens with lower density are characterized by a microstructure that most of pores size is greater than that of the particles size, and the adjustment of these big pores during wetting is responsible for the strong collapsibility