Microstructural analysis of collapsible soil before and after collapse and with loading and unloading cycle

Aspects related to the volume variation of collapsible soils due change in water content are influenced by several factors, including microstructure. The microstructure analysis soil is especially important order understand these aspects. This paper shows a comparative three samples Yellowish Red Sand from district Petrolina (northeast Brazil), carried out means two techniques: Scanning Electron Microscope (SEM) and X-Ray Computed Tomography. Three undisturbed sample were used: first no pressure was applied, second an one-dimensional compression 160 kPa applied then unloaded, third, between decompression, flooded with occurrence structural collapse. In sample, matrix predominance grains sand clothed iluvial clay interconnected pores that confers instability. showed reduction macropores after loading. third structure remained simple packing arrangement, however, there greater grains, addition wetting-induced softening particles fill voids. It also observed, through radiodensity at top bottom increase stress relief not observed central section samples. techniques complementary.