Investigation of the collapse potential of Malan loess from different regions on the Loess Plateau in terms of pore size distribution and clay distribution form

Loess microstructure and collapsibility show regional differences on the Loess Plateau. Characterization and comparison of loess microstructure and its evolution during collapse in different loess regions help to better interpret the intrinsic mechanism of loess collapse, while related research is still limited. In this study, the microstructures of loess from Lanzhou (LZ), Qingyang (QY), Hengshan (HS) and Jingyang (JY) were characterized, and pores changes in response to loading and wetting were quantitatively analyzed using micro-computed tomography (mu-CT) scanning and mercury intrusion porosimetry (MIP). The results indicate that inter-particle (aggregate) pores with a size ranging from tens of microns to a few microns are favorable for collapse deformation at a low pressure, the small pores of a few microns provide space for collapse under high pressures. The pore size distribution and clay distribution form within loess considerably influence its collapse potential. Loess with skeleton particles connected by clay bridges, forming concentrated inter-particle pores (i.e., LZ loess), are more likely to collapse at a low pressure. Loess with more clays distributed among particles or as buttresses (i.e., JY loess) usually shows great collapse potential at a high pressure, with the precondition of enough small pores for compaction. The limited pore space in loess (i.e., QY loess with a relatively low void ratio) constrains the collapse potential with pressure. Clay coatings adhering to skeleton particles predominant in loess (i.e., HS loess) have little influence on inducing particle movement and collapse deformation.