Abstract: To investigate the collapsibility of loess in long-distance water conveyance projects in Xinjiang, comprehensive field monitoring experiments were carried out. The experiments assessed the collapsibility, moisture content, and void ratio of channel foundation loess at various burial depths, using collapsible loess from the Ili River long-distance water conveyance project in Xinjiang as the research subject. Detailed analyses of the spatial distribution patterns of loess collapsibility within the channel foundation loess were conducted. Concurrently, laboratory-based self-weight collapse tests and immersion compression tests were performed to quantitatively evaluate the collapse characteristics and pore structure of undisturbed loess across different moisture levels. By integrating scanning electron microscope (SEM) and particle and crack image recognition systems, the study explored the relationship between the collapse characteristics and the internal microscopic pore structure of undisturbed loess under varying collapse frequencies and vertical stress conditions. The results show that: (1) The collapsibility of the loess in the water transport channel is primarily controlled by the moisture content. Lower moisture content correlates with more pronounced micro-pore structure characteristics and greater collapsibility deformation, indicating a certain level of “residual” collapsibility. (2) The collapsible deformation process of loess exhibits particle softening and polymer effects, leading to a gradual decrease in pore structure and significant collapsible deformation. The characteristics of collapsibility deformation are more pronounced in a low moisture content state. (3) The collapsibility of loess in long-distance water conveyance channels gradually decreases with increasing burial depth. Additionally, the collapsibility of loess in the canal base occurs multiple times, being greater in the early stages and smaller in the later stages.

Key words: long distance channel, undisturbed loess, collapsibility, moisture content, microstructure, damage