MECHANISM OF COLLAPSIBILITY DEGRADATION OF SALINE COMPACTED LOESS UNDER WETTING AND DRYING CYCLES

In recent years, soil salinization has become more and more serious in the Loess Plateau. It is very important to understand the collapsibility evolution of salinized compacted loess under the action of dry-wet cycles for the safety of local filling engineering. In this paper, the law of collapsibility degradation and its microscopic mechanism of saline-compacted loess during the dry-wet cycle were studied by scanning electron microscope and indoor collapsibility test on the compacted loess with different dry-wet cycle times and content. The results show that the coupling effect of dry-wet and salt erosion makes the loess structure tend to be loose, resulting in the increase of collapsibility coefficient. However, the coefficient of collapsibility growth decreases with the increase of the number of wet and dry cycles, showing slow degradation characteristics. It increases with the increase of salinity, presenting accelerated degradation characteristics. When the salt content is more than 0.5%, the degradation of the salt corrosion collapsibility effect is more significant than the dry and wet cycles. Finally, an empirical model considering both the number of dry-wet cycles and salt content was established to describe the collapsibility evolution of the saline-compacted loess under the dry-wet cycles.