Mechanisms of mineralogical transformation and microstructural characteristics of loess during hydrocollapse

This study delves into the mechanisms of mineralogical transformation and microstructural characteristics of loess during hydrocollapse, with a particular focus on the dissolution of carbonates and the hydration of albite. The research reveals that the particle size distribution of loess is strongly influenced by albite hydration, leading to the fragmentation of coarse particles and a redistribution of particle sizes. Carbonates undergo significant dissolution followed by precipitation, with the dissolution rate peaking at the mid-stage of immersion and stabilizing afterward. Albite hydration induces the transformation into secondary minerals such as montmorillonite and kaolinite, with the dominant hydration products shifting over time. The collapse mechanism of Lanzhou loess exhibits stage-dependent characteristics: early collapse is mainly driven by salt dissolution, whereas long-term deformation is dominated by framework reorganization induced by albite hydration. Through a series of dissolution and hydration experiments, along with advanced analytical techniques like XRD, ICP-MS, laser granulometry, and SEM, the study provides a comprehensive understanding of the mineralogical evolution and microstructural changes in loess. This research offers critical insights into the stability and safety of engineering projects in regions with collapsible loess, highlighting the importance of understanding the complex interplay between mineral evolution and the collapse behavior of loess.