Research on the disintegration characteristics of fissured loess under water–vibration coupling effect

Fissured loess slopes along the railway in the Loess Plateau frequently suffer from disintegration disasters under the coupled effects of rainfall and train vibrations, causing soil collapse that covers tracks and severely threatens railway safety. To reveal the disaster mechanisms, this study conducted water-vibration coupled disintegration tests on fissured loess using the self-developed EDS-600 vibration disintegration apparatus, based on the measured dominant vibration frequencies (12-46 Hz) of the Lanzhou-Qinghai Railway. The influence patterns of vibration frequency (f) and fissure type (t) on disintegration rate (S), disintegration velocity (V), and disintegration velocity growth rate ([Formula: see text]) were systematically investigated, with scanning electron microscopy (SEM) employed to uncover microstructural evolution mechanisms. Results indicate that vibration frequency and fissure type significantly accelerate disintegration: V reaches its maximum at f = 20 Hz, and under the same frequency, V increases with the growth of fissure-water contact area. Under two fissures and f = 20 Hz, V increases by 225% compared to the without vibration and fissures scenario, with the [Formula: see text] value peaking at 137.23% and the synergistic effect index exceeding the single-factor superposition value by 45.99%. Microscopically, water-vibration coupling disrupts clay mineral cementation, reconstructs pore networks, and forms dominant seepage channels, leading to reduced interparticle bonding strength, heterogeneous water film distribution, and stress concentration, thereby inducing fractal propagation of secondary fissures and shortening moisture absorption and softening stages. Combined with unsaturated soil mechanics theory, the study reveals a cross-scale progressive failure mechanism involving simultaneous degradation of matric suction, cementation force, and macroscopic strength. A theoretical framework integrating vibration energy transfer, seepage migration, and structural damage is established, along with a quantitative relation linking vibration frequency, fissure parameters, and disintegration velocity. This provides multi-scale theoretical support for disaster prevention and control of railway slopes and foundations in loess regions.