Mechanism of rainfall‐induced toppling in loess collapses

Abstract

AbstractTo study the formation mechanism of rainfall‐induced soil erosion, collapse and landslides in the Loess Plateau based on the unsaturated soil seepage theory and the effective stress principle, the failure process of collapse with cracks under heavy and long‐term rainfall was investigated using the finite element method. The results showed that under the action of heavy rain, surface run‐off quickly gathered in cracks to form a dominant flow, resulting in a rapid increase in the water level and hydrostatic pressure in the cracks. The strength of the soil at the tip of the crack decreased rapidly under the softening effect of the water, and tensile failure occurred. The crack accelerated downward to the foot of the slope, causing the steep slope to collapse. Long‐term rainfall acts directly on the soil near the crack, resulting in faster saturation than the soil inside the slope body. When the rainfall time exceeded a certain value, the soil near the crack reached a saturated state, and the soil strength was minimized. Simultaneously, the seepage force generated when rainwater inside the collapsed body seeps from its outer edge increases the overturning moment of the collapsed body. Under the continuous action of rainfall, the cracks gradually extended to the foot of the slope, causing the collapsed body to fail. These research results provide a theoretical basis for the prevention and control of land degradation and collapse disasters on the Loess Plateau.