Structural dynamic constitutive model of uncompacted saturated loess based on experimental results

Uncompacted saturated loess retains its residual pore structure without artificial compaction, making it highly sensitive to environmental changes such as dehydration-rehydration cycles. This study investigates the dynamic characteristics of uncompacted saturated loess in the Xi'an area, where infrastructure projects are commonly affected by the soil's instability. Dynamic triaxial tests were conducted under varying confining pressures and dehydration-rehydration cycles to examine the dynamic stress–strain relationship, dynamic modulus, and damping ratio variation. The methodology involved multi-stage loading using dynamic triaxial equipment, with cycles of drying and rehydration applied to replicate field conditions. A hyperbolic tangent function was used to model the dynamic stress–strain behavior, and structural parameters m1​ and m2​ were introduced to quantify the soil's stability and variability. Key findings show that dynamic stress increases with dehydration-rehydration cycles, while dynamic modulus and damping ratio decrease, especially during the initial cycles. The results provide critical insights into the behavior of uncompacted saturated loess under dynamic conditions, offering practical guidelines for managing soil stability in infrastructure projects across the Xi'an region.