Dynamic mechanical response of multisource coal-based solid waste backfill considering strain rate effects

To address dynamic stability challenges in open-pit mining, the mechanical response of a novel multisource coal-based solid waste backfill was investigated using Split Hopkinson Pressure Bar (SHPB) and Digital Image Correlation (DIC). Results demonstrate significant positive strain rate sensitivity, where peak stress and strain increase monotonically, exhibiting a dynamic strengthening effect. Energy dissipation analysis reveals that high strain rates shorten the damage accumulation window, causing a transition from localized yielding to through-going brittle fracture. This rate-induced embrittlement is quantified by fractal dimensions increasing from 1.18 to 1.93. Furthermore, a dynamic damage constitutive model based on energy principles and the two-component medium hypothesis was developed. The model agrees well with experimental data, accurately describing the entire process of elastic growth, plastic yielding, and failure softening, thus providing a reliable theoretical basis for evaluating backfill stability under impact loading.