Mechanical properties and damage evolution mechanism of rubber-gangue cemented backfill under different loading rates

Abstract This study investigates the rate-dependent mechanical behavior and damage evolution of rubber-modified cemented gangue backfill through multi-scale macroscopic and microscopic tests. A piecewise statistical damage constitutive model based on the Weibull distribution is established to quantitatively characterize the dynamic failure process of modified backfill. The results reveal that rubber particle incorporation eliminates the critical loading rate effect observed in conventional backfill materials and remarkably improves the ductility of backfill specimens. The compressive strength and elastic modulus exhibit clear loading-rate sensitivity and decrease gradually with increasing rubber content. Both higher loading rate and larger rubber dosage effectively restrain the growth of internal damage variables, allowing the backfill to sustain greater deformation before final failure. Microscopic analysis further indicates that rubber particles expand internal pore distribution and promote progressive crack propagation, which dominates the transition of failure mode from brittle microcracking to ductile macroscopic fracture. The proposed constitutive model accurately reproduces the rate-dependent damage behavior of rubber-modified backfill, providing a reliable theoretical reference for the safety evaluation and engineering application of modified filling materials.