Dynamic Mechanical Properties of Sandstone Weaken Under Multiple Impacts Based on SHPB Experiments

Due to multiple dynamic disturbances caused by mining activities, the internal fractures in the surrounding rock of the roadway continue to expand, resulting in the continuous weakening of the mechanical properties of the sandstone. Based on the split Hopkinson pressure bar (SHPB) tests, this study investigates the dynamic mechanical properties of surrounding rock sandstone under repeated impact loading. Through experiments on the dynamic response of sandstone samples under different impact frequencies and strain rates, the strength degradation and toughness variation during repeated loading were analyzed. The experimental results indicate that as the number of impacts increases, the dynamic compressive strength and modulus of sandstone gradually decrease, exhibiting a pronounced weakening trend. Simultaneously, the failure mode of sandstone transitions from brittle failure in the initial stage to plastic deformation in the later stage, reflecting the gradual destruction and rearrangement of the material′s internal microstructure. The variation in strain rate significantly impacts the degree of weakening, with a more pronounced decline in sandstone strength under high strain rates. The findings reveal that energy dissipation increases significantly due to multiple impacts, suggesting that the long‐term stability of sandstone materials under repeated loads warrants attention in practical engineering applications. This study provides experimental evidence for understanding the mechanical behavior of sandstone under dynamic loading conditions and serves as a valuable reference for related engineering design and safety assessments.