Cumulative dynamic damage evolution and differentiated blasting control in fractured hydrothermally altered rock masses

Abstract

Fractured hydrothermally altered rock masses around roadway excavations are highly susceptible to repeated blasting disturbance, yet the transfer from specimen-scale cyclic degradation to engineering-scale contour deterioration remains insufficiently understood. To address this gap, this study establishes a cross-scale framework integrating repeated-impact SHPB testing, RHT constitutive calibration, multi-cycle LS-DYNA simulation, field vibration monitoring, and field assessment. The vibration records exhibit pronounced multi-pulse characteristics and site-dependent attenuation. Repeated-impact tests show that the altered ore rock undergoes progressive dynamic degradation, characterized by decreasing peak stress and increasing deformation under successive high-rate loading. The calibrated RHT model reproduces the principal peak-stress degradation trend of the 0.5 MPa calibration dataset, with a maximum relative difference of 4.56%. Multi-cycle simulations further demonstrate progressive accumulation of stress concentration, damage, and contour deterioration under successive excavation cycles. Based on this response, a differentiated charging strategy was implemented to reduce explosive loading adjacent to the retained contour while maintaining sufficient internal rock breakage. A representative field assessment indicates that the estimated loosening-zone extent decreased from 1.36 m to 1.15 m after optimization. The results provide a mechanism-based framework for linking cyclic material degradation with cumulative excavation damage and for guiding low-disturbance blasting in hydrothermally altered rock masses.