Abstract: The damage progression in retained rock masses during high rock slope excavation is attributed to cumulative effects from repeated multi-step blasting. Understanding the damage formation mechanism under frequent blasting disturbances is critical for ensuring slope stability. This study examines the excavation of rock slopes at the Baihetan Hydropower Station. Initially, single-hole and multi-hole acoustic wave tests were conducted on the arch shoulder slope blasting. Continuous assessments of the cumulative damage to the retained rock mass after multiple blasts revealed that, in homogeneous rock slopes, damage primarily originates from blasting at the same step, followed by lower steps. Beyond three to five steps, the influence on cumulative damage becomes negligible due to increasing distance from the blast center. Additionally, the complete restart technology in LS-DYNA was employed to model the excavation of rock slopes on the left bank of the Baihetan Hydropower Station (at elevations between 700 m and 650 m), simulating cumulative damage evolution under five-step cyclic blasting. Results demonstrate that cumulative damage in homogeneous rock slopes exhibits localized characteristics, with the current step accounting for 70%–82% of damage and adjacent steps contributing 10%–20%. Numerical simulations corroborate field data in terms of cumulative damage extent. The blasting damage formation mechanism was analyzed based on strain discrimination. Cumulative damage in high rock slopes results from the combined effects of step-local compression damage, middle/far-area tension damage, and tensile stress induced by blasting stress waves from lower steps. A damage prediction model was developed using regression analysis, correlating blasting frequency with damage severity and depth. The results indicate that the cumulative damage during stepped excavation is closely related only to the current and two adjacent blasting steps. The damage severity in the affected zone exhibits an exponential decay characteristic as the number of blasting load disturbances increases. Consequently, stricter safety control standards for blasting vibrations, accounting for cumulative damage effects, are proposed. Compared to single blasting events, the safety control standards under frequent blasting disturbances are stricter, implying current standards may inadequately ensure safety.

Key words: rock high slopes, blasting load, cumulative damage, evolution, control standards