Blasting damage mechanism and excavation stability of surrounding rock of shallow-buried metro station

Abstract

Given the significant impact of damage on the deformation and stability of surrounding rock in shallowly buried metro stations, understanding the behaviors of rocks, with the blasting vibration effect considered, is crucial. This study examines the blasting damage mechanism, including an analysis of damage factors and radii. The results revealed a nonlinear decreasing relationship between the damage factor and the distance from the blasting source. Hence, equations for the radii of the surrounding rock's crushing and crack zones are established under the influence of blasting shock and stress waves. On-site acoustic testing indicated that the surrounding rock suffers severe damage within a 0–0.6 m range from the blasting source. A damage disturbance zone exists within a 0.7–1.7 m range while the rock remains intact within a 1.7–4.7 m range. The on-site measured radius of the crushing zone differs by 9.59% from the theoretical value, and the crack zone's radius deviates by 16.47%. In addition, a simulation model is developed to investigate the stability of surrounding rock under different rock span ratio (RSR). For shallowly buried, large-span hard rock stations, the findings suggested that with RSR between 0.15 and 0.25, a smaller ratio correlates with increased settlement of the surrounding rock, higher horizontal stress values, and larger plastic zone areas post-excavation, confirming the evaluation index's rationality and scientific validity.