During tunnel blasting excavation in water-rich layered rock masses, blasting vibrations can readily induce severe over-excavation. To investigate the disturbance of vibration loads on layered rock masses, this study assumes layered rock as a viscoelastic composite material and proposes a constitutive model for impact damage differentiation in layered rock based on viscoelastic theory. By integrating impact dynamics tests, we analyze the synergistic influence of layered structures and hydro-mechanical coupling on impact damage differentiation. The results show that as the layered inclination angle increases, the difference in impact damage variable D between the soft interlayer and hard rock layer expands significantly, and the main crack of impact failure in layered rock gradually shifts from the direction of the impact loading toward the direction of the soft interlayer. The soft interlayer becomes softened upon water saturation, in this zone with D = 1 that is prematurely under impact loading. With increasing layered inclination angle, the impact dynamic strength of layered rock initially decreases and then increases, reaching a minimum at 60°. The enhancement effect of hydro-mechanical coupling on this dynamic strength progressively diminishes. The greater the impact loading, the higher the dynamic strength of the layered rock, and the more cracks are generated. The critical strength of impact failure increases when D = 1. The results offer theoretical foundations for efficient blasting rock breaking and precision control of vibration damage zones in layered rock masses, with implications for engineering safety and efficiency in tunnel construction. However, this study primarily focuses on the effect of layered angle and does not account for the spatial distribution of layered structures or the thickness of soft interlayers.
Tao et al. (Thu,) studied this question.