Investigation of the fractal characteristics of cumulative damage to tunnel surrounding rock under blasting vibration

Abstract In this work, the cumulative damage effect of tunneling and blasting on the rock surrounding a tunnel is studied. Ground penetrating radar (GPR) is used to detect the damage of tunnel surrounding rock during blasting. and EEMD–HHT transform is used to process the obtained radar signals to obtain an intuitive representation of the damage. The relative relationship between fractal dimension and degree of damage is established to analyze the damage evolution of the tunnel surrounding rock quantitatively. The results show that the instantaneous amplitude parameter obtained by the EEMD–HHT transform could reflect the damage characteristics of the original signal and analyze the characteristics of damage evolution quantitatively. The effect of cyclic blasting causes a great direct disturbance to the area near the blast source and generates new fissures, which could aggravate the damage. The impact of blasting on areas located far from the blast source is mostly manifested as the expansion and penetration of existing cracks. The fractal dimension of the damage area is closely related to the damage evolution of the rock mass; the greater the change in fractal dimension, the more intense the damage expansion and evolution. This study quantitatively analyzes changes in the damage of tunnel surrounding rock through fractal dimensions, enriches the theoretical system of damage evolution in rock masses, and explores a new strategy to study blasting disturbances in tunnel surrounding rock.