Study on Precise Delay Time Technology and Application of V-Cut Blasting in Tunnel Excavation

To reduce the vibration intensity of wedge-shape excavation blasting in tunnel, the precisely controlled delay time technology of tunnel V-cut blasting was proposed based on the Mohr-Coulomb strength criterion, the maximum tensile stress, and Anderson superposition theory. Firstly, the mechanism of segmental blasting of V-cut is revealed through theoretical analysis. Secondly, the function of blasting vibration waves was obtained by fitting the Gauss function. Finally, the precise delay time of reducing blasting vibration was obtained by superimposing different delay times with Matlab. The results show that: The stepped V-cut blasting improves the free surface conditions of blasting, and weakens the vibration propagation energy by reducing the amount of blasting charge in a single stage. Based on the Qi Jiazhuang tunnel of National Highway 109, the vibration strength of V-cut blasting was reduced by about 60% when the delay time was 13 ms. The engineering practice showed that the relative error between the theory and the field monitoring data was 13.9%, which verified the validity of the technology.