The Safety Control Technology of the Blasting Construction of the Tunnel in Close Distance with the Historic Site

In order to reduce the safety threat of tunnel blasting construction to sensitive buildings such as adjacent monuments, based on the new Shibangou No.1 highway tunnel project, through on-site monitoring and numerical simulation, the vibration reduction law of different cutting hole types and propagation medium parameters on adjacent monuments is revealed. By monitoring the whole section blasting construction stage of the upper bench, it is found that the main factor affecting the peak vibration velocity of the control point is the cutting hole blasting, and the horizontal vibration velocity V_R in the temple is significantly larger. V_R reaches 0.961 cm/s at the blasting section about 60 m away from the temple, which is about to exceed the safety limit of 1.0 cm/s. It is suggested to adjust the blasting scheme with 60 m as the dividing line. In order to take into account the construction efficiency and blasting vibration reduction, the numerical simulation is used to study the construction parameters of the cutting type and the step method. The analysis shows that the influence of the cutting type and the inverted arch excavation on the control point is sectional. The inclined hole cutting type, the timely excavation of the inverted arch, the increase of the step length and the step height can reduce the peak vibration velocity of the control point by 0.071 cm/s, 0.039 cm/s, 0.097 cm/s and 0.065 cm/s, respectively. In order to ensure the smooth progress of the project, the three-section small pilot tunnel first blasting construction scheme and related auxiliary shock absorption measures are finally proposed, which effectively controls the vibration impact of tunnel blasting on ancient sites.