Dynamic characteristics and safety control of mortar bolts under tunnel blasting vibration loads

Mortar bolts are an important part of the tunnel support structure, and tunnel blasting can cause vibration hazards to the existing bolt support structure. According to the theory of blasting elastic wave theory, a dynamic mathematical model of bolts mortar bolts considering initial surrounding rock stress was established. Based on the blasting excavation example of the Longnan tunnel of a high-speed railway from Ganzhou to Shenzhen in China, the blasting dynamic response characteristics of mortar bolts in 0 -3 days, 3 -7 days, and 7 -28 days curing time under the blasting excavation of Classification-II, Classification-III, Classification-IV, and Classification-V surrounding rock were calculated and studied. The dynamic failure mechanism of mortar bolts with different curing time under blasting vibration was clarified. According to the limit axial force of the mortar bolts, the blasting safety distance and vibration velocity of the tunnel mortar bolts support structure was proposed.