SIMULATION OF TUNNEL PRESSURE RELIEF BLASTING AND ROCKBURST SUPPRESSION BASED ON CDEM

Rockburst disasters during excavation of hard rock tunnels are closely related to the stress state of tunnel surrounding rock. Pressure relief blasting can reduce the stress concentration of surrounding rock mass,which is a direct and effective rockburst prevention and control measure. This paper takes the pressure relief blasting of the rock burst section of the Mountain Mi-Cang Tunnel of Bashan Expressway as an example and carries out the numerical simulation analysis of tunnel step-by-step excavation considering high geostress and rock heterogeneity conditions using GDEM-BlockDyna software. It then takes the pressure relief blasting as the only variable and carries out the numerical simulation comparison analysis of two sets of schemes(whether or not pressure relief blasting is carried out). It uses the microseismic monitoring data and tests the effect of pressure relief blasting on the surrounding rock of the tunnel. Under the condition of surrounding rock pressure relief blasting,the stress concentration of the surrounding rock and the degree of damage are reduced,and the rockburst risk is suppressed. Comparing the two sets of simulation results,the damage is concentrated on the vault and the arch bottom. The damage radius ratio(pressure relief/non-pressure relief) is 3.4 times at vault and 1.47 times at arch bottom. The damage volume ratio(pressure relief/non-pressure relief) is 5.36 times. But the maximum damage value of the area is reduced from 1((no pressure relief) to 0.6 pressure relief). The peak stress of the surrounding rock is reduced by about 5 MPa. The stress gradient is reduced by 0.8 MPa/m. These results indicate that the surrounding rock is still self-stability and the risk of rockburst is reduced. The relevant results can provide a theoretical basis for the implementation of pressure relief blasting and reasonable design of pressure relief blasting in the surrounding rock section of tunnel high ground stress.