Numerical Simulation Study Of Rock Mass Damage Effect Under Explosion Load

As one of the more widely used construction technologies in China’s infrastructure construction projects,blasting technology has shown its superiority in projects such as mine,highways,railways,and tunnels that require a large amount of earthwork excavation work.Smooth blasting technology is one of the commonly used excavation methods for tunnel blasting construction.Reasonable parameter design and construction methods can effectively reduce construction costs and increase economic benefits.Blasting excavation must meet the requirements of rock mass crushing and reduce the damage to surrounding rock.Therefore,the damage effect of rock mass under blasting load is studied,so that the blasting project can estimate the rock mass impact of the blasting operation at the beginning of the design.The scope of influence is of great significance for a reasonable assessment of the safety status of the reserved rock mass.In this paper,the HJC material model is selected as the theoretical model for numerical calculation of blasting damage of rock mass by comparing several damage models commonly used in current research.Meanwhile,the blasting effect in rock mass is analyzed.According to the Acoustic Approximation Principle and Mises stress criterion,the calculation formula of the damage range of rock mass is deduced.The damage range is 0.15-0.8 m in the radius of crushing area and 0.95-1.7 m in the radius of fracture area.Taking the tunnel blasting project in a certain area in southwestern China as the background,using ANSYS/LS-DYNA numerical simulation analysis software to establish a blasting damage model,study the damage development process of the rock mass near the blast hole,and analyze the damage caused by uncoupling coefficient,charge structure and guide hole,it is concluded that:(1)with the increase of the blast center distance,the damage degree of the rock mass decreases with an “S” curve.The increase of the uncoupling coefficient reduces the damage range;(2)the damage range of the eccentric side of the eccentric uncoupled charge is about twice that of the non-eccentric side,and the peak stress of the eccentric uncoupled charge is about 1.5 times of the center uncoupled;(3)the stress concentration effect of the pilot hole is mainly manifested in the direction of the connection ofthe two holes,and the maximum increase in stress is 53% compared with the non-guide hole.Analyze the numerical simulation results and calculate the damage range.the radius of the crushing area is 0.4-1.1 m,the radius of the fracture zone is 1.05-1.6 m.Comparing the damage range calculated by numerical simulation,theoretical calculation and empirical formula,the difference between the calculation results is small,which verifies the accuracy of the theoretical and numerical simulation methods.Based on the peak particle vibration velocity,three methods are used to determine the critical value of the rock mass blasting damage particle peak vibration velocity,the peak velocity of the former two is twice that of the latter,which is in line with the damage threshold of intact rock mass 63-100 cm/s.