Research on the Damage and Rupture Characteristics of Surrounding Rock in Slightly Weathered Granite Tunnel and Blasting Technology
In order to solve the problem of drilling and blasting tunnel in slightly weathered granite,the Xin Village Tunnel of the Zhangwu Expressway from Yongding to Shanghang was taken as the research object.Using indoor testing methods,the ultrasonic velocity changes of slightly weathered granite samples before and after blasting were tested,and the characteristics of surrounding rock damage and fracture under the action of blasting were analyzed.Based on this,the blasting process was studied.The results show that the release of a large amount of energy generated by blasting causes damage,cracks,and fragmentation inside the rock mass.After blasting,the initial arrival time of the ultrasonic longitudinal wave in the sample significantly increases,the sound wave velocity significantly decreases,and the amplitude vibration frequency of the wave increases significantly after the initial arrival;the damage factor curve shows an S-shaped monotonically decreasing function with the increase of center distance.According to the decay rate of the damage factor,the damage area can be divided into explosive crushing and rupture zone,explosive damage disturbance zone,and explosive micro disturbance zone;the blasting method of combining long and short peripheral holes can effectively reduce the damage to the surrounding rock caused by blasting impact,with a damage range of about 0.5 times that of the working condition beyond the blast hole,effectively maintaining the integrity of the surrounding rock.
slightly weathered granitetunnel engineeringsurrounding rock damagefracture characteristicsblasting technology
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