Study on Damage Evolution Law of Rock Under Multi Hole Millisecond Blasting
At present,the drilling and blasting method is mostly used in the excavation of mountain tunnel,but the phenomenon of over excavation and under excavation and serious damage of surrounding rock will inevitably occur during the blasting construction,which will directly affect the construction safety.Through the establishment of constitutive model and finite element analysis software ANSYS/LS-DYNA,the blasting crack law under different joint fissure angles and the evolution law of rock damage under hole-by-hole initiation and interval blasting sequences as well as different millisecond interval times are studied.It is concluded that the rock fragmentation effect is poor when the joint fissure and the center line of blast hole are at an angle of 60°～90°,and the rock fragmentation effect is best when the joint fissure and the center line of blast hole are at an angle of 45°;under the condition of interval initiation,the propagation length of the blasting crack initiated first in the middle hole is relatively uniform,which can be applied to the auxiliary hole to facilitate rock fragmentation and reduce the rate of large blocks.It provides a technical reference for the actual tunnel engineering.
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