Model test studies of damage evaluation of frozen rock wall under blasting loads

Model test studies based on the similarity theory was conducted to solve the safety problem of frozen rock wall in the mines driving with the freezing-blasting method. The model was constructed with a ratio of 1:15. The degree of damage of the model was evaluated by the change of the ultrasonic velocity after blasting. Three velocity sensors were placed in the slot at the top of the model, and the sensors recorded the rock vibrating velocities of the measuring spots during each blasting process. Results show that the vibrating velocity is the largest in the radical direction, medium in the axial direction and the lowest in the tangential direction. The vibration has directional difference. The damage of frozen wall exhibits an obvious cumulative effect, and the damage factors near the blasting holes are larger than those in other places. In the vertical direction, the upper end of the model is damaged most seriously. The vibration of rock satisfies Sadovski formula with the media parameter K = 57.52 and the attenuation coefficient α = 1.74. The largest vibrating velocity is caused by the third group detonators in the differential blasting process, and the velocity of rock vibration is very different in different directions and is the largest in the radical direction, medium in the axial direction and the lowest in the tangential direction.