This study focuses on the blast pressure characteristics of small-scale blasting in rescue work. It was found that the peak overpressure at the borehole side was larger than that at the back side in the single-charge experiments. The peak overpressure for a Type A fracture, which created a crater only at the borehole side, was larger than the peak overpressure of a Type B fracture. Since a Type B fracture generates craters on both sides of the wall, it was expected that more energy would be expended in fracturing the wall than in Type A. However, the peak overpressure at the back side in our experiments was nearly the same in Type A and B fractures.
The effectiveness of a blasting sheet in reducing peak overpressure at the borehole side was evaluated in model disaster scene experiments. The blasting sheet decreased peak overpressure by approximately 80% compared to when no blasting sheet was used, for the largest peak overpressure, occurring at a scaled distance of 3.5m·kg-1/3. We set a safety standard for overpressure in small-scale blasting, based on the results of previous studies. We observed that peak overpressure was much lower than this safety standard when the blasting sheet was used.
blast pressure, small-scale blasting, fracture type, borehole side, blasting sheet