Ground and Air Vibrations Caused by Surface Blasting. Volume 5. Air Vibrations: Monitoring and Predictor Assessment

摘要

Airblasts were monitored at four coal strip mines and at a limestone quarry. Thirty-seven production blasts were monitored with 3 seismographs resulting in 111 complete air pressure records. Instrumentation selection and use is described. Data analysis includes an assessment of the predictability of peak overpressures by means of the cube root scaled distance law. It was found that predictability for the cases studied is not good. An extensive discussion of possible explanations is included. A detailed analysis of the frequency content of the observed airblasts, of considerable importance in evaluation potential annoyance problems, was made for all records. A computer program was written to simulate airblasts induced by multiple-hole blasts. A series of small experimental blasts were detonated and monitored to allow an assessment of the program. It is clear that airblasts, especially when induced by very small charges and monitored at very close distances, are highly sensitive to detonation times. Retrofitting of airblast records occasionally was possible, but considerably improved field work is required to validate or refute the computer model.