In Situ Measurement of Blast Damage Underground by Seismic Refraction Surveys
Disturbed zones of rock exist around explosively excavated underground openings similar to those documented for surface excavations. The seismic refractive technique can be successfully applied underground to accurately determine blast induced damage/disturbance depth. The degree of disturbance within the disturbed zone is a measure of the velocity ratios between disturbed and intact rock. For ideal blasting conditions and configurations, the minimum depth of disturbed rib rock is achieved by the use of fracture control blasting. This is followed closely by pre-splitting, then by smooth-walling and the worst technique is standard bulk blasting. The use of fracture control in small diameter tunnels can reduce blast disturbance to less than 0. 3m, whereas no perimeter protection can result in disturbance depths in excess of 2. 5m (8ft. ) for only 38mm ANFO loaded holes. There appears to be no difference in disturbance depth for rib or pillar rock, using the same excavation technique.
P. N. Worsey, "In Situ Measurement of Blast Damage Underground by Seismic Refraction Surveys," Proceedings - Symposium on Rock Mechanics, CRC Press, Jan 1985.
Research & Engineering Applications in Rock Masses, Proceedings of the 26th US Symposium on Rock Mechanics.
Mining and Nuclear Engineering
Article - Conference proceedings
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