Observation of the shock resistance of emulsion explosives in rock blasting
- CANMET Experimental Mine, Val d`Or, Quebec (Canada)
- ICI Explosives Group Technical Centre, McMasterville, Quebec (Canada)
- ICI Australia Operations Pty Ltd., Kurri Kurri, New South Wales (Australia)
- ICI Explosives USA Inc., Tamaqua, PA (United States)
Laboratory studies have indicated that the crystallization and desensitization of microballoon sensitized emulsion explosives start immediately after shocking or pre-compression. However, the question of whether or not the shocked emulsion could be worsened by the growth of crystallization or recovered by rebounding back to lower densities has been rarely examined under actual rock blasting conditions. This study was primarily intended to investigate the desensitization characteristics of two commonly used emulsion products in terms of blasthole spacing and delay duration. In the experiment, two parallel blastholes, 32 mm in diameter and 1.7 m deep, were drilled downwards in an underground drift. Full coupling was achieved by tamping the explosives in the wet holes. The donor hole was always loaded with the same explosive while changing the explosive in the receptor hole. The receptor hole is initiated with a delay following the donor hole in order to observe the timing effect on the explosives being shocked. High frequency vibration monitoring was used to identify the detonation or failure of the receptor hole. The spacing was varied to modify the shock pressure the receptor charges are subjected to. Dynamic pressures in the receptor hole were also measured at different distances from the donor hole. The shock resistance was measured by the minimum spacing without desensitization. In general, the Superfrac{trademark} exhibited better shock resistance than Magnafrac{trademark}. The shock resistance of both emulsions was not affected by delay times. The delay-independence of tested emulsions indicates that the crystallization of emulsion may happen immediately after the shocking, however, the shocked emulsion is not worsened, nor recovered. The observation results also give the typical spacing values for field consideration to avoid the problems of explosives malfunction with the use of either long or short delay detonators.
- OSTI ID:
- 398344
- Report Number(s):
- CONF-9502142--
- Country of Publication:
- United States
- Language:
- English
Similar Records
A laboratory study of explosives malfunction in blasting
Explosives malfunction from sympathetic detonation to shock desensitization