In addition, there are documented occurrences in which the heat from the oxidation of pyrite in the vicinity of the main explosive charge of ANFO (ammonium nitrate-fuel oil mixtures) within the borehole has prematurely detonated holes within a shot.
The case presented in the DOE Working Group report, in which 40,000 lb. of explosives simultaneously detonated at a large western surface coal mine, has illustrated this issue. Sympathetic detonations of such large quantities of explosives are rare; those related directly to the quality and reliability of explosive products or devices are even rarer. However, external geological and environmental conditions that may contribute to sympathetic detonations are of interest for future study.
Research in the area of programmable detonator use as a means of improving the precision of explosive initiation times may be of interest. In reality, however, the improvement of timing accuracies they promise may only marginally improve errors inherent to existing electric and nonelectric detonators. These errors in timing of explosive initiation are currently only a few percent of the design delay times. Resulting marginal improvements may not be detectable at far-field distances.
Nonetheless, the degree of improvement does need to be quantified. Several U.S. companies are developing programmable detonators. They are a few years away from marketing these devices. More field-scale and production tests are necessary to verify the accuracy of the devices. Research in this area may be limited to providing access to mine sites for detonator manufacturers in order to conduct production testing. This is an area of research in which the mining industry should take the lead and coordinate with the explosive manufacturers.
Further research is needed to understand and control the mechanisms associated with planned and unplanned failures. The following two approaches should be considered: (1) controlled tests conducted in the field and analysis of these results using geomechanical principles and models, and (2) an expansion of efforts to record, predict, and analyze unplanned ground failures. These efforts would be beneficial for developing seismic fingerprints of these events, particularly unplanned failures such as bumps and rock bursts. In addition, such research could provide important information for improving mine design and for developing warning systems prior to the occurrence of these failures.
One area of research that could greatly benefit the mining industry is the development of affordable monitoring equipment with a higher resolution level