Exploring Rock–Explosive Interaction Through Cross Blasthole Pressure Measurements

The detonation of the explosive in a blasthole generates pressure to the tune of several giga-pascals that in turn drives the breakage of rockmass in several complex ways. However, nature and the interactions of such pressure with the surrounding rockmass are not explicitly known. This is primarily due to the destructive and rapid nature of the process that hinders measurements in or around the blasthole. Accordingly, such tests are quite cumbersome, complex and costly. The instrumentation has to have standard specifications with several mega-samples per second monitoring capacity. Also, the sensors deployed for the purpose should have a steep rise time because of the fact that the event is transitory in nature. This may be one of the reasons that the focus of researchers has been on determination of energies involved in the process by indirect means. There have been attempts to understand the blasthole pressure and its interactions with the nearby rockmass but due to expensive nature of testing, the progress is not as anticipated. This study attempted the cross blasthole pressure measurements by placing pressure sensors at a distance from the blasthole. The paper presents some examples of cross borehole pressures measured in varied type of rock masses with a good range of acoustic impedance of the rockmass and its joint spacing. Attempt has been made to explain the pressure traces with the aim that further studies in this domain will lead to better understanding of rock–explosive interaction. The method is quite in infancy and it is expected that future studies shall aid in standardisation of the method thus developed.