Introduction
The role of gas pressurization in rock fragmentation and flyrock prevention is critical in the context of blasting operations, particularly in mining and construction. Understanding how gas pressure influences these processes can lead to more effective blasting techniques, reducing the risk of flyrock and improving overall safety.
Gas Pressurization Mechanisms
Rock Fragmentation
Gas pressurization occurs during the detonation of explosives, generating high-pressure gases that play a significant role in rock fragmentation. The explosive charge creates a shock wave, which generates stress waves that propagate through the rock. As these waves interact with pre-existing fractures, they can extend and create new cracks, facilitating the fragmentation process [1][3].
Kutter and Fairhurst (1971) highlighted that after an explosion, the remaining high-pressure gas penetrates into the cracked zone around the borehole, forming an “equivalent cavity.” This cavity generates a static stress field sufficient to propagate cracks further, leading to extensive fragmentation of the rock mass[1].
Flyrock Generation
Flyrock refers to rock fragments that are propelled away from the blast site due to explosive forces. The development of excessive gas pressure can significantly contribute to this phenomenon. When gas pressure exceeds the structural integrity of surrounding rock, it can propel fragments over considerable distances[2][4]. Factors such as geological anomalies and inadequate confinement during blasting can exacerbate this issue, leading to unpredictable flyrock behavior[2].
Key Factors Influencing Flyrock
Explosive Energy vs. Rock Strength: A mismatch between explosive energy and the geomechanical strength of the surrounding rock is a primary cause of flyrock. Geological features like fractures or voids can weaken rock integrity, making it more susceptible to being displaced by gas pressure[2].
Stemming Practices:Proper stemming is crucial as it contains high-pressure gases within the borehole during detonation. Insufficient stemming can allow gases to escape too early, resulting in violent fragmentation at the collar zone and increased risk of flyrock[2][5].
Design:The layout and loading of blast holes must consider geological conditions to minimize flyrock risks. Irregularities in blast hole placement or explosive concentration can lead to uneven stress distributions, increasing the likelihood of flyrock generation[2][4].
Conclusion
Gas pressurization plays a pivotal role in both rock fragmentation and the prevention of flyrock during blasting operations. By understanding and managing the dynamics of gas pressure, including its interaction with geological features and proper blast design practices, operators can enhance safety and efficiency in mining and construction activities. Continuous research into predictive models for flyrock behavior will further aid in mitigating risks associated with explosive blasting.
Citations
[1] https://www.saimm.co.za/Journal/v123n12p557.pdf
[2] https://www.cdc.gov/niosh/mining%5C/UserFiles/works/pdfs/fiib.pdf
[3] https://www.sciencedirect.com/science/article/abs/pii/S0032591020312134
[5] https://www.linkedin.com/pulse/flyrock-part-02-03-blasting-trainings
[6] https://www.researchgate.net/publication/250154548_Rock_Fragmentation_Control_in_Blasting
[7] https://www.linkedin.com/pulse/flyrock-part-01-03-blasting-trainings
