Review of the Effect of Blast initiation Delay Timing on Blasting fragmentation
By Taiwo Blessing Olamide
GIANT MINER
INTRODUCTION
Do you know that;
Explosive energy is higher when the shock energy supply for the initiation is high and accurate.
Also that, most mining operations uses inaccurate blast time and initiation timing. Two things affect Blasting efficiency appart from the blast parameters and rock properties.
These are;
1. the initiation system and
2. the initiation approach.
This article give a brief review on Professor Takis Katsabanis and Nikolaos Gkikizas-Lamptopoupos work.
Professor Takis is an explosive Engineer, lecturer in Queen's university Ontario, Canada.
Prof Takis of Queen's university Canada with one of His master's student Nicholaos Gkikizas worked on a project relating to this in 2016. The Thesis focus on examination of the effect of Time delay on fragmentation.
The project was effectively experiments in the university Rock Excavation Laboratory under the full supervision of Prof. Takis Katsabanis.
The work involved two series of experiments.
First series involved tests on small scale grout and granite blocks to determine the moment of burden detachment. The instrument use for these experiments consist but not limited to strain gauge and Piezoelectric sensors, high speed camera. The result of the first series experiment shows that the time of rock particle detachment for the thesis set up is between 300 and 600 micro second. Meaning, as the Explosive shock wave fractures the rock and the gas energy perf
The major aim of blasting is to detach the rock into handable sizes, the important of studying the detachment time as indicated by Prof. Takis student was to ensure that the burden movement timing is accurately design between inter row and intra row drill holes. Each detachment time affect the fragmentation efficiency of the blasting. The major approach adopted in the thesis was to optimize the charge timing and get the detachment time right for efficient fragmentation.
The second series of the project involved blasting of a 2m high granite bench and it's purpose was to determine the hole to hole delay that will provide optimum fragmentation. Nicholaos Gkikizas worked reflect on this objective by adopting image analysis software for fragmentation efficiency examine for each delay observed. Also, he examine the produce vibration from the blast and also record the blast with high speed cameras such as Olympic i-SPEED 2 camera.
The result of the second series suggest that fragmentation was optimum when delays between 4-6 Ms were used for the experiment set up. It was also found that the moment at which gases first appear to be venting from the face was consistently around 6ms after detonation. In one of my blog article had take time to explain the concept of shock energy and gas energy release sequence during detonation. Nikolaos in his thesis indicated that the timing difference between the initiation period and gas explosion period was 6ms, this shows that from the initiation point to 5:59ms, the fracturing process was fully taking place. The crushing zone process, the tensile slabing process and the shearing.
The Research work of Prof. Takis Katsabanis student also shows that the mean fragmentation size changes with time delay. The experiment shows that the fragmentation mean size was higher at low delay timing and higher at timing greater than 8ms. Which shows that from 2ms to 8ms, the X50 is low with 8ms been the optimum delay second.
Nikolaos work also revealed that the delay timing affects the vibration level for the experiment conducted. Ground vibration is one of the most serious blast illness after flyrock. The energy distribution from explosive result into displacement of rock and earth crust material at a define frequency level. Such is also depending on the Maximum instantaneous charge per initiation. Prof. Takis student also shows that the shorter the delay timing the higher the possibility for overlaps (constructive wave interference) 6-8ms delay produces separation of pulses as indicated by the result from the vibration results.
Conclusion
This work had shown that the efficiency of blast production and safety also depends on the charge initiation and the timing allocation.
The productiveness of blasting Operation is the main aim and Target of blasting. Ensuring safety and profitability is also a great task.
To ensure this is fulfil, there is a need for proper design and optimization of blast timing and design to achieve this great task.
Mining and safety is our main focus
Giant Miner is committed to safe mining and campaign against poor and unsafe mining. First in Nigeria and then to the whole world.
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Reference
https://qspace.library.queensu.ca/handle/1974/15321
