INTRODUCTION
Operations in mining industry is mainly effected by the mine work because more cost is involved and safety is required.
Blasthole Drilling shows the creation of holes into the rock mass for the placement of Explosive with the intention of fragmentation. According to Barry, (2016) liberation process begin from the mine. Though libration occur in two ways, the intra granular and inter granular libration, both occur during Blasting and during comminution.
All Mining Engineering is concern about is extracting the ore from the earth crust safely and getting it to the beneficiary plant for processing, in a bit to achieve this we have the earth stress field been Disturbed and the safety of men been questioned as the various activities in Mining affect both the biosphere and the Abiosohere. This article discuss the process of Blasting as a key way to getting the rock insitu fragmented and the place of safety Paramount as far as profit is concerned. The article also centered on ways to prevent misfire and other blast related impact.
Blasting operation in view
During Blasting operation, the Explosive wave travels within the rock mass and create stress redistribution within the intact mass rock. At the concentration region the rock fails toward the free face under crushing, at the relaxation zone within the elastic and plastic region, it fails under shearing and tension slabbing. The definition of Blasting becomes complete when the job is done safely. When Explosive is use for industrial purpose and Explosion is achieved successfully without any injury or hazard, with good production, such then is define as a good Blasting. What really makes Blasting dangerous is not the Explosive to say, but the Explosion energy generated from the Explosive at Detonation.
Basically during the interface between initiating energy and the Explosive charge, two energy is generated,
1.Shock wave (Energy)
2. Gas energy
By CJ model explanation from the above image, two pressure is defined to exist, the explosion pressure and the Detonation pressure. The Detonation pressure is the pressure at the CJ plane usually calculate by the expression below
P=0.25*De*VD^2
Where , De is the Explosive density in kg/m2, VD is the velocity of Detonation in m/s, p is the Detonation pressure in Kpa. The explosion pressure is the pressure generate behind the CJ plane at the disintegration process of the Explosive, it is half of the Detonation pressure. It grows incrementally to shock wave and gas Energy which Perform micro-fracturing and Explosion (rock movement).
Explosive can burn or deflagrate if enough shock Energy is not available to start the exothermic reaction within the Explosive chemical composition. Deflagrated Explosive is when it burns gradually with gas energy and toxic gases release from it. I will be partially worried if I don't talk about the issue of oxygen balance and it effects.
Oxygen balance is the balance of gases generated from Explosive at Detonation such that nontoxic gases are generate from the Explosive and only environmental fumes like oxygen, carbon IV oxides are those release at complete Detonation. There are three type of oxygen balance, zero OB, negative OB and positive OB. Zero OB is when the Explosive at Detonation release enough oxygen require to react with compound and elements like Nitrogen, carbon and hydrogen to form nontoxic gases like water vapor, Co2 e.t.c
Positive oxygen balance is when the Explosive at Detonation release excess oxygen which is sufficient to neutralize or react with elements like Nitrogen, hydrogen, carbon to for nontoxic gases and fume.
Negative Oxygen balance when the Explosive at Detonation release insufficient oxygen content for the neutrality of toxic gases. Such situation support generation of Co, NOx e.tc which are toxic and irritant to human, plant and general ecosystem.
This makes the issue of proper supervision and Orientation of mine workers handling and using Explosive imperative, all Explosive manufacturers have designed the Explosive product to be a balance oxygen Explosive, therefore the addition of other Explosive components to add to Detonation result affects the Explosive oxygen balance and can also lead to Explosive deflagration (burning with low or zero shock wave). Explosive can be widely classified into two basically,
1. Industrial Explosive
2. Military Explosive.
The industrial Explosive are those use for mine Blasting and construction blast works. They are designed for peace and not for war!! Many try to ask the basic different between the military Explosive and the Industrial Explosive. Actually the major difference is that, the military Explosive contain high percentage of primary (high) Explosive like Trinitrotoluene (TNT), Nitroglycerin Among others which are highly sensitive and release high amplitude shock wave that travels faster than the speed of sound.
Components I industrial Explosive
Industrial Explosive are basically made with the following components, oxider, retarder, stabilizer, combustive and Energy material like charcoal e.t.c
This components are add together at different proportion which increase in one can affect the other.
Note: As a mine Engineer, poor use of Explosive is when you try to blend or add other compound or material to Explosive during charge time to increase it output. Some may work but most will affect the Explosive oxygen balance, leading to the release of brown-pink color gas indicating Nitrogenous gas compound. Never should you add anything to the Explosive to avoid change in composition and Explosive constitutes at decomposition point behind the CJ plane.
Also, misfire which is the incomplete Detonation of Explosive, play high key role in release of toxic gases to the environment, the incomplete decomposition of Explosive chemical before the fire cut will affect the complete release of oxygen from Explosive compound for the neutrality of Nitrogen, carbon and other elements preventing the generation of toxic gases.Avoid misfire by checking holes before charging, use FIFO (First in, first out) in Explosive magazine to avoid expired Explosive, stop all charge operation at cloudy or about to rain time. Check all electric connect well with necessary device before exploder is switched on, check exploder current sufficiency, check all surface connection and timing to avoid cut in sequence wave traveling, in hole connection should be done with precaution and avoid cord damage, tapping should be done professional, do not pull cartridge Explosive with the lead wire during charging process, ensure proper priming, among others.
Contribution to Blast result improvement and M2M efficiency
Benefit of good Blasting
A good fragmentation is that which gives good size distribution and casting, low environmental impact generation such as flyrock, ground vibration and others, strong and smooth wall and toe face, ease and fast loading. Major the Blasting Damage zone (BDZ) is the region with low strength at the bench face, such zone fails easily under dynamic load such as movement of trucks, drilling and impacting, Blasting must be carefully carry out to ensure that excavation face have high strength to withstand the newly induced stress.
Let all blasting operation be carryout successfully in such that company smiles and all workers rejoice... Say no to Explosive mishandling, say no to manage of safety fuse, say no to poor Explosive transportation scheme, say no to poor Explosive storage, let all magazine be build to standard and let all personnel understand the concept of SAFETY FIRST.. Explosive is for peace and not for war.. It for industrial use and not for war.. let the use of Explosive not be a problem to human, plant, and biosphere in general.. release of aerosol will affect the ozone layer, cause global warming, support acid rain and acid mine drainage.. let say no to ecosystem damage, let the tectonic plate be stable for us all.
We mine it for the people's use and for the safety of the biosphere.... All workers must return home safely and have the night meal in happiness with their families...
We work in team as a Miner!!!!
®Giant Miner
A final year student of Federal University of Technology Akure Nigeria
Mining Engineering department
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