Blast hole drill

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1. SEMINAR ON BLAST DRILL HOLES Presented by:- PAVANKUMAR

2. What is blast hole drill ? It is a technique used in mining whereby a hole is drilled into the surface of the rock, packed with explosive material and detonated.

3. DESCRIPTION Blast hole drilling is most commonly used in the exploration of minerals.  Blast hole drilling  is done by the use of explosives. The rock is blasted and crushing and removing of the rock and other materials. Charging cavities are created and explosives are placed into these cavities. Thus a blast hole is not the after effect of an explosion, instead it is the hole created in which the explosives, as well as the various components that go along with the detonation of the explosives, are placed. 

4. CONTINUE… The drilling part of the  blast hole drilling process  is that most expensive part of the project. it is the most important part of the project. If the initial drilling is done wrong then the future of the project could end up being a problem .

5. Limitations : Fragmentation desired Rock quality/character Site condition Safety Equipments /materials

6. Advantages : Potential environmental impact in terms of noise, dust and sensitive receive are significantly reduced. Blast would significantly reduced vibration as compared with bored tunneling.

7. Disadvantages : Potential hazard associated with establishment of a temporary magazine site for overnight of explosive shall be addressed through avoiding populated areas in the site selection process.

8. Typical cycle of blast hole drill

9. The typical cycle of excavation by blasting is performed in the following steps : Drilling blast holes and loading them with explosives. Detonating the blast, followed by ventilation to remove blast fumes. Removal of the blasted rock (mucking). Scaling crown and walls to remove loosened pieces of rock. Installing initial ground support. Advancing rail, ventilation, and utilities.

10. Drilling and Blasting Method 1- Drilling : Before the blasting takes place , the drilling rig bores the drill holes – determined in advance in a blasting plan. A jumbo is used to drill holes in the rock face. This one has three drilling arms and an operator tower. It is run by electric cable; a hose brings water to the drills. The drills are pneumatic. That means that the drill bits both hammer and rotate. Broken bits of rock are flushed out by water. These drill holes are 2.4-3.6 metres long.

11. The first sets are straight holes (parallel cut) located around the edge of the face and in the middle. A second set (V-cut) is angled toward the center. These allow the rock to be blown away from the face into the drift (tunnel).

12. Drill hole patterns 1.square 2.rectangular 3.staggered

13. 2- Loading and Blasting : The drill holes are now filled with explosives, detonators are attached to the explosive devices and the individual explosive devices are connected to one another. The holes are blasted in a proper sequence, from the center outward, one after the other. Although more than 100 explosions may be set off, one after the other, the blast sequence is completed in several seconds.

14. 3- Ventilating : The blast causes lots of rock to be flung through the tunnel, dispersing clouds of dust that then mix with the combustion gases of the explosion. So that the miners can resume work in the tunnel, the bad air must be removed from the tunnel. This is done by using so-called air-ducting systems, long steel or plastic pipes, which are attached to the roof of the tunnel and blow fresh air onto the working face. This gives rise to localized excess pressure and the bad air is pushed towards the tunnel exit.

15. 4.Dislodging : Dislodging refers to the stripping away and removal of loose pieces of rock, which were not completely released from the rock during the blasting procedure. This working step is completed by a robust tunnel excavator.

16. TYPES OF EXPLOSIVE ADDED BASED ON DIFFERENT CONDITION DYNAMITE ANFO (AMMONIUM NITRATE & FUEL OIL MIX) GUN POWDER

17. PROCESS OF BLASTING 1.The blast holes are made and cleaned by using the tools. 2.The charge of explosive placed at the bottom. 3.Remaining portion is filled with clay and tamped. 4.Fuse is inserted, kept projecting 15-20 cm above the rock surface. 5. Thereafter free end of fuse is fired by detonator.

18. Thank you