PARAMETERS AND SOME TECHNIQUE TO REDUCE FLYROCKS DURING BLASTING IN OPEN CAST MININF

1. MITIGATION OF FLYROCKS IN SURFACE
MINING DURING BLASTING
GAGAN GUPTA
16152004, M.TECH(PART-1),IIT-BHU

2. INTRODUCTION
Blasting is the most accepted and practiced technique for the breakage of
rock. When we do blasting then generation of some side products take
place that includes Ground Vibration, Dust Generation, Noise, Flyrocks,
Air Blasting etc.

3. FLYROCKS
During blasting operation the rock which is generated due to blasting process and
some of the Rock which is projected beyond the normal blast affected area is known
as Flyrock.

4. FACTORS
There are two factors due to which flyrocks generation take place :-
1. Uncontrollable
2. Controllable

5. UNCONTROLLABLE
• Natural joints
• Fractures
• Cavities
• Mud seam
• Strength of rock

7. BEDDING PLANES

8. CONTROLLABLE
• SPACING-BURDEN RATIO
• DEPTH OF BORE HOLE
• DIAMETER OF BORE HOLE
• QUANTITY OF EXPLOSIVE
• STEMMING LENGTH
• STEMMING MATERIAL
• INADEQUATE BURDEN

11. INCLINATION OF BORE HOLE

12. INADEQUATE DELAYAND INITIATION SYSTEM

13. • INITIATION BY DETONATING CORD
• BLAST HOLE PATTERN
• SKILLS OF BLASTING CREW

14. MITIGATION
STRATA BLAST MINING METHOD
SOURCE:- ORICA COMPANY(HUNTER VALLEY AUSTRALIA)

18. SINGLE SEAM

19. TWO COAL SEAM

20. SHOCK TUBE INITIATION SYSTEM

21. DECKING

22. Tire Blasting Mats For Fly Rock Prevention

23. • DECKING IN JOINTS, CAVITIES, FRACTURES.
• EXPLOSIVE ACCORDING TO ROCK STRENGTH.
• BURDEN.
• BURDEN-SPACING RATIO.
• DEPTH OF BORE HOLE.
• DIAMETER OF BORE HOLE.
• QUANTITY OF EXPLOSIVE.
• STEMMING LENGTH.
• STEMMING MATERIAL.

24. • SKILLS OF BLASTING CREW
• BLAST HOLE PATTERN
V SQUARE V1 V2

25. V3

26. CASE STUDY 1
• A study was recently conducted in Limestone quarry. The quarry is a captive mine
of a Cement Plant. The quarry produces the cement grade Limestone which is fed
to the Plant. The quarry has the limestone deposits which belong to the sediments
of Chhattisgarh basin, which are horizontal, thick bedded and classified as
stromatolitic Limestone of Raipur Group.

27. The geotechnical properties of the deposit are
given below :-
• Uniaxial Compressive Strength, M Pa: 40-45
• Density , g/cc: 2.40-2.52
• Young’s Modulus, G Pa: 44-49
• Porosity, %: 5-7
• Joint Spacing (Vertical), m: 2-3
• Joint Spacing (Horizontal), m: Around 1.0 m
• The overburden consists of hard Laterite and clay with an average thickness of 6.0
m.

28. Blasting Pattern
RESULTS BLAST NO.1 BLAST NO.2 BLAST NO.3
FLYROCKS, m 200 274 300

29. Modified Blast Design
RESULTS BLAST NO.1 BLAST NO.2 BLAST NO.3 BLAST NO.4
FLYROCKS, m 10 16 8 12

30. CASE STUDY 2
• DATE-September 22nd 2010, at 17hr 10min
• Working place - Quality Control lab-Cement testing room near the dam site.
• Size of the boulder - 3m, 1.5m and 1.6m in (length, breadth , height )
• Secondary blasting- drill two holes of 45mm diameter , spacing 0.6m , depth 1.5m.
Explosive cartridge -40mm (390gm/cart.) ,300mm length with a detonating cord of
10g/m. Charging of 1560gm explosive per single hole ,0.3m stemming.
When the blasting occurred a huge sound was heard and two flyrocks ejected from the
boulder which covered a distance of 550m from the blasting site to the Quality control
laboratory .

34. THANK YOU

35. REFERENCES
• Faramarzi Farhad , Ebrahimi Farsangi Mohammad Ali, Mansouri Hamid,
“Simultaneous investigation of blast induced ground vibrations and airblast on
safety level of structures and human in surface
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of Blasting in Okorusu Fluorspar Mine, Namibia”, International Journal of
Engineering and Technology Volume 4 No. 2, February, 2014.
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Indian limestone mines using neural networks”, Journal of Rock Mechanics and
Geotechnical Engineering, Vol 6, 2014, pp 447 to 454.
• Sushil Bhandari, “Engineering Rock Blasting”, AA Balkema, Rotterdam,
Brookfield, 1997.

36. • Bajpayee T.S., Rehak T.R., Mowrey G.L., and Ingram D.K., (2004), Blasting
injuries in surface mining with emphasis on flyrock and blast area security, Journal
of Safety Research, vol. 35, pp. 47 – 57.
• Siskind DE, Kopp JW [1995]. Blasting accidents in mines: a 16-year summary. In:
Proceedings of the 21st Annual Conference on Explosives and Blasting Technique.
Cleveland, OH: International Society of Explosives Engineers, pp. 224-239.
• Adhikari, G.R. 1999. Studies on Flyrock at Limestone Quarries. Rock Mechanics
and Rock Engineering, 32(4): 291-301.