Drilling & Blasting Pattern.pptx

Blasting Safety with Proper Techniques ENVIRONMENTAL ISSUES Ground Vibration, Air Blast, Fly Rock, Premature Detonations and Misfires IMPORTANT  free faces  clean the bench floor and  direction of shot or blasting

Blast holes can be drilled in either square pattern or staggered pattern.  A staggered pattern produces a more uniform distribution of explosive effect

To overcome these hazards, proper blasting pattern to be designed and followed as given in the Table below; Sr. # Parameters Units 1 Bench Height Meter 2 Hole Depth Meter 3 Sub-Drilling Meter 4 Burden Meter 5 Spacing Meter 6 Stemming Per Hole Meter 7 Per Blast Hole Nos. 8 Bottom Charge Height Meter 9 Column Charge Height Meter 10 Bottom Charge Per Hole Kg 11 Column Charge Per Hole Kg 12 Total Charge Per Hole Kg 13 Volume of One Hole M³ 14 Density of Limestone Tons/M³ 15 Tonnage of Blast Tons 16 Loading Density Kg./M 17 Drilling Yield M³/m 18 Powder Factor 19 Yield

BLASTING TERMINOLOGY

DRILLING PATTERN

Min 5.5 6 0.5 2.5 3.5 3 20 1 2 3 11 14 48 2 96 2.33 8.02

Max 7.5 8 0.5 2.5 3.5 3 30 2 3 4.5 14 19 66 2 131 2.31 8.20

0.29

0.28

Tons/Kg 6.88

7.09

Kg./M³

BLAST HOLE DESIGN

BLASTING PATTERN Trunk Line Delay Pattern

Chevron Patterns

This system has particular application where ground vibration problems put restrictions

on

the

detonated per delay.

Delay Intervals

charge

mass

A closed chevron pattern gives a high profile rock pile with a possible secondary blasting due to impacts between rocks projected from opposite directions

 Delay interval provides free face to the next blasted hole or row 

It should vary between 6 ms to 19 ms per meter of burden



For limestone quarries delay interval is 15 ms per meter of burden

An open chevron patterns gives evenly spread rock piles particularly suitable for frontend loaders and may produce less toe problems

BEST DELAY INTERVAL ADVANTAGES

Too short a delay between rows may lead to problem of fly rock from the back row

Perfect delays between rows resulted in best rock fragmentation, no fly rocks, no boulders

GOLDEN RULES OF SAFETY  Never carry detonators or explosives in pockets of trousers, shorts or shirts  Never smoke when working with explosives  Never work with explosives if there is a possibility of a thunderstorm  Never leave explosives unguarded or unsupervised  Never use deteriorated initiators or explosives

PUBLIC SAFETY All blasting should be conducted between

sunrise & sunset