Blasting

Question 1

3 keys to blast efficiency

Answer 1

• energy distribution
• energy confinement
• energy level

Question 2

Bench Height

Answer 2

controls vertical energy distribution

Question 3

Blast hole diameter

Answer 3

1/50 (closely jointed) - 1/80 (bench height, massive rock)

Question 4

Stemming

Answer 4

17-25 times the blast hole, best to select 20

Question 5

Burden distance

Answer 5

1.5-1.0 times the stemming length (lower burden promotes forward throw)

Question 6

Spacing

Answer 6

1.15-1.5 times the burden (1.15 chosen to achieve equilateral triangle )

Question 7

Energy distribution

Answer 7

S=B*1.15

Question 8

Subdrilling

Answer 8

0-10 times the blast hole diameter

hard rock:7

Question 9

Explosive mass per hole

Answer 9

area of the hole: pi*(D/2)^2
amount of emulsion: area * density
charge length = subdrill + bench-stemming length
Required= amount * charge length * 1000

Question 10

Powder Factor

Answer 10

Mass/(bench heightburdenspacing)

Question 11

Timing Design

Answer 11

Inter-hole:1-9m/s (spacing)

Inter-row:3-30m/s (burden)

Question 12

Ground Vibrations

Answer 12

V=K(R/Q^.5)^1.6
50%: K=1140 B=1.6
95%: K=1.5-2 times 50%, B=1.6
Q= maximum instantaneous charge