CE 3220 12 Blasting Rock.pdf

8/17/2019 CE 3220 12 Blasting Rock.pdf

1/58

Blasting Rock


2/58

BLASTING

ROCK

Practical

Exercise

Blast Design


3/58

PRACTICAL EXERCISE Design a delayed initiation blast

(would like to shoot a minimum of

10 holes per delay). Base the

plan on the following:

Rock - limestone, in thin layers

w/tight joints

Bench height - 24 ft


4/58

PRACTICAL EXERCISE

Explosive - bulk ANFO, SG

e

0.8 dry holes, no liner

required.

Explosive - dynamite, SG

e

1.4 Cartridge size: 2 to 3.5

inch diameter in ¼ in.

increments, by 16 in. long.


5/58

PRACTICAL EXERCISE

Drills can use 6 in.

bits.

Regulatory scale

distance factor 55

Nearest structure is

1,400 ft away


6/58

STEP 1:

BURDEN DISTANCE

?


7/58

STEP 1:

BURDEN DISTANCE

Explosive density empirical

formula for burden distance:

B ft

SG

SG D ine

r

e( ) . ( )

2

1 5

Equ. 13.1


8/58

STEP 1:

BURDEN DISTANCE

SG

e

ANFO = 0.8

SG

r

Limestone (Table 13.2)?

D

e

= ? try 6 in. the maximum

B ft SG SG

D ine

r

e( ) . ( )

2 1 5


9/58

STEP 1:

BURDEN DISTANCE

SG

r

Limestone (2.4 - 2.9)

Lets use an average

number of 2.7

B ft SG

SG D ine

r

e( ) . ( )

2 1 5


10/58

STEP 1:

BURDEN DISTANCE

B 2 0.8

2.71.5 6

= 12.6 ft


11/58

STEP 2:

BURDEN

corrected

Burden distance corrected for

geological conditions (Table 13.3).

B B K K corrected d s

K

d

= 1.00, no information assume

“other cases ”

K

s

= 1.10, thin layers w/tight

joints


12/58

STEP 2:

BURDEN

corrected

Burden distance corrected

for geological conditions.

Bcorrected 12 6 1 0 1 1. . .

Bcorrected = 13.8 ft


13/58

STEP 3:

STIFFNESS RATIO

Need a Stiffness Ratio of

3 or greater.

Bench height = 24 ft

Burden

corrected

= 13.8

ft

SRbench height

burden distance

24

13.81.7


14/58

STEP 4: BURDEN

ADJUSTED

Want a Stiffness Ratio of 3

therefore: 3 24

Bcorrected

B 24

38

corrected


15/58

STEP 4: BURDEN

ADJUSTED

ft8useBDo not complicate the

field work, try to use

one foot or half foot

increments.


16/58

STEP 4: BURDEN

ADJUSTED

Burden distance corrected

for geological conditions.

1101BBcorrected ..

ft371101Bft8 ...


17/58

STEP 5: EXPLOSIVE

DIAMETER

)( . )( inD51SG

SG2ftB e

r e

eD3

1.5

2.70.827.


18/58

STEP 5: EXPLOSIVE

DIAMETER

3.52.09

7.3

eD

Explosive Diameter

3 1/2 in.


19/58

STEP 6: BLASTHOLE

SIZE

Bulk ANFO dry holes, no

blasthole liner, explosive

diameter and blasthole size

are the same.

Use a 3

1/2

in. size bit,

therefore

3

1/2

in.


20/58

STEP 6: BLASTHOLE

SIZE

Bulk ANFO, explosive

diameter and blasthole

size are the same, i.e.

there is no liner.

EXPLOSIVE

BORE HOLE


21/58

Explosive diameter and

blasthole size are the same.

ANFO


22/58

Worked

with awooden

pole to

prevent

bridging.

ANFO


23/58

STEP 7: STEMMING

Stemming depth (T) =

5.6

T B 0.780.7T


24/58

STEP 8: SUBDRILLING

J B 0.380.3J

Subdrilling depth (J) = 2.4

use 2 ft


25/58

STEP 9: SPACING

Delayed initiation: SR greater than1 but less than 4 (Equ. 13.8)

Spacing controlled by initiation

timing and stiffness ratio.

S L B 78


26/58

STEP 9: SPACING

L (bench height) = 24 ft.

B (burden distance) = 8

ft.

8

8)(724

SSpacing = 10 ft


27/58

STEP 9: SPACING

Spacing in the field should be

within plus or minus 15 of the

calculated value.

Calculated spacing

+15-15


28/58

STEP 9: SPACING

Spacing = 9, 10, 11 ft?

If this is an

estimate

for a

bid it might be better to be

conservative and use an 9 ft

spacing.

That would mean more

holes and a higher drilling

cost.


29/58

STEP 9: SPACING

Spacing = 9, 10, 11 ft?

If we are in the field

drilling for the first shot

we might try a 10 ft

spacing. This would

lower cost.


30/58

STEP 9: SPACING

Pull the first shot and evaluate the

results: fragmentation etc. If it is ok,

use 11 ft, if it is not satisfactory

reduce the spacing.


31/58

Throw rock

STEP 9: SPACING don’t

forget -- SAFETY


32/58

STEP 10:

POWDER COLUMN

Powder column length is the blasthole

depth minus the stemming depth.

Blasthole Depth = 26 ft

Bench height (24 ft)

+ Subdrilling ( 2 ft)

Powder column = 26 ft - 6 ft

= 20 ft


33/58

STEP 10:

POWDER COLUMN

Powder column = 20 ft or 240 in.

Dynamite cartridge size: 2 to 3.5

inch diameter in 1/4 in.

increments, by 16 in. long.

Dynamite:

16 in or 1.3 ft


34/58

STEP 10:

POWDER COLUMN

Powder column = 240 in.

ANFO

240” powder column

- 16” dynamite

= 224 in

or

18.6 ft


35/58

STEP 11:

LOAD DENSITY

Have to prime the

dynamite to fire the

shot.


36/58

STEP 11:

LOAD DENSITY

3

1/2

in. borehole

Dynamite

: Cartridge size:

2 to 3.5 inches in 1/4 in.

increments. Use

3

in.

diameter

cartridges, will fit

easily into the hole.

NFO

: 1/2 in. diameter


37/58

STEP 11: LOAD DENSITY

Dynamite Cartridge


38/58

STEP 11: LOAD DENSITY

Dynamite: 3 in dia. SG

e

= 1.4

ANFO: 3 1/2 in dia. SG

e

= 0.8

Explosive Loading Density

Table 13.5

Dynamite: 4.29 lb/ft

ANFO: 3.34 lb/ft


39/58

STEP 12:

AMOUNT of EXPLOSIVE


40/58

STEP 12:

AMOUNT of EXPLOSIVE

Amount of explosive (lb) =

powder column (ft)

X

loading density (lb/ft)

Dynamite: 1.3 ft X 4.29 lb/ft = 5.6 lb

ANFO: 18.6 ft X 3.34 lb/ft = 62.1 lb

Explosive per blasthole 67.7 lb


41/58

STEP 13:

AMOUNT of ROCK

Amount of rock (cy) =

pattern area (ft

2

)

X

depth to grade (ft)

X

1/27 (ft

3

/cy)

Rock per blasthole:

cy5

27

248896.


42/58

STEP 14:

POWDER FACTOR

Powder Factor (lb/cy) =

Amount of explosive (lb)Amount of rock (cy)

Powder Factor:

lb/cy1.19cy56.9

lb67.7


43/58

D

s

= 55

d = 1,400

Want to shoot 10 holes per delay.

W = 10 X 67.7 lb or 677 lb

STEP 15: VIBRATION

D d

W s

Check vibration formula

13.12

53.8677

1,400sD


44/58

STEP 15: VIBRATION

D

s

= 55

A scaled distance value of 55

or greater is required for this

location.

Therefore, can not

shoot 10 holes at one

53.8 55


45/58

STEP 15:

VIBRATION

How many holesat one time.


46/58

STEP 15: VIBRATION

D

s

= 55

?W

1,40055

lbW 647.955

1,4002


47/58

STEP 15: VIBRATION

Therefore, can only

shoot

9 holes at one time.

9.6

67.7

647.9HolesNo.


48/58

Shoot 9 holes at one


49/58

PRESPLITTING

ROCK

To limit overbreak,develop apresplitting blast

plan, for theprevious example.


50/58

STEP 1:

EXPLOSIVE LOAD

28

3.5 2 ) / ( ftlbloadExplosive

Explosive load = 0.4375 lb/ft

Equation 13.10


51/58

STEP 2:

AMOUNT of EXPLOSIVE

Explosive load = 0.4375 lb/ft

Amount of explosive / hole =

(24 ft X 0.4375 lb/ft)

+ (3 X 0.4375 lb)

= 11.8 lb/hole


52/58

STEP 3:

HOLE SPACING

Hole spacing = 10 X 3 ½ in.

= 35 inches


53/58

FIRE IN

THE HOLE


54/58

FIRE IN THE HOLE


55/58


56/58


57/58


58/58

Time to load and haul.

CE 3220 12 Blasting Rock.pdf

Documents

Transcript of CE 3220 12 Blasting Rock.pdf