data on blasting

8/6/2019 Data on Blasting

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Data on Blasting


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PRODUCTION BLASTING

PIT: MAIN 2

BENCH:1345-1340

BLAST NO: 25 DATE:

25-04-08

BLAST QUANTITIES

HOLE NO PLANNED DEPTH(m)

ACTUAL

DEPTH(m) CHARGE(40kg/Hole)

DESIGN

STEMMING

LENGTH(m)

ACTUAL STEM

LENGTH(m)

DESIGN

CARGE

DENSITY

ACTUAL

CHARGE

DENSITY

16346 5.7 6.5 40 2.2 3.0 1.2 1.4

16347 5.7 6.7 40 2.2 3.2 1.2 1.7

16348 5.9 6.8 40 2.2 3 1.2 1.5

16350 6 6.8 40 2.4 2.8 1.2 1.9

16370 5.6 6.8 40 2.2 2.3 1.2 1.2

16371 5.7 6.9 40 2.2 2.3 1.2 1.2

16372 5.7 6.5 40 2.2 2.5 1.2 1.5

16373 5.7 6 40 2.2 2.3 1.2 1.2

16374 5.7 6.7 40 2.2 2.7 1.2 1.3

16376 6 6.3 40 2.4 2.5 1.2 1.3

16446 5.7 7 40 2.2 3.2 1.2 1.4

16444 5.6 6.8 40 2.2 2.8 1.2 1.5

16442 5.6 6.4 40 2.2 2.5 1.2 1.2

16440 5.6 6.5 40 2.2 2.9 1.2 1.5

16438 5.7 6.5 40 2.2 2.6 1.2 1.5

16436 5.7 6.6 40 2.2 2.6 1.2 1.3

16257 5.5 5.9 40 2.2 2.3. 1.2 1.2

16257 5.5 6.1 40 2.2 2.6 1.2 1.216260 5.7 7 40 2.2 3.0 1.2 1.2

TABLE 1: CHARGE DENSITIES AND CHARGE MASSES (INEFFECTIVE CHARGING PROCESS)


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TABLE 3: CHARGE DENSITIES AND CHARGE MASSES (INEFFECTIVE CHARGING PROCESS)

PRODUCTION BLASTING

PIT: MAIN 2 BENCH:1345-1340 BLAST NO:

25 DATE: 25-04-08

BLAST QUANTITIES

HOLE NO PLANNED DEPTH(m) ACTUAL DEPTH(m) CHARGE(40kg/Hole)

DESIGN STEMMING

LENGTH(m)

ACTUAL STEM

LENGTH(m)

DESIGN CHARGE

DENSITY

ACTUAL

CHARGE

DENSITY

16346 5.7 6.5 40 2.2 3.2 1.2 1.4

16347 5.7 6.7 40 2.2 3.2 1.2 1.7

16348 5.9 6.8 40 2.2 3.2 1.2 1.5

16350 6 6.8 40 2.2 3.2 1.2 1.9

16370 5.6 6.8 40 2.2 3.2 1.2 1.2

16371 5.7 6.9 40 2.2 3.2 1.2 1.2

16372 5.7 6.5 40 2.2 3.2 1.2 1.5

16373 5.7 6 40 2.2 3.2 1.2 1.2

16374 5.7 6.7 40 2.2 3.2 1.2 1.3

16376 6 6.3 40 2.2 3.2 1.2 1.3

16446 5.7 7 40 2.2 3.2 1.2 1.4

16444 5.6 6.8 40 2.2 3.2 1.2 1.5

16442 5.6 6.4 40 2.2 3.2 1.2 1.2

16440 5.6 6.5 40 2.2 3.2 1.2 1.5

16438 5.7 6.5 40 2.2 3.2 1.2 1.6

16436 5.7 6.6 40 2.2 3.2 1.2 1.3

16257 5.5 5.9 40 2.2 3.2 1.2 1.2

16257 5.5 6.1 40 2.2 3.2 1.2 1.2

16260 5.7 7 40 2.2 3.2 1.2 1.2


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Effects of over-stemming blastholes

Over-fragmentation of the

ground in the lower part

of the blasthole after

blasting

Ground

surface

Large boulders left in

the top part of the

blasthole (due to over-

stemming) after

blasting

Position of

blasthole


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Stemming

Effects of Ineffective Stemming Effects of Effective Stemming


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Evidence Boulders At Kansanshi

Mine

Boulders


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EVIDENCE OFPOOR STEMMING MATERIAL (UNGRADED STONE AGGREGATES) AT

KANSANSHI


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Optimum stemming Thus, confining the gasses in the hole for as long as possible is important in maximizing the

blast efficiency

The following errors of stemming can occur:

Too little stemming will allow the explosive gasses to vent, creating fly rock and air blast

problems as well as reducing the effectiveness of the blast.

Too much stemming will result in poorly fragmented rock near the top. This is especially

apparent with hard cap rock formations.

Over-stemming of blastholes causes creation of boulders on the topparts of blasthole whilethe bottom of the blasthole is over-fragmented. Over-stemming is very rampant at Kansanshi

mine.

Short stemming length results in loss of energy into the atmosphere. This leads to:

Excessive fly rock and dust.

Excessive air blast.

Possible poor fragmentation, especially in the toe region. High bottoms likelihood. Reduced heave of the rock mass.


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OPTIMUM STEMMING LENGTH

STEMMING LENGTH

The optimum length of stemming depends mainly on the hole diameter. The longer the

stemming length, the higher the confining pressure. Optimum stemming length should be in

range the 20-30 the blasthole diameter depending the rock strength and type of stemming

material. Standard stemming lengths based on the hole diameter are as follows:

For hard capping layer, use 15 hole diameter as stemming length.

For normal blasting, use 20 hole diameter as stemming length.

To limit fly rock, use 25 hole diameter as stemming length.

For no fly rock at all, use 30 hole diameter as stemming length


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Stemming materials arranged according their effectiveness

AIR

CLAY

WATER

GRADED CRUSHED AGGREGATE

WITH STEM PLUG

DRILL CUTTINGS COARSE WITH

STEM PLUG

GRADED CRUSHED AGGREGATE

DRILL CUTTINGS FINES GRAINS

UNGRADED CRUSHED

AGGREGATE

DRILL CUTTINGS COARSE

GRAINSBEST

STEMMING

MATERIAL(mosteffective or best

option)

WORST

STEMMING

MATERIAL(less

effective or worst

option)

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