Blasting Techniques and Factors Quiz

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Questions and Answers

What type of blast pattern has drilled spacings larger than drilled burdens?

Circular blast pattern

Square blast pattern

Rectangular blast pattern (correct)

Staggered blast pattern

What is the timing between holes in a row and between rows in a shot that dictates the movement and fragmentation of the shot?

Hours

Milliseconds (correct)

Minutes

Seconds

What does the gas pressure created by a blast do to the rock?

Moves the rock out from the blast face at 50 to 100 ft/s (correct)

Stops the movement of the rock

Moves the rock at a constant speed

Causes the rock to implode

What happens to the relief toward the free face as the number of rows increases in a blast?

Reduction due to low velocity of moving rock Signup and view all the answers

What is the formula for powder factor?

$\pi \times \rho_e \times d^2 \times \text{Charged length} / (4,000 \times B \times S)$ Signup and view all the answers

What is the loading density for a charge diameter of 152.4 mm?

15.5 kg/m Signup and view all the answers

What is the range for small diameter blasthole drilling?

65 - 165 mm Signup and view all the answers

What are the three main factors that influence rock breakage according to the text?

Drilling, explosives, and geology Signup and view all the answers

What is the formula for loading density interpolation?

$(16.88 - 15.42) / (159 - 152.4)$ Signup and view all the answers

What is the formula for the length of bottom charge for large diameter blasthole?

H + L^2 Signup and view all the answers

What is the main property of explosives that influences the explosives selection?

Ability to safely obtain the lowest unit cost of material produced Signup and view all the answers

When is the Final Exam scheduled?

Dec 7th Signup and view all the answers

What is the formula for powder factor?

q= We Vr Signup and view all the answers

What does a detonator do?

Triggers a larger explosive Signup and view all the answers

What does the powder factor value range from for normal bench blasting?

0.1 to 0.7 kg/m3 Signup and view all the answers

What is the key parameter for bench blasting that indicates the relationship between rock breakage and explosive usage?

Powder factor Signup and view all the answers

What is the formula for the weight of explosive charged (We)?

We = q * Vr Signup and view all the answers

What factors are considered in the selection of explosives?

Economic, performance, safety, rock strength, and field conditions Signup and view all the answers

What does the detonator provide for the larger explosive?

Initial energy for detonation Signup and view all the answers

What does the powder factor value depend on?

Rock blastability, fragmentation, explosive performance, and charge distribution Signup and view all the answers

What does the detonation sequence include for different blast patterns?

Rows shooting parallel to the highwall, a 'V' pattern, or chevron Signup and view all the answers

What is the volume of rock to be blasted in the formula for powder factor?

Vr Signup and view all the answers

What is the weight of rock to be blasted in the formula for powder factor?

Wr Signup and view all the answers

What is the key parameter for bench blasting that indicates the relationship between rock breakage and explosive usage?

Powder factor Signup and view all the answers

Study Notes

Blasting Techniques and Factors

Detonation sequences include rows shooting parallel to the highwall, a "V" pattern, or chevron for different blast patterns
Preparations for blasting involve cleaning holes with compressed air, charging them with explosives, and checking circuit resistance for electric detonators
A detonator is a small device triggering a larger explosive, while initiation systems provide the initial energy for detonation
Selection of explosives considers economic, performance, and safety factors, as well as rock strength and field conditions
Powder factor, a key parameter for bench blasting, indicates the relationship between rock breakage and explosive usage
Powder factor value ranges from 0.1 to 0.7 kg/m3 for normal bench blasting, affected by rock blastability, fragmentation, explosive performance, and charge distribution
The formula for powder factor (q) is q= We Vr or q= We Wr, where We is the weight of explosive charged, Vr is the volume of rock to be blasted, and Wr is the weight of rock to be blasted
Calculating the powder factor involves determining loading density, charge length, charge weight per hole, and rock volume per blast hole
An example calculation for open pit mine bench blasting includes determining loading density, charge length, charge weight per hole, and rock volume per blast hole
An example calculation yields a loading density of 15.5 kg/m, charge length of 10.3 m, charge weight per hole of 159.65 kg, and rock volume per blast hole of 327.6 m3
The powder factor for the example is 0.49 kg/m3, calculated using the formula q= We Vr
The example involves a charge diameter of 152.4 mm, explosive density of 0.85 gm/cm3, bench height of 14 m, subdrill length of 1 m, burden of 4.5 m, spacing of 5.2 m, and no inert deck.

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Description

Test your knowledge of blasting techniques and factors with this quiz. Explore detonation sequences, preparations for blasting, selection of explosives, and the calculation of powder factor. Gain insight into key parameters for bench blasting and understand how to apply formulas to real-world examples.