60 Questions
What is the primary goal of the blast design mentioned in the text?
Safe, efficient, and productive blasting
What is the proper burden dimension based on?
Hole diameter, relative rock density, and explosive used
What is the distance between adjacent blastholes in a row called?
Spacing
What is critical to all aspects of a blasting operation?
A safe and stable highwall
What is the function of stemming in bench blasting?
Contain explosive energy within a blasthole
What is the purpose of sub-drilling in bench blasting?
Ensure smooth pit floor
What happens with close hole spacings in bench blasting?
Cause crushing and cratering between holes
What is the measurement of spacing when the shot progresses at an angle to the free face in bench blasting?
At that angle
What are the main factors that influence rock breakage in bench blasting?
Drilling, explosives, and geology
What is the recommended material for stemming in bench blasting?
Sized crushed stone or drill cuttings
What is the distance drilled below the floor level in sub-drilling?
To ensure the full face of the rock is capable of being removed
What is the impact of wide spacing in bench blasting?
Inadequate fragmentation
What is the primary difference between a square blast pattern and a rectangular blast pattern?
The drilled spacings are equal to the drilled burdens in a square blast pattern, while the drilled spacings are larger than the drilled burdens in a rectangular blast pattern
What is the purpose of a staggered blast pattern?
To facilitate row firing, where the holes in one row are fired before the holes in the row immediately behind them
What dictates the movement and fragmentation of a shot in millisecond delay blasting?
The timing between holes in a row and between rows in a shot
Why is the movement of rock important in designing a blast for optimal fragmentation?
The low velocity of the moving rock can cause a reduction in relief toward the free face, leading to more vertical rock movement
What is the main difference between a square blast pattern and a rectangular blast pattern?
The drilled spacings in a square blast pattern are equal to the drilled burdens, while in a rectangular blast pattern, the drilled spacings are larger than the drilled burdens.
What is the purpose of a staggered blast pattern?
To enable row firing, where the holes in one row are fired before the holes in the row immediately behind them.
What dictates the movement and fragmentation of a shot in millisecond delay blasting?
The timing between holes in a row and between rows in a shot.
What is the importance of rock movement in designing a blast for optimal fragmentation?
The low velocity of the moving rock causes a reduction in relief toward the free face, leading to more vertical rock movement.
What is the formula for calculating powder factor in bench blasting?
$rac{ ho_e imes d^2 imes ext{Charged length}}{4000 imes B imes S}$
What is the loading density for a charge diameter of 152.4 mm?
15.5 kg/m
What is the range for small diameter blasthole drilling?
65 - 165 mm
What are the three main factors that influence rock breakage in bench blasting?
Drilling, explosives, and geology
What is the main property of explosives that influences their selection?
Ability to safely obtain the lowest unit cost of material produced
What is the recommended length of bottom charge for large diameter blastholes?
Depends on specific applications
What is the distance between adjacent blastholes in a row called?
Spacing
What are the key factors for effective blasting, as mentioned in the text?
Compression waves pressure, reflection of the pressure wave, and gas pressure
What is the formula for powder factor (kg/m3) mentioned in the text?
$\pi \times \rho_e \times d^2 \times \frac{1}{4000} \times B \times S$
What is the loading density (kg/m) for a charge diameter of 152.4 mm according to the given interpolation?
15.5 kg/m
What is the range for small diameter blasthole drilling mentioned in the text?
65 - 165 mm
What are the three main factors that influence rock breakage in bench blasting according to the text?
Drilling, explosives, and geology
What is the recommended length of bottom charge for large diameter blastholes?
L2
What is the date of the Guest Lecture 3 mentioned in the text?
Nov 9th
What is the primary goal of effective blasting as mentioned in the text?
To safely obtain the lowest unit cost of material produced
What is the measurement of spacing when the shot progresses at an angle to the free face in bench blasting?
S
What is the formula for powder factor (q) in bench blasting?
$q = \frac{We}{Vr}$
What does the powder factor value indicate in bench blasting?
Relationship between rock breakage and explosive usage
What is the range of the powder factor value for normal bench blasting?
0.1 to 0.7 kg/m3
What is the function of a detonator in blasting?
Triggering a larger explosive
What do initiation systems provide in blasting?
Initial energy for detonation
What factors are considered in the selection of explosives for blasting?
Economic, performance, safety, rock strength, and field conditions
What is the key parameter for bench blasting that indicates the relationship between rock breakage and explosive usage?
Powder factor
What does the loading density involve in bench blasting?
Determining the amount of explosive per unit volume of rock
What is the example calculation for open pit mine bench blasting used to determine?
Loading density, charge length, charge weight per hole, and rock volume per blast hole
What is the formula for the powder factor in the given example?
$q = \frac{We}{Vr}$
What is the powder factor for the example calculation in open pit mine bench blasting?
0.49 kg/m3
What is the function of subdrill length in bench blasting?
Determining the depth of the blast hole
What is the formula for powder factor (q) as mentioned in the text?
q= We Vr
What is the range of the powder factor value for normal bench blasting as per the text?
0.1 to 0.7 kg/m3
What does the detonator do in a blasting sequence?
Triggers a larger explosive
What factors are considered in the selection of explosives for blasting?
Economic, performance, safety, rock strength, and field conditions
What does the powder factor (q) indicate in bench blasting?
Relationship between rock breakage and explosive usage
What is involved in calculating the powder factor as per the text?
Determining loading density, charge length, charge weight per hole, and rock volume per blast hole
What is the loading density in the example calculation provided in the text?
15.5 kg/m3
What is the charge weight per hole in the example calculation for open pit mine bench blasting?
159.65 kg
What is the volume of rock to be blasted in the example calculation?
327.6 m3
What is the charge diameter mentioned in the example calculation for open pit mine bench blasting?
152.4 mm
What is the explosive density mentioned in the example calculation?
0.85 gm/cm3
What is the bench height in the example calculation for open pit mine bench blasting?
14 m
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.
Test your knowledge of blast design and highwall stability in mining optimization with this quiz. Explore key concepts such as safe blasting practices, rock fragmentation, operation cost optimization, highwall stability, and more.
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