Blasting Techniques and Factors Quiz
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Questions and Answers

What is the defining characteristic of a rectangular blast pattern?

  • Drilled spacings are smaller than drilled burdens
  • Drilled spacings are irregular
  • Drilled spacings are larger than drilled burdens (correct)
  • Drilled spacings are equal to drilled burdens

    • What is the purpose of a staggered blast pattern?

  • To facilitate row firing (correct)
  • To enhance vertical rock movement
  • To ensure equal distribution of explosives
  • To minimize gas pressure

    • What is the typical timing for rock fragmentation after detonation?

  • 20 to 30 milliseconds
  • 1 to 3 seconds
  • 30 to 45 milliseconds
  • 5 to 15 milliseconds (correct)

    • How does the movement of rock change as the number of rows in a blast increases?

    <p>Low velocity causes reduction in relief toward the free face</p> Signup and view all the answers

    What is the formula for powder factor (kg/m3)?

    <p>$\pi \times \rho_e \times d^2 \times \frac{Charged length}{4,000 \times B \times S}$</p> Signup and view all the answers

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

    <p>15.5 kg/m</p> Signup and view all the answers

    What is the equation to calculate the loading density for different charge diameters?

    <p>$\frac{16.88 - 15.42}{x - 15.5} = 15.5$</p> Signup and view all the answers

    What is the range for small diameter blasthole drilling?

    <p>65 - 165 mm</p> Signup and view all the answers

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

    <p>Drilling, explosives, and geology</p> Signup and view all the answers

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

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

    What is the equation to calculate the length of bottom charge for large diameter blasthole?

    <p>$L_2 = H \cos(\beta)$</p> Signup and view all the answers

    What are the key steps of the rock fragmentation process by blasting according to the text?

    <p>Compression waves pressure, reflection of the pressure wave, and gas pressure</p> Signup and view all the answers

    What is the formula for powder factor (q)?

    <p>$q = We/Vr$</p> Signup and view all the answers

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

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

    What is the purpose of a detonator in blasting?

    <p>Triggering a larger explosive</p> Signup and view all the answers

    What factors are considered in the selection of explosives for blasting?

    <p>Economic, performance, and safety factors</p> Signup and view all the answers

    What does the powder factor indicate?

    <p>Relationship between rock breakage and explosive usage</p> Signup and view all the answers

    What are the preparations for blasting?

    <p>Cleaning holes, charging with explosives, and checking circuit resistance</p> Signup and view all the answers

    What is the role of initiation systems in blasting?

    <p>Provide initial energy for detonation</p> Signup and view all the answers

    What does the formula $q = We/Vr$ represent?

    <p>Powder factor</p> Signup and view all the answers

    What is the key parameter for bench blasting?

    <p>Powder factor</p> Signup and view all the answers

    What is the purpose of cleaning holes with compressed air before blasting?

    <p>To remove debris and ensure proper explosive placement</p> Signup and view all the answers

    What is the range of the powder factor value for normal bench blasting?

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

    What is the weight of rock to be blasted represented by in the formula $q = We/Vr$?

    <p>Vr</p> Signup and view all the answers

    What is the primary goal of blasting according to the text?

    <p>Safe, efficient, and productive blasting</p> Signup and view all the answers

    What is the purpose of maintaining a stable highwall in a blasting operation?

    <p>Ensuring safety and stability for equipment and personnel</p> Signup and view all the answers

    What does the term 'burden' refer to in bench blasting?

    <p>Distance from a single row to the free face of the excavation</p> Signup and view all the answers

    What does the term 'spacing' represent in bench blasting?

    <p>Distance between adjacent blastholes in a row</p> Signup and view all the answers

    What is the function of stemming in bench blasting?

    <p>To contain explosive energy within a blasthole</p> Signup and view all the answers

    What is the purpose of sub-drilling in bench blasting?

    <p>To ensure that the full face of the rock is capable of being removed to the desired excavation limit</p> Signup and view all the answers

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

    <p>Drilling, explosives, and geology</p> Signup and view all the answers

    What is the potential consequence of close hole spacings in bench blasting?

    <p>Crushing and cratering between holes, boulders, and toe problems</p> Signup and view all the answers

    What material can be used as stemming in bench blasting?

    <p>Sized crushed stone or drill cuttings</p> Signup and view all the answers

    What is the distance drilled below the floor level in sub-drilling used for?

    <p>To ensure that the full face of the rock is capable of being removed to the desired excavation limit</p> Signup and view all the answers

    What is the potential consequence of wide hole spacing in bench blasting?

    <p>Inadequate fragmentation</p> Signup and view all the answers

    What is the role of spacing in row-to-row shooting in bench blasting?

    <p>To measure the spacing between holes in a row</p> 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.

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