CES CES Blasting Operations & Techniques 2 — Questions and Answers
Question 1: What is the purpose of using electronic detonators (EDs) compared to pyrotechnic delay detonators?
- EDs are cheaper and easier to manufacture
- EDs provide programmable, highly accurate delay times reducing scatter and misfires (Correct answer)
- EDs require no lead wire connections
- EDs eliminate the need for stemming material
Correct answer: EDs provide programmable, highly accurate delay times reducing scatter and misfires
Electronic detonators allow precise programmable delays with timing accuracy in the sub-millisecond range, dramatically reducing timing scatter compared to pyrotechnic delays.
Question 2: What is 'controlled blasting' as used in highway construction and excavation near structures?
- Blasting performed only at night to avoid traffic
- Techniques such as presplitting, smooth blasting, or cushion blasting to limit damage beyond the design perimeter (Correct answer)
- Using only half the normal powder factor
- Blasting controlled by remote radio signal only
Correct answer: Techniques such as presplitting, smooth blasting, or cushion blasting to limit damage beyond the design perimeter
Controlled blasting techniques like presplitting and smooth blasting use closely spaced, lightly loaded perimeter holes to create a fracture plane that limits overbreak and damage.
Question 3: Which instrument is used on a blast site to measure ground vibration levels at nearby structures?
- Barometer
- Seismograph (seismometer) (Correct answer)
- Transit level
- Hygrometer
Correct answer: Seismograph (seismometer)
A seismograph records peak particle velocity (PPV) and frequency of ground vibration, providing data to compare against regulatory limits and damage criteria.
Question 4: What blast design parameter most directly controls the airblast overpressure generated at the surface?
- Stemming length and confinement of the explosive charge (Correct answer)
- The color of the stemming material used
- The time of day the blast is fired
- The number of workers present at the site
Correct answer: Stemming length and confinement of the explosive charge
Adequate stemming length and confinement prevent explosive gases from venting rapidly to atmosphere, which is the primary source of airblast overpressure.
Question 5: In a 'deck loading' blast hole configuration, what separates the explosive decks?
- Steel pipe spacers
- Air gaps or inert stemming decks between explosive charges (Correct answer)
- Water
- Additional detonators only
Correct answer: Air gaps or inert stemming decks between explosive charges
Deck loading separates explosive charges within a single hole using air decks or inert stemming to improve energy distribution and reduce overbreak.
Question 6: What is 'flyrock' in surface blasting, and what is its primary cause?
- Dust generated during drilling; caused by dry rock
- Rock fragments propelled beyond the blast zone; caused by insufficient burden, inadequate stemming, or weak rock zones (Correct answer)
- Airblast pressure wave; caused by too many holes firing simultaneously
- Smoke and fumes released post-blast; caused by incomplete detonation
Correct answer: Rock fragments propelled beyond the blast zone; caused by insufficient burden, inadequate stemming, or weak rock zones
Flyrock is uncontrolled rock projectile displacement caused by inadequate burden, short stemming, or geological anomalies that allow explosive gases to escape rapidly.
CES CES Blasting Operations & Techniques 2
What is the purpose of using electronic detonators (EDs) compared to pyrotechnic delay detonators?