Construction and mine blasting risk assessment presents several challenges. A blaster must accurately determine blast area bounds and manage safety issues.
A blaster’s decision in estimating the bounds of the blast area is greatly influenced by the engineering design of the blast, geology of the blast, regulatory requirements, and company policy.
Schneider (1995) stated that a blaster must make an estimate of the maximum possible distance fly rock could travel from a blast. Furthermore, a blaster should not assume that a blast being fired will behave like other blasts previously fired at the same operation. (You all know what ASS-U-ME means?)
Mine blasting risk assessment
Brnich & Mallett (2003) advanced the concept of conducting a hazard and risk assessment in order to prevent mining injuries. A site-specific hazard and risk assessment based on the probability of an event and its severity is an excellent tool for the blasting community.
Mine blasting releases a tremendous amount of energy within a very short time and is considered a hazardous operation. An analysis of site-specific risk factors will help in understanding and mitigating possible hazards.
A site-specific hazard and risk matrix should be drawn up and discussed during mine blasting and miners job assignments, safety discussions, and training sessions. (Ensure the appointed miner/blaster received proper hazard identification and risk assessment training.)
Brulia (1993) reported that about 80-90% of all accidents are caused by human factors, and listed five salient elements which contributed to these accidents:
- Negligence – failure to observe safety rules and instructions, or awareness/ignorance
- Hasty decisions – acting before thinking usually leading to hazardous shortcuts, or inability to comprehend
- Inadequate instruction – untrained or improperly trained personnel, not competent
- Overconfidence – taking chances, or known as a risk taker
- Lack of planning – insufficient understanding of a blasting situation, not competent
Mine blasting incidents
Mine blasting incidents can occur when:
- explosives are handled,
- during the preparation of a blasting site.
- or when setting off a blast.
Hazards and causes of explosions or mine blasting accidents
1. Explosives: Uncontrolled explosives and accessories (i.e.: Detonators)
Explosives can cause mine blasting incidents due to:
- Failure to comply with mine blasting procedures
- Failure to comply with explosives management procedures
- Inadequate storage and transportation of explosives
- Not obeying legal requirements
2. Fly rock: Material which is projected outside the declared danger zone by a quarry blast. Fly-rock may be caused by poor blast design or unexpected zones of weakness in the rock.
Fly rock can be the cause of mine blasting incidents due to:
- Poor communication
- Inadequate demarcation of blasting areas
- Inadequate evacuation of personnel
- Inadequate placement of guards
- Inadequate warning of blast
Accident data indicate that blasters and helpers often suffer injuries due to lack of adequate shelter from a blast. The blaster and blasting crew are typically closer to a blast than other employees and need to use shelter that will provide complete protection from fly rock that may be projected from a blast. Fly rock from a blast can travel vertically and does not fall like gentle rain. Fly rock can also travel along a horizontal path and become a deadly projectile.
3. Lightning storms: A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm, is a form of turbulent weather characterized by the presence of lightning and its acoustic effect on the Earth’s atmosphere known as thunder.
Adverse weather can also be a cause of mine blasting incidents.
4. Electromagnetic fields: The field of force associated with electric charge in motion, having both electric and magnetic components and containing a definite amount of electromagnetic energy.
2-way radios or cell phones used on the mine blasting block can cause incidents.That is why it is one of the most critical controls that need to be in place to ensure reasonable practicability: signages, guard, supervision, look out for your own and that of your fellow employees
Blast area shall be properly barricaded off, required warning signs to be placed at the blast entrance. Signs and/or contraband boxes to be placed e.g.:
- No smoking
- No naked flames
- No cell phones
- No two-way radios
- No unauthorised entry
5. Spontaneous ignition: Spontaneous combustion is a type of combustion which occurs by self heating (increase in temperature due to exothermic internal reactions), followed by thermal runaway (self heating which rapidly accelerates to high temperatures) and finally, ignition.
Spontaneous ignition can be caused by:
- Substandard explosives transport equipment
- Not separating critical types of explosives
- Containers not secured on vehicle
Ensure you are adhering to the Explosives regulations and Transporting of Dangerous Goods regulations at all times.
Your responsibilities and contribution to safety
- Do not enter demarcated areas and areas where “no entry” signs are erected
- Before entering a blasting area ensure the miner/blaster is aware of your presence in the area and get permission
- Never go past a blasting guard
- Never play with a detonator – report to the blaster
- Do not use your cell phone or 2-way radio on a blast block
- Obey blasting guard instructions
- Always react to blasting alarms. Evacuate the area to beyond the blasting guard control points
- Only authorized blasters may handle explosions
- Never handle or tamper with explosives
- Never smoke near explosives or on blast block
“Be alert and share information; know the blasting time, blast area and clearing procedure; and DO NOT enter the blast area until an “all-clear” signal is sounded”.
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