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What is rock blasting?

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Rock blasting is the process of drilling holes in a rock mass at depths, and spacing to allow an explosive to fracture the rock.  In this process, the rock must fracture enough to be broken down to the size intended.

It is practiced most often in mining, quarrying, and civil engineering such as dam, tunnel, or road construction.

But how exactly does this process work and what does it involve?

Let's dive into everything you need to know about rock blasting.

  1. How does rock blasting occur?
  2. How is rock blasting performed?
  3. Is rock blasting precise?
  4. What explosive is used for rock blasting?
  5. Is rock blasting safe?
  6. Why do mining companies blast?
  7. Do I need an engineer to plan rock blasting?

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How does rock blasting occur?

After detonating, chemical energy from the explosive is released, causing the explosive to transform into a glowing gas with large amounts of pressure. In a densely packed hole, this pressure can exceed 1,500,000 psi.

The high pressure released is what shatters the area surrounding the drill hole and exposes the rock beyond to high levels of stresses (and strains), stresses, and strains that cause the rock to crack.

While under pressure, the cracks in the rock extend, and the rock in front of the drill hole yields and move forward. If the distance of the hole to the closest surface is not too great, the rock in front of the hole will break free.

How is rock blasting performed?

Rock blasting is performed to fracture rocks so that these can be excavated for construction, extracting through mining operations, or quarried for processing.

This process is completed by discharging explosives in a confined manner (for instance mud capping) or confined in a borehole.

The explosives used for blasting are usually commercial grade and formulated to provide a controlled amount of energy release as it is detonated. The explosive itself has little effect on the way in which the rock fractures, but instead, the geometry of the drilled hole and the manner in which it is loaded with explosives affects this.

For instance, a deeper hole will produce a larger fracturing radius and a higher explosive concentration will cause the rock to break into smaller pieces.

Is rock blasting precise?

Rock blasting's design is not an exact process, but an iterative process of designing the blast hole layout and estimating the number of explosives needed to blast the rocks.  This process requires professional assistance and experience. 

Therefore, it is possible to produce the desired result in all rock blasting situations (considering the unique rock formations).

When blasting is designed correctly, the minimum number of explosives can be used, which will reduce costs and minimize the environmental impact of blasting.

Also, it’s important to take into account that blast vibrations may affect surrounding buildings and structures if not carefully monitored and controlled.

What explosive is used for rock blasting?

Ammonium nitrate fuel oil (ANFO) is used as an explosive in mining, quarrying, and tunneling construction.

Ammonium nitrate can be transported and stored and mixed with fuel oil when needed. ANFO is made of about 94% ammonium nitrate and 6% fuel oil.

Over the years, consumption of ammonium nitrate explosives has grown because of its safety advantage over other products such as dynamite.

Is rock blasting safe?

Over the years, the United States Bureau of Mines (USBM) and the Office of Surface Mining (OSM), universities, and private groups have conducted extensive research about rock blasting.

Research findings have led to the development of acceptable vibration standards that greatly reduce the risk of off-site impacts. Ground vibration levels have been set by law to avoid off-site damage and should feel the same as a loaded truck or bus going 50 to 100 feet away.

One of the greatest challenges of rock blasting is to accurately determine the bounds of the blast area. This is particularly true in geologically disturbed rock that is to be blasted. The determination of the bounds of the blast area is the first step in ensuring safety.

Mine operators prevent injury to people or damage to equipment when a scheduled blast is detonated by having a blast area security system. Most blasting accidents occur during scheduled blasting and are due to inadequate blast area security. 

With today's technological advances in the civil engineering industry, operators can now explore blasting areas remotely using drones.  This can help them locate potential hazards and ensure that blasting is done safely and accurately.

Why do mining companies blast?

Blasting is the most cost-effective technique for breaking rock. As a result, blasting lowers the costs of manufactured goods like as electricity, sand, gravel, concrete, aluminum, copper and other minerals extracted from the ground. “If it can't be cultivated, it must be mined” has never been more accurate.

Blasting is also the most efficient method for creating ore access tunnels and haul roads. These are essential in a mine to ensure the safe and efficient movement of personnel and equipment while providing access to mineral deposits.

Finally, rock blasting is used as part of environmental remediation projects by breaking down hazardous waste sites or landfills in order to facilitate their proper treatment and disposal.

Do I need an engineer to plan rock blasting?

Yes, you will need to hire a civil and or structural engineer. A professional engineer/blaster is required to use the latest technology and techniques in order to determine the precise amount of explosives needed for a particular blasting project. This includes calculating safe vibration levels for nearby structures, creating computer models, or carrying out a pre-blast survey of the site. The engineer/blaster must also design the blast to minimize ground vibration and airblast, as well as other potential hazards associated with blasting.

A professional engineer/blaster can help you save money by minimizing explosives usage and ensuring that a safe, efficient rock blasting job is done correctly. Rock blasting can be a cost-effective way to achieve your project goals, but it must be done carefully and correctly. Using a professional engineer/blaster is essential for this.

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