Planning for vibration when blasting

Planning ahead of a blast to ensure burdens aren’t too heavy and shots are properly spaced is a must for operations looking to limit vibration. Photo: P&Q Staff

Vibration is an inevitable part of the blasting process.

While most of the energy from a blast goes toward breaking rock, some of it travels away from the blast site through the ground and airwaves, according to GeoSonics/Vibra-Tech. These waves can cause houses to vibrate or shake and, because humans are sensitive to vibration, quarry neighbors might feel or hear the effects – even at low levels.

Even when feeling or hearing vibration from a blast, the chance of significant damage to a home is relatively small.

“Sometimes neighbors [of quarries], especially if they don’t know too much about blasting, might be concerned that it might damage their house, which is highly unlikely,” says Bethan Witter, a field consultant at Dyno Nobel. “But that’s a concern. If you’re in a really close proximity, sometimes people will hear a bit of a noise or have a cabinet rustle a bit if they’re closer. But it’s not actually enough vibration to do anything really.”

Improving performance

Operators can combat these issues and possibly limit the number of neighbor complaints by focusing on the frequency and velocity of blasts. Witter says keeping a low velocity and mid-range frequency is preferable, as those are the least perceivable.

Using vibration software to analyze a signature hole’s blast prior to larger-scale blasting can provide valuable data to inform operators of any adjustments that should be made. This entails loading and firing a hole as similar as possible to a normal hole, as well as gathering the data provided to optimize future blasts.

“You take the waveform from that one hole and put it in the software, along with some basic information like your blast pattern, how many holes you’re doing and the shape,” Witter says. “The tool directly calculates the best timing you can use in your class for that shot.”

Achieving such blasting goals requires more than just planning. Factors such as excess burdens or overly wide patterns can negatively impact how energy from a blast is expended. If burdens are too heavy, the rock can’t be crushed and moved, Witter says.

“If your energy can’t properly go into heating and crushing rock, it could be wasted with heavier burdens on vibration,” she says. “[It can cause] shaking instead of being able to do what it wants to do. It can’t fully crush and move the rock like it wants to, so more of the energy is wasted and goes to vibration.”

Proactive approach

Keeping these factors in mind ahead of a blast can not only improve an operation’s blasting process, but also, potentially, relationships with neighbors. To enhance community relations, Witter says it is important to have open and honest communication with neighbors to let them know what is really going on.

“When it comes to community relations, ignorance is our enemy,” she says. “The less people know, the more scared, uncertain or concerned they’re going to be. The more we can educate people and tell them what is going on and what they can expect from a blast, the more secure and empowered they will feel about what is going on.”

Related: Utilizing technology to produce safer blasts