Scaled Distance Formula for Blasting

[Reeltime2]

I'm working with a municipality toward implementing some restrictions on blasting bedrock. The town wants to define a reasonable radius for pre-blast surveys. I found a couple references to the Scaled Distance Formula, but have seen it used and defined in many different ways. One community in Maine adopted a radius formula as follows: D(radius)=200 x W^1/2, where W equals the maximum weight of explosives in pounds.

Does anyone have any input on this approach?

 

[exploengineer]

Using scaled distance to define pre-blast redius is extremely conservative and in most cases will cause undue hardship to the contractors. If they have imposed this in a town in Maine, they probably do not want blasting. What they do not realize is that hammer vibration is usually more detrimental then construction and quarry blasting vibration due to the low frequencies and long term durations.

Blast vibration from construction and quarry are extremely safe. It is rare that damage occurs from these types of blasting activities. If damage does occur it is usually cosmetic in nature.

Due to vibration attenuation, the closest houses are the ones that need to be surveyed. A good safe distance is usually defined as houses within 250 feet or the closest residential structures. If the closest residence is 500 feet, then that is the distance.

Maine would be better off to impose a blasters' license. They are one of the only states that a blaster's license is not needed.

Frank Lucca M.I.Exp.E.

http://www.terradinamica.com