Cowley speaks with Crains New York senior reporter Aaron Elstein:
See link below:
Jan 25, 2016
http://www.crainsnewyork.com/article/20160124/REAL_ESTATE/160129960
Cowley interviewed on News 12 Westchester regarding site blasting and its effects on neighboring properties.
I explained the (3) factors associated with blasting. Fly rock, vibration and air blast overpressure (ABOP) but my lucid, engineer speak explanation didn’t make the cut. What people experience most is the air blast over pressure, not the vibration. ABOP is measured in Decibels, vibration is particle velocity and is measured in Hertz. Fly rock is controlled using mats – and is very rarely an issue.
Allowable ABOP is equivalent to a 20 mph wind gust and is caused by the compression of the surrounding air due to the expansion of the blast gases. Vibration (particle velocity) is allowable up to speeds of 50 mm/sec.
A tell tale sign that ABOP is in excess of allowable is if glass breaks. ABOP is limited to 133 decibels…poor quality glass breaks at about 150 Decibels.
When inside a structure, the structure type is a significant factor in how much ABOP is felt by the occupants. That is why a person outside the structure doesn’t necessarily notice the ABOP as much.
Human perception of blast effects is unreliable
Click video below:
Jan 22, 2015
Site Safety: Overhaul Needed?
June 2014 Ask the Engineer – Safety
Know Your Building
May 2010
Expert Advice
May 2005 Feature – Building maintenance
Sidewalk Shed Safety
March 1997