CD Perry is currently at work on a very interesting piledriving job across the Hudson River from Albany NY as a subcontractor to LG Constructors. Faced with many challenges during the bid phase, CD Perry approached APE and together we came up with a system that would allow for the successful driving of the piles while meeting an extremely strict noise ordinance.
The design called for driving 12×84 H-Piles between 60ft and 75ft long thru zero blowcount material into glacial till ultimately achieving a 200ton capacity. However local noise ordinances limited the maximum noise that could be generated at the protery line from the piledriving operation to 65 decibels, which is quieter than a normal conversation between 2 people. Taking into consideration that using an impact hammer on an h-pile when 75ft of it is above ground greatly amplifies the impact, in a textbook example of line source noise, the determination was made to vibrate the piles in thru the very soft upper layers of soil to the top of the till. Once in the ground, with less of a line source,the pile could be impacted and create less noise.
The plans called for a dynamic test pile program to assure capacity could be achieved, which was the perfect testing ground to see if this system would keep the noise below 65dB. The piles were vibrated in, then impacted to the required capacity without any problem. However the 65 decibel noise requirement at the property line was exceeded by 10 decibels. A way to shave 10 dB off of the noise being produced by the diesel hammer driving the h-beams needed to be found.
This was accomplished by building a noise shroud around the leads for the diesel hammer using fireproof noise cancelling blankets. CD Perry designed and fabricated a “cocoon” on the lower section of leads around the diesel hammer and pile, and a 2nd test pile program was undertaken. The 2nd test showed that the decibel levels at the property line were now below the maximum allowable and the project could move forward.
Currently CD Perry has 3 vibros; an APE Model 50, a J&M Model 216 and J&M Model 11-23, all riding in APE 8×26 leads, to vibrate in the h-piles. Then they use two APE D19-42 diesel hammers with the noise abatement system on each set of leads, as well as an APE 150T vibro to drive the sheeting that is part of the foundation contract.