Rammed aggregate piers 1

[MotorCity]

Is there a method to determine how close you can excavate next to a rammed aggregate pier without affecting its integrity? Are there general rules of thumb, such as don't excavate within XX pier diameters? Seems to me that excavating near a rammed aggregate pier would not be nearly as forgiving as excavating near a drilled concrete pier.

 

[oldestguy]

The safe way would be to consider it as if it were stored aggregate. Consider it may have a load on it with significant pressure exerted laterally in all directions. However there may be legal issues if you are on a different property, such as you may have no liability with excavations down to some limited depth, below which you must support adjacent property.

 

[PEinc]

I know that for a recently completed rammed aggregate pier project designed by GeoStructures, the plans show not being allowed to dig in a zone starting about 2.5 foot from the edge of the footing and then extending downward at an angle of 45 degrees. See attached PDF. This restriction caused the structural engineer for a new addition to redesign an elevator pit (raise it up) so that its excavation will not disturb the piers' surrounding soil.

This is my third recent project where this issue has arisen. Owners and engineers like the initial foundation cost savings but don't realize the possible future restrictions.

www.PeirceEngineering.com

 

[MotorCity]

Thanks for the info PEinc. I expected that its based on rules of thumb. I have done some internet searching but have not come across any examples or methods.

 

[PEinc]

Talk to Shana Carroll, P.E. at GeoStructures, Inc. in Ellicot City, Maryland. She can probably explain the restriction guidelines.

http://www.geostructures.com

http://www.PeirceEngineering.com