Ground Improvement Question - Migration of Fines into Compacted Stone Columns / Aggregate Piers

[Blairsy]

Should the migration of soil fines into non-grouted compacted stone columns be considered during design if the stone columns are expected to penetrate fill comprised of sand with less than 15% fines and terminate at the top of a dense native sand stratum? The stone columns will be constructed using 3/4-inch clean, angular, uniform stone.

 

[ATSE]

What is the construction process for the stone columns in question: vibro-replacement or open hole (traditionally called Rammed Aggregate Piers)
Are the stone columns purely for ground improvement (say, for increased allowable pressure at foundation contact) or for drainage also?

The boundary between the new clean crushed rock and the existing soil will not be neat, and the boundary will certainly be dirty. This is usually not a problem for stone column application, unless drainage is the primary function.

 

[Okiryu]

I think that migration of fines is due to water flow. If you do not have groundwater flow and provide good surface drainage, migration of fines may not be an issue.