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How to confirm stone columns where installed successfully? 2

pelelo

Geotechnical
Joined
Aug 10, 2009
Messages
363
Location
DO
Engineers,

I am involved in a project which the original geotechnical investigation recommended stone columns due to the soil conditions.

Client is asking to the geotechnical consultant (not to the stone column contractor) if there is a way to confirm if the stone columns really densified or improved the ground.

It is my understanding that running a plate load test could be an option.

Also another option I think could be to run SPTs nearby the original SPTs and compare.

Any thoughts?. Thanks.
 
In soft soils, stone columns offer very little improvement. Only in generally firm CLAY and granular material do they offer some improvement in the ground between the columns.

A plate load test on top of the column on confirms the E' of the column material. This can be checked against the design assumption.

The best verification of a stone column improved ground is by a zone load test , typically a 2-3m square foundation placed on the columns. The position of the ZLT in relation to the column can be up for debate i.e. ZLT centered over a column, or placed on ground between columns
 
In soft soils, stone columns offer very little improvement. Only in generally firm CLAY and granular material do they offer some improvement in the ground between the columns.

A plate load test on top of the column on confirms the E' of the column material. This can be checked against the design assumption.

The best verification of a stone column improved ground is by a zone load test , typically a 2-3m square foundation placed on the columns. The position of the ZLT in relation to the column can be up for debate i.e. ZLT centered over a column, or placed on ground between columns
About the load test, are you referring to "ASTM D1196 - Standard Test Method for Nonrepetitive Static Plate Tests of Soils and Flexible Pavement Components for Use in Evaluation and Design of Airport and Highway Pavements"?

Please let me know.
 
Stone columns are exactly what they say - they are columns, basically a cheaper version of a pile. They do nothing for the crappy ground between the piles so the phrase in the the OP "really densified or improved the ground" implies that someone thinks it does. It doesn't.

You lay some overall slab or strip reinforced foundations on top of those columns and it won't subside anywhere near the same amount as if they weren't there.
 

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