Organic Sands

[ktwannabe]

I am looking for a good reference that discusse the settlement behavior of organic sands. Especially if it correlates % organic content to increased settlement. We have a project that is partially underlain by 5 feet of dry to moist,loose to medium dense organic sands with up to 15% organic content as measured by loss of ignition. The snads appear to be possible incinerator waste but more sand than ash. There will be a road constructed over this and I would like to use a geogrid to stabilize the areas that "pump when rolled" but am worried about long term settlement due to the organics. Does anyone know of a good reference?

 

[SlideRuleEra]

Take a look at the ADS technical support website at this link:

http://www.ads-pipe.com/us/en/technical/geotech.shtml

Some of the available downloads should be of help.

 

[cbosy]

What you could do to ROUGHLY estimate worst case settlement is to take .15 by your layer thickness of 5 ft (this assumes everything degrades). I would then take an arbitrary reduction factor(say 1/2) based on how much you really think would degrade, e.g., 1/2*.15*5'=.375' which would typically be OK for a road.

 

[fndn]

I am not aware of any publication directly dealing with this topic. However, you could consider the following scenario:

Assuming your pavement thickness is 18" above Subgrade.

Remove the top 24" of Organic Sands. Place Geofabric at the bottom, then place 18" of polyfoam blocks followed by 6" of lean concrete.

Build per plan above the SG.

The lean concrete or the mud slab will prevent the lt wt foam from uplift problems, and will also reduce asphalt cement liquids from attacking the foam.