Compaction Wet clay

[Jomando]

Hi to all, this is my first post.

Building an embankment, 3m avg height for a future motorway, with Stoney clay, with borderline levels of moisture. Would laying a starter layer of 200m of pebble-like material help dry the clay faster, and so achieve better CBR values?

Thanks

 

[BigH]

Doubtful - and are you wanting better "dry" or "soaked" CBR values? The most appropriate ways are to (1) find a borrow pit where the moisture content is near optimum or (2) excavate the material, lay it in an open site to dry out to near optimum then transport it to the site and compact.

 

[oldestguy]

My experience says that one shouold be cautious about that first layer, if the site is wet. Compaction equipment seems to have the ability to pump that moisture up into dryer material.

Likewise, after rain, compacting of the upper less moist material will bring moisture up also.

So using a starter layer of material less susceptible to moisture is a good idea.

 

[BigH]

oldestguy - agree with your premise - but it won't help the clay he is placing dry faster as he wanted or help in his CBR values.

 

[iandig]

Are you using the granular layer as a drainage blanket to increase the rate of consolidation prior to the construction of the road - i.e. reduce the drainage path, and if so are you also using surcharging to improve the ground?

 

[Jomando]

Thanks for the anwers.

I cannot stockpile because if I do it I run the risk of getting the material wetter if it rains (very often here).

The idea is first not to get moisture from the ground up into the first layers of embankment when we compact. Also what iandig says. So if I have a 8 meter embankment I am thinking of using a sandwich layer halfway up.

The ones we have done without this layer are giving us rutting problems in localised points. I want to avoid using lime...

We started today, I will tell you if it works..

 

[dirtsqueezer]

Just as an aside, if you're building a layer that won't perc up the groundwater you should be using angular rock, as the rounded rock will tend to not support your upper layers as well. You probably already know this, just the terminology 'pebble' tends to refer to a pea gravel material, not a crushed base. Also if you're using clay like material, best to compact in thin lifts, probably 150-300mm, the thinner the better. Though in all honesty some free-draining imported gravel would be the better option if you're building for the long term. Clay tends to do funky things when exposed to wet weather.