How can I solidify excessively wet soils? 10

[ever7grene]

We have an earthwork dilemma at a 13 acre site in NJ that is jeapordizing both the cost and schedule of a school addition. The onsite soil, slated for cut to fill, is unsuitable as controlled compacted fill for use under roads, parking lots, etc because it is too wet and will not reach 95% compaction densities. Is there anything that can be done that will allow us to use this soil besides importing clean dry fill, which will be costly, or spreading the wet soil in 1' lifts and waiting for it to dry, which is taking too long and delaying the project?

 

[exploengineer]

It works real well in wet soils. I've done it in soils with clay and it worked. I would imagine it would be dependent on the clay percentaqe.

Frank Lucca M.I.Exp.E.

http://www.terradinamica.com

 

[Focht3]

Hmmm,

I'm with [blue]cvg[/blue] on this one. Where would the water go?

Most of my clients would take a pretty dim view of even trying it. And with all of the military bases in my area (5 within 30 minutes' drive) the use of explosives is discouraged.



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[exploengineer]

The water bubbles up out of the drill holes. Its an amazing thing to see. I didn't believe it until I saw it work.

The company with the most experiance in this is Vet's Explosives in Torrington, Connecticut.

Frank Lucca M.I.Exp.E.

http://www.terradinamica.com

 

[Focht3]

Well, seeing is believing. Guess I'll reserve final judgement for now -



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[chicopee]

I would create an weather protected impoundment with a pitched surface ( 2% to 5%) and store the fill for a couple of weeks to let water run off. The fill can be spread out or piled however you may want to give it some thought on the best storage procedure.
I dont think the authority will let you add a drying medium and have the material be used as a clean fill.

 

[gbowen]

In the Midwest, (I am located in Columbus, OH) additives such as kiln dust, fly ash, lime and portland cement are used very commonly to dry or stabilize soil. The additive is selected based upon the soil type and the required stability. The process of drying versus stabilizing is also dependent upon the desired outcome. For example, lime works extremely well with soils with a high clay content and cement is preferred for soils with lower clay contents. It gets complicated because there are many types of lime with different levels of hydration. Fly ash and kiln dust are byproducts of other processes and tend to be significantly cheaper than lime or portland cement but are less effective at stabilizing soils.

One of the big issues we are dealing with is the concept of drying vs. stabilizing. Drying is adequate for materials that need to be dried but do not need additional strength for bridging over soft soils. Stabilization on the other hand will result in strengths much stronger than the original soils and can often form a layer that will "bridge" over softer soils.

The issue here has been if drying is used it is not very complicated but if stabilization is proposed than the unconfined strength of the modified soil is measured and in the future credit may be given for this additional strength towards the pavement design.

Back to the original post, if drying is all that is needed it can be very inexpensive and can produce very quick results with the right additives and equipment. I have seen 3000 feet roadway stabilized in a period of a couple of days. One of the limitations is the equipment available. We have specialized companies here with large mixers(similar to the ones that mill asphalt)but they are still only capable of about 18" of mixing. The next question is how deep can the compactor effectively compact? We have found anything beyond 12" to be questionable. In cases where 12" of drying/stabilization was not sufficient we have done it in multiple 12" lifts.

This information may be more than anyone here wants to read. But I have worked with soil modification exstensively for the last 5 years and if anyone has questions I would be happy to try to answer.

 

[iandig]

Just a quick addition to the theme of this thread. In southern France, Italy, Spain and a lot of other southern European Countries (maybe States is a better word now?) they are so used to using lime to stabilise soils, that they apply it to dry dusty soils. The use of lime here is not to dry the soil, it is already in a desscicated state, but to control the soil during very dry and very wet periods. As the lime needs moisture to work properly, they have developed a technique whereby the lime is added in liquid form from spray bars after pre-mixing with water immediatley before application. They call the liquid 'milk of lime' (lime milk), and it has proved very succesful. There is a massive industry in Europe with the use of lime for road and building construction with earthworks, and it is the standard way in which a lot of Countries build.

 

[Focht3]

This also happens here in the "States" as well. We have found that the use of lime sluury is limited for dry soils unless it is mixed with the soil/dust, however, because the calcium hydroxide that doesn't bind with clay minerals tends to combine with other chemicals/materials. You just don't get the "bang for the buck" that is otherwise expected -



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[Grouser]

If the time table is critical enough you could consider renting a portable asphalt plant to pass the wet soil through for drying and stockpiling or replacement. Perhaps a combination of heated drying with reduced lime addition would produce a desireable material. There would be considerable handling cost involved therefore, a cost/benefit analysis would have to be performed to evaluate the practicality for your project.

Good Luck!

 

[zman44]

I feel for you. I am presently working on a project in Southeastern Virginia. The structural fill we have been provided with is an SM (barely, on the line with an ML)and with all the rain this summer it has not dried out at all. We are achieving good compaction but when the material is prood rolled it is not stable at all. I looked into Lime Stabilization. There is a company in Maryland that specializes in this. I'll try to locate their name/number. I saw a caution in another post regarding the white cloud and painting of cars. I have been warned about this and as our project is in close proximity to many vehicles we are not going this route. The engineer has advised us to cut an additional 12" of material off the roads and replace with compacted stone base. We'll see how that goes. We gave up on the disking method. Too much rain and if the material is left in furrows when it rains you end up with a bigger problem.

Since it is now October, what was your final fix?

 

[dirtsqueezer]

We're dealing with wet conditions at a site in Washington that is mostly due to the rain.

This is going to sound pretty obvious, but we noticed that the fill we had on site was still in the ground- it was only when we left stockpiles exposed to wet weather that we saw problems with compaction.

With a fair amount of finageling with the General, we saw big improvement using many rolls of visqueen and as many bags of sand and some timely off-days when the rain became excessive. I believe we increaced our time out there by at least a month and a half. The contractor had a special method of weighting the liners using twine for windier areas at the site.

This method in the end still left us with a few wet stockpiles, but for the most part was testing in the neighborhood of 7%, where previously I had readings upwards of 20%. I was surprised to be the only one excited on site! (I think the rest of them were sick of me .

Anyway, for what it's worth, we're going through the same thing in the Evergreen State as well.


ds

PS. We also tried compaction of exposed stockpiles, but in the end liners proved far and away the best method for wet weather.